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ASME Power Transmission and Gearing Conference

2009;():3-11. doi:10.1115/DETC2009-86229.

The paper reformulates the theory of the measurement over spheres of conical involute gears by simplifying its algebra and extending it to internal gears. Moreover, a five-measurement technique is proposed that retrieves information about all basic parameters of a conical involute gear. Numerical examples show application of the reported results to case studies.

Topics: Gears
Commentary by Dr. Valentin Fuster
2009;():13-19. doi:10.1115/DETC2009-86241.

Gear drives with modified elliptical centrodes allows obtaining an asymmetric derivative function of the gear ratio. In this paper, the geometrical aspects of modification of elliptical centrodes as well as their analytical determination have been considered. A general equation for the center distance of modified elliptical gears that can be applied for conventional elliptical gear, oval gears, and gears with lobes has been derived. The results of application of modified elliptical gears to drive the crank member of a crank-slider linkage with the purpose of modification of the working and free-running cycles of a conventional crank-slider mechanism are presented. Two examples of tandem design of modified elliptical gears coupled with a crank-slider linkage have been considered.

Commentary by Dr. Valentin Fuster
2009;():21-28. doi:10.1115/DETC2009-86249.

Toothed gears with an internal and an external gearing are widely dispersed nowadays. The extent and versatility of these gears are increasing not only in mechanical engineering. It is necessary to use high quality FEM software for a competent assessment of these gearings. However one problem occurs here — it is not easy to create an input data file describing the tooth profile shape and its root fillet in a 3D space. Moreover with regard to the type of a tooth profile curve (an involute), it is very difficult to enumerate equidistant spacing among points laying on this curve when preparing data for a FEM calculation. This equidistant spacing is important for good contact stress analysis during teeth meshing. It is impossible to get these data by ordinary methods. This contribution presents a numerical method suitable for calculating these equidistant spacing coordinates of points.

Commentary by Dr. Valentin Fuster
2009;():29-38. doi:10.1115/DETC2009-86252.

A new approach for generation of functions based on application of a multi-gear drive is proposed. The approach provides solution to the functional Ψ (α ) = gn (gn−1 (⋯(g1 (α )))) wherein Ψ (α ) is the function assigned for generation and gi (α ), i = 1 ,⋯,n, is the transmission function of pair i of conjugated non-circular gears. The specifics characteristics of the proposed approach are: (a) integrated impact by application of n synchronized gear drives, (b) favourable shape of centrodes, and (c) observation of limits of pressure angle. The developed theory is illustrated with several detailed numerical examples.

Topics: Design , Gears
Commentary by Dr. Valentin Fuster
2009;():39-46. doi:10.1115/DETC2009-86291.

A planetary gear train is used in a transmission in many fields, because it has a smaller size, a lighter weight, and a larger gear ratio than a conventional gear train. However, a planetary gear train has a lower efficiency than a conventional gear train. Self-locking sometimes occurs, in which case the planetary gear train can not be driven, because of a significant low efficiency. In this study, we theoretically analyzed the efficiency of a 2S-C type planetary gear train composed of external gears, and presented the condition in which the self-locking occurs. Furthermore, we examined the self-locking of 2S-C type planetary gear train composed of external gears using several gear sets with different numbers of teeth by the practical test. As the result, the condition of the self-locking which was analyzed theoretically agreed with experimental result.

Commentary by Dr. Valentin Fuster
2009;():47-59. doi:10.1115/DETC2009-86406.

To achieve a gearset which will maintain the beneficial properties of using involute shaped teeth, while allowing the gear ratio to vary, a new gear profile has been identified. This new gear profile termed the “Hybrid Involute Profile”, maintains the unique characteristics of an involute gear profile with the addition of a specified angular acceleration. This allows for one gear to be engaged with another gear while the ratio between the two gears is changing. The development of the Hybrid Involute Profile exploits involutometry relationships and properties. The derivation of the Hybrid Involute Profile along with validation case studies are presented.

Topics: Gears
Commentary by Dr. Valentin Fuster
2009;():61-69. doi:10.1115/DETC2009-86548.

Face-hobbing is a continuous generating process employed in manufacturing spiral bevel and hypoid gears. Due to machining dynamics and tolerances of machine tools, exact tooth surface geometry may not be obtained from the machining process using theoretical machine tool settings. Repeatable tooth surface geometric errors may be observed. The tooth surface errors will cause unfavorable displacement of tooth contact and increased transmission errors, resulting in noisy operation and premature failure due to edge contact and highly concentrated stresses. In order to eliminate the tooth surface errors and ensure precision products, a corrective machine setting technique is employed to modify the theoretical machine tool settings, compensating for the surface errors. This paper describes a method of correcting tooth surface errors for spiral bevel and hypoid gears generated by face-hobbing process using computer numerically controlled (CNC) hypoid gear generators. Polynomial representation of the universal motions of machine tool settings is considered. The corrective universal motion coefficients are determined through an optimization process with the target of minimization of the tooth surface errors. The sensitivity of the changes of tooth surface geometry to the changes of universal motion coefficients is investigated. A numerical example of a face-hobbed hypoid pinion is presented.

Topics: Gears , Errors
Commentary by Dr. Valentin Fuster
2009;():71-80. doi:10.1115/DETC2009-86663.

Power loss in a transmission is strongly related to the properties of the gear lubricant. Viscosity of the lubricant determines the no-load splash and churning losses. The losses in the EHD regime depend on the base oil type. In the boundary and mixed lubrication regime losses are mainly related to the chemical composition of the additive system. A test method was developed to evaluate the frictional properties of candidate transmission lubricants in relation to a mineral reference oil ISO VG 100 with a typical sulphur-phosphorus additive package. The test results can be expressed in simple correlation factors for no-load, EHD and boundary lubrication conditions, in comparative steady-state temperature development for given mean values of operating conditions, and in a ranking scale of different candidates. For a more detailed analysis of the expected power loss in a transmission in practice the results of the efficiency test can be introduced into an equation for the mean coefficient of gear friction for the respective oil. Thus the test results can be applied to any gear in practice at any operating conditions for any gear geometry. Examples of the influence of viscosity, base oil and additive type on the frictional behavior of gear lubricants and their effect on power loss reduction and energy savings in a gearbox are discussed.

Topics: Lubricants , Gears
Commentary by Dr. Valentin Fuster
2009;():81-87. doi:10.1115/DETC2009-86676.

This paper firstly presents a mathematical model in order to calculate the load distribution, single contact stiffness and meshing stiffness as well as transmission error. in this way, there is no need to use finite element like methods and also the calculation time is dramatically reduced. Presented method is based on definition of a statically undetermined problem that is formulated using energy method. Some assumptions considered to convert this problem to a statically determined problem and get the mathematical models. Then a numerical method is employed in order to solve the mathematical model using a double iteration flowchart to close the problem. This model is flexible to adapt for any modification in spur gear profile geometry. Finally, this model is verified using previous works that have been utilized finite element and experimental model.

Commentary by Dr. Valentin Fuster
2009;():89-94. doi:10.1115/DETC2009-86793.

The Wolfrom gear is suitable for high speed ratios with an efficiency which is not optimal, but still acceptable. The version with single-rim satellites has significant design and technological advantages. However, the determination of the most appropriate modification coefficients poses a technical problem as the modifications are now related instead of being chosen independently. The geometrical calculations of the single-rim satellites version are performed in the paper. Speed ratio, number of teeth of the satellites, pressure angles and modification coefficients are determined. Advisable values for these parameters are given. As an example a specific design problem for the replacement of a three-stage planetary reducer (consisting of 15 gears) with a Wolfrom gear train (6 gears) the following calculations were performed.

Topics: Gears , Trains
Commentary by Dr. Valentin Fuster
2009;():95-103. doi:10.1115/DETC2009-86838.

In this study, results of an experimental and theoretical study on the influence of rim thickness of the ring gear on rim deflections and stresses, and planet load sharing of a planetary gear set are presented. Experimental study consists of measurement of ring gear deflections and strains for gear sets having various numbers of planets, different ring gear rim thicknesses as well as various carrier pin hole position errors. Root and hoop strain gauges and displacement probes are placed at various locations so that the variations due to external splines of the stationary ring gear can also be quantified. A family of quasi-static deformable-body models of the test gear planetary gear sets is developed to simulate the experiments. The predictions and the measurements are compared to assess the accuracy of the models within wide ranges of parameters. Influence of rim thickness on ring gear stresses and deflections and planet load sharing are quantified together with the interactions between the rim flexibility and the spline conditions. The results from this study confirm that the ring gear deflections and the ring gear support conditions must be included in the design process as one of the major factors.

Commentary by Dr. Valentin Fuster
2009;():105-111. doi:10.1115/DETC2009-86843.

The spherical gear is a new type of gear proposed by Mitome et al. [1]. Different from that of the conventional spur or helical gear sets, the spherical gear set can allow variable shaft angles and large axial misalignments without gear interference during the gear drive meshing [1, 2]. Geometrically, the spherical gear has two types of gear tooth profiles, the concave tooth and convex tooth. In practical transmission applications, the contact situation of a spherical gear set is very complex. To obtain a more realistic simulation result, the loaded tooth contact analysis (LTCA) has been performed by employing the finite element method (FEM). According to the derived mathematical model of spherical gear tooth surfaces, an automatic meshes generation program for three-dimensional spherical gears has been developed. Beside, tooth contact analysis (TCA) of spherical gears has been performed to simulate the contact points of the spherical gear set. Furthermore, the contact stress contours of spherical gear tooth surfaces and bending stress of tooth roots have been investigated by giving the design parameters, material properties, loadings and boundary conditions of spherical gears.

Commentary by Dr. Valentin Fuster
2009;():113-123. doi:10.1115/DETC2009-86932.

This paper presents an automatic procedure to optimize the loaded tooth contact pattern of face-milled hypoid gears with misalignments varying within prescribed ranges. A two-step approach is proposed to solve the problem: in the first step, the pinion tooth micro-topography is automatically modified to bring the perturbed contact patterns (as the assembly errors are varied within the tolerance limits) match a target area of the tooth, while keeping them off the edges; in the second step, a subset of the machine-tool settings is identified to obtain the required topography modifications. Both steps are formulated and solved as unconstrained nonlinear optimization problems. While the general methodology is similar to the one recently proposed by the same authors for the optimization at nominal conditions, here the robustness issues with respect to misalignment variations are considered and directly included in the optimization procedure: no a posteriori check for robustness is therefore required. Numerical tests show that nominally satisfactory and globally robust hypoid pairs can be designed by a direct process and within a unified framework, thus avoiding tiresome trial-and-error loops.

Topics: Gears , Optimization
Commentary by Dr. Valentin Fuster
2009;():125-130. doi:10.1115/DETC2009-87092.

This paper presents contact force and torsional rigidity analysis of a cycloid drive considering finite bearing and Hertz contact stiffness. Contacts between the disk and pin-rollers are simplified as linear spring elements, and the bearing is modeled as a rigid ring that has frictional contact to the disk and an elastic support. FE (finite element) analysis for contact force and Hertz theory calculation for contact stiffness are performed iteratively until the contact stiffness converges less than 1%. Contact force and pressure distributions under different contact and bearing stiffness are analyzed. In addition, effects of cycloid disk rotation are discussed. Finally, torsional rigidity of the cycloid drive is analyzed and compared with experimental result.

Topics: Bearings , Stiffness
Commentary by Dr. Valentin Fuster
2009;():131-138. doi:10.1115/DETC2009-87179.

The traditional methods for computation of the efficiency of cylindrical gear transmissions are based on the hypotheses of constant friction coefficient and uniform load distribution along the line of contact. However, the changing rigidity of the pair of teeth along the path of contact produces a non–uniform load distribution, which has significant influence on the friction losses, due to the different relative sliding at any point of the line of contact. In previous works, the authors obtained a non-uniform model of load distribution based on the minimum elastic potential criterion. This load distribution was applied to compute the efficiency of spur and helical gears, resulting in slightly greater values of the efficiency than those obtained if the load distribution along the line of contact is assumed to be uniform. In this work, this non-uniform model of load distribution is applied to study the efficiency of involute spur gears with transverse contact ratio between 1 and 2 (i.e., the load is shared among one or two pairs of teeth), assuming the friction coefficient to be constant along the path of contact. Analytical expressions for the power losses due to friction, for the transmitted power and for the efficiency are presented. A study of the influence of some transmission parameters (as gear ratio, pressure angle, etc.) on the efficiency is also presented.

Topics: Gears , Spur gears
Commentary by Dr. Valentin Fuster
2009;():139-147. doi:10.1115/DETC2009-87302.

The demand of large-sized spiral bevel gears has increased in recent years and hereafter the demand may increase more and more. The large-sized spiral bevel gears with equi-depth teeth are usually manufactured based on Klingelnberg cyclo-palloid system. In this paper, the tooth contact pattern of large-sized spiral bevel gears in this system are investigated analytically and experimentally. First, the tooth contact pattern and transmission errors of such gears are analyzed. The analysis method is based on simultaneous generations of tooth surface and simulations of meshing and contact. Next, the large-sized spiral bevel gears are manufactured and the tooth contact pattern of these gears is investigated experimentally. Moreover, the real tooth surfaces are measured using a coordinate measuring machine and the tooth flank form errors are detected using the measured coordinates. It is possible to analyze the tooth contact patterns of the spiral bevel gears with consideration of the tooth flank form errors expressing the errors as polynomial equations. Finally, the influence of alignment errors due to assembly on the tooth contact pattern is also investigated analytically and experimentally. These analyzed results were compared with experimental ones. As a result, two results showed a good agreement.

Topics: Gears
Commentary by Dr. Valentin Fuster
2009;():149-165. doi:10.1115/DETC2009-87485.

This work investigates the nonlinear vibration of gear pairs, where the nonlinearity is due to portions of gear teeth contact lines losing contact (partial contact loss). The gears are modeled as rigid bodies that admit motion in six degrees of freedom. A network of distributed stiffnesses models the nonlinear gear contact. The distributed stiffness scheme is obtained by discretizing the kinematic contact lines into segments, each with the possibility of losing contact. Whether these segments are actually in contact or not is determined by the gear deflections and tooth modifications. The modeling is verified with finite element analysis and experimental measurements from the literature. The combination of a translational and a tilting spring is proven to be identical to the distributed stiffness model. This equivalent representation of the mesh identifies a nonlinear tilting mesh stiffness that accompanies the well-known translational gear mesh stiffness typically modeled by a single spring. Modal analysis reveals a mesh tilting vibration mode where this spring dominates, in addition to the mesh deflection vibration mode. Computational dynamic analysis of a helical gear pair near the natural frequencies of the mesh tilting and deflection modes exhibit nonlinear vibrations. Both cases involve nonlinearity due to partial contact loss where only part of a nominal contact line loses contact at an instant.

Commentary by Dr. Valentin Fuster
2009;():167-176. doi:10.1115/DETC2009-87494.

This paper examines the vibration modes of single stage helical planetary gears in three dimensions with equally spaced planets. A lumped-parameter model is formulated to obtain the equations of motion. The gears and shafts are modeled as rigid bodies with compliant bearings at arbitrary axial locations on the shafts. A translational and a tilting stiffness account for the force and moment transmission at the gear mesh interface. The modal properties generalize those of two-dimensional spur planetary gears; there are twice as many degrees of freedom and natural frequencies due to the added tilting and axial motion. All vibration modes are categorized as planet, rotational-axial, and translational-tilting modes. The modal properties are shown to hold even for configurations that are not symmetric about the gear plane, due to, for example, shaft bearings not being equidistant from the gear plane. Computational modal analysis are performed to numerically verify the findings.

Commentary by Dr. Valentin Fuster
2009;():177-186. doi:10.1115/DETC2009-86132.

Helical synchronous belt drives are effective for reducing the noise and transmission error per single pitch of a pulley in comparison with conventional synchronous belt drives. However, the helix angle of the tooth trace causes axial belt movement. When the belt comes into contact with the pulley flange or the belt moves away from the pulley flange due to bidirectional operation, the accuracy of finishing on the belt side face affects the transmission error. In addition, it is considered that various factors such as transmitted torque, installation tension, pitch difference between the belt and the pulley, and alignment error between the driving and driven pulleys in the axial direction affect the behavior of the transmission error. In the present study, the influence of various factors on the transmission error in a helical synchronous belt with the error on the belt side face was investigated. Specifically, the case in which a flanged pulley is rotated in bidirectional operation under the quasi-static condition and transmitted torque was examined. The transmission error in bidirectional operation considering the error on the belt side face increased with the increase in transmitted torque, but was reduced when the installation tension was set to be high and when the pitch difference on the driving side was smaller than that on the driven side. In addition, the accuracy of rotation transmission improved when the alignment between the pulleys in the axial direction was set so that the belt on the driving side came into contact earlier with the pulley flange than did the belt on the driven side.

Topics: Errors , Belts , Timing belts
Commentary by Dr. Valentin Fuster
2009;():187-196. doi:10.1115/DETC2009-86638.

The mechanical behavior of V-belt variators during the speed ratio shift is different from the steady operation as a gross radial motion of the belt is superimposed to the circumferential motion. The theoretical analysis involves equilibrium equations similar to the steady case, but requires a re-formulation of the mass conservation condition making use of the Reynolds transport theorem. The mathematical model of the belt-pulley coupling implies the repeated numerical solution of a strongly non-linear differential system. Nevertheless, an attentive observation of the numerical diagrams suggests simple and useful closed-form approximations for the four possible working modes of any pulley, opening/closing, driver/driven, whose validity ranges over most practical cases. The present analysis focuses on the development of such simplified solutions, succeeding in an excellent matching with the numerical plots, and on the comparison of the theory with some experimental tests on a motorcycle variator, revealing a very good agreement.

Topics: Rubber , Belts
Commentary by Dr. Valentin Fuster
2009;():197-203. doi:10.1115/DETC2009-86695.

Traditionally, transmission error (TE) has been used in order to asses the noise properties of gears. Measurements of gear noise for a complete truck gearbox have been used to correlate noise from a gear pair with the concept of calculated static transmission error as noise excitation. Two gear pairs with very similar macro geometry but different micro geometry was used. Both transmission error as excitation and the excitation proposed by P. Velex and M. Ajmi which is the difference between the loaded and unloaded transmission error, are compared with measured noise. The result shows that the difference between the loaded and unloaded TE correlates well with measure noise for gear pair A but no excitation correlates with the measurement result gear pair B. A big difference between gear pair A and B can be seen in the contact pattern. The contact pattern of gear pair B shows that despite a large tip relief, edge contact occurs where the tip relief starts. This can be one explanation to the lack of correlation between TE and the measurement result for gear pair B. Another explanation can be other excitations such as friction and bending moments. The results show the limitations of only considering transmission error when designing quiet gears.

Topics: Noise (Sound) , Gears , Errors
Commentary by Dr. Valentin Fuster
2009;():205-215. doi:10.1115/DETC2009-87525.

A finite element formulation for the dynamic response of gear pairs is proposed. Following an established approach in lumped parameter gear dynamic models, the static transmission error is used as the excitation in a frequency domain solution of the finite element vibration model. The nonlinear finite element/contact mechanics formulation provides superior calculation of static transmission error and average mesh stiffness that is used in the dynamic simulation. The frequency domain finite element calculation of dynamic response correlates to numerically integrated (time domain) finite element dynamic results and previously published experimental results. Simulation time with the proposed formulation is two orders of magnitude lower than numerically integrated dynamic results. This formulation admits system level dynamic gearbox response, which may include multiple gear meshes, flexible shafts, rolling element bearings, and housing structures.

Commentary by Dr. Valentin Fuster
2009;():217-231. doi:10.1115/DETC2009-87553.

Tooth wedging occurs when a gear tooth comes into contact on the drive-side and back-side simultaneously. Tooth wedging risks bearing failures from elevated forces. This work studies the nonlinear tooth wedging behavior and its correlation with planet bearing forces by analyzing the dynamic response of an example planetary gear based on a real application of a wind turbine geartrain. The two-dimensional lumped-parameter model [1] is extended to include tooth separation, back-side contact, tooth wedging, and bearing clearances. The simulation results show significant impact of tooth wedging on planet bearing forces for a wide range of operating speeds. To develop a physical understanding of the tooth wedging mechanism, connections between planet bearing forces and tooth forces are studied by investigating physical forces and displacements acting throughout the planetary gear. A method to predict tooth wedging based on geometric interactions is developed and verified. The major causes of tooth wedging relate directly to translational vibrations caused by gravity forces and the presence of clearance-type nonlinearities in the form of backlash and bearing clearance.

Commentary by Dr. Valentin Fuster
2009;():233-243. doi:10.1115/DETC2009-86119.

An algorithm is developed for the execution of motions on the CNC hypoid generating machine using the relations on the cradle-type machine. The algorithm is based on the condition that since the tool is a rotary surface and the pinion/gear blank is also related to a rotary surface, it is necessary to ensure the same relative position of the head cutter and the pinion on both machines. The algorithm is applied for the execution of motions on the CNC hypoid generator for the manufacture of spiral bevel gears, based on the machine-tool setting variation on the cradle-type hypoid generator conducted by optimal polynomial functions up to 5th order. By using the corresponding computer program, the motion graphs of the CNC hypoid generator are determined for the manufacture of spiral bevel gears based on the optimal variation of the velocity ratio in the kinematic scheme and of the cradle radial setting on a cradle-type generator.

Commentary by Dr. Valentin Fuster
2009;():245-254. doi:10.1115/DETC2009-86786.

Manufacturing errors typically cause real (measured) spiral bevel and hypoid gear surfaces to deviate from the theoretical ones globally. Tooth surface wear patterns accumulated through the life span of the gear set are typically local deviations that are aggravated especially in case of edge contact conditions. An accurate and practical methodology based on ease-off topography is proposed in this study to perform loaded tooth contact analysis of spiral bevel and hypoid gears having both types of local and global deviations. It starts with definition of the theoretical pinion and gear tooth surfaces from the machine settings and cutter parameters, and constructs the theoretical ease-off and roll angle surfaces to compute unloaded contact analysis. Manufacturing errors and localized surface wear deviations are considered to update the theoretical ease-off to form a new ease-off surface that is used to perform a loaded tooth contact analysis according to the semi-analytical method proposed earlier. At the end, a numerical example with locally deviated surfaces is analyzed to demonstrate the effectiveness of the proposed methodology as well as quantifying the effect of such deviations on load distribution and the loaded motion transmission error.

Topics: Gears
Commentary by Dr. Valentin Fuster
2009;():255-262. doi:10.1115/DETC2009-86970.

The double flank gear rolling testing is a method by which a master gear is rolled together, in tight mesh, with a testing gear. As the gears roll, slight variations of center distance are measured and recorded as an indicator of gear quality. The double flank gear rolling testing is easy and low coast, therefore, it is widely used in gear industry. In this study, the mathematical models of standard master gears and testing gears with various errors are carried out first according to the theory of gearing. Then, the process of double flank gear rolling testing is simulated by applying the concept of tooth contact analysis (TCA). Tooth contact types including surface-to-surface contact and tip-to-surface interference are considered, and three possible combinations of these two contact types occurring on each tooth flanks are discussed as well. The results of this study can provide the industry a significant process to establish the analysis and capacities for double flank testing.

Topics: Simulation , Gears , Testing
Commentary by Dr. Valentin Fuster
2009;():263-270. doi:10.1115/DETC2009-87199.

Nowadays, the basic requirements of gear transmissions are not limited only to the more usual ones (like resistance, reliability ...), but often include also good efficiency and low vibration and noise emissions. Supporting structures, gear macro and micro geometry and textures are the key-points in the design of a geared system that fulfil the latter two requirements. The expected results can be obtained only if the gears actually meet the design specifications: this is one of the main reasons for the improvement and the optimization of the finishing processes, like shaving and grinding. A great deal of work has been done on defining the gear tooth flank topology that minimizes gear transmission error and consequently its noise emission, but usually, the practical realization of this micro-geometry is not taken into account. The actually available axes of the grinding machines and their laws of motion limit, in fact, the obtainable flank topology, and then it is often difficult to determine the optimal machine tool settings. In the paper, first it is presented a method to simulate gear form grinding with a disk tool; then a strategy to determine the combination of tool geometry and axes’ motions that best fulfil the gear design geometrical requirements is presented and discussed.

Commentary by Dr. Valentin Fuster
2009;():271-279. doi:10.1115/DETC2009-86164.

The method for loaded tooth contact analysis is applied for the investigation of the influence of misalignments and tooth errors on load distribution, stresses and transmission errors in mismatched spiral bevel gears. By using the corresponding computer program the influence of pinion’s offset and axial adjustment error, angular position error of the pinion axis and tooth spacing error on tooth contact pressure, tooth root stresses and angular displacement of the driven gear member from the theoretically exact position based on the ratio of the numbers of teeth is investigated. The obtained results have shown that in general, the misalignments in spiral bevel gears worsen the conjugation of contacting tooth surfaces and in extreme cases cause edge contact with high tooth contact pressures. But, some mismatches, as are the axial movement of the pinion apex towards the gear teeth or the tip relief of pinion teeth (in this analysis it is represented by the tooth spacing error) reduce the maximum tooth contact pressure. Also it can be concluded that the misalignments and the tooth spacing errors significantly increase the angular position error of the driven gear from the theoretically exact position based on the numbers of teeth and make the motion graphs unbalanced.

Topics: Stress , Gears
Commentary by Dr. Valentin Fuster
2009;():281-288. doi:10.1115/DETC2009-86323.

Synchronous belts are rubber-composite materials with rubber, helical cords and facing fabrics. The helical cord is the tension member of the belt and is made of glass fibers, aramid fibers, or steel wires. Recent trends require increasingly high stiffness for the rubber belts. The use of carbon fibers and hybrid cords with carbon fibers are considered to be an effective way to achieve high stiffness for helical cords. This paper presents the study is to improve the bending fatigue strength of hybrid cords, where the center strand is made of carbon fibers, and the outer strands are made of glass fibers. The optimum cord composition for good bending fatigue durability is discussed following experimentation, mechanical analysis using a simplified mechanical model and FEM analysis. The model reasonably explained the initiation of the fatigue failure initiation site in the hybrid cords. The optimum cord composition was proposed for the bending fatigue strength basing on the simplified mechanical model. This was verified by experimental data showing good fatigue life. The use of such helical cords can considerably extend the operating life of synchronous belts.

Commentary by Dr. Valentin Fuster
2009;():289-294. doi:10.1115/DETC2009-86358.

One of the most important methods to solve the edge loading problem due to excess misalignment and deflection in aerospace actuation gearing is to localize tooth bearing contact by crowning the teeth. Irrespective of the applied load, if the misalignment and/or deflection are large enough to cause the contact area to reduce to zero, the stress becomes large enough to cause damage. The edge loading could cause the teeth to break or pit, but too much crowning may also cause the teeth to pit due to concentrated loading. In this paper, a proposed method to localize the contact bearing area and calculate the contact stress with crowning is presented and demonstrated on some real life examples in aerospace actuation systems.

Commentary by Dr. Valentin Fuster
2009;():295-304. doi:10.1115/DETC2009-87313.

This paper presents a study on effects of case depth, side-face carburizing and helix angle on the residual stress and the bending fatigue strength of case-carburized helical gears. The carbon content of each element of the FEM gear models due to carburizing was obtained. A heat conduction analysis and an elastic-plastic stress analysis in the case-carburizing process of helical gears were carried out by the three-dimensional finite-element method, and then residual stresses were obtained. Effects of the case depth, the side-face carburizing, the helix angle and the face width on the residual stress of case-carburized helical gears were determined. Bending fatigue tests were carried out for case-carburized helical gears and S-N curves and bending fatigue limit loads were obtained. Effects of the case-depth, the side-face carburizing and the helix angle on the bending fatigue strength of the case-carburized helical gear were determined.

Commentary by Dr. Valentin Fuster
2009;():305-311. doi:10.1115/DETC2009-86112.

This research presents a rotor dynamic, finite element model of a rotary-wing transmission based on first principles. The transmission and model formulation are presented. The effects of the different gearing configurations within the model are discussed. The natural frequencies and mode shapes are extracted using conventional eigenvalue analysis. The frequencies are compared and shown to correspond with experimental results. Observations on the resulting system mode shapes are presented. The model exhibits great potential for use in health monitoring of rotary-wing systems and sensor optimization algorithms.

Commentary by Dr. Valentin Fuster
2009;():313-319. doi:10.1115/DETC2009-86255.

This paper presents an analysis of the contact pressures and the contact area of mating disks in a frictional transmission. Hertz’s formulations are adopted to determine the maximum contact pressures as well as the size of the contact area resulting from elastic deformation due to the clamping force. Hertz’s formulations are expressed in terms of geometrical features of the active surface of mating disks. The obtained relationships can be readily applied for quantitative estimation of the contact pressures and the contact area parameters for different ranges of transmission ratio. Samples of numerical results are presented in graphical form.

Commentary by Dr. Valentin Fuster
2009;():321-328. doi:10.1115/DETC2009-86982.

Most small hydropower stations drive trains include a gearbox to increase the speed of the turbine shaft to the generator. An increase in speed is needed because the hydro turbines shafts turn at a much lower speed than is required by most electrical generators. The range in which the input angular speed must be increased is 4–8. The speed increasers for this kind of applications must have an acceptable efficiency, reduced overall dimensions and complexity and, therefore, a reduced technological cost. The paper objective is to enlarge the base of speed increasers for small hydro stations with chain transmissions. The concept of the proposed chain transmission to be used as speed increaser is developed using a conceptual design algorithm. The algorithm is based on the VDI model and consists in the following steps: 1°. Requirements list establishment; 2° Global function establishment; 3°. Global function description by structures of sub-functions; 4°. Solving structures generation by: solving the sub-functions, sub-solutions composition and elimination of inadequate solution; 5°. The best solving structure selection by evaluation. The speed increaser function is detailed as part of a hydropower station. The sub-functions of the speed increaser are further analyzed in order to generate the solving structures. Sixteen distinct structural variants are presented in the paper. But only those structural variants, whose technical characteristics fulfill, quantitatively, the requirements, are considered as solving structures (for the speed increaser function). In order to select the solving structures, the synthesis of the sprockets teeth numbers for all the structural variants is performed and their efficiency is calculated. Then, their evaluation is made taking into account the technical-economic criteria; thus, the optimal solution that fulfils the requirements list (the principle solution) is found. The principle solution is an innovative concept of the chain speed increaser and represents an input data for the embodiment design phase.

Commentary by Dr. Valentin Fuster
2009;():329-335. doi:10.1115/DETC2009-87224.

Drivetrains are a major source of vibration, noise and system failures. Accordingly, a significant amount of time and effort is being invested developing simulation methods in order to better understand and avoid potentially damaging vibrations, even before prototypes are created for testing. The first step in simulating any drivetrain is creating suitable virtual models to investigate particular phenomena. Too much model detail leads to long computation times and difficulties in interpreting results, while too little may fail to include desired effects. Because the various levels of detail available in multi-body simulation (MBS) are practically limitless, a significant amount of attention must be given in order to choose the appropriate modeling elements. In the simplest form an entire drivetrain can be modeled as several rigid masses connected with torsional springs, which is justifiable for fundamental concept analyses. For other analyses, full three dimensional modeling with complex components may be necessary. Higher frequency analyses may even necessitate the inclusion of material bending for achieving accurate results. The various available elements for modeling specific components must be well understood in order that appropriate choices are made. Modeling requirements for the elements commonly used in the simulation of drivetrains will be discussed. For example: bearings, gearwheels, universal and constant velocity joints, frequency and amplitude dependent mounts, flexible components (e.g. shafts and gearbox housings), etc. Once virtual models are available, various analysis methods are applied in order to aid designers in identifying and quantifying potentially damaging vibrations. Again the application and limitation of these methods must be well understood in order to generate meaningful results. The following methods will be compared and discussed: resonance analysis, linear system analysis, run-up Fast Fourier Transformation analysis, order analysis, transfer path analysis and durability analysis. These drivetrain modeling techniques and analysis methods are not limited to any specific field of engineering, but can be applied to an extensive range of engineering disciplines. Analyses applied to virtual models out of the automotive and wind turbine sectors will be shown.

Topics: Modeling
Commentary by Dr. Valentin Fuster

3rd International Conference on Micro- and Nanosystems

2009;():339-344. doi:10.1115/DETC2009-86035.

In many drug dispensing devices, such as syringes and inhalers, a rubber ring is used as a seal. During device actuation the seal is subjected to friction which in turn causes it to deform. This can lead to suboptimal performance of the device and as a consequence variability in the delivered dose. Seal friction is complex, arising from adhesion of rubber in contact with a moving counterface, viscous action of a thin film of entrained fluid into the contact and ploughing of seal asperities. Therefore, the first step in the understanding of the conjunctional behaviour of rubber seals is the fundamental study of these friction mechanisms. A developed model can then be validated against measurements, prior to its use in a multi-body dynamic model of the inhaler valve to predict product performance, robustness and variability due to manufacturing tolerances. This paper undertakes two distinct studies. Firstly, a friction model for the rough elastomeric material, typically used for valve seals is developed. The model is then validated against measurements in nano-scale. Friction data is presented for nitrile rubber, using a silicon nitride AFM tip for nano-scale interactions. The validation is then extended to macro-scale motion of an instrumented trolley, incorporating an elastomeric surface sliding on a polymeric counterface. These tests are carried out for polybutylene terephthalate (PBT). Secondly, the validated friction model is used in an elastomeric seal model in-situ within the valve and in contact with a polymeric stem surface and subject to both global fittment deformation and canister pressure. Reasonable agreement is found between the measurements and model predictions for the nano-scale coefficient of friction of rubber against silicon nitride. Similarly, good agreement has been obtained for the mean coefficient of friction of rubber against PBT. In addition, the mechanism of adhesion between contacting surfaces of gasket and stem is taken into account.

Topics: Friction , Rubber
Commentary by Dr. Valentin Fuster
2009;():345-346. doi:10.1115/DETC2009-86398.

Using molecular dynamics, the behavior of nanoparticles during manipulation process is investigated in this paper. The system consists of a tip, cluster and substrate. The focus of the present research is on ultra-fine metallic nanoclusters. The system of concern is made of different transition metals. Two criteria have been proposed for evaluation of success in a pushing process. Such criteria describe the intactness of nanoparticle/substrate pair. The effects of cluster material and manipulation speed on the success of the process are investigated by atomistic simulations. Such qualitative simulation studies can evaluate the level of success of manipulation regarding different working conditions before consuming high experimental expenses.

Commentary by Dr. Valentin Fuster
2009;():347-351. doi:10.1115/DETC2009-87314.

A novel boundary condition is introduced to calculate the adhesion of similar and dissimilar thin-walled microstructures. By casting the energy release rate for debonding in terms of a discontinuity in bending curvature at the contact boundary, it is possible to study such systems using conventional plate theory. This result is of particular importance in modeling the aggregation of heterogeneous carbon-nano-tubes or spherical cells, where the contacting microstructures have a different radius and/or bending stiffness.

Commentary by Dr. Valentin Fuster
2009;():353-362. doi:10.1115/DETC2009-87462.

Costal cartilage is one of the load bearing tissues of the rib cage. Literature on the material characterization of the costal cartilage is limited. Atomic force microscopy has been extremely successful in characterizing the elastic properties of articular cartilage, but no studies have been published on costal cartilage. In this study AFM indentations on human costal cartilage were performed and compared with macro scale indentation data. Spherical beaded tips of three sizes were used for the AFM indentations. The Hertz contact model for spherical indenter was used to analyze the data and obtain the Young’s modulus. The costal cartilage was found to be almost linearly elastic till 600 nm of indentation depth. It was also found that the modulus values decreased with the distance from the junction. The modulus values from macro indentations were found to be 2-fold larger than the AFM indentation modulus.

Commentary by Dr. Valentin Fuster
2009;():363-366. doi:10.1115/DETC2009-87660.

This paper reports the measurement of the mechanical and piezoelectric properties of Lead Zirconate Titanate (PbZr52 Ti48 O3 , PZT) nanofibers. Partially aligned PZT nanofibers were fabricated by sol-gel electrospinning process. The diameters of the fiber were tuned from 50 to 150 nm by changing the concentration of the sol-gel in the precursor. The fiber consists of nanocrystal grains with average grain size of 10 nm. The Young’s modulus of individual fiber was obtained by nanoscale three-point bending using Atomic Force Microscope (AFM), which was 42.99GPa. Titanium strip was used as the substrate to collect the nanofibers for the three-point bending test to measure the piezoelectric response. The output voltages from the nanofibers under different strain were recorded by Labview, and the highest value of the output voltage was 0.17±0.005V. These results have shown that PZT nanofibers have great potential in nano sensor and actuator applications.

Topics: Nanofibers
Commentary by Dr. Valentin Fuster
2009;():367-373. doi:10.1115/DETC2009-87667.

The paper highlights the complex issues involved in impact dynamics at nano-scale, prevalent in MEMS. The role of protective layers on the silicon substrate is investigated. It is found that the expected viscoelastic behavior of these layers is not activated due to the very short (almost instantaneous) impact times.

Commentary by Dr. Valentin Fuster
2009;():375-382. doi:10.1115/DETC2009-86093.

Inhalation therapy is being applied in the home care field to a gradually increasing degree, and therefore two issues of great importance are the convenience and portability of medical devices. Hence, this paper presents a novel highpower MEMS atomizer device that includes a ring-type piezoelectric actuator and a cymbal-shaped micro nozzle plate (CSNP). The latter can focus energy on the center of the nozzle plate and induce a large force, which provides the MEMS atomizer with the high power necessary to spray medical solutions of high viscosity and increase the atomization rate. The high-power MEMS atomizer can reduce liquids to droplets of an ultra-fine size distribution (Mass Median Aerodynamic Diameter, MMAD), increasing the nebulizing rate and enabling the spraying of high-viscosity fluids (cP>3.5). In this research, the ultra-fine droplets were of a MMAD of less than 4.07 μm at 127.89kHz and the atomization rate was 0.5ml/min. The drive voltage of this high-power MEMS atomizer device was only 3V, and the power consumption only one-tenth that of conventional ultrasonic atomizers at 1.2W. The simulation and experiments carried out in this study proved that the droplets are much smaller than those produced by current conventional devices and the device is of greater efficiency; therefore, the high-power MEMS atomizer is suitable for use in the development of a convenient and portable inhalation therapy device.

Commentary by Dr. Valentin Fuster
2009;():383-388. doi:10.1115/DETC2009-86222.

Recently, there has been an increasing interest to develop rapid, reliable and low-concentration detection methods of micro-organisms involved in bioterrorism, food poisoning, and clinical problems. How to detect virus at concentration below the threshold will be challenging with respect to specificity, selectivity, and sensitivity. Among all parameters, sensitivity is probably the most critical consideration. If the sensitivity is not satisfied for real-time detection, researchers need to duplicate numerous numbers of viruses. However, it will substantially increase processing times and experimental hazard. To increase the sensitivity of virus sensors, this paper discusses how to increase the density of linkers and viruses on sensor’s surface in the microfluidic channels. In the future, researcher could use emerging technology, such as PT-PCR, QCM, C-V and I-V measurements, etc, to detect viruses on sensor’s surface. Usually microorganisms, molecules, or viruses in the fluidic environment are at very low Reynolds numbers because of tiny diameters. At very low Reynolds numbers, viscous forces of molecules and viruses will dominate. Those micro- or nanoparticles will stop moving immediately when flows cease and drag forces disappear. Of course, molecules and viruses are still subject to Brownian motion and move randomly. In order to increase the adhesion density of micro- and nanoparticles on sensor’s surface, designs of the flow movements in microfluidic channel is proposed. Adhesion density of linker 11-mercaptoundecanoic acid (MUA) and turnip yellow mosaic virus (TYMV) with specific quantum dots were measured by confocal microscope. Results show that TYMV and MUA layers disperse randomly by dipping method. Infusion rate, flow rate, and transverse flow could affect the adhesion densities of recognition layers on sensors’ surface. Adhesion densities of MUA and TYMV can be reached 70∼80% by microfluidic method to contrast just 10% by dipping method.

Commentary by Dr. Valentin Fuster
2009;():389-395. doi:10.1115/DETC2009-86265.

Gas vesicles are low-density, gas-filled protein organelles found inside various microorganisms. They have a lipid-free membrane with an average thickness of 2 nm and provide their hosts with buoyancy. In this study we characterized gas vesicle proteins synthesized by the Halobacterium sp. NRC-1 strain making use of molecular modeling methods and molecular dynamics (MD) simulations. The tertiary structure of GvpA protein, the major constituent of the gas vesicle membrane, was predicted using the De Novo computational design method available in the Rosetta Suite 2.3.1 software and was found to be in agreement with experimental data available from previous studies conducted by others and the consensus of different secondary structure prediction web servers. Optimization of the predicted structure was first carried out by energy minimization and simulated annealing. Subsequently, the mechanical properties of GvpA were investigated via constant pressure and temperature (NPT) aqueous MD simulations, in which two approaches were used to study the isothermal compressibility: quantification of the fluctuations in protein volume at constant pressure and temperature, and quantification of the volume changes induced through changes in the simulation pressure. Long term we plan to incorporate this information into multi-scale models of whole gas vesicles.

Commentary by Dr. Valentin Fuster
2009;():397-400. doi:10.1115/DETC2009-86436.

By biofunctionalizing magnetic nanoparticles with bioprobes, magnetic nanoparticles are able to specifically label bio-molecules. With the association between magnetic nanoparticles and bio-molecules, the mixed-frequency AC magnetic susceptibility generated with the physical rotation of individual magnetic nanoparticles under external AC magnetic fields is reduced. This detection technology is so-called immunomagnetic reduction (IMR) assay. In the experiment, several kinds of proteins and small-molecule chemicals were detected via IMR. The characteristic curves, i.e. the reduction versus the concentration of protein/chemical, for these proteins or chemicals can be scaled to one universal curve.

Topics: Nanoparticles
Commentary by Dr. Valentin Fuster
2009;():401-408. doi:10.1115/DETC2009-87134.

Recently, Focused Ion Beam (FIB) instruments have begun be applied to organic materials such as polymers and biological systems. This provides a novel tool for sectioning biological samples for analysis, or microfabrication with environment friendly materials. The modeling of nano/micro scale geometry accurately sculptured by FIB milling is crucial for generating the milling plan and process control, and for computer simulation for prediction and visualization of the milled geometry. However, modeling of the ion milling process on compound materials, especially for high aspect ratio feature, is still difficult due to the complexity of target material, as well as multiple physical and chemical interactions involved. In this study, a comprehensive model of ion milling with organic targets is presented to address the challenges using a simulation based approach. This platform has also been validated by milling different features on water ice in a cryogenic environment, and the simulation and experiment results show great consistency. With the proliferation of nanotechnology to biomedical and biomaterial domains, the proposed approach is expected to be a flexible tool for various applications involving novel and heterogeneous milling targets.

Commentary by Dr. Valentin Fuster
2009;():409-414. doi:10.1115/DETC2009-87299.

The main function of red blood cells (RBCs) is to circulate oxygen and carbon dioxide throughout the human body. Accurate modeling of the transportation mechanism of RBCs inside microvessels will lead to better clinical diagnosis and prophylaxis of blood disease. This study combined hydrodynamics and basic circuit theory to produce a model and calculate the fluid mechanisms of the circulation of blood cells inside microvessels. The variations of physical properties inside the microvessels due to clogging by RBCs were analyzed. A lab-on-a-chip for RBC diagnosis was fabricated using soft lithography. Real experiments were conducted to verify the theoretical analysis and illustrate the capability of the device which was able to detect pathological changes in RBC deformability. The proposed device could be a convenient tool in the field of blood rheology and clinical applications.

Commentary by Dr. Valentin Fuster
2009;():415-421. doi:10.1115/DETC2009-87413.

We are developing a new technique, called nanoinjection, to insert foreign DNA into a living cell. Such DNA transfection is commonly used to create transgenic organisms vital to the study of genetics, immunology, and many other biological sciences. In nanoinjection, DNA, which has a net negative charge, is electrostatically attracted to a micromachined lance. The lance then pierces the cell membranes, and the voltage on the lance is reversed, repelling the DNA into the cell. This paper presents a mathematical model to predict the motion (trajectory) of DNA particles within a cell in the presence of the electric field developed by the lance and the substrate. The model is used to predict the scattering of DNA through the cell due to electrostatic repulsion. We are currently preparing experiments which will be used to validate the model.

Commentary by Dr. Valentin Fuster
2009;():423-432. doi:10.1115/DETC2009-86147.

The miniaturization of metallic and ceramic molded components is limited by technological restrictions in conventional manufacturing techniques. Thus shape and material deviations cannot be scaled down in the same proportion as the micro parts. Systems including such components should be designed to accommodate the individual component’s wide geometrical variation and usually require large clearance. A study of the effects introduced thereby is needed to understand the system’s limits and to be able to forecast their output’s performance. To save time and resources, costly prototypes and test runs should be avoided in favour of computer simulation. The method proposed by the authors is exemplified on a micro technology demonstrator system developed by the Collaborative Research Center 499. It consists of a one stage planetary gear train in a sun-planet-ring configuration. The simulation procedure relies on ordinary Multi Body Simulation methods and subsequently adds other techniques to further investigate details of the system’s behaviour and to predict it’s response. In order to quantify the variability and to reveal the most critical points of the system, a whole-mechanism Sensitivity Analysis is performed. A reduced set of relevant parameters could be derived for further investigation and to feed a final optimization process, whether as optimization parameters or as external perturbation collective. The lack of previous knowledge about the system forced different DOE methods, involving small and large amount of experiments, to be tested. In this particular case the parameter space can be divided into two well defined groups, one of them containing the gear’s profile information and the other the components’ spatial location. This has been exploited to explore the different DOE techniques more promptly. Comparison and an analysis of the most successful DOE methods is included. In a final optimization step, the 10 most relevant perturbation factors and 4 to 6 prospective target parameters are included in a new, simplified model. All of these, and the objective functions, are affected by the production variability and the problem becomes an optimization of the system’s robustness and reliability exercise. Different techniques are discussed with examples. The study shows a first step in the development path of methods for designing and optimizing complex micro mechanisms composed of wide tolerated elements, accounting for the robustness and reliability of the systems’ output.

Commentary by Dr. Valentin Fuster
2009;():433-436. doi:10.1115/DETC2009-86686.

Piezoelectric inkjet technology is critical to documentation, graphic arts and manufacturing applications. Physical modeling plays an essential role in the development of this technology. In this paper, we present a comprehensive, multi-level, inter-disciplinary simulation approach for piezoelectric inkjet design. This includes a high-fidelity, inter-disciplinary detailed simulation method for architecture investigation, and a much faster reduced-order modeling approach that enables interactive design of voltage waveforms. Simulation results are compared with experimental data. The multi-level inter-disciplinary simulation methodology presented here can be applied to designing MEMS and microfluidic devices and systems [1].

Commentary by Dr. Valentin Fuster
2009;():437-443. doi:10.1115/DETC2009-86763.

This paper describes the servo pneumatic control technique, which is applied to the biomedical and biological technology. A cell micromanipulator is built by a 3-axes servo pneumatic micromanipulator system, which is set horizontally or vertically and driven by pneumatic cylinders. Due to the nonlinear characteristic of the air flow and the compressibility of air, the system is highly nonlinear system. Therefore, the compensators must be designed to reject those nonlinear effects and to improve the positioning precision. The dead-zone of the 3 axes pneumatic servo micromanipulator is measured, and the relation of velocity and voltage is plotted. Finally, a hybrid fuzzy controller, with dead zone, and velocity compensation, is designed to control the positioning precision of the 3 axes pneumatic servo micromanipulator. From the experimental results, the pneumatic servo micromanipulator has the positioning accuracy of 40 nm with different displacements. The system can be potentially used for the cell extraction, puncture, cutting and microinjection of the biological technology.

Commentary by Dr. Valentin Fuster
2009;():445-452. doi:10.1115/DETC2009-86879.

AC electrokinetics in microfluidic systems has been extensively investigated for its great potential in microfluidic pumping applications. The oscillating flow pattern in a microchannel with planar floor configuration restricts the pumping capacity due to the fast recirculating vortices over the electrode surface positioned in the microchannel floor. Patterned microgrooved floor in a fluidic microchannel can be employed to modify the flow pattern and make it uniaxial thus increase the net flow rate. Silicon KOH wet etching can be utilized to fabricate the microgrooved floor of the channel for its highly smooth surface quality and precise and reproducible configuration. We have developed an optimization methodology for the design of microgrooved configuration for a microfluidic pump using alternating current electrothermal (AC ET) actuation mechanism. The flow rate for the AC ET pumping system with optimized microgrooved floor can be higher as compared to the planar case without any significant increases of the temperature profile. In this paper, we are presenting the results of an optimum microgrooved floor configuration for an effective pumping application.

Topics: Microfluidics , Design , Pumps
Commentary by Dr. Valentin Fuster
2009;():453-457. doi:10.1115/DETC2009-86905.

This paper presents the design and simulation of a 3-D active micromixer. The mixer utilises two magnetic rotors to agitate the entering flows. Each rotor has three blades connected through a hub. The width of the blades increases linearly to enhance their impact on the surrounding flow. The performance of the mixer is studied within the rotation speeds of 150–275 rpm. Results indicate that the mixing efficiency increases linearly from 88.91% to 93.58% within the range of 150–250 rpm. Further increasing of rotor speed does not improve the mixing due to the resistance of corner flows. The proposed mixer can be applied as a component of lab-on-a-chip systems for medical applications.

Commentary by Dr. Valentin Fuster
2009;():459-464. doi:10.1115/DETC2009-87301.

This paper presents research on the large-displacement linear-motion planar compliant mechanism (X-Bob) specific to MEMS applications. The X-Bob’s potential for high off-axis stiffness makes it a strong candidate for precision MEMs applications. Understanding the characteristics and performance of the X-Bob can lead to the ability to modify it to fit specific applications. In this work, an X-Bob design is optimized for increased off-axis stiffness while maintaining a small footprint. The results are compared to previous X-Bob designs and to folded beam suspensions. Advantages and disadvantages of each design are explained.

Commentary by Dr. Valentin Fuster
2009;():465-474. doi:10.1115/DETC2009-87386.

In this paper, we present three designs for a decoupled, two-dimensional, vision-based μN force sensor for microrobotic applications. There are currently no reliable, off-the-shelf, commercially-available force sensors to measure forces at this scale, that can be easily integrated into standard microrobotic test-beds. In our previous work, we presented a design consisting of a planar, elastic mechanism with known force-deflection characteristics. It was inspired by the designs of pre-existing MEMS suspension mechanisms. A CCD camera is used to track the deformation of the mechanism as it is used to manipulate objects in a micro/meso-scale robotic manipulation test-bed. By observing the displacements of select points in the mechanism, the manipulation forces can be estimated. Here, a building block approach for conceptual synthesis of compliant mechanisms methodology is used to design for decoupled displacements for the tracking points when the tip is subjected to forces in the XY-plane. By designing mechanisms with circular compliance and stiffness ellipses along with zero magnitude compliance and stiffness vectors, we are able to achieve our design requirements. Validation of this approach with macro-scale prototypes and recommendations for scaling the designs down for microrobotic applications are offered along with a sensitivity analysis of the final designs yielding insights for microfabricating such designs.

Topics: Design , Force sensors
Commentary by Dr. Valentin Fuster
2009;():475-483. doi:10.1115/DETC2009-87537.

The goal of this investigation is to develop a simulation-based control strategy to eliminate flow-maldistribution in parallel microchannels. An accurate simulation of fluid flow through parallel microchannels is achieved by utilizing a fictitious domain representation of immersed objects, such as microvalves and bubbles. System identification techniques are employed to produce a lower dimensional model that captures the essential dynamics of the full nonlinear flow, in terms of a relationship between the valve angles and the exit flow rate for each channel. The resulting linear model is incorporated into a model predictive control scheme to identify flow maldistribution from exit flow velocities and prescribe actuation of channel valves to effectively redistribute the flow. Flow simulations in a three parallel microchannel geometry including bubbles illustrates the effectiveness of the control design, which quickly and efficiently varies channel valves to remove the bubble and equalize the flow rates in each channel.

Commentary by Dr. Valentin Fuster
2009;():485-489. doi:10.1115/DETC2009-87618.

We present a custom built Biosensor Microassembly Platform (BMP) for assembling a nanoparticles-based microscale in-vivo biosensor. Conducting directed assembly of nanoparticles on a 0.01 mm2 microchip is a very challenging problem. Complexities arise from assembling micro-components of different materials, and assembling antibody functionalized nanoparticles into their predetermined nanoscale trenches on the biosensor. Using our designed platform, we merge vision information with motion control efficiently, so that precise manipulation of the stages and microscopes facilitates the assembly process of the in-vivo biosensor. Along with Biosensor Microassembly Platform system design and automation, we demonstrate assembly of an in-vivo biosensor which has numerous applications in biomedical and health industry.

Commentary by Dr. Valentin Fuster
2009;():491-500. doi:10.1115/DETC2009-87716.

This paper presents the design and fabrication of a novel chipscale micromanipulator with multiple fingers that can be independently actuated and coordinated to manipulate and assemble micro-scale objects within a predefined workspace on the chip. The manipulator chip has an overall footprint of 5 mm × 5 mm and the workspace area for micromanipulation is about 4600 μm2 . The micromanipulator is integrated with tiny piezoelectric actuators and enclosed in a specially designed and precision machined compact housing, which has an overall size of 5 cm × 5 cm × 1.5 cm, to isolate the workspace area of the manipulator to minimize external disturbances. The topology and shape of the miltifingered micromanipulator chip were obtained through a systematic design optimization process maximizing the operating workspace of the micromanipulator, and a prototype was fabricated in silicon using the standard microfabrication processes. Preliminary experiments have confirmed the predicted behavior of the micromanipulator fingers as well as the feasibility of controlling multiple fingers to achieve a coordinated action to grasp a micro-scale object as commanded by the user.

Commentary by Dr. Valentin Fuster
2009;():501-505. doi:10.1115/DETC2009-86157.

Lead Zirconate Titanate Oxide (PbZrx Ti1−x O3 or PZT) is a piezoelectric material widely used as sensors and actuators. For microactuators, PZT often appears in the form of thin films to maintain proper aspect ratios. This paper is to present a simple and low-cost method to measure piezoelectric constant d33 of PZT thin films, which is a major challenge encountered in the actuator development. We use an impact hammer with a sharp tip to generate an impulsive force that acts on the PZT film. The impulsive force and the responding voltage are then measured to calculate the piezoelectric constant d33 . The impulsive force has large enough amplitude so that a good signal-to-noise ratio can be maintained. Furthermore, the impulsive force has extremely short duration, so the discharge effect (i.e., the time constant effect) of the PZT circuit can be ignored. Preliminary testing on bulk PZT through this new method leads to two conclusions. Firstly, boundary conditions of the specimen are critical. In particular, the specimen must be securely fastened. Since the impulsive load only acts on a tiny area, loose boundary conditions can introduce spurious results from other piezoelectric constant d31 . Secondly, size of the specimen is critical. Specimen of smaller size leads to more accurate measurements of the piezoelectric constant d33 .

Topics: Measurement , Hammers
Commentary by Dr. Valentin Fuster
2009;():507-512. doi:10.1115/DETC2009-86344.

This paper is to study actuation displacement of a Lead Zirconate Titanate (PbZrx Ti1−x O3 or PZT) thin-film membrane actuator via finite element modeling and laser-Doppler measurements. In particular, this paper is to identify possible parameters that could cause discrepancies between the finite element predictions and experimental measurements. A twofold approach is used. First, we conduct additional experiments to measure actuator dimensions, which are subsequently used as input to the finite element model. We also measure natural frequencies of the membrane actuators to compare with the finite element predictions in addition to the actuator displacement. Second, we have conducted a parametric study via the finite element model to identify possible parameters that could cause the discrepancies. Parameters varied include dimensions, material properties, residual stresses and linearity of the PZT thin-film membrane actuator. Simulation results indicate that the residual stresses are the most probable cause of the discrepancy between the theoretical predictions and the experimental results.

Commentary by Dr. Valentin Fuster
2009;():513-520. doi:10.1115/DETC2009-87594.

Microactuators provide controlled motion and force for applications ranging from RF switches to rate gyros. Large amplitude response in piezoelectric actuators requires amplification of their small strain. This paper studies the performance of a uniflex actuator in terms of its displacement and blocking force compared to uniflex and flextensional actuators. A uniflex microactuator combines the strain amplification mechanisms of a unimorph and flexural motion to produce large displacement and blocking force. Analytical models for displacement and blocking force for all the three actuators are used in optimization, to study their relative performance. The uniflex actuator outperforms both unimorph and flextensional actuators in displacement, but, the unimorph actuator generates more blocking force. The uniflex actuator can therefore be used in applications that demand higher displacement and lower blocking force compared to a unimorph actuator.

Commentary by Dr. Valentin Fuster
2009;():521-529. doi:10.1115/DETC2009-87819.

High density aligned multi-walled carbon nanotubes (CNTs) and the CNT/epoxy composite are fabricated. To predict the energy dissipation in composites with vertically aligned multi-walled CNTs, a structural damping model of composite unit cell composed of resin, sheath and nanotube is developed. In this paper, the resin is described as viscoelastic material using Maxwell model. The CNT/epoxy composite is modeled based on the “stick-slip” mechanism, to describe the load transfer behavior between the CNT and its sheath. In order to further study the damping mechanism of the CNT composite, key parameters, such as length, center-to-center distance and critical stress of CNTs that are expected to affect the composite damping performances are studied. The simulation results show that loss factor of the CNT composite with varying parameters is sensitive to the applied stress.

Commentary by Dr. Valentin Fuster
2009;():531-538. doi:10.1115/DETC2009-86144.

This paper investigates electrostatically actuated resonator micro-sensor response near natural frequency. The Casimir effect is included. Both the electrostatic force and the Casimir force introduce nonlinearities in the system. Hamilton’s principle is used to derive the partial-differential equation of motion for the general case of nonuniform sensors. The method of multiple scales is then used in a direct approach of the problem. Two approximation problems resulting from the direct approach are solved. The phase-amplitude relationship is obtained. Numerical results for uniform capacitive resonator micro-sensors are provided.

Topics: Sensors
Commentary by Dr. Valentin Fuster
2009;():539-544. doi:10.1115/DETC2009-86254.

The purpose of this paper is the enhancement of the AFM sensitivity through the selection of an optimized FGM micro cantilever beam. In this paper, resonant frequencies and sensitivities of first two modes of micro cantilever which is made of functionally graded materials are investigated and a relationship is developed to evaluate the sensitivity of FGM micro cantilever. Effect of volume fraction of materials and surface contact stiffness on the resonant frequencies and sensitivities are studied. The rectangular FGM beam is modeled by an Euler-Bernoulli beam theory. It is assumed that beam is made of a mixture of metal and ceramic with properties varying through the thickness following a simple power law of n. This variation is a function of the volume fraction of the beam material constituents. The interaction between AFM tip and surface is modeled by a linear spring which expresses the contact stiffness. Results show that, increasing the ceramic volume fraction increases the resonant frequencies of both modes 1 and 2. When contact stiffness is small, for both modes, as ceramic volume fraction increases, sensitivities decreases, while for large contact stiffness, as ceramic volume fraction increases the sensitivities will be increased. Results also show that at each contact stiffness, there is a unique value of n at which the sensitivity is maximized. Using these values for n, the high quality and high contrast images can be obtained.

Commentary by Dr. Valentin Fuster
2009;():545-552. doi:10.1115/DETC2009-86450.

A specific type of Microsystems or MEMS is the so called RF-MEMS switch. In contrast to MEMS resonators switches generally do not operate in a vacuum. Therefore at the small scales of MEMS fluid (or air) damping is the most dominant damping form. This means that if one is interested in transient or frequency behavior a proper damping model is required. This paper presents a way of using the non-linear Reynolds equation to model the squeeze film damping that is often the type of fluid damping present in these switches. The formulation is provided ready for FEM implementation. Also the tangent matrices required for linearized eigen frequencies are derived. The equations are tested on a model of simple micro switch. The results show that with this model it is possible to predict the damped motion as well as the frequency behavior. The frequency results also show that damping shifts the zero frequency point away from the pull-in point. With a simple mechanical contact model it is also possible to model the closing and opening transient of a microsystem.

Commentary by Dr. Valentin Fuster
2009;():553-562. doi:10.1115/DETC2009-86479.

The dynamic response of an atomic force microscope cantilever probe is studied for off-resonance excitation and interactions with a soft silicone rubber material. The dynamic response of the probe is simulated using a three-mode approximation of the Euler-Bernoulli beam model for excitation at two-and-a-half times the probe’s fundamental frequency. These simulations are conducted in order to reproduce the period-doubling bifurcation experimentally observed in the response of the probe of a commercial atomic force microscope. In order to duplicate this behavior, parameters within the surface force model are tuned to account for variations in the characteristics of the sample material. Through this work, the relationship between the sample material’s effective stiffness and the response behavior of the probe are studied in an effort to develop the means to identify the local material properties of a sample by characterize the nonlinear response of the probe.

Commentary by Dr. Valentin Fuster
2009;():563-567. doi:10.1115/DETC2009-86518.

In this paper a multiphysics simulation of nanotube based nano-electromechanical systems is reported. Assuming continuum mechanics, the nonlinear deformation of the nanotube is simulated using reduced order modeling method. In particular, we study singly and doubly clamped nanotubes under electrostatic actuation. The simulation emphasizes the prediction of the pull-in voltage of the device, a key design parameter. Moreover, the nonlinear behavior associated with finite kinematics (i.e., large deformations), neglected in previous studies, are investigated in detail. The multiphysics simulation results agree well with the theoretical predictions verifying that the numerical model is valid. The results show that nonlinear kinematics results in an important increase in the pull-in voltage of doubly clamped nanotube devices, but that it is negligible in the case of singly clamped devices. These models provide a guide on the effect of the various geometrical variables and insight into the design of novel devices.

Commentary by Dr. Valentin Fuster
2009;():569-574. doi:10.1115/DETC2009-86623.

In this paper, primary resonance of a double-clamped microbeam has been investigated. The Microbeam is predeformed by a DC electrostatic force and then driven to vibrate by an AC harmonic electrostatic force. Effects of midplane stretching, axial loads and damping are considered in modeling. Galerkin’s approximation is utilized to convert the nonlinear partial differential equation of motion to a nonlinear ordinary differential equation. Afterward, a combination of homotopy perturbation method and the method of multiple scales are utilized to find analytic solutions to the steady-state motion of the microbeam, far from pull-in. The effects of different design parameters on dynamic behavior are discussed. The results obtained by the presented method are validated by comparing with literature.

Commentary by Dr. Valentin Fuster
2009;():575-581. doi:10.1115/DETC2009-86889.

Improvement of microcantilever-based sensors and actuators chiefly depends on how comprehensively they are modeled and precisely formulated. Atomic Force Microscopy (AFM) is the most widespread application of microcantilever beam as a sensor, which is usually influenced by the tip-sample interaction force. For this, vibration of AFM microcantilever probe is analyzed in this paper, along with analytical, numerical and experimental investigation of the influence of the sample interaction force on the microcantilever vibration. Nonlinear integro-partial equation of microcantilever vibration subject to the tip-sample interaction is then derived and numerically simulated. Moreover, multiple time scales method is utilized to estimate the tip amplitude while it is vibrating near the sample. An experimental setup is developed using AFM in order to validate the theoretical and simulation results. Hysteresis, instability and amplitude drop can be identified in the experimental curves inside the particle attraction domain. These are likely related to the interaction force between the tip and sample as well as the presence of the water layer during the experiments. A fair agreement is observed between the theoretical analysis, numerical simulation and experimental findings which obviously demonstrates the effectiveness and applicability of the developed model.

Commentary by Dr. Valentin Fuster
2009;():583-595. doi:10.1115/DETC2009-86909.

In this work, we investigate dynamic pull-in in MEMS devices actuated with a DC voltage superimposed to an AC harmonic voltage. We focus on the role of the AC frequency and amplitude in triggering instabilities. Dynamic pull-in is treated here in the context of a broader concept in nonlinear dynamics, which is the escape-from-potential-well phenomenon. The escape is defined where, for specific AC frequency and amplitude, the system exhibits the pull-in instability. We investigate dynamic pull-in experimentally in a polysilicon microcantilever beam, a cantilever and clamped-clamped microbeams made of gold, and a capacitive accelerometer. It is found experimentally that, despite the differences in their structures, the tested devices exhibit similar escape behavior near their fundamental natural frequency (primary resonance). A series of experiments are conducted using the capacitive accelerometer to study the effect of pressure (damping), excitation amplitude and frequency, resonance type (primary and subharmonic at twice the device’s natural frequency), and sweeping type (sweeping the AC amplitude or sweeping the AC frequency) on the escape zones. It is found that, except for the sweeping type, these factors have significant effect on shaping the escape zones. A nonlinear lumped-parameter model is used to capture the dynamics of the capacitive accelerometer. A shooting method is utilized to predict the theoretical zones of inevitable escape, where it is impossible for a resonator to oscillate in a stable state. An attempt has been made to relate the inevitable escape bands to the pull-in bands measured experimentally. We found that both pull-in bands and inevitable escape bands are correlated. However, we concluded that experimental testing is still needed to estimate accurately the instability bounds of each electrostatically actuated resonator.

Commentary by Dr. Valentin Fuster
2009;():597-606. doi:10.1115/DETC2009-86977.

Beam structures are widely used in MEMS sensors and actuators. MEMS micro beams are usually curled due to residual stresses and the characteristics of micro beams subjected to both residual stress gradients and electrostatic forces must be investigated for providing accuracy information for designing sensors and actuators. In this work, a novel semi-analytical formulation to address the above needs is proposed. By assuming an admissible deformation shape and utilizing energy method to determine the coefficients of the shape functions, it is possible to find the pull-in characteristics of the curled cantilevers. Detail parametric studies are subsequently performed to quantify the influence of various geometry and processing parameters on the pull-in characteristics of those micro beams. The method and results presented in this work would be very useful for related micro sensors and actuator designs.

Topics: Stress , Microbeams
Commentary by Dr. Valentin Fuster
2009;():607-616. doi:10.1115/DETC2009-87024.

In this paper, we investigate theoretically and experimentally the static and dynamic behaviors of electrostatically actuated clamped-clamped micromachined arches when excited by a DC load superimposed to an AC harmonic load. A Galerkin based reduced-order model is used to discretize the distributed-parameter model of the considered shallow arch. The natural frequencies of the arch are calculated for various values of DC voltages and initial rises of the arch. The forced vibration response of the arch to a combined DC and AC harmonic load is determined when excited near its fundamental natural frequency. For small DC and AC loads, a perturbation technique (the method of multiple scales) is also used. For large DC and AC, the reduced-order model equations are integrated numerically with time to get the arch dynamic response. The results show various nonlinear scenarios of transitions to snap-through and dynamic pull-in. The effect of rise is shown to have significant effect on the dynamical behavior of the MEMS arch. Experimental work is conducted to test polysilicon curved microbeam when excited by DC and AC loads. Experimental results on primary resonance and dynamic pull-in are shown and compared with the theoretical results.

Commentary by Dr. Valentin Fuster
2009;():617-622. doi:10.1115/DETC2009-87035.

In this study, using analytical method, the torsional resonant frequency and torsional sensitivity of the first four modes of an AFM cantilever with sidewall probe including a horizontal cantilever and a vertical extension is analyzed and a closed form for torsional sensitivity of the probe is derived. In addition, the effect of relative parameters such as ratio of vertical extension length to horizontal cantilever length is investigated. According to this study, the results show that as contact stiffness increases, the resonant frequencies of all vibration modes increases until they reach constant values at very high values of contact stiffness. It is also can be found that low-order modes are more sensitive than high-order one. When contact stiffness increases, the torsional sensitivities of all vibration modes decrease and the graphs converge at very high values of contact stiffness. In addition, enhancement of ratio of vertical extension length to cantilever length decreases the resonant frequency of mode 1 for all values of the contact stiffness and decreases torsional sensitivity for low values of the contact stiffness. But for high values of contact stiffness, there is a peak for torsional sensitivity. Finally the result shows that increase of the tip mass, decreases the torsional sensitivity with a light slope.

Commentary by Dr. Valentin Fuster
2009;():623-634. doi:10.1115/DETC2009-87059.

Resonant microelectromechanical systems (MEMS) offer distinct utility in signal processing and wireless communications applications due to their comparatively-high quality factors, low power consumption, and ease of integration with existing integrated circuit (IC) technologies. While a number of efforts have previously demonstrated the use of mechanically-coupled microresonators in bandpass signal filtering applications, the vast majority of these works have emphasized the use of resonator chains coupled in an open configuration, wherein the terminating (end) elements in the array are coupled to only a single resonator and the interior resonators are coupled solely to their nearest neighbors. While this configuration suffices for many MEMS-based filter designs, it is not guaranteed to be an optimal coupling architecture. The present work explores an alternative class of MEMS bandpass filters based on cyclically-coupled, closed-chain resonator configurations and specifically examines the pertinent performance metrics (effective quality factor, shape factor, bandwidth, ripple, and maximum transmission) associated with each architecture. By varying coupling strength and the quality factor of individual resonators over wide, yet realistic, parameter ranges, regions of superior performance for both open- and closed-chain filter architectures have been observed. Of particular interest here, is the fact that preliminary results indicate that cyclically-coupled resonator configurations exhibit improved ripple metrics, reduced frequency dependence within the passband, and, generally speaking, more robustness to process-induced variations than their open-chain counterparts. As such, cyclically-coupled filter designs, with further refinement, may ultimately lead to an improved MEMS bandpass filter capability.

Commentary by Dr. Valentin Fuster
2009;():635-645. doi:10.1115/DETC2009-87236.

Results of theoretical investigation of the transient dynamics of an initially curved electrostatically actuated clamped-clamped micro beam are presented. A reduced order model of the shallow Euler-Bernoulli arch developed using the Galerkin procedure with eigenmodes of a straight beam as a basis accounts for the distributed electrostatic and inertial loading, fringing electric fields and nonlinear squeeze film damping. Due to the unique combination of mechanical and electrostatic nonlinearities which is intrinsic in micro devices but is not encountered naturally in large-scale structures, the voltage-deflection characteristic of the sufficiently curved beam may have two maxima implying the existence of sequential mechanical (snap-through) and electrostatic (pull-in) instabilities. Phase plane analysis performed for the case of a suddenly applied electrostatic loading along with the simulation results show that critical voltages corresponding to the dynamic snap-through and pull-in instabilities are lower than their static counterparts while the minimal curvature required for the appearance of the dynamic snap-through is higher than in the static case. Clear functional advantages of this kind of structures, namely extended stable deflections and ability to tune the device frequencies in a very large range may result in improved performance of switches, inertial sensors and micromechanical non-volatile memory devices.

Commentary by Dr. Valentin Fuster
2009;():647-654. doi:10.1115/DETC2009-87441.

Mechanically coupling microscale or nanoscale resonators in more than one dimension requires a departure from classic beam resonator designs. A square paddle resonator is a simple geometry that allows easy coupling into two-dimensional arrays. These resonators can have high quality factors in the fundamental vibration mode if operated in vacuum. In this paper we summarize the behavior of such a resonator and describe several design considerations. We develop an expression for the inter-resonator coupling in terms of coupling beam geometry, estimate energy dissipation due to a variety of physical mechanisms, and empirically determine the vibration amplitude at which geometric nonlinearity becomes significant. Future experimental studies can exploit the expressions presented here, which facilitate design of two-dimensional arrays of square-paddle resonators that will be useful for a variety of potential applications.

Commentary by Dr. Valentin Fuster
2009;():655-661. doi:10.1115/DETC2009-87551.

We propose a technique to increase the sensitivity and simplify the process of measuring minute masses using electrostatically-actuated MEMS. The sensor is composed of a cantilever beam connected to a rigid plate at its free end and coupled to an electrode underneath it. The method depends on the observation that the sensitivity of an electrostatically-actuated MEMS is highly enhanced when the driving voltage is close to the pull-in limit. We study two cases: the device actuated by a static force (DC voltage) and a dynamic force (combined AC and DC voltage). Sensitivity analysis is used to estimate the minimum detectable mass near static pull-in and near a dynamic pull-in point due to a cyclic-fold bifurcation.

Commentary by Dr. Valentin Fuster
2009;():663-670. doi:10.1115/DETC2009-87563.

The effect of the shape and distribution of perforations in parallel plate capacitive MEMS devices on squeeze-film damping is presented. The squeeze film effect is the most important damping effect on the dynamic behavior of most MEMS devices that employ capacitive sensing and actuation, which typically employ narrow air gaps between planar moving surfaces [1, 2]. The stationary plate of a capacitive device is often perforated to reduce the damping and sensor noise and improve the frequency response. The formula for determining the total viscous damping in the gap contains a coefficient Cp that is associated with the geometry and distribution of the holes on the stationary plate. In this study, the coefficient Cp is determined using the finite element method using ANSYS by analogy with heat conduction in a solid with internal heat generation. Round, elliptical, rectangular, and oval holes that are distributed either aligned or offset are analyzed and compared. It is shown that the surface fraction occupied by the perforations is not the only factor that determines Cp. Both the shape and distribution strongly affect the damping coefficient [3, 4]. By using elongated perforations that are properly distributed, the squeeze film damping could be minimized with the minimum amount of perforation. The analysis performed in this work is quite general being applicable to a very large spectrum of frequencies and to various fluids in capacitive sensors. These results can facilitate the design of mechanical structures that utilize capacitive sensing and actuation, such as accelerometers, optical switches, micro-torsion mirrors, resonators, microphones, etc.

Topics: Damping , Shapes
Commentary by Dr. Valentin Fuster
2009;():671-679. doi:10.1115/DETC2009-87576.

This paper presents a theoretical model on the vibration analysis of micro scale fluid-loaded rectangular isotropic plates, based on the Lamb’s assumption of fluid-structure interaction and the Rayleigh-Ritz energy method. An analytical solution for this model is proposed, which can be applied to most cases of boundary conditions. The dynamical experimental data of a series of microfabricated silicon plates are obtained using a base-excitation dynamic testing facility. The natural frequencies and mode shapes in the experimental results are in good agreement with the theoretical simulations for the lower order modes. The presented theoretical and experimental investigations on the vibration characteristics of the micro scale plates are of particular interest in the design of microplate based biosensing devices.

Commentary by Dr. Valentin Fuster
2009;():681-687. doi:10.1115/DETC2009-86188.

This paper is devoted to the characterization of the surface defects using a recently developed AFM technique named as frequency and force modulation AFM (FFM-AFM). The simulated system includes a recently developed gold coated AFM probe which interacts with a sample including single-atom vacancy and impurities. In order to examine the behavior of the above system including different transition metals, molecular dynamics (MD) simulation with Sutton-Chen (SC) interatomic potential is used. Along this line, an imaging simulation of the probe and sample is performed, and the effects of the horizontal scan speed, the effective frequency set-point, the cantilever stiffness, the tip-sample rest position and the cantilever quality factor on the resulting images are investigated. Using a proposed optimum controlling scheme for the excitation force amplitude, the cantilever horizontal speed can be maximized.

Commentary by Dr. Valentin Fuster
2009;():689-694. doi:10.1115/DETC2009-86482.

In a recently submitted paper, a technique is presented for the force calibration of atomic force microscopy (AFM) cantilevers under heavy fluid loading conditions, such as those commonly found in liquid environments. A Matlab program had been made available that automates this technique. In this paper, the analysis performed by this program is explained with specific attention to the details that do not appear in the original description of the calibration technique, but arise in the automated implementation.

Commentary by Dr. Valentin Fuster
2009;():695-705. doi:10.1115/DETC2009-86687.

A technique to measure the trapping force in an optical tweezers, without making any prior assumptions about the trap shape, has been extended to two-dimensions. The response of a trapped micro or nanoparticle to a step input is measured and then used to calculate the trapping force experienced by the particle as a function of its position in the trap. Langevin dynamics simulations have been implemented to evaluate the performance of this measurement method in two-dimensions and to evaluate whether the particle’s motion away from the measurement plane due to diffusion gives rise to an error in the trapping force measurement. Preliminary experimental results are also presented to demonstrate this method in the laboratory. This force measurement method provides insight into the trapping behavior of micro and nanoparticles in an optical trap beyond the region, close to the trap center, where the trapping force is assumed to vary linearly with the particle’s displacement. The measured trapping forces, from simulations and laboratory experiments, are then integrated to recover the shape of the optical trapping potential.

Commentary by Dr. Valentin Fuster
2009;():707-716. doi:10.1115/DETC2009-86844.

The ability of atomic force microscopy (AFM) to acquire tip-sample interaction force curves has allowed researchers to understand the mechanical behavior of numerous materials at the nanoscale. However, AFM force spectroscopy with the most commonly used techniques can be a slow process for non-uniform samples, as it often requires the measurement to be performed at one fixed surface point at a time. In this paper we present two dynamic AFM based spectroscopy methods, one requiring operation in single-frequency-modulation mode and another using dual-frequency-modulation, which could allow a more rapid acquisition of topography and tip-sample interaction force curves. Numerical simulation results are provided along with discussions on the benefits and limitations of both.

Commentary by Dr. Valentin Fuster
2009;():717-723. doi:10.1115/DETC2009-86892.

Piezoresponse force microscopy (PFM) is proposed in this article as a new technique for identification of elastically distributed thin layers on top of microcantilever sensors. Using the conventional actuation methods such as base excitation, the ratio of stiffness over the layer mass per unit length affects the resonant frequencies of the system as a single parameter. However, due to tip/sample elastic contact in PFM, these two parameters can be separately identified using the frequency shifts before and after attaching the layer. The concept is theoretically proven here using the modal analysis of the system. For practical verification, three gold-coated AFM microcantilevers were primarily tested for their initial resonant frequencies. The Focused Ion Beam (FIB) technique was then employed to deposit thin layers of Pt-based material in different configurations on the cantilevers’ surfaces. The microcantilevers were then reexamined for their new resonances, and the properties of the deposits were identified using a robust system identification procedure. Results indicate acceptable estimation of the cantilevers’ added mass and stiffness, making the technique suitable for detection of elastically distributed biological species.

Topics: Force , Microscopy , Stiffness
Commentary by Dr. Valentin Fuster
2009;():725-730. doi:10.1115/DETC2009-86914.

This paper presents the architecture for a remotely controllable and interactive MEMS laboratory. There have been significant advances in computer simulations of MEMS devices, but laboratory testing of devices still plays a crucial role in developing a detailed understanding of MEMS performance. New computer and networking technologies, have allowed the construction of remotely controllable labs for fields spanning education and technology. The main idea of this work is to allow a user in any part of the globe to carry out real-time experiments on a MEMS device using a computer with internet connectivity. The user also has the option of using a commercially available haptic device to feel the magnified nano/micro-scale forces associated with the devices while actuating them. The present interface was tested on a two degree-of-freedom (XY) electrostatic MEMS positioning microstage and a MEMS microgripper.

Commentary by Dr. Valentin Fuster
2009;():731-736. doi:10.1115/DETC2009-87378.

In atomic force microscope based force spectroscopy, it is often necessary to minimize the tip-sample contact force. While it is possible to control the contact force using force feedback, this method is susceptible to sensor drift and is often under-utilized due to the noise associated with the feedback process. Here we present a method to control the tip-sample contact force for repeated pulling cycles without relying on force feedback or tedious user-controlled z-stage step increments. The custom pulling program uses the data recorded during the previous retraction cycle to automatically reposition the sample surface to account for changes in topography and system drift. Using this method we were able to complete 250 automated pulling cycles, 76% of which had evidence of tip-sample contact. Of those pulling cycles with tip-sample contact, the average contact force was 83 pN, with the maximum contact force not exceeding 292 pN.

Commentary by Dr. Valentin Fuster
2009;():737-743. doi:10.1115/DETC2009-87556.

In this effort, an optical tweezers setup is used to measure the forces between polystyrene microspheres on the interface between mineral oil and water. Colloidal interaction between particles on an interface is more complicated than their interaction in bulk. Knowing the forces between colloidal particles on an oil-water interface is important in order to improve aggregation and emulsion models and understand many phenomena in fluid dynamics and rheology. A two beam trap is used to control the distance between two interfacial particles. A long working-distance objective allows for the interface to be significantly far from the coverslip and for an extremely sensitive force measurement. The forces were found to follow a combination of Coulomb’s law and dipole-dipole interaction, but for much less charge than is specified by the manufacturer to be on the surface of the microspheres. These measurements will aid in the creation of models that can predict interfacial colloid phenomena.

Commentary by Dr. Valentin Fuster
2009;():745. doi:10.1115/DETC2009-87518.
FREE TO VIEW

Large-displacment MEMS are susceptible to motion in off-axis directions, or motion deviating from the desired path of the device. The multi-layer means of guiding large displacement devices prevents the shuttle from moving away from the substrate, and effectively constrains the transverse motion; the guiding device does not inhibit the motion necessary for proper function of the device. The novelty of the device lies in the placement of the guide; positioning the guide inside of the the shuttle constrains the device without increasing the footprint size.

Commentary by Dr. Valentin Fuster
2009;():747. doi:10.1115/DETC2009-87523.
FREE TO VIEW

A miniature replica of “Temple of Zeus” has been built on a 1cm2 silicon die. The micro components have been fabricated on SOI (silicon-on-insulator) wafer using photolithography patterning and DRIE (deep-reaction-ion-etching) process. These micro components have been picked up and manipulated using a vacuum micro needle mounted on a high precision microassembly robot. After alignment the components are bonded to the silicon substrate using epoxy adhesive. A spherical sapphire lens has also been mounted on a micro tower made of silicon. This lens acts as a light source which illuminates the micro temple by diffusing a ray of light onto it. This micro replica of “Temple of Zeus” and other micro structures as well, have been built as a part of research on automated 3D microassembly at ARRI’s Texas Microfactory which demonstrates the versatility in developing robust, cost efficient and heterogeneous microsystems of future.

Commentary by Dr. Valentin Fuster
2009;():749-750. doi:10.1115/DETC2009-87544.
FREE TO VIEW

The picture shows a unique MEMS robot. It is highly dextrous with our degrees of freedom (two in-plane and two out-of-plane) and has the largest work volume of 50μm × 50μm × 75 μm amongst MEMS based positioners. The robot incorporates novel cable based transmission systems to couple in-plane actuators with out of plane bi-directional flexure joints. Constructed out of Deep Reactive Ion Etching and microassembly, this robot is designed to transmit upto 200mN of force along all four axes, precise to ten’s of nanometers and configured to carry a variety of end-effectors such as Atomic Force Microscope probe tip arrays and microgrippers. The microrobot presents the dawn of next generation in top down manipulation systems.

Commentary by Dr. Valentin Fuster
2009;():751. doi:10.1115/DETC2009-87581.
FREE TO VIEW

The nanoinjector is a MEMS device that has been successfully used to inject foreign genetic material into fertilized mouse egg cells (zygotes). This scanning electron micrograph shows a nanoinjector grasping a 100 μm diameter latex sphere. The sphere is roughly the size of a mouse zygote, and it can withstand the harsh environment in the electron microscope better than a mouse zygote. The nanoinjector’s two constraining mechanisms (at left and top-right) and lance mechanism (bottom right) are fabricated from two planar layers of polysilicon through MEMSCAP’s polysilicon Multi-User MEMS Processes (polyMUMPs)

Commentary by Dr. Valentin Fuster
2009;():753. doi:10.1115/DETC2009-87584.
FREE TO VIEW

This scanning electron micrograph shows a cross section of a cleaved silicon-on-insulator (SOI) wafter. The wafer cleave passed through a partially released device that included the array of etch release holes visible in this image. The patterned monocrystalline silicon layer had a different crystalline orientation than the much thicker monocrystalline silicon substrate. When the wafer was cleaved, substrate silicon fractured along a single crystalline plane, leaving a flat, smooth surface. The patterned layer did not share this crystalline plane, and fractured in many directions resulting in an irregular, multi-faceted surface.

Commentary by Dr. Valentin Fuster
2009;():755. doi:10.1115/DETC2009-87606.
FREE TO VIEW

This photo shows a bistable microelectromechanical (MEMS) device that incorporates many common elements of microsystems, including the comb drive and force gage. This device also is designed to exhibit bistable behavior. The photo emphasizes the symmetry of the device.

Commentary by Dr. Valentin Fuster
2009;():757. doi:10.1115/DETC2009-87622.
FREE TO VIEW

This photo shows a force gage attached to a tristable microelectromechanical (MEMS) device. While the force gage is common in Microsystems, this photo shows how movement during shipping can jostle the device out of its manufactured position.

Commentary by Dr. Valentin Fuster
2009;():759-768. doi:10.1115/DETC2009-86427.

Thin-film lead-zirconate-titanate (PZT) actuators are a potential enabling technology for autonomous micro-robots with locomotion abilities rivaling biological systems. Actuators capable of supplying the large forces and extended displacements needed to drive terrestrial micro-robotic locomotion have been designed and tested. These actuators use a combination of upward and downward unimorph bending to generate in-plane robotic joint motion. 500 μm by 100 μm actuators have demonstrated forces greater than 5 mN over almost 1 μm stroke length at just 20 V. These actuators can be leveraged to drive angular displacement of high-aspect ratio silicon flexures. Actuators are currently being integrated into flexural arrays to produce joint angles comparable to insects. Stacks of these silicon joint structures may be used to reinforce load-bearing capacity of the completed micro-robotic legs. Dynamic simulations of hexapedal and many-legged robots less than one centimeter in length utilizing these actuator-joint structures indicate potential payloads ranging from 50 to 200 mg, depending on the joint design, and walking speeds up to approximately 4 cm/s.

Commentary by Dr. Valentin Fuster
2009;():769-776. doi:10.1115/DETC2009-86463.

The Fourier Transform (FTIR) microspectrometer discussed in this paper is an example of a complex Micro-Opto-Electro-Mechanical System (MOEMS) configured as an optical bench on a chip. It is an important benchmark application for microtechnology due to increased demands for the use of miniature wavelength detection instruments in bio, nano and material science. This device can be manufactured using automated microassembly and precision alignment of hybrid silicon and glass components, and in particular, of a micro-beamsplitter cube along 3 rotational degrees of freedom. In this paper, a piezoelectric microgripper with four degrees of freedom was attached to a precision robot in order to enhance its dexterity and align the beamsplitter to arcsecond angular tolerance. The modeling and control of the microgripper, and the alignment algorithm utilizing a novel spot-Jacobian servoing technique are discussed. Experimental results obtained during joint on-going work in Texas and in France are presented, demonstrating the advantage of using the microgripper for optical alignment of the microspectrometer.

Commentary by Dr. Valentin Fuster
2009;():777-783. doi:10.1115/DETC2009-86888.

A MEMS (Micro Electro Mechanical Systems) based four degree of freedom articulated microrobot is presented as an example of next generation miniaturized top down manipulators. The robot occupies 6mm3 in total volume with room for further down scaling. The operating work volume is 50μm × 50μm × 75μm with a 2P2R (Prismatic Prismatic Revolute Revolute) kinematic configuration — X, Y, Pitch and Yaw. The presented microrobot design rises above commonly encountered performance tradeoff’s of previous MEMS positioners such as range of motion vs. exerted force and range of motion vs. precision. It is constructed using a combination of hybrid microassembly and high aspect ratio micromachining. Structurally, the first version of the microrobot consists of Silicon 2 1/2 D parts and a 30μm diameter Cu wire. The robot joints and attachment of the end effector are accomplished by microassembly using compliant snap-fasteners, monolithic flexure joints, and epoxy glue. Actuation is carried out by two banks of in-plane electrothermal actuators, one coupled through an out of plane compliant socket, and the other one coupled remotely using a 30 μm diameter Cu wire. In this paper we present the microrobot kinematic design, and experimental identification of the robot Jacobian. Preliminary experimental characterization of the microrobot shows that it is repeatable to less than 0.5 μm along XY axes and 0.015 degrees along Pitch and Yaw DOFs. Finally, the robot was configured to carry an AFM tip and we demonstrate nano indentation sequences on a Parylene substrate.

Commentary by Dr. Valentin Fuster
2009;():785-796. doi:10.1115/DETC2009-87113.

Automated transport of multiple particles using optical tweezers requires the use of motion planning to move them simultaneously while avoiding collisions amongst themselves and with randomly moving obstacles. This paper develops a decoupled and prioritized stochastic dynamic programming based motion planning framework by sequentially applying a partially observable Markov decision process algorithm on every particle that needs to be transported. An iterative version of a maximum bipartite graph matching algorithm is used to assign given goal locations to such particles. The algorithm for individual particle transport is validated using silica beads in a holographic tweezer set-up. Once the individual plans are computed, a three-step method consisting of clustering, classification, and branch and bound optimization is employed to determine the final collision-free paths. Simulation results in the form of sample trajectories and performance characterization plots are presented to illustrate the usefulness of the developed approach.

Commentary by Dr. Valentin Fuster
2009;():797-805. doi:10.1115/DETC2009-87231.

This report provides an overview of ongoing research at the U.S. Army Research Laboratory regarding the development of piezoelectric MEMS-enabled millimeter-scale robotics. Research topics include the development of enabling technologies for terrestrial locomotion, insect-inspired micro-flight, gecko-inspired reversible adhesives, and piezoelectric energy harvesting. The development of complementary lead zirconate titanate thin film MEMS devices, applicable to highly integrated millimeter-scale robotics, is also reviewed.

Topics: Robotics
Commentary by Dr. Valentin Fuster
2009;():807-812. doi:10.1115/DETC2009-87285.

Innovative types of actuators are required for several applications, especially in the field of medicine, robotics and micro-systems. In this context, Electroactive Polymers represent a promising group among all smart materials. They can change their dimensions and shape when an external voltage is applied, and their mechanical flexibility and ease of processing offer advantages over traditional electroactive materials expanding the options for different mechanical configurations. Dielectric elastomers are among the most promising EAPs for many applications, including actuators and sensors for the microfactory: they work in a dry environment, can achieve great deformations and support high voltage. They can be represented by a parallel plate capacitor: under an electric field the elastomer is squeezed in the thickness causing expansion in the transverse direction. Dielectric EAP actuators require large electric fields (hundreds of kV/mm) but can produce very large strain (up to 400%). Due to their unique properties and potential applications, in this paper the study of the electromechanical behaviour of a dielectric elastomer and a possible application related with the microfabrication of hybrid microsystem is presented.

Topics: Elastomers , Actuators
Commentary by Dr. Valentin Fuster

11th International Conference on Advanced Vehicle and Tire Technologies

2009;():815-829. doi:10.1115/DETC2009-86003.

A new rigid ring model with additional parameters was developed to model an off-road tire running on soil. In order to create this new rigid ring model, an FEA off-road truck tire was created and used to determine the in-plane and out-of-plane parameters for a tire running on soil. The soil, dense sand in this case, was modeled as an elastic-plastic solid with material properties obtained from published data. The longitudinal forces and the normal stress and shear stress distributions in the soil are compared with published data as preliminary validation. The general trends of soil flow from a rigid wheel model running on soil were used to validate the soil model. In addition, a model of a standard circular plate was used to determine the vertical pressure-sinkage curves and then these simulations were compared with available published measured data.

Commentary by Dr. Valentin Fuster
2009;():831-836. doi:10.1115/DETC2009-86068.

Non-pneumatic tires have been developed and being investigated, but not much prevalent. Many design studies are yet needed from the viewpoint of material, pattern, and structures. No systematic research for such important design issues have been reported in the literature. In this paper, as the first important step of design, topology optimization was utilized to determine optimal topological patterns of non-pneumatic tires, with the goal of matching the static stiffness of the current pneumatic tires. Under the optimization formulation with weighted compliance and a volume constraint, several different patterns were obtained depending on the number of patterns, volume fraction, and weighting factors. Among them, three representative patterns were chosen and analyzed for their possible applications under specific working condition. This paper proposes a systematic and efficient tool for designing the topological patterns of non-pneumatic tires.

Commentary by Dr. Valentin Fuster
2009;():837-847. doi:10.1115/DETC2009-86325.

Within companies dealing with the automotive market, and in particular for product designers, the usage of numerical simulations is a well established technique to help achieving faster development cycles. Focusing on the very first phase of the design development chain conceptual (ID) modeling software is better suited. Furthermore considering the multiphysics nature of vehicle subsystems, a multidisciplinary system modeling tool is required, which has to be enriched with optimization capabilities in order to produce a suitable design of complex systems involving multiphysics functionalities (for instance for active safety and energy management). The purpose of this paper is to summarize a procedure that has been applied for the optimal design of an active suspension with hydraulic actuation, governed by a general control strategy based on the sky-hook approach, to be manufactured by Tenneco. A 15 Degrees of Freedom (DOF) vehicle model, built in a commercially available 1D simulation environment, has been validated as a first step towards achieving a good correlation with experimental results obtained on the test tracks. As a next step, the sky-hook based control strategy was implemented to take into account the active behavior of the system, and to define the load profiles acting on the suspension dampers while the vehicle is virtually tested on ride roads. Optimization loops were performed in a nested architecture in order to define the optimal gains needed to meet certain performance requirements dictated by the vehicle manufacturer. A detailed model of the damping system was implemented in LMS Imagine.Lab AMESim capturing its multidisciplinary nature including mechanical, hydraulic and electrical aspects. The mission profiles (force-velocity couples at the dampers) were used as input to the simulations to investigate the damping system design parameters considering performance achievement and energy efficiency goals. The results of this project have been used by Tenneco as guidelines for the physical prototype implementation of the active suspension system.

Commentary by Dr. Valentin Fuster
2009;():849-856. doi:10.1115/DETC2009-86350.

Rack and pinion steering systems have been synthesized and designed for many automotive applications. A steering system must be optimized for best steering characteristics to reduce tire wear and to assure safety and stability. Unfortunately, each design is slightly different because of differing car parameters and different space constraints. Designers need a tool that can quickly provide optimally synthesized steering systems. A precise and efficient method has been developed to assist designers in finding an optimum planar mechanism design for rack and pinion steering systems. It can be used to design central take-off or side take-off steering systems that are in a leading or trailing configuration. This method combines a modified Freudenstein equation with numerical optimization. Because of the combination of methods, an optimized solution may be found quickly. Thus, the tool is well adapted for preliminary designs and for design iteration.

Commentary by Dr. Valentin Fuster
2009;():857-861. doi:10.1115/DETC2009-86568.

Diesel engine is a major source of power of the future but the major growing concern is the emissions of nitrogen oxides and diesel particulates. This work deals with the particulate emission control of diesel engine exhaust using ceramic filter. The selection of CFT with suitable size, geometry, cell density, wall thickness and microstructure becomes most important. In order to achieve required particulate matter emission limits and lower backpressure, optimization of porosity, pore size distribution, mean pore size and pore connectivity in CFT is crucial. CFT are developed and tested on the basis of porosity, diameter and length of CFT with necessary recommended trials. Further experiments were carried out to understand the effect of porosity, diameter and length of CFT on the back pressure, rate of back pressure rise, filtration efficiency and break power of diesel engine. The investigation of the research work provides adequate relevant information about the development of ceramic type ceramic filter trap (CFT) with naturally available material and effect of CFT on particulate matter concentration and on engine performance. Use of CFT reduced smoke drastically without increasing back pressure beyond tolerable back pressure limit. Performance of developed CFT was compared with established CFT and matches with it. Cost of developed CFT is the distinct advantage which will promote cottage industries in undeveloped nations, and provide rural employment.

Commentary by Dr. Valentin Fuster
2009;():863-868. doi:10.1115/DETC2009-86801.

This contribution contains the conception, the components modeling, the realization, and first results for active disturbance decoupling including the experimentally checked ability of the concept for energy harvesting. The investigated mechanical structure consists mainly of a torsional spring. At one side of the spring the disturbances (time-dependent torques with varying frequencies) are driven by a position controlled hydraulic cylinder. The other side of the spring is locked and a force sensor is applied. Due to different torsion angles a torque between the left and right side of the torsion spring is induced. To eliminate or at least to reduce the torque in a passive system it is theoretically sufficient to adjust the stiffness of the spring situation-dependent, although this is practically not possible. For that reason an active disturbance control is presented here. The torque of the spring has to be controlled independently of the displacements at the right and left side. This sophisticated strategy is described in the following. In this contribution the concept and realization of a new active mechanism is realized by dividing the spring into two halves and inserting an electro-mechanical actuator. Hence, the active mechanism compensates the different torsion angles (resp. torques) by adjusting the rotor angle. The results of related test-rig experiments will be shown and the possibility to decouple the torques from each other, which can be interpreted as disturbances, is demonstrated. The strategy of active disturbance decoupling is based on the measured displacement of the hydraulic cylinder and the measured force. In chapter 2 the idea and conception of the test-rig is discussed and the realized solution is shown. The following chapter deals with the system model and especially with the idea of torque control. Furthermore the chosen disturbance profiles are shown and the effects of active decoupling are discussed. In the last chapter results of experimental tests for energy harvesting are given, showing principally the efficiency as well as the limits of todays technology.

Commentary by Dr. Valentin Fuster
2009;():869-878. doi:10.1115/DETC2009-86823.

In this paper, three motorcycle models of increasing complexity are introduced. The first, and most simple, can be considered an extension of the model developed by Neil Getz in which the non-holonomic constraints have been removed to take into account the sideslip in tires. Also, this model can be viewed as an extension of the popular bicycle model, widely used in analyzing car dynamics. It has been extended with an additional degree of freedom essential to study motorcycle dynamics: the roll angle. Such a model, simple yet detailed enough, will be used as the basis in the development of a virtual rider. The second model is much more complex than the previous one. It includes the real geometry of the steering system and circular tire profiles which greatly increases the size of the equations. This is a multibody model of a complete rigid motorcycle (i.e. it has no suspensions) consisting of 4 bodies: rear wheel, main frame, fork and front wheel. The last model incorporates the front and rear suspensions together with all the features of its predecessor. It has 13 degrees of freedom, 11 of the mechanical system and 2 of the tire relaxation equations. It will be used as a full model for simulation and rider validation. The models presented in this article have been developed using Maple mathematical software which allows symbolic manipulation of equations. Thus, with this set of models, one can study in depth the phenomena that govern motorcycle dynamics since all the equations are available symbolically.

Commentary by Dr. Valentin Fuster
2009;():879-886. doi:10.1115/DETC2009-87264.

This paper aims to elaborate the challenges and possibilities in automotive winter testing in Sweden, in particular the use of fleet management framework and steering robots, which have shown to be an interesting area for future automotive winter testing. Data was collected from a number of interviews, workshops and surveys. Automotive manufacturers (OEMs), Tier 1 suppliers and service providers (e.g. test track owners and winter test entrepreneurs) contributed to the data collection. In general, service providers want to approach their customers in the value chain to provide new or extended services. From the data, the automotive industry is constantly pressed by shorter projects, fewer prototypes and the lack of state-of-the-art test methods. Service providers find the use of remote technologies, such as fleet management, an important part of their service, especially connected to the safety of test-drivers and overall test track safety. Service providers also consider further research in the area of fleet management and remote technologies as a base for future services. The automotive industry states that the possibility to replay the last run from logged data in the vehicle enhances the services. The use of steering robots during winter testing can provide an opportunity to run repeatable and standardized testing. However, the views here vary a lot between companies regarding the usability of the steering robots during winter testing. This indicates that further research on the issue of providing standardized winter testing is necessary. Work to extend a fleet management framework and a pre-study of the usability of steering robots in winter testing have begun, using the studies presented in this paper as a basis for this work.

Topics: Testing
Commentary by Dr. Valentin Fuster
2009;():887-892. doi:10.1115/DETC2009-86085.

Retractable suspension system is used to lift the auxiliary axle of a multi axle vehicle. The article summarizes the current state of knowledge of the lifting mechanisms, which are used for lifting and lowering the auxiliary axle. Various designs of liftable axle are described. To proper use of the auxiliary axle, important guidelines are given for suppliers, OEMs and customers. Several viable steerable and non-steerable liftable axles are developed with various load carrying capacities using air bellows. In these liftable axles, the air bellows expands when compressed air is supplied to the air bellows at a required pressure. The air bellows activates the lifting mechanism; thereby the tires of the auxiliary axle are lifted from the road surface. When the air is released from the air bellows, the tires are lowered to engage the road surface.

Topics: Vehicles
Commentary by Dr. Valentin Fuster
2009;():893-904. doi:10.1115/DETC2009-86402.

Many parameters in mechanical systems cannot be measured physically with good accuracy, which results in parametric and external excitation uncertainties. This paper compares two new computational approaches for parameter estimation. The first approach is a polynomial-chaos based Bayesian approach in which maximum likelihood estimates are obtained by minimizing a cost function derived from the Bayesian theorem. The second one uses an Extended Kalman Filter (EKF) to obtain the polynomial chaos representation of the uncertain states and the uncertain parameters. The two methods are illustrated on a nonlinear four degree of freedom roll plane vehicle model, where an uncertain mass with an uncertain location is added on the roll bar. Both approaches can work with noisy measurements and yield results close to the actual values of the parameters, except when different combinations of uncertain parameters lead to essentially the same time response than the measured response. In that case, the aposteriori probability densities of the estimated parameters obtained with the EKF approach cannot be trusted. The Bayesian approach identifies that problem since the Bayesian cost function has an entire region of minima, and can use regularization techniques to yield most likely values in that region based on apriori knowledge.

Commentary by Dr. Valentin Fuster
2009;():905-912. doi:10.1115/DETC2009-86429.

The coefficient of friction (CoF) is one of the most important parameters for the contact between the wheel and the rail. Accurate estimation or measurement of the CoF has a very important role, both in terms of modeling the train dynamics and in terms of reducing operational costs in the long-term. For ease of implementation, since the nature of the wheel-rail contact dynamics is very complex, the assumption of a constant CoF is still used in most theoretical studies. Nevertheless, experimental work indicates that the CoF depends on dynamic changes in various wheel-rail conditions, like sliding velocity, contact patch shape and size for stick and sliding region, wheel and rail geometry, wheel vibration, rail surface roughness and/or lubrication, etc. In this paper we present the proposed equation to model the nonlinear dry friction coefficient at the wheel-rail contact. The friction coefficient is calculated at the three different values for change in the damping ratio while maintaining all the other conditions the same. As expected, the analysis performed to estimate the dry friction coefficient based on the proposed equation and using NUCARS® simulation results shows that the coefficient of friction has a highly nonlinear dependence on its parameters.

Topics: Friction , Modeling , Rails , Wheels
Commentary by Dr. Valentin Fuster
2009;():913-919. doi:10.1115/DETC2009-87267.

In the modern era of vehicle design, the use of computer simulation and shaker rigs is crucial. To utilize these essential design tools, topographical measurements of appropriate terrains must be collected. While it is obvious that high-resolution data is critical for quality testing, there is no clear definition for what resolution is actually required in practice. This required level of fidelity can only be determined by considering all aspects of the end use. This paper will establish a general set of guidelines by which the required resolution can be determined to meet specific application needs. The use of these guidelines will be demonstrated through an experimental case study of a vehicle driving over a very simple terrain profile.

Commentary by Dr. Valentin Fuster
2009;():921-929. doi:10.1115/DETC2009-87404.

Flexible-wheel (FW) suspension concept has been recently proposed and regarded to be one of the novel technologies for future ground vehicles as well as planetary surface rovers. The FW concept generally integrates stiffness/damping components within an airless tire and wheel unit, to offer considerably potential benefits in decoupled ride and handling, compact and lightweight design, enhanced traction, road-holding, road-friendliness, driving safety and fuel efficiency. This study attempts efforts to develop generalized models for fundamental stiffness and damping properties of the FW suspension concept. Based on the generalized models, suspension properties are analyzed for two different FW design configurations. The generalized analytical formulations of the suspension properties of conceptual FW suspension designs would serve as a preliminary theoretical foundation for the development of FW suspension systems for future vehicle applications.

Topics: Modeling , Wheels
Commentary by Dr. Valentin Fuster
2009;():931-941. doi:10.1115/DETC2009-86101.

This paper reports the planning efforts on reducing fuel consumption rate in the current fleet of medium-duty tactical truck. A strategic plan was developed through investigation of current and future technology offerings from original equipment manufacturers and aftermarket suppliers. Research efforts consisted of an initial phase where a broad range of integration candidates were collected and a secondary phase where in-depth analysis was conducted to target those to consider for inclusion in the strategic plan. Each product was evaluated on its technical merits with consideration given to the needs and strategic goals of government agencies. The strategic plan lays out the integrated technologies in the near-term including hydrogen injection and auxiliary electrification of engine cooling fan. For the mid-term timeframe, the plan involves implementing an engine stop/start system and electrifying other auxiliaries. The final step in the plan is the development and implementation of a full (strong) hybrid population.

Commentary by Dr. Valentin Fuster
2009;():943-949. doi:10.1115/DETC2009-86716.

More and more planetary gear mechanisms are being used in Hybrid Electric Vehicle (HEV) as multi-energy coupling mechanisms because of their compact structure, high transmission efficiency and strong load bearing capacity. In order to get all the planetary gear schemes that satisfy the requirements of topological characteristics and select the optimal scheme for Hybrid Electric Vehicle Planetary Gear Coupling Mechanism (HEV-PGCM) as the references for the following analysis and structure design. Firstly, a variety of HEV-PGCM schemes with required topological characteristics are designed by applying the Creative Design Method. Secondly, according to the design requirements of planetary gear transmission and HEV power coupling mechanism, combined with Matrix Theory, the scheme evaluating indicators and method for HEV-PGCM are presented and used for scheme analysis and optimal selection. The results indicate that this method is general for common use and it can provide reference schemes for the following structure parameter design and analysis of HEV-PGCM.

Commentary by Dr. Valentin Fuster
2009;():951-957. doi:10.1115/DETC2009-87110.

The objective of this paper is to optimize the belt tensioning mechanism, known as the Twin Tensioner. The optimized tensioner achieves the minimum magnitude of belt tension in a Belt-driven Integrated Starter-generator (B-ISG) system. The B-ISG is an emerging hybrid transmission that closely resembles conventional serpentine belt drives. The system contains an integrated starter-generator (ISG) unit that performs a start-stop function on the engine. A derivation of the system’s equation of motion is simulated in this paper. A parametric study evaluates the Twin Tensioner’s parameters with respect to their impact on static tensions. Design variables are selected from these parameters for optimization. The optimization uses the genetic algorithm (GA) and the sequential quadratic programming (SQP) searches. Computations for belt tension based on the optimized design variables indicate the optimal system contains spans with static tensions that are significantly lower in magnitude than in the original design.

Commentary by Dr. Valentin Fuster
2009;():959-966. doi:10.1115/DETC2009-87190.

The paper describes some simple modelling to investigate whether there are potential benefits to incorporating a geared transmission in electric vehicle driveline. The overall conclusion is that considerable benefits in energy consumption are available if a continuously variable gearbox system is incorporated; performance improvements of 6 to 19.2% are predicted over a range of European, USA and Japanese driving cycles. Furthermore, the use of a much simpler, two speed gearbox an improve performance significantly — by for example 9.2% over the NEDC cycle — although similar improvements are not predicted over other driving cycles. Overall, the results suggest not only that direct benefits in terms of energy reductions are obtainable, but also that significant reductions in motor and driveline sizing may be an alternative approach to exploiting the introduction of a transmission system.

Commentary by Dr. Valentin Fuster
2009;():967-975. doi:10.1115/DETC2009-87596.

This paper outlines the controller development for a physics-based two-zone thermo kinetic model of HCCI/CAI engine presented in the previous work. The model accounted for both temperature and concentration inhomogeneities in the cylinder, which ultimately resulted in better prediction of the combustion parameters. The discrete nonlinear model is linearized about an operating point and the resulting linearized model is used to create an effective tracking controller. The model inputs include the variable valve timings needed to effectively control peak pressure, ignition timing and exhaust temperature. Since some of the model states cannot be monitored under transient conditions, an observer was developed to estimate the states. Two controller-observer models: controller-current observer and controller-predictor observer were designed and simulated using the same engine model. A significant difference was observed between the performances of these two models. Simulation results showed that linear controller can drastically enhance the control of combustion phasing, thereby making the control of HCCI engines practical.

Commentary by Dr. Valentin Fuster
2009;():977-985. doi:10.1115/DETC2009-86363.

The integration of customer demands in the early phase of product development process is one of most important aspects in the field of automotive engineering. In addition to a customer survey which generally requires drive tests of the real prototypes, methods based on the virtual product design have been applied more and more frequently. Due to the potential of simulation methods, the development time can be shortened and the costly prototypes as well as the time-consuming drive tests can be partially excluded. Earlier studies have demonstrated a capability of the developed methods and tools to support the customer-oriented drive train design by means of the prediction of the subjective comfort evaluation. In this case, the potential customers are classified into three groups based on their comfort expectation and style of driving. The rating from the customer point of view is accordingly achieved by modeling of the human sensation from the way the individual passengers make their evaluation by means of the Artificial Neural Networks (ANN). The objective of the current research is to implement the developed methods in the design phase of the drive train development process to enhance the customer comfortability. This article presents a systematic approach to apply the simulation methods in order to investigate different design parameters of the drive train and to determine the consequent customer comfort evaluation during each driving situation, the vehicle start-up as an example. For this purpose, the modification of the elaborated vehicle model is carried out by variation of the comfort-relevant design parameters, such as the friction coefficient gradient of the clutch friction pair, the mass of inertia and the damping of the components, like the dual mass flywheel. Depending on each drive train configuration and driver demand on the vehicle start-up, the simulated driving situation with different effects on the occurrence of the rotary vibration is evaluated by means of the human sensation model. This is developed during the drive tests on the basis of driver rating behavior. Based on the predicted comfort evaluations from different types of customer, the decisions made by the developer such as the determination of the clutch disk property or the damping setting of component can be efficiently supported during the drive train design. Hence, a new drive train concept can be tested and improved in such a way that the satisfaction of a target customer group from the first prototypes is obtained.

Commentary by Dr. Valentin Fuster
2009;():987-995. doi:10.1115/DETC2009-86628.

The principal method for reducing meshing transmission error has been to design the gear with as many teeth as possible. However, while such design methods have focused on decreasing gear noise, they have not considered the relationship between gear noise and the background noise of vehicle interiors. Therefore, we propose a new design method of low noise gear that is based on human aural characteristics. The proposed method is a gear design that controls the frequency of the gear noise by changing the number of tooth. First, human aural characteristics were researched in a special acoustic environment in a vehicle. Second, the characteristics of vehicle interior sound were investigated. Third, the relationship between the number of teeth and the sound level of the gear noise was investigated. Finally, we demonstrated that the design of our proposed method, which was effective due to the design of optimum number of gear teeth considering human aural characteristics. It was able to be proven that the case of advancement of vehicle interior sound is achieved by considering human aural characteristic.

Commentary by Dr. Valentin Fuster
2009;():997-1002. doi:10.1115/DETC2009-86929.

This paper presents the research results of the first stage of the Marie Curie Project, MYMOSA (MotorcYcle and MOtorcyclist SAfety). One of the aims of MYMOSA is increasing safety of motorcycle’s rider by better understanding of its road behaviour. It can be achieved by simulations of the motorcycle-rider system during road manoeuvres and pre-/crash scenarios. The process of the motorcycle-rider system development and initial results of the road behaviour simulations are presented. The system is divided into three separate elements: controller, motorcycle and rider’s body models. The co-simulations of motorcycle, rider and controller, are performed to determine the behaviour of the system on the road. Obtained simulation results are compared with results from the system without multibody rider’s model. During further work, kinematic and dynamic properties of the rider’s body parts will be used as inputs for crash simulations with detailed rider’s model to determine positions and severity of injuries caused by crash.

Commentary by Dr. Valentin Fuster
2009;():1003-1009. doi:10.1115/DETC2009-87051.

Motor vehicle crashes claim over 40,000 lives and injure over two million people each year in the United States. To reduce the number of injuries and fatalities through vehicle design improvements, it is important to study occupant kinematics and related injury mechanisms during crashes. Occupant motion in crash tests is typically measured with high speed video, spatial scanning, direct field sensing, and inertial sensing. In this work, we present simulation and testing results on inertial sensing of dummy kinematics based on a novel algorithm known as Quaternion Fuzzy Logic Adaptive Signal Processing for Biomechanics (QFLASP-B). This approach uses three angular rates and three accelerations (one gyroscope-accelerometer pair about each axis) per rigid body to compute orientations (roll, pitch and yaw), positions and velocities in the inertial (fixed) reference frame. In QFLASP-B, quaternion errors and gyro biases are calculated and used in an adaptive loop to remove their effects. The Fuzzy Estimator at the core of the algorithm consists of a fuzzification process, an inference mechanism, a Rule Base and a defuzzification process. In this paper, we examine those aspects of the QFLASP-B Fuzzy Estimator critical to accurate kinematics sensing, hardware and software implementations and experimental results compared with traditional approaches.

Topics: Kinematics
Commentary by Dr. Valentin Fuster
2009;():1011-1019. doi:10.1115/DETC2009-87379.

Nowadays, the use of the Finite Element Method [1] by means of simulation computer tools has made possible a substantial step forward in the field of calculation and optimization of vehicle structures. More specifically, these modern calculation tools are achieving great cost reductions corresponding to the experimental tests necessary to verify the appropriate performance of a vehicle in impact cases. On the other hand, great efforts will have to be done to develop correct numerical models for calculation. Once these numerical models have been validated with experimental tests, elimination of experimental costs compensates for these calculation efforts. A greater flexibility in decision making with respect to design and optimization alternatives will be achieved as well. The objective of this paper is to obtain an appropriate test simulation methodology for a specific vehicle and a specific impact case: There have been carried out the simulations of two different rollover test typologies in order to verify an adequate and safe behaviour of a semitrailer designed for hydrogen transport. After results of these two simulations are obtained, they will be compared in order to set which is the most restrictive and therefore the most appropriate. A lightened configuration has been also considered so as to carry out a sensibility analysis of material and thickness of some structural parts over numerical results in both test typologies in order to verify these simulations.

Commentary by Dr. Valentin Fuster
2009;():1021-1029. doi:10.1115/DETC2009-86081.

Seat suspension system is critical to the ride comfort experience of a vehicle’s driver and passengers. The use of a magnetorheological (MR) damper in a seat suspension system has been shown to offer significant benefits in this regard. Most research on seat MR dampers has applied active control strategies to command the MR damper, which is an inherently semi-active device. This paper introduces a more suitable semi-active control strategy for an MR damper used in a seat suspension, enabling more effective control. The proposed control system comprises a system controller that computes the desired damping force using a sliding mode control algorithm, and a neural-based damper controller that provides a direct estimation of the command voltage that is required to track the desired damping force. The seat suspension system is approximated by base-excited single degree of freedom system. The proposed semi-active seat suspension is compared to a passive seat suspension for prescribed base displacements. These inputs are representative of the vibration of the sprung mass of a passive or semi-active quarter-vehicle suspension under bump or random-profile road disturbance. Control performance criteria such as seat travel distance and seat acceleration are evaluated in time and frequency domains, in order to quantify the effectiveness of proposed semi-active control system. The simulated results reveal that the use of semi-active control in the seat suspension provides a significant improvement in ride comfort.

Commentary by Dr. Valentin Fuster
2009;():1031-1037. doi:10.1115/DETC2009-86096.

Current and future motor vehicles are incorporating more and more sophisticated chassis control systems to improve vehicle handling, stability and comfort. These control systems often operate independently and thus interactions and performance conflicts among the control systems occur inevitably. To address the problem, this study proposes a two-layer hierarchical control architecture for integrated control of electric power steering (EPS) system and anti-lock brake system (ABS). The upper layer controller is designed to coordinate the interactions between the EPS system and the ABS. While in the lower layer, the two controllers including the EPS system and the ABS, are designed independently to achieve their local control objectives. Simulation results show that the proposed hierarchical control system is able to improve the vehicle lateral stability, and at the same time ensure the vehicle steering agility, and the braking performance.

Commentary by Dr. Valentin Fuster
2009;():1039-1045. doi:10.1115/DETC2009-86506.

The main focus of the present paper is on the design of a modified sky-hook control of a semi-active Macpherson suspension system by means of H∞ Output Feedback Control (OFC) theory. To this end, a new dynamic model, incorporating the kinematics of the suspension system, is used for the controller design. The combination of a Linear Matrix Inequality (LMI) solver and Genetic Algorithm (GA) is adopted to regulate the static output feedback control gain so that the stability conditions are fulfilled and control objectives are achieved. Meanwhile, a three-dimensional kinematic model of the system is incorporated to investigate the influence of the control force variation on the steering, handling and stability of the vehicle. A geometric relation of the vehicle roll center is employed to study one more extra aspect of the comfort and stability of the vehicle. The results show that the proposed controller improves the kinematic and dynamic performances of the suspension well compared with those of the passive system. Moreover, it is concluded that a superior stability of the vehicle during the cornering can be achieved by adjusting the height of the vehicle roll center passively so that the stability of the vehicle is improved while the forward motion specifications can be modified by an appropriate suspension control design.

Commentary by Dr. Valentin Fuster
2009;():1047-1052. doi:10.1115/DETC2009-86557.

Through the simulation study of a semiactive quarter car suspension, this paper is to expatiate on the control algorithm documented in the United States Patent 6,873,890 [1]. That patent presents a new method to design semiactive suspension controls in the frequency domain. As is well known, suspension related dynamics has two dominant modes in the working frequency range up to 25Hz. As such, the suspension dynamic system has three distinguishable frequency sections. In order to achieve better performance, different controls have to be applied to each frequency section, respectively. The significant core part of the patented algorithm is to provide an approach to identify the excited frequencies in real time that are transmitted through the vehicle suspension. Then different controls of such as skyhook, groundhook and other damping strategies are combined accordingly to accomplish the best performance overall. Thus through the suspension control the vehicle dynamics (such as ride and handling) is expected to be improved in the broad frequency range in comparison to passive suspensions with a trade-off design.

Commentary by Dr. Valentin Fuster
2009;():1053-1059. doi:10.1115/DETC2009-86732.

This paper addresses the effect of different optimization criteria for the control purpose of vehicle suspension. In the present study, active vibration control system for a 5 degree-of-freedom (DoF) pitch-plane suspension model with bounce and pitch motions is investigated. In the proposed vehicle model, the impact of the wheel-axle-brake assemblies’ masses is also considered. The developed model is controlled using a fuzzy logic controller (FLC) to minimize the vibration of the driver’s seat. The controller is designed to control the applied force to the seat. Furthermore, in order to determine the optimal value of fuzzy system parameters, genetic algorithm (GA) optimization search is used based on minimizing both vibrations and accelerations of the driver’s seat. In other words, two different criteria are chosen for optimization of the controller: minimizing either absolute displacement or absolute acceleration which is related to ride comfort. In each case, the simulation is implemented and the results are presented. It is shown that optimization according to only one criterion may lead to undesirable results in other system parameters. In addition, it is demonstrated that considering absolute displacement as the only factor to be minimized is ineffective. Finally, another criterion which is a combination of the two previous criteria has been suggested and tested and the obtained results are presented. The combinational criterion can suppress the vibration as well as decreasing the vehicle acceleration.

Commentary by Dr. Valentin Fuster
2009;():1061-1067. doi:10.1115/DETC2009-87748.

In this study a novel control strategy for independent control of front wheels’ steering angles, using fuzzy logic control, has been developed. For this purpose at first the appropriate vehicle dynamic models have been introduced. A simplified two-degree-of-freedom model is considered as the reference model and then a comprehensive eight-degree-of-freedom model is developed as the simulation tool. In the next step, the comprehensive control system has been designed. The control system based on the yaw rate error of the actual vehicle comparing to the predefined reference model, the actual vehicle side slip angle and also lateral acceleration of the actual vehicle, calculates the correction steering angles of the front inner and outer wheels. Finally, a sophisticated precise numerical simulation is performed. In order to ponder the performance of the proposed controller, an optimal control system as an active steering control (ASC) has been used for comparison. The simulation results show considerable improvement in handling and stability of the vehicle compared to the conventional non-controlled system and also a vehicle equipped with an optimal controller ASC.

Commentary by Dr. Valentin Fuster

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