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Mechanical Systems and Control

2008;():5-12. doi:10.1115/IMECE2008-66046.

ICF (Inertial Confinement Fusion) drivers are large-scale precision optical facilities. Structure stability is an important design index for ICF drivers and it has a direct influence on the quality of beam shooting. The total positioning error budget designed for the SG-III Technical Integration Experiment Line (TIL) built in China is 30 micrometers (μm) at the target plane or its equivalent, among which the allocated stability budget is 27μm and the translation of a single optical element should be less than 1μm under the effect of ambient loads. Based on the previous evaluation of the TIL environment, the microvibration and thermal load are two main factors which can affect stability of the optical system. To obtain the data of the two ambient loads, acceleration seism sensors and high precision temperature sensors are used to measure the ambient vibration and temperature change for a long time. The finite element model is then built for a typical optical element and its support structure and the measured loads are exerted on the model to obtain the response of the optical system. The results show that both stability of a single optical element and stability of the laser beam can satisfy the designed index. This research is very helpful for the building of the SG-III main facility.

Topics: Stability , Stress
Commentary by Dr. Valentin Fuster
2008;():13-18. doi:10.1115/IMECE2008-66077.

This paper analyze the deformation of large aperture optical components under the thermal load based on the finite element model developed using the ANSYS software, which are used for inertia confinement fusion (ICF) experiments. High precision sensors are used to measure the temperature around the optical components in the target building and to form the temperature changing curve. The biggest temperature change is 0.3°C during 2 hours based on the measurement. The change is then loaded on the finite element model of a typical large aperture optical component to get the deformation of the optical component. The results indicate that the deformation of the optical component can satisfy the stability requirement in the current environment. Meanwhile, the deformation of the optical component is calculated for different temperature changes and the results show that the deformation of the optical component have a direct relationship with the change of temperature.

Commentary by Dr. Valentin Fuster
2008;():19-25. doi:10.1115/IMECE2008-66080.

The computation of the generalized velocities from the generalized momenta of a multibody system is a part of the numerical solution of the dynamics equations when they are given in the Hamiltonian form. The states of these equations are the generalized coordinates and momenta, (q, p). The generalized velocity, , is defined by = J−1 p, where J is the system mass matrix. The effort in solving by direct methods is order(N3 ) where N is the number of bodies in the system. This paper presents an order(N) recursive algorithm to compute for flexible multibody systems.

Commentary by Dr. Valentin Fuster
2008;():27-36. doi:10.1115/IMECE2008-66108.

In this paper, the characteristics of two rotary tables driven by worm gear and roller gear cam are measured and compared. The positioning accuracy and repeatability as specified in ISO 230-2 are measured together with the rotational fluctuation, backlash, friction torque, frequency response of the systems and also the influence of unbalance mass on rotational motion. Two rotary encoders which were attached to motor and output axis were used for measurements. The motor, controller, and the rotary encoders were kept the same for both tables to ignore the effects of these units on results. Furthermore, the simulations were carried out by mathematical models which were proposed by two of the authors and the results were compared with measured results. From the simulation results, the torsional stiffness and friction torque were identified and also compared. The results show that the measured and simulated data have a good agreement and therefore it can be said that the identified parameters from simulations are accurate. The result shows that the performances of the rotary table driven by roller gear cam is better than that of rotary table driven by worm gear.

Commentary by Dr. Valentin Fuster
2008;():37-43. doi:10.1115/IMECE2008-66163.

In the past few years, parallel manipulators have become increasingly popular in industry, especially, in the field of machine tools. Hexaglide is a 6 DOF parallel manipulator that can be used as a high speed milling machine. In this paper, the kinematics and singularity of Hexaglide parallel manipulator are studied systematically. At first, this robot has been modeled and its inverse and forward kinematic problems have been solved. Then, formulas for solving inverse velocity are derived and Jacobian matrix is obtained. After that, three different types of singularity for this type of robot have been investigated. Finally a numerical example is presented.

Topics: Kinematics , Robots
Commentary by Dr. Valentin Fuster
2008;():45-52. doi:10.1115/IMECE2008-66398.

Cutting force is a common monitoring parameter reflecting the behaviour of a production process. As monitored cutting conditions are used to adjust a process’s performance to its highest feasible level, control strategies for machining operations are claimed. To ensure a control’s functionality, an accurate measurement of the cutting conditions is required. In this paper the impact of a work piece’s mass onto a sensor’s dynamic behaviour is presented. For this purpose, at different setups the measurement characteristics of piezoelectric force sensors are researched and verified. Different trials are carried out, not only taking the natural frequencies of the sensors, but also the vibration characteristics of the whole machinery into account. Based on this, methods to improve and condition a measurement system’s dynamic accuracy are approached.

Commentary by Dr. Valentin Fuster
2008;():53-60. doi:10.1115/IMECE2008-66537.

A methodology is presented for evaluating the structural integrity of metallic nuclear waste disposal containers (waste packages) subject to impact events. The LS-DYNA finite element analysis (FEA) computer code and massively parallel processing (MPP) is used for nonlinear, dynamic-plastic, large-distortion impact simulations. The acceptance criterion is based on minimum-strength, bilinear, stress-strain curves and the ASME Boiler and Pressure Vessel Code primary stress intensity limits. The evaluation uses component stress classifications based on force-moment response trends from a series of reduced-modulus elastic analyses. FEA examples are provided for a waste package that is supported on an emplacement pallet (pallet) and dropped from the transfer vehicle.

Commentary by Dr. Valentin Fuster
2008;():61-70. doi:10.1115/IMECE2008-66538.

A methodology is presented for estimating the ultimate structural capability (fragility) of metallic nuclear waste disposal containers (waste packages) subject to impact events. The LS-DYNA finite element analysis (FEA) computer code and massively parallel processing (MPP) is used for nonlinear, dynamic-plastic, large-distortion impact simulations. The fragility estimate for risk assessments uses strain energy concepts, a ductile-rupture damage criterion and tri-linear stress-strain curves adjusted for material cold-forming triaxiality and weldment toughness scatter. FEA examples are provided for waste package impacts on ground support structures.

Commentary by Dr. Valentin Fuster
2008;():71-79. doi:10.1115/IMECE2008-66585.

In this effort, the nonlinear dynamics of a machine-tool spindle system supported by ball bearings is investigated. Considering the loss of contact between the inner race and ball in the ball bearing, the system is described by a set of second order nonlinear differential equations with piecewise stiffness and damping. The nonlinear responses of the system exhibit the softening behavior due to the loss of contact. As the initial preload is applied to the spindle system and the balls are fully contacting with the inner race of the bearing, the nonlinear responses of the system switche to the hardening behavior. Due to the 3/2 nonlinearity, resonance are found when the excitation frequency is close to one-third of the first natural frequency, one-half of the first nature frequency, two-third of the first natural frequency, and the first natural frequency. The route of the period-doubling bifurcation to chaos and the tori doubling process to chaos which usually occurs in the impact system are also observed in this spindle-bearing system.

Commentary by Dr. Valentin Fuster
2008;():81-88. doi:10.1115/IMECE2008-66607.

Bearings are among the most widely used machine elements and are critical to almost all forms of rotating machines. In order to prevent unexpected bearing failure, defects that can occur in bearings should be detected as early as possible. It is widely recognised that Acoustic Emission (AE) is gaining ground as a monitoring method for health diagnosis on rotating machinery. The advantage of AE monitoring over vibration monitoring is that the AE monitoring can detect the growth of subsurface cracks whereas the vibration monitoring can detect defects only when they appear on the surface. The present work involves studying the variation of AE signals obtained from spindle bearing housing of a lathe for various cutting conditions. Simple functional relationships between the parameters were plotted to arrive at possible information on bearing condition. But these simpler methods of analysis did not provide any information about the status of the bearing. Thus, there is a requirement for more sophisticated methods that are capable of integrating information from multiple sensors. Hence, methods like multiple regression analysis and GMDH have been applied for the estimation of AE Counts and AE Energy. From the Experimental data it was observed that as the cutting condition increases there is an increase in the signal level of AE parameters. This is due to increase in load acting on the bearing at higher cutting conditions. Estimates from multiple regression and GMDH were compared and it was observed that, GMDH with regularity criterion gives better results.

Topics: Bearings
Commentary by Dr. Valentin Fuster
2008;():89-96. doi:10.1115/IMECE2008-66753.

Deterioration in the machine running conditions always produces a corresponding increase in the vibration level. By monitoring vibration level it is possible to obtain information about the machine condition. Here, drilling machine was considered for the analysis. Spindle bearings and gearbox are found to be the critical elements of the machine tools on which condition monitoring has to be concentrated. To analyze the condition of the existing machine elements, finite element method has been used. An attempt has been made by modeling drilling machine to find out the response of the structure for various defects in machine elements. The finite element model of the machine tool was developed by using finite element package ANSYS. Modal analysis has been carried out to determine the natural frequencies and mode shapes of the structure. Frequency response analysis was used to determine the response of the structure due to the unbalance forces. Transient response analysis was used to study the effect of assumed defects on the machine tool structure. A defect was assumed on the outer race of the spindle bearing and on the gear and responses were observed at the spindle bearings location. From the analysis for the assumed defect in the outer race of the bearing, it was observed that the vibration velocity increases with the increase in depth of defect and depends on location of the defect. From the vibration signature resulting due to assumed destructive pitting defect in all teeth of the driven gear, it was observed that the vibration velocity level decreases with increase in spindle speed. This is because, at lower speeds time taken by each tooth to mesh with its counterpart is more, and hence persistence of disturbing force due to defect in meshing gear is more at lower speeds. Experimentation was carried out on the drilling machine by using the instrument Machine Condition Tester T-30. The experimental data obtained were used to analyze the condition of the machine elements. The vibration velocity was measured on the spindle bearings location for different spindle speed. From the Experimental analysis it was observed that with the increase in spindle speed, the vibration velocity also increases. Finally, theoretical results were judged against the experimental results. Thus the present work shows that the FEM is a valuable tool in finding sources of undesirable vibrations from various defects present in the machine elements of the machine tool structure.

Commentary by Dr. Valentin Fuster
2008;():97-106. doi:10.1115/IMECE2008-66756.

The cutting tool is the only element in a machine tool that requires frequent changes due to failure. Drill bit wear can cause catastrophic failure that can result in considerable damage to the work piece and the machine tool. Hence, there is an imperative need to keep a watch on the condition of the cutting tools during the machining process. Over the years, a wide variety of on-line or off-line techniques have been investigated for monitoring abnormal cutting tools. A variety of signals such as tool-tip temperature, forces, power, thrust, torque, vibrations, shock pulse, Acoustic Emission (AE) etc., have been used for monitoring tool failure by on-line technique. The detection and monitoring of AE is commonly used to predict tool failure. Present work involves estimation tool flank wear in drilling based on AE parameters viz., RMS, energy, signal strength, count and frequency by empirical methods of analysis like Multiple Regression Analysis and Group Method of Data Handling (GMDH). The experimental work consisted of drilling S.G Cast iron using high-speed steel drill bit and measuring AE parameters from the workpiece using AE measuring system for different cutting conditions. Machining was stopped at regular intervals of time and tool flank wear was measured by Toolmakers microscope. The experimental data were subjected to simpler methods of analysis to obtain a clear insight of the signals involved. The study of AE-time plots showed a similarity with three phases of tool wear, which implies that the measured AE parameters can be related to tool wear. Multiple Regression Analysis and Drilling is a major material removal process in manufacturing. Infact, the drills have been used widely in industry since the industrial revolution. It was estimated that 40% of all the metal removal operations in the aerospace industry is by drilling. Similar to the other cutting tools, after a certain limit, drill wear can cause catastrophic failure that can result in considerable damage to the work piece even to the machine tool [1]. GMDH methods were successful in estimating flank wear based on measured AE parameters. By Multiple Regression Analysis better estimation was obtained at lower cutting conditions. Three criterion functions of GMDH viz., Regularity, Unbiased and Combined were used for estimation with 50%, 62.5% and 75% of data in the training set. Estimation was done upto Level-4. The results of GMDH estimation showed that regularity criterion functions correlates well for the set of input variables compared with unbiased and combined criteria and least error of estimation was found when 75% of data was used in the training set. The optimum level of estimation increased with the increase in the percentage of data in the training set. Comparison of the performance of Multiple Regression Analysis and GMDH indicated that estimation by regularity criterion of GMDH had an edge over Multiple Regression Analysis.

Commentary by Dr. Valentin Fuster
2008;():107-118. doi:10.1115/IMECE2008-66766.

In the context of simulating the frictional contact dynamics of large systems of rigid bodies, this paper reviews a novel method for solving large cone complementarity problems by means of a fixed-point iteration algorithm. The method is an extension of the Gauss-Seidel and Gauss-Jacobi methods with over-relaxation for symmetric convex linear complementarity problems. Convergent under fairly standard assumptions, the method is implemented in a parallel framework by using a single instruction multiple data computation paradigm promoted by the Compute Unified Device Architecture library for graphical processing unit programming. The framework supports the analysis of problems with a large number of rigid bodies in contact. Simulation thus becomes a viable tool for investigating the dynamics of complex systems such as ground vehicles running on sand, powder composites, and granular material flow.

Commentary by Dr. Valentin Fuster
2008;():119-125. doi:10.1115/IMECE2008-66868.

This paper addresses the issues of energy efficiency in robotic fish design by use of hydrodynamic models. The use of Lighthill’s small-amplitude elongated body theory for designing of robotic fish, obtaining optimal kinematics and dynamic analysis with emphasis on compliant mechanism is presented. Simulation results for a sample case have demonstrated the importance of proposed approach in robotic fish design.

Topics: Design , Robotics
Commentary by Dr. Valentin Fuster
2008;():127-132. doi:10.1115/IMECE2008-66875.

Shape Memory Alloy (SMA) actuators have broad application prospects in many fields, but due to the nonlinearity of inherent hysteresis of SMA, the precise position control has become the biggest obstacle for the wide application of SMA actuators in the fields of smart structures. Therefore, research on the control technology of push-pull type SMA actuators is rather important for extending the application of SMA actuators. A thermomechanical hysteresis model of push-pull type SMA actuators based on the one-dimensional constitutive laws developed by Tanaka-Liang et al. is presented. The Fuzzy-PID composite controller and the adaptive Fuzzy-tuned-PID controller are applied to the control of nonlinear hysteresis of push-pull type SMA actuators system. The movement characteristic and the control effect of push-pull type SMA actuators are simulated and the advantages and disadvantages of different controllers are analyzed. The results of simulation and analysis provide theoretical reference for the precise control of push-pull type SMA actuator systems.

Commentary by Dr. Valentin Fuster
2008;():133-140. doi:10.1115/IMECE2008-67008.

Friction has been made use of in various kinds of mechanical systems and sometimes induces unexpected vibration or noise such as “shudder” in clutch systems and “squeal” in brake systems in automobile applications. The studies to decrease vibration in wet friction have been performed mainly in the tribology field by developing lubricants filling sliding surfaces. Although the development of appropriate lubricants is very effective prevention of friction vibration, it may occur due to degradation of lubricants and be amplified according to structure of clutch systems. In addition, even a little vibration energy can induce loud noise when it transmits to thin elements in clutch systems and modes of out-of-plane vibration predominantly comes out. There are not so many studies of vibration in the structure of clutch systems as brake systems. In this paper, vibration in wet friction systems with paper-based materials as seen in wet clutches in automatic transmissions was investigated theoretically and experimentally. The experimental setup was designed simply and essentially in order to investigate vibration phenomena themselves due to friction on sliding surfaces filled with a lubricant. The experiments were conducted in detail under various conditions of lubricating oils, surface velocities and normal loads. It was shown that the vibration phenomena in this wet friction system depended greatly on the relationship of the friction force to the relative velocity characterizing lubricating oils. It was suggested that the vibration phenomena could be classified using the relationship of the relative velocity between the sliding surfaces to the surface velocity of one sliding surface. In addition, the actual vibration phenomena according to the actual structure of wet clutch system were investigated by modal analysis using a finite element method. As a result, some of the modes and natural frequencies to likely lead to noise were shown.

Commentary by Dr. Valentin Fuster
2008;():141-147. doi:10.1115/IMECE2008-67027.

Though it is well known that the vibration and the noise of agricultural machinery during running on a road are strongly influenced by the tire lug form, few studies have been carried out to clarify this mechanism, while many studies were done on the characteristics of automobile tire. In the previous studies for automobile tire, the tire is typically modeled as a thin, cylindrical beam on a continuously distributed elastic foundation representing the sidewall stiffness. However, this model cannot be directly applied to agricultural tire, because of non-uniform stiffness effect caused by tire lugs. In this research, natural frequencies and mode shapes of a non-rotating agricultural tire are assessed by the experimental modal analysis method for two boundary conditions: without the ground contact and with the ground contact. Then, the tire is modeled as a thin, cylindrical beam with multiple radial spring attachments, which represent tire lugs with non-uniform radial stiffness. A calculation procedure based on the receptance method for obtaining the natural frequencies of tire is formulated, then applied to the said two boundary conditions. Furthermore, the fundamental parameters of tire are identified from the measured natural frequencies using Downhill Simplex method. As a result, the influence of boundary conditions on the parameter is clarified.

Commentary by Dr. Valentin Fuster
2008;():149-160. doi:10.1115/IMECE2008-67067.

The design of a reduced-complexity dual-arm robotic manipulator for compact substrate handling platforms is presented. The manipulator utilizes a common component, which forms the left upper-arm link and right upper-arm link of the robot arm, and two forearm links, each of which carries an end-effector and can move substrates in the radial as well as circumferential directions. A unique feature of the design is that a novel transmission mechanism is used to couple a single drive motor to the two forearm links. The advantage of using such a transmission mechanism is that one less motor is required to achieve the desired motion. This article outlines the concept of the robotic manipulator and the transmission mechanism, presents a kinematic and dynamic model of the combined system, and discusses a design methodology so as to satisfy the motion requirements in a compact substrate-handling platform. The feasibility of the proposed concept is demonstrated on a fully functional prototype.

Topics: Manipulators
Commentary by Dr. Valentin Fuster
2008;():161-165. doi:10.1115/IMECE2008-67075.

Hydraulic engine mounts are widely used in automotive powertrain for vibration isolation. A lumped mechanical parameter model is a traditional approach for modeling and simulation of such mounts. This paper presents a mathematical model of passive hydraulic engine mounts with a double-chamber, an inertia track, a decoupler, and a plunger. The model is developed based on analogy between electrical systems and mechanical-hydraulic systems. The model is created to capture both the low and high frequency dynamic behavior of hydraulic mounts. The model will be further used to find the approximate pulse responses of the mounts in terms of the force transmission and top chamber pressure. The close form solution from the simplified linear model may provide some insight into the highly nonlinear behavior of the mounts. Various operational scenarios are also discussed.

Commentary by Dr. Valentin Fuster
2008;():167-173. doi:10.1115/IMECE2008-67096.

The current approaches to the design of the handling of towed cable systems onboard surface ships rely heavily on empirical methods and time-consuming/expensive prototype testing. This paper presents a new nodal position finite element method (FEM) as a design tool to simulate the dynamics of towed body system effectively. By solving for the position of cable directly instead of indirectly via the displacement, the new FEM does not need to decouple the elastic deformation from the rigid body rotation and thus eliminates the error source arising from the linearized incremental approximation in existing FEM. Analysis results demonstrate the new FEM algorithm is simple and robust by comparing with numerical benchmark test and experiments including sea trial data.

Commentary by Dr. Valentin Fuster
2008;():175-180. doi:10.1115/IMECE2008-67103.

The present work investigates the effect of pertinent parameters such as the hose tension, tow point disturbance and vortex wake on the dynamic stability of the aerial refueling hose and drogue system by using the finite element method with an accurate and computationally efficient three-noded, curved beam element. The analysis results show that the conventional spectrum method is inappropriate for the dynamic stability analysis of the aerial refueling hose/drogue system. This is because the mechanism of instability due to the tow point disturbance is not the resonance of the refueling hose/drogue system but the wave propagation along the hose absorbing energy from the airflow as it travels downstream from the tow point, if the propagation speed is less than the airflow speed. The study also demonstrates that the vortex wake has a significant impact on the dynamics of the system. The short hose system will orbit with the vortex and the orbiting behavior will diminish as the hose length increases.

Commentary by Dr. Valentin Fuster
2008;():181-187. doi:10.1115/IMECE2008-67115.

Adaptive Surface Control (ASC) technologies are being developed to enable extremely large deployable high RF mesh antenna reflectors for future NASA missions. This paper presents the results that are obtained from an initial study on the ASC technologies for the mesh reflector. A three-dimensional nonlinear truss model is developed to describe large deformation of the reflector during deployment. The deployment process of the reflector involves mounting a network of truss elements on a rigid frame through use of tension ties. An initial profile of the undeformed truss structure is to be determined to achieve required surface accuracy after deployment. The mathematical description of this surface mounting leads to a nonlinear optimization problem. An iterative algorithm is devised to obtain the initial profile of the undeformed reflector. The proposed model and surface optimization algorithm are applied to an 835-node reflector. Numerical simulation shows that the algorithm converges fast at low computational costs, and that the solutions obtained are accurate to computer’s digits. The reflector model and surface optimization algorithm are readily applicable to adaptive surface control of the antenna reflector under thermal loads.

Commentary by Dr. Valentin Fuster
2008;():189-197. doi:10.1115/IMECE2008-67190.

Main purpose of the study presented in this paper is to demonstrate the boundary controllers design by singular perturbation approach for trajectory tracking of two-link flexible arm. Applying the two-time scale control theory on the nonlinear PDE model, a control scheme is elaborated which makes hubs’ angles track a desired trajectory while damping out the links vibration. In the proposed controller, fast (flexible) subsystem controller will damp out the vibration of the flexible links by a Lyapunov-type design and the other slow (rigid) subsystem Inverse Dynamic controller dominates the trajectory tracking. These two controllers constitute the composite control scheme. The method does not require any information about the vibration of the links along the links for the proposed fast control law as well as discretizing the PDE of arm vibration to set of ODEs. Therefore, the method excludes the effect of both observation and control spillover instability. The simulation results confirm that the proposed boundary controllers are quite effective in performance.

Commentary by Dr. Valentin Fuster
2008;():199-204. doi:10.1115/IMECE2008-67249.

In this article, dynamic interaction is investigated theoretically between several circular cavities in an infinite piezoelectric medium under time-harmonic incident anti-plane shear wave load. The theoretical formulations are based upon the use of complex variable and multi-coordinates. Dynamic stress concentration factors at the edges of the circular cavities are obtained by solving boundary value problems with the method of orthogonal function expansion. As examples, some calculating results of two interacting circular cavities in an infinite piezoelectric medium are plotted to show how the frequencies of incident wave, the piezoelectric characteristic parameters of the material and the structural geometries influence on the dynamic stress concentration factors.

Topics: Cavities
Commentary by Dr. Valentin Fuster
2008;():205-210. doi:10.1115/IMECE2008-67250.

In this study, a new concept of power delivery system is developed. Power Shift Drive (PSD)-Axle vehicle modeling and dynamic movement analysis are performed by simulation. The dynamic vehicle model is constructed from data obtained from the derived equation, considering the specific characteristic of each part. The model is composed of a torque converter, a gear box, a differential, hub reduction and an engine, which is the power source of the 1st forward and reverse PSD-Axle, as the principle parts. By unifying the mathematical equation of each component, a mathematical model of the 1st forward gear is derived. The system dynamic model is created using Matlab/Simulink based on the mathematical model. Simulation is carried out using simulink to estimate the dynamic behavior of the PSD-Axle. Also, the dynamo test result is used to verify the reliability of the system dynamic model. This study can be used to establish the basic design concept for the forward and reverse PSD-Axle multi gear system.

Commentary by Dr. Valentin Fuster
2008;():211-217. doi:10.1115/IMECE2008-67305.

Humans are able to well recognize mixtures of speech signals produced by two or more simultaneous speakers. This ability is known as cocktail party effect. To apply the cocktail party effect to engineering, we can construct novel systems of blind source separation such as current automatic speech recognition systems and active noise control systems under environment noises. A variety of methods have been developed to improve the performance of blind source separation in the presence of background noise or interfering speech. Considering blind source separation as the characteristics of human, artificial neural networks are suitable for it. In this paper, we proposed a method of blind source separation using a neural network. The present neural network can adaptively separate sound sources on training the internal parameters. The network was three-layered. Sound pressure was output from two sound sources and the mixed sound was measured with two microphones. The time history of microphone signals was input to the input layer of neural network. The two outputs of hidden layer were corresponding to the two sound pressure separated respectively. The two outputs of output layer were corresponding to the two microphone signals expected at next time step and compared with the actual microphone signals at next time step to train the neural network by a backpropagation method. In this procedure, the signal from each sound source was adaptively separated. There were two conditions of sound source, sinusoidal signals of 440 and 1000 Hz. In order to assess the performance of neural network numerically and experimentally, a basic independent component analysis (ICA) was conducted simultaneously. The results obtained are as follows. The performance of blind separation by the neural network was higher than the basic ICA. In addition, the neural network can successfully separate the sound source in spite of the position of sound sources.

Commentary by Dr. Valentin Fuster
2008;():219-223. doi:10.1115/IMECE2008-67308.

Ordinary stepped power transmission systems that used in industry, exhibit abundant energy dissipation, complicated handling and costly maintenance. On the other hand, continuously-variable power transmissions (CVTs), which are recently considered to be used in the industry, despite their high capabilities, face a number of drawbacks including such as : limited torque transmission capacity, high-precision manufacturing and installation requirements, low cost effectiveness and relatively modest power transmission efficiencies. Therefore, innovative power transmission systems that intend to resolve or lessen one or more of these disadvantages are critical in power transmission from pinion to wheel in electric traction motors (motors) of both diesel and electric locomotives; especially when active and advanced control of traction effort and adhesion is of high importance and are going to be welcomed by rail industries. The controlling subsystem of QCPTS includes a micro control system consisting of rotational velocity sensor, power supplier source, and intelligent pins. In each rotational velocity range the velocity sensor sends a signal to the micro controller for processing which causes one intelligent pins become activated and the previously activated pin become deactivated simultaneously. As a result, depending on the rotational velocity change of the rotating output shaft the QCPTS engages a pair of gears. The intelligent magnetic pins have two Start and End work stations. The Start station activates the gear by receiving a starting signal from micro controller and also the End station deactivates the gear by receiving the End signal from micro.

Topics: Control systems
Commentary by Dr. Valentin Fuster
2008;():225-234. doi:10.1115/IMECE2008-67384.

We extend the application of temporal and spectral Proper Orthogonal Decomposition (POD) to study the sound propagation and sound-structure interaction of systems combined of acoustic and structural subsystems. We consider a prototypical system consisted of two adjacent rooms separated by a sound insulating plate. Approximation to the steady-state and transient response is obtained with the aid of the finite element method. We define the temporal (real) and spectral (complex) variations of POD to tackle acoustical and structural degrees of freedom. We apply the method to process the numerical databases of the finite element solutions. It is shown that the steady-state and transient response may be represented by a small number of dominant POD modes. The extracted frequencies and spatial shapes are evaluated and linked to the modal properties of the system. It is shown that POD analysis may provide significant insight on the properties of coupled structural-acoustic systems.

Commentary by Dr. Valentin Fuster
2008;():235-240. doi:10.1115/IMECE2008-67418.

Reducing vibrations in well drilling has a significant effect on improving the overall performance of the drilling process. Vibrations may affect the drilling process in different ways, i.e., reducing durability of the drillstring’s elements, reducing the rate of penetration, and deviating the drilling direction. In rotary drilling, which is used to open mine and oil wells, torsional vibration of the drillstring is an important component of the overall system’s vibration that has received less attention in the literature. In this paper, we propose a finite element model for a sample blasthole drillstring used to open mine wells to investigate its torsional vibrations. Boundary conditions and elements’ specifications are applied to this model. In the model, the interaction between the insert and the rock is represented by a set of repetitive impulses according to the insert pattern. The steady-state response of the system to the repetitive impulses is found and natural frequencies, kinetic energy, and potential energy of the drillstring are calculated. The root mean square (RMS) of the total energy can be used as the measure for reducing the torsional vibration of the system. Finally, an optimum combination of inserts on the cone’s rows was found based on minimizing the total vibratory energy of the drillstring. The optimum design can reduce the torsional vibrations of the drillstring and improve the drilling performance.

Commentary by Dr. Valentin Fuster
2008;():241-247. doi:10.1115/IMECE2008-67544.

This paper presents an investigation on the sensitivity enhancement of a resonant accelerometer by operating it in the nonlinear regime. The accelerometer is excited by a DC load superimposed to an AC harmonic load. The electric load is tuned such that the accelerometer is driven at primary resonance with a softening-type behavior. Upon the application of a small acceleration, the nonlinear resonance frequency of the accelerometer shifts to a smaller value. This frequency shift is used as an indication for the detected acceleration. This shift is much larger compared to the shift of the resonance frequency of the accelerometer when operating in the linear regime. The concept of the nonlinear excitation is demonstrated by simulation on a commercial capacitive accelerometer. A nonlinear single-degree-of-freedom (SDOF) system is used to model the accelerometer. Several results are shown for the effect of the DC and AC voltages on enhancing the sensitivity of the accelerometer.

Topics: Accelerometers
Commentary by Dr. Valentin Fuster
2008;():249-255. doi:10.1115/IMECE2008-67580.

In this paper Wavelet Transform (WT) and Hilbert-Huang Transform (HHT) are used as bearing diagnostics tools in drives executing arbitrary motion profiles. This field is increasingly drawing the attention of the industries because the modern electric motors work as electric cams inducing the shaft to move with a cyclic variable-velocity profile. The literature papers take into account only a constant velocity profile and they are not suitable for such applications. In fact literature methods analyse the signal only in the frequency domain, while in variable-velocity condition the bearing diagnostics should be performed in time domain. Both WT and HHT are time-frequency techniques which describe an input signal as a sum of specific functions. These functions are compared with a signal which simulates the expected vibrations of a bearing with a given fault, e.g. on the outer race. The comparison is done through a cross-correlation between the expected signal and the time-frequency techniques output. WT and HHT are used separately in an industrial case, which consists in bearing fault prediction in an automated packaging machine. In the end of the paper the WT and HHT results are discussed to analyse the different responses.

Topics: Motion , Ball bearings
Commentary by Dr. Valentin Fuster
2008;():257-264. doi:10.1115/IMECE2008-67698.

Delays in supply chains due to decision making (of managers) and lead time (in production) cause undesirable effects to inventory levels. Via system’s thinking, key mechanisms leading to such effects are investigated by analyzing the stability of an inventory, departing from a commonly studied model. On this model, two distinct delays and a PI controller to remove offset in inventory, are incorporated. On the plane of delays, stable and unstable operational behavior of inventory level are identified on so-called stability maps. Next, effects of PI controller to stability are revealed and this controller is optimized for avoiding oscillatory nature of inventory level. Case studies are provided to demonstrate counter-intuitive effects of delay presence to supply chain management and how stability maps may serve as decision-making tools for managers in achieving better control on inventory behavior.

Commentary by Dr. Valentin Fuster
2008;():265-275. doi:10.1115/IMECE2008-67718.

In this paper, the transient motion of a three unit intelligent Pipe Inspection Gauge (PIG) while moving across anomalies and bends inside gas/oil pipeline has been investigated. The pipeline fluid has been considered as isothermal and compressible. In addition, the pipeline itself has also been considered to be flexible. The fluid continuity and momentum equations along with the 3D multi body dynamic equations of motion of the pig comprise a system of coupled dynamic differential equations which have been solved numerically. Pig’s position and velocity profiles as well as upstream and downstream fluid’s pressure waves are presented as simulation results which provide a better understanding of the complex behavior of pig motion through pipelines. This study has been conducted as a part of the design procedure for the Pig which is currently under construction.

Commentary by Dr. Valentin Fuster
2008;():277-284. doi:10.1115/IMECE2008-67778.

In this research, an uncoiled scale gerbil cochlea is designed and fabricated. The cochlea model is an uncoiled, 16 times scale model of the real gerbil cochlea and has only one duct. Both the basilar membrane width and the duct size vary along the length of the device, in analogy to the physiology. The cochlea duct is filled with silicone oil and driven by a modal exciter (shaker) at different frequencies. The movement of the basilar membrane is measured using laser vibrometry at different locations along the basilar membrane. The ratio of the basilar membrane velocity to drive velocity is computed and plotted. The characteristic frequency of the model varies from 7000 Hz at 2 cm from the base of the cochlea to 350 Hz at the 15 cm from the base. Two different viscosities silicone oil, 20 cSt and 500 cSt are used for the basilar membrane movement measurements. A WKB method is applied to the calculation of the basilar membrane movement of the scale cochlea model, in which the fluid motion is fully three dimensional.

Commentary by Dr. Valentin Fuster
2008;():285-291. doi:10.1115/IMECE2008-67838.

In this research, a numerical technique is used to study the performance of high-contact-ratio (HCR) spur gears with asymmetric teeth. Asymmetric teeth have been shown to minimize dynamic loads and to increase the load carrying capacity. This is due to the fact that these teeth have a larger pressure angle on the drive side compared to the coast side. In literature, symmetric gear teeth with HCR have been shown to also yield low dynamic loads and high load capacities. HCR gears have these positive attributes because for gears in a mesh, the number of tooth pairs sharing the transmitted load alternates between two and three. In this study, the separate benefits of an HCR gear and asymmetric teeth are unified into a spur gear with asymmetric teeth. In this case, the effect of the gear contact ratio, addendum factor, mesh stiffness, pressure angles, and operation speeds on dynamic tooth loads are considered. The influences of these parameters on dynamic response are presented and discussed. A comparison between standard and non standard gear pairs in literature is also presented, with respect to dynamic tooth loads. Sample simulation results, which were obtained by using an in-house computer program, are discussed. The results obtained are shown to match well with some related analytical and experimental results in literature. It is further demonstrated that HCR spur gears with asymmetric teeth do provide a marked advantage compared to the conventional spur gears with symmetric teeth.

Commentary by Dr. Valentin Fuster
2008;():293-303. doi:10.1115/IMECE2008-68003.

The Fermi acceleration oscillator is extensively used to interpret many physical and mechanical phenomena. To understand dynamic behaviors of a particle (or a bouncing ball) in such a Fermi oscillator, a generalized Fermi acceleration model is developed. This model consists of a particle moving vertically between a fixed wall and the piston in a vibrating oscillator. The motion switching bifurcation of a particle in such a generalized Fermi oscillator is investigated through the theory of discontinuous dynamical systems. The analytical conditions for the motion switching are developed for numerical predictions. Thus, periodic motions in the Fermi-acceleration oscillator are given and the corresponding local stability and bifurcation are presented. Periodic and chaotic motions in such an oscillator are presented via the displacement time-history. From switching bifurcation and period-doubling bifurcation, parameter maps of periodic and chaotic motions will be developed for a global view of motions in the Fermi acceleration oscillator. To illustrate motion switching phenomena, the acceleration responses of the particle and base in the Fermi oscillator are presented. Poincare mapping sections are also used to illustrate chaos, and energy dissipation in chaotic motions can be evaluated.

Topics: Bifurcation , Chaos
Commentary by Dr. Valentin Fuster
2008;():305-312. doi:10.1115/IMECE2008-68010.

In this paper, a generalized theory for interactions of two separable dynamical systems is presented. The corresponding mathematical conditions are developed to determine the motion complexity of the two systems, which is caused by the interaction between two systems. This theory presents a different point of view about the interactions of dynamical system.

Topics: Dynamic systems
Commentary by Dr. Valentin Fuster
2008;():313-320. doi:10.1115/IMECE2008-68011.

Based on the photovoltaic effect and the converse piezoelectric effect, the lanthanum-modified lead zirconate titanate (PLZT) actuator can transform the photonic energy to mechanical strain/stress — the photodeformation effect. This photodeformation process can be further used for non-contact precision actuation and control in various structural, biomedical and electromechanical systems. Although there are a number of design configurations of distributed actuators, e.g., segmentation and shaping, been investigated over the years, this study is to explore a new actuator configuration spatially bonded on the surface of shell structures to broaden the spatial modal controllability. A mathematical model of a new multi-degree-of-freedom (DOF) photostrictive actuator configuration is presented first, followed by the photostrictive/shell coupling equations of a cylindrical shell structure laminated with the newly proposed multi-DOF distributed actuator. Distributed microscopic photostrictive actuation and its contributing components are analyzed in the modal domain. Effects of shell’s curvature and actuator’s size are evaluated. Parametric analyses suggest that the new multi-DOF distributed actuator, indeed, provides better performance and control effect to shell actuation and control. This multi-DOF configuration can be further applied to actuation and control of various shell and non-shell structures.

Topics: Actuators , Modeling , Shells
Commentary by Dr. Valentin Fuster
2008;():321-329. doi:10.1115/IMECE2008-68188.

Vibration analysis of beams traversed by moving load is an old and well known topic in structural mechanics, and has been of great interest for researchers of different fields, such as mechanical, railway and civil engineering. Many researchers have conducted different investigations in this field. In the present research, the nonlinear vibration of the system is studied and consequently the response of the system to a moving load is determined as a closed form solution. Furthermore, the effects of load amplitude on the response of the system are investigated. Galerkin’s method is first utilized to truncate the governing equation of motion and then MMS (Method of Multiple Scales) perturbation method is applied to study the nonlinear vibration of the system, in the presence of the internal resonance. Effects of damping of the foundation as well as magnitude of the moving load on the frequency responses are investigated. The proposed methodology and obtained results can be used to investigate the behavior several systems among which railway system shows a good compatibility.

Commentary by Dr. Valentin Fuster
2008;():331-341. doi:10.1115/IMECE2008-68353.

The exact solutions of switching linear dynamical systems with arbitrary discontinuous forcing are investigated. The switching system consists of countable prescribed linear subsystems with specified external excitations. The traditional treatments are to smoothen the discontinuity between two subsystems in such a switching system. In this paper, a method is introduced to obtain an exact solution of such a switching system. Under periodic piecewise forcing and random forcing, the exact solutions and stochastic responses of switching systems are given to help one better understand random responses in stochastic dynamical systems. For periodic forcing, the periodic responses and stability of the switching system are presented.

Commentary by Dr. Valentin Fuster
2008;():343-348. doi:10.1115/IMECE2008-68354.

In this investigation the propagation of a harmonic disturbance on the surface of ground is considered. The medium is assumed to be a homogeneous and isotropic, continuous and infinite which can be modeled as an elastic half space medium. Implementing elasto-dynamics analysis, the governing equation of motion for the system is developed. The developed mathematical model formulates the displacement and stresses in the medium in terms of elastic dilatation and rotations and reduces the governing equations into three wave equations in terms of elastic dilatation and rotations. These equations are solved and boundary stresses are satisfied in Fourier domain and the displacement on the surface are provided in this domain.

Commentary by Dr. Valentin Fuster
2008;():349-356. doi:10.1115/IMECE2008-68384.

In this paper we consider a thin narrow rectangular isotropic plate subjected to a small surface load and supported laterally by a continuous nonlinear elastic foundation. The both short ends of plate are clamped while the longitudinal sides are completely free, so that their points can move along the boundary, along the normal to the boundary, and in a vertical direction. At initial time the uniformly distributed in-plane compressive stresses are suddenly applied to the short ends in the longitudinal direction. Our goal is to find the asymptotic formulas for values of static and dynamic buckling load in the case of the narrow elastic plate and estimate their values as function of the imperfection parameter. We apply the geometrically nonlinear theory for the thin rectangular isotropic plate laterally supported by the continuous softening or stiffening foundation to formulate an associated nonlinear spectral problem for the load parameter. This problem contains a small natural parameter δ - the ratio of the width of the rectangular plate to its length and can be integrated using the asymptotic method developed in the work by Srubshchik, Stolyar and Tsibulin [1]. Accordingly we approximate the solution of the original problem by the leading term of the finite expansion in δ which is described by the motion equations of an axially compressed elastic column on the nonlinear continuous elastic foundation which has only one spatial dimension and can be investigated more comprehensively. The formulas for asymptotic values of the static and dynamic buckling compressive loads are obtained by means of the perturbation theory and by one-term Fourier’s approximation respectively. The specific numerical results for these asymptotic values are presented.

Topics: Buckling
Commentary by Dr. Valentin Fuster
2008;():357-362. doi:10.1115/IMECE2008-68610.

Ultrasonic cavitation is a well-known phenomenon that plays an important role in several physical systems and its applications are commonly utilized in different fields of physics and technology. The cavitation phenomena can be described by means of a field theory that should be able to predict the values of the macroscopic quantities, introducing physical parameters specifically for the bubbly liquid to be considered as a continuum; while on the other hand, the goal is to solve the problem of single bubble dynamics in an ultrasonic field as a starting point towards a multibubble theory. Usually the theory of single bubble dynamics in ultrasonic cavitation is constructed by primarily imposing the conditions of spherical symmetry on the bubble interface and a viscoelastic liquid, thus obtaining a significant simplification of the equations of motion and a single nonlinear equation for the interface. This approach can be satisfactory in several cases, but the situations in which the bubble deviates from its spherical shape (i.e. the collapse on a rigid boundary) and the problem of the stability of the interface motion, which turns out to be very important in sonoluminescence, cannot be treated by this theory. In the field of ultrasonic cavitation numerical analysis is a further means of investigation besides the analytical approach and experimental measurements, and it is necessary at least for two reasons. Specifically, an exact analytical treatment of the equations that model this phenomenon is substantially impossible due to their high nonlinearity; and furthermore the typical order of magnitude of the measurable quantities (object sizes in the range of microns, time intervals in the range of microseconds with nanosecond resolution) makes experiments difficult to perform. Hence we numerically analyze the relationships between amplitude and frequency by the use of SPECTRA PLUS software. The method is tested analyzing forced oscillations of cavitation bubbles excited by ultrasonic standing waves at different pressure amplitudes, showing characteristic behaviour of nonlinear dynamical systems; frequency spectra are obtained, stability analysis is performed. It is important to note that we observe subharmonic behaviour of the volume mode of the bubble prior to the instabilities due to shape modes. If one further increases the value of pressure amplitudes, one can clearly observe surface instabilities and deformations that lead to the destruction of the bubble. This evidence may suggest that the subharmonic behaviour leads to chaos in ultrasonic cavitation.

Commentary by Dr. Valentin Fuster
2008;():363-371. doi:10.1115/IMECE2008-68613.

Vibration and acoustic-based health monitoring techniques are presented to monitor structural health under dynamic environment. In order to extract damage sensitive features, linear and nonlinear dimensional reduction techniques are applied and compared. First, a vibration numerical study based on the damage index method is used to provide both location and severity of impact damage. Next, controlled scaled experimental measurements are taken to investigate the aeroacoustic properties of sub-scale wings under known damage conditions. The aeroacoustic nature of the flow field in and around generic aircraft wing damage is determined to characterize the physical mechanism of noise generated by the damage and its applicability to battle damage detection. Simulated battle damage is investigated using a baseline, and two damage models introduced; namely, (1) an undamaged wing as baseline, (2) chordwise-spanwise-partial-penetration (SCPP), and (3) spanwise-chordwise-full-penetration (SCFP). Dimensional reduction techniques are employed to extract time-frequency domain features, which can be used to detect the presence of structural damage. Results are given to illustrate effectiveness of this approach.

Commentary by Dr. Valentin Fuster
2008;():373-379. doi:10.1115/IMECE2008-68796.

A novel design of compliant slider crank mechanism is introduced and utilized as an impact force generator and contact force generator. This class of compliant slider mechanisms incorporates an elastic coupler which is an initially straight flexible beam and buckles when it hits the stopper. The elastic pin-pin coupler (a buckling beam) behaves as a rigid body prior to the impact pushing the rigid slider. At a certain crank angle the slider hits a stopper generating an impact force. Impact force can be changed by changing the angular velocity of the crank, therefore; achieving a desired velocity of the slider. Moreover, after the impact when the vibrations die out the maximum contact force can also be predetermined by designing the coupler dimensions (length, width, thickness and the amount of compression). Contact duration (crank angle) can also be changed and adjusted in this mechanism by changing the adjustable location of the impacted object.

Topics: Force , Generators
Commentary by Dr. Valentin Fuster
2008;():381-389. doi:10.1115/IMECE2008-68797.

Shape Memory Alloys (SMAs) have several attractive features that make them potentially useful concepts as bending micro actuators. SMA linear actuators are among those producing the highest strains and highest forces available, and when employed in a bending mode, their deflection capability is enhanced even more leading to potential new applications. This paper addresses the basic design concept for a bi-material actuator modeled as an initially curved composite beam with one active layer, the SMA material, and one conventional elastic layer. This device must be accurately controlled to achieve an optimal range of motion and to serve in many new applications so we have designed a nonlinear and adaptive control scheme based on Lypaunove stability theory to prevent erratic motion and even component separation and partial buckling. In addition, this control scheme is able to achieve high precision tracking without the need for detailed system parameters. Simulation is conducted which confirm the effectiveness of the proposed method.

Topics: Microactuators
Commentary by Dr. Valentin Fuster
2008;():391-399. doi:10.1115/IMECE2008-68999.

In this paper, the feasibility of implementing a nonlinear compensator technique in reducing noise transmitted into a three dimensional enclosure through a flexible panel is presented. A spherical wave, which is generated by a noise source located in the near field, is transmitted into a rectangular enclosure through a flexible panel. Piezoelectric patches, which are bonded symmetrically to the top and bottom surfaces of the panel, are used as actuators. The analytic model used here accounts for panel interactions with both the external and enclosed sound fields and the bonded piezoelectric patches, and this feature makes it appealing for a broad field of model-based active, passive, and hybrid noise control schemes. The nonlinear compensation scheme aims to increase the damping of the flexible panel linearly with the panel vibration amplitude and, thus, attenuates noise fields associated with structural resonance frequencies. Simulation results show that, despite the simple structure of the nonlinear compensator, high attenuation levels could be achieved. Results also show that the control input of the nonlinear compensation scheme is reduced, when compared to optimal control schemes.

Topics: Noise control , Sound
Commentary by Dr. Valentin Fuster
2008;():401-408. doi:10.1115/IMECE2008-69005.

This paper presents a new hysteresis model, based on the LuGre friction model, to analyze the dynamic behavior of large-scale Magneto-Rheological (MR) damper (MR-9000 type MR-damper [1]) accurately and efficiently. The gradient based optimization technique and the least square method will be utilized to identify the modal parameters. The dynamic behavior of MR-damper under different types of excitation and input current have been predicted using the proposed model and then compared with those predicted using modified Bouc-Wen model to verify the validity of the proposed model.

Topics: Friction , Dampers
Commentary by Dr. Valentin Fuster
2008;():409-415. doi:10.1115/IMECE2008-69017.

In this article, the stabilization problem of two flexible one-link and two-link manipulators is solved using boundary control method. To account for the flexibility of links, Timoshenko beam theory is adopted and using Lyapunov stability theorem, forces and torques necessary to be applied at the joints of the manipulators are calculated. Finally the problem of trajectory tracking for this robot is briefly discussed.

Commentary by Dr. Valentin Fuster
2008;():417-427. doi:10.1115/IMECE2008-69050.

In this paper, periodic and chaotic behaviors in the Chua’s circuit system are discussed. The solutions of the system in different regions with different parameters are obtained. The switching boundaries are introduced for systems switching because of different system parameters. In the vicinity of the switching boundary, the normal vector-field product is introduced to measure the flow switching on the separation boundary, and the grazing and passable conditions to the discontinuous boundary are presented. The basic mappings are defined and periodic responses of such a system are predicted analytically from the mapping structures. The local stability and bifurcation analysis are carried out.

Commentary by Dr. Valentin Fuster
2008;():429-438. doi:10.1115/IMECE2008-69087.

This work presents the dynamic modelling of a multibody systems in cross form constituted of a central body which is connected four flexible arms, at each end of arm is connected a rotor. A particular attention is given to the influence of flexibility on the dynamic behaviour of system. For elaborate the complete dynamic model, one consider the sub-structuration technique in using the Lagrangian approach based on the relatives coordinates method of central body. One establishes then the mathematics equations permitting to obtain the dynamic model of motion for the simulation and the control study. The aerodynamic loads and the gravity force are taking into account for the dynamic complete model. At the end, one considers the case of stationary flight of a miniature Quadrotor. The numerical results permit to simulate the motion of Quadrirotor in flight. But also to compare the flexible and rigid model in order to resort the flexibility effects.

Commentary by Dr. Valentin Fuster
2008;():439-446. doi:10.1115/IMECE2008-69156.

The dynamics of an axially-moving flexible medium are examined in the context of an application where the medium is partially supported by a frictional surface, that actively-orients itself relative to the direction of transport. The stability and motion of the medium are of interest in a magnetic tape data storage application where the orientation of a sensing surface is continuously altered in order to ‘follow’ the medium’s motion. Moving media that are in contact with such guiding surfaces experience friction excitations induced by the relative motion in addition to what is observed with a stationary guiding surface. Friction-induced bending moments, as well as tension fluctuation beyond the permissible limits for the flexible material can erode the potential benefits of such active positioning. This paper describes some of these dynamic phenomena using the simplified example of a planar guiding surface whose orientation is dynamically altered relative to the moving medium. A physical model for the friction-induced excitation of the moving medium is developed, and the dynamics are analyzed for their effect on critical design parameters such as the achievable bandwidth of the active control algorithm, as well as with respect to constraints on the geometry and positioning of the guiding surface.

Commentary by Dr. Valentin Fuster
2008;():447-450. doi:10.1115/IMECE2008-69161.

Embedded wireless sensor networks are part of a strategy for implementing improved structural health and usage monitoring in rotorcraft. In order to realize this goal, methods of powering the embedded sensors have to be identified. One approach is to make the power supply become an integral part of the sensor. This integrated monitoring system will then be less intrusive and, therefore, easier to integrate into existing systems. Piezoelectric materials can be an important part of this strategy. One method to harness power is to use piezoelectric materials to recover energy lost due to vibration and rotation of the equipment. This recovered energy can then be used to provide energy to power sensors directly or to extend the lifespan of batteries which power the sensors. This paper investigates the potential of using strains on a rotating blade to power sensors during flight. The preliminary numerical investigation indicates that this may be a promising approach.

Commentary by Dr. Valentin Fuster
2008;():451-458. doi:10.1115/IMECE2008-69275.

This article presents a method for determination of meshing force distribution on contact region of spur gear teeth. In this method it is assumed that there are inter-connected springs on the teeth profile. These springs treat as capacitive fields. The compliance matrices of these fields are determined from the results of finite element analysis done on 3-D model of a gear. The tooth compliance matrix is used as a reference data to determine the tooth deformations for any meshing situation. The meshing force distribution is calculated using this reference data and Hertz theory for contacting bodies. The results of this analysis help in stress analysis under real operation conditions and more reliable design of gears without needing 3-D contact model. So by this method the volume of the calculations is reduced remarkably. The method is applied to a spur gear pair, and the meshing force distribution and meshing stiffness is determined for two cases of ideal and misaligned contacts.

Topics: Force , Gears , Spur gears
Commentary by Dr. Valentin Fuster
2008;():461-471. doi:10.1115/IMECE2008-66310.

Mechanisms associated with interaction of the wheel and the rail in the vertical and horizontal direction are investigated. The noise-generating characteristics and the calculation model of wheels are studied theoretically. An improved railway wheel added with viscoelastic constrained damping layers has been researched out theoretically and experimentally. Design equations and graphs are developed for the geometrical parameter of viscoelastic constrained damping layers used in wheels. Using existing theory, the procedures are developed for predicting the structure loss factor of structural composites with different numbers of constrained damping layers. The structure loss factor of wheels attached with symmetrical three constrained layers is optimally calculated using MATLAB. A number of experiments with pulse excitations in the laboratory are carried out from the number of constrained damping layers, the material of constrained layers, as well as the position added to the wheel. From the experiments, steel is chosen as the material of constrained layer, and rubber with high loss factor and wide temperature range is chosen as the material of elastic layer. Both materials are experimentally measured. The theoretical predictions of the noise reduction effect is compared with the experimental measurements. The results shown that the wheel noise is obviously reduced.

Commentary by Dr. Valentin Fuster
2008;():473-480. doi:10.1115/IMECE2008-67351.

Non-conventional rheological models based on non-integer order differential operators can be used to describe the viscoelastic behavior of materials, especially of polymers. These models are usually selected and then validated by means of creep and relaxation tests. However, engineers dealing with structural dynamic problems may need to obtain model identification from vibration measurement data. In this case, however, the direct identification of an optimal set of parameters of a viscoelastic model from time or frequency domain measurements is a difficult task, especially if the structural dissipative contributions are slight. In this paper, an indirect approach is adopted, based on the concept of damping ratio. When dealing with standard linear viscous dissipative models, a damping ratio modal parameter ζn can be analytically defined and experimentally estimated. But this theoretical parameter shows a dependency from the modal frequency that may dramatically fail in fitting the experimental data. On the contrary, it is known that a better agreement between theory and experiments can be achieved by means of non-integer order differential models, even though in this case analytical expressions for ζn are difficult to find. To overcome this difficulty, a method of general validity for viscoelastic models is developed, based on the concept of equivalent damping ratio and on the circle-fit technique. The proposed method is applied to experimental damping estimates from plane flexural vibrations of clamped-free beams, obtained from specimens of different size made of materials such as Polyethylene, Polyvinyl-chloride and Delrin.

Topics: Damping
Commentary by Dr. Valentin Fuster
2008;():481-488. doi:10.1115/IMECE2008-67369.

A novel vibration control method utilizing magnetically mounted piezoelectric actuators is described. Piezoelectric actuators are bonded to permanent magnets, which are attached to the surface of a steel cantilever beam through their magnetic attraction. The magnetic-piezoelectric control mounts are an alternative to traditional epoxy attachment methods for piezoelectrics which allows easy in-the-field reconfiguration. In model and laboratory measurements, the beam is driven through base excitation and the resonant shunt and synchronized switching techniques are applied to two magnetic-piezoelectric control mounts to attenuate vibration. The coupled system is discretized using a Galerkin finite element model that incorporates relative axial motion between the beam and the mounts, which is governed by the sticking contact stiffness per unit length of the beam-magnet interface. The control mounts are designed using a magnetic array configuration which increases the attraction force for a given magnet thickness. Results show that the magnetic-piezoelectric control mounts provide attenuation, while also providing the flexibility to easily adjust the actuators along the length of the beam.

Commentary by Dr. Valentin Fuster
2008;():489-497. doi:10.1115/IMECE2008-67997.

Circular cylindrical shells are common components in aerospace structures and many other engineering systems, e.g., rockets, tubes, piping systems, peristaltic pumps, storage tanks, etc. Electromechanical actuators laminated on the shell surfaces can certainly strengthen the shell when needed. Or, regulated inputs to the surface actuators can introduce prescribed surface waves to control the shell oscillation. This study is to evaluate spatial actuation characteristics of circular cylindrical shells using segmented electrostrictive actuators. Electrostrictive actuations induced by surface laminated electrostrictive actuators are defined first. Governing equations of a hybrid circular cylindrical shell/electrostrictive actuator system are formulated. The total electrostrictive actuation and its contributing circumferential membrane/bending and longitudinal bending components are evaluated with respect to shell modal characteristics, design parameters and control voltages. The actuator’s quadratic behavior only generate a positive control force or moment and thus an actuator patch can suppress (or amplify) the vibration in the positive (or negative) displacement. Accordingly, the quadratic electrostrictive actuation suggests that appropriate input voltage(s) need to be carefully applied to specific actuator(s) or regions in order to control, but not to amplify, the shell oscillations. Based on the spatially distributed modal actuation, generic design guidelines and optimal actuation locations are proposed.

Commentary by Dr. Valentin Fuster
2008;():499-509. doi:10.1115/IMECE2008-69077.

Energy dissipation in mechanical joints occurs as a result of micro-slip motion between contacting rough surfaces. An account of this phenomenon is especially challenging due to the vast differences in the length and time scale differences between the macro-mechanical structure and the micron-scale events at the joint interface. This paper considers the contact between two nominally flat surfaces containing micron-scale roughness. The rough surface interaction is viewed as a multi-sphere elastic interaction subject to a periodic tangential force. It combines the Mindlin’s formulation [1, 2] for the elastic interaction of two spheres with the Greenwood and Williamson’s [3] statistical approach for the contact of two nominally flat rough surfaces so as to develop a model for multi-sphere problem in which sphere radii, contact load and the number of spheres in contact can only be known in a statistical sense and not deterministically.

Commentary by Dr. Valentin Fuster
2008;():511-522. doi:10.1115/IMECE2008-69079.

In this paper we consider the contact between two rectangular rough surfaces that provide normal and tangential contact force as well as contact moment to counteract the net moment imposed by the applied forces. The surfaces are permitted to develop slight angular misalignment and thereby contact moment is derived. Through this scheme it is possible to also define elastic contribution to friction since the half-plane tangential contact force on one side of an asperity is no longer balanced by the half-plane tangential force component on the opposite side. The elastic friction force however is shown to be of a much smaller order than the contact normal force. Approximate closed form equations are found for contact force and moment as functions of separation, asperity radius of curvature sum, mean plane slope and nominal contact dimension. The approximate equations are shown to give error within seven percent.

Commentary by Dr. Valentin Fuster
2008;():523-529. doi:10.1115/IMECE2008-66056.

The need for precise positioning technique draws significant attention for optical engineering, semi-conductor industry, biotechnology, and nanotechnology, etc. This paper presents a novel piezoelectric (PZT) actuated precision fast positioning system (PFPS), which consists of control module, PZT driving module, precision fast positioning mechanism (PFPM), and micro-displacement measure module. It provides fast and precise control in tilt and piston movements. The driving, mechanism and measure integrative model of the PPS is built. Due to the inherent hysteresis nonlinearity, the PZT actuator always causes positioning error in the open-loop operation and instability in the closed-loop operation. In order to improve the positioning accuracy and response speed, a control method for PZT actuator based on a PID feedback controller with a feedforward compensation is proposed. Finally, the tracking control experiments of piezoelectric actuators for a desired sinusoidal trajectory are performed according to the proposed control method. The experimental results demonstrate that the positioning precision is noticeably improved. The maximum error in tracking a sinusoidal signal is lowered about one order of magnitude in comparison with only using PID controller.

Commentary by Dr. Valentin Fuster
2008;():531-544. doi:10.1115/IMECE2008-66272.

Passive mounts/springs with negligible damping and low stiffness are highly effective in isolating vibration but have poor shock isolation characteristics. This and other contradictory traits of passive mounts, make the realization of an ideal, uncompromised isolation system unfeasible. To avoid an isolation system design based on a compromise among its conflicting requirements, a degree of real-time, on-demand adjustability should be built into the mounting system. Air springs/mounts, because of their inherent adjustability, are the best candidate for such adjustable isolation; other passive mounts, e.g. elastomeric, would require the introduction of an additional active element/actuator to work in parallel with the mount. In this proposed adjustable air mounting system, shock isolation can be enhanced without undermining the vibration isolation effectiveness by using an on-demand, active damping scheme which adds various levels of damping to an air mounted/suspension application, e.g., the cab in a truck, depending on the instantaneous urgency of shock isolation over vibration isolation. In addition, the proposed adjustable isolation scheme contains an on-demand, active stiffness control working in parallel with the active damping scheme. Depending on the operating conditions, the stiffness of the mount will be lowered to better its vibration isolation or increased to enhance its shock isolation. The active damping and stiffness control along with other on-demand adjustment tactics for an air isolation system are described, numerically examined, and experimentally demonstrated.

Topics: Damping , Stiffness
Commentary by Dr. Valentin Fuster
2008;():545-551. doi:10.1115/IMECE2008-66281.

Amphibious single wheel robot consists of a sharp-edged wheel actuated by a spinning flywheel for steering and a drive motor for propulsion. The spinning flywheel acts as a gyroscope to stabilize the robot and also can be tilted to achieve steering. In this paper, the kinematics of a single wheel robot in water, Gyrover, is analyzed and then a simple mechanism for driving it is proposed. In previous studies, Lagrange approach is used for hydrodynamic modeling of the robot. A nonlinear position controller is designed to bring the robot to any desired position. Based on the designed controller, a tracking controller is augmented to the robot. For simplicity the added mass effect has been neglected in hydrodynamic analysis. Since the robot under consideration is compact and slow enough, this assumption is not far from reality.

Commentary by Dr. Valentin Fuster
2008;():553-566. doi:10.1115/IMECE2008-66290.

Aerodynamic instabilities that will limit the operating range, performance, and reliability of gas turbine engines include rotating stall and surge. These aerodynamic instabilities occur in the compressor at low flow rates. Enabling technologies that have been used to demonstrate the stabilization of compression systems and operating range extension by means of active feedback control include the manipulation of compressor flow field with inlet guide vanes, bleed valves, and air injection. A potential application of the performance improvement associated with active feedback control is to reduce the weight of an aircraft engine. The number of compressor stages required to achieve the same overall pressure rise can be reduced by using active feedback control to extend the operating range of a compressor with steep speed-lines. And since the compressor makes up a large percent of the weight of an aircraft engine, reducing the number of compressor stages will reduce the engine weight thus increasing its thrust to weight ratio. This paper presents a full state nonlinear distributed model of rotating stall and surge with an air injection actuation system, a nonlinear controller design, and a closed loop simulation architecture that can be used for evaluating different control algorithms. The full state nonlinear distributed model was validated with stall inception data from a transonic compressor, and a sliding mode nonlinear controller was designed using the validated nonlinear distributed model. The closed loop simulation setup was then used to compare the performance of existing baseline linear controllers with the nonlinear controller model presented in this paper. The simulation results showed that more operation range extension can be obtained with robustness to compressor disturbances by using single-sided sliding mode control law.

Commentary by Dr. Valentin Fuster
2008;():567-573. doi:10.1115/IMECE2008-66321.

This paper presents an analytical study of the stability of the steady state solutions of a gene regulatory network with time delay. The system is modeled as a continuous network and takes the form of a nonlinear delay differential-integral equation coupled to an ordinary differential equation. Two examples are given in which the critical delay causing instability is computed.

Topics: Delays , Equations
Commentary by Dr. Valentin Fuster
2008;():575-581. doi:10.1115/IMECE2008-66355.

The Ionic polymer-metal composites (IPMCs) form an important category of electroactive polymers which generate large deformation under a low driving voltage. In this paper an empirical model of IPMC is developed by measuring the step response of a 23 mm×3.6 mm×0.16 mm IPMC strip in a cantilever configuration. Moreover, a model-based precision position control of an IPMC base on the fuzzy logic is presented. Open-loop position responses of an IPMC are not repeatable, and hence closed-loop precision control is of critical importance to ensure proper functioning, repeatability and reliability. A CCD camera was used to observe the closed loop response of the IPMC strip in order to control this electro-mechanical actuator experimentally. The IPMC actuator could follow various commanded position trajectories such as sinusoidal and square position profiles. The control architecture presented includes a fuzzy system whose structure and parameters were designed by trail-and-error beside a gain scheduled PID controller using fuzzy system. The performance of the IPMC strip is investigated and compared under these controllers.

Commentary by Dr. Valentin Fuster
2008;():583-588. doi:10.1115/IMECE2008-66405.

In this paper an adaptive axial force control for gun drilling of small drilling diameters is presented. The system is applicable to CNC drilling and gun drilling machine tools, which are equipped with a fast analog NC input and an axial force measurement system. An online identification algorithm discretely investigates the actual transfer function of the control path. Based on this information proper controller parameters are allocated. Experimental tests of the adaptive control system show the functionality in drilling a material transition from steel 100Cr6 into cast iron ADI 800 and exemplary illustrate the disturbance reaction, introduced by activated changes of the path behavior.

Commentary by Dr. Valentin Fuster
2008;():589-598. doi:10.1115/IMECE2008-66555.

The paper addresses one of the key problems in structural health monitoring — how to separate defects, both microscopic and macroscopic, accumulated in structural members from damage in the joints and boundaries. It is suggested to use a simultaneous set of measurements — nonlinear vibration frequencies and electrical conductivities — to distinguish between three distinct types of defects. Nonlinearities occur as a result of breathing internal cracks and slapping in damaged joints. The use of proper orthogonal decomposition and a local equivalent linear stiffness method allows for model updating to account for the damage. The theory is presented for full three-dimensional elastic solids and illustrated via the problem of a beam damaged both internally as well as at the boundaries.

Commentary by Dr. Valentin Fuster
2008;():599-602. doi:10.1115/IMECE2008-66582.

This dissertation mainly introduces Fuzzy-PID Control which are used in the PFPL (Pseudo-flexible Production Line). The servo system plays an important role in the NC machine. The performance of servo system decide the quality of NC machine in very great degree This dissertation research and develop a milling and paring manufacture unit of open CNC system – Numerical control unit of PFPL. By using the GT-SV motion controller, put up the software and hardware platform of NC unit rapidly with module design method and the target-oriented programming idea. Take NC milling machine as the process platform, this dissertation use intellectual PID control method to improve the servo control of motion controller, through the pointing accuracy survey of the milling machine, confirmed the actual effect of Fuzzy-PID control.

Commentary by Dr. Valentin Fuster
2008;():603-607. doi:10.1115/IMECE2008-66584.

The reduction of the Vehicle interior noise has been the main interest of NVH engineers. The driver’s perception on the vehicle noise is affected largely by psychoacoustic characteristic of the noise as well as the SPL. In particular, the HVAC sound among the vehicle interior noise has been reflected sensitively in the side of psychology. In previous study, we have developed to verify identification of source for the vehicle HVAC system through multiple-dimensional spectral analysis. Also we carried out objective assessments on the vehicle HVAC noises and subjective assessments have been already performed with 30 subjects. In this study, the linear regression models were obtained for the subjective evaluation and the sound quality metrics. The regression procedure also allows you to produce diagnostic statistics to evaluate the regression estimates including appropriation and accuracy. Appropriation of regression model is necessary to R2 value and F-value. And testing for regression model is necessary to Independence, Homoscedesticity and Normality. To enhance sound quality, we applied active noise control (ANC) which is effective in the low-frequency bandwidth. Primary noise of the HVAC system is less than 500Hz. As a result of ANC application, sound quality is improved by more quiet, powerful, expensive, smooth.

Commentary by Dr. Valentin Fuster
2008;():609-616. doi:10.1115/IMECE2008-66651.

As satellite on-orbit service operations become increasingly aggressive and complex (such as on-orbit refueling, rescuing, repairing, etc.), the need for identifying varied inertial properties of a satellite is becoming a critical task. The importance of this task stems from the dependence of spacecraft’s guidance, navigation and control system on these properties. In order to accurately control a spacecraft, its control system must be capable of fully identifying these properties as they change. Previous techniques use thruster firing or momentum wheels to accomplish this task. However a newly developed robotics based method requires measuring the spacecraft’s velocity changes only, which can be induced by an onboard robotic arm powered by solar energy. This paper gives a brief overview of this method and then focuses on the design of experimental verification of the method. The verification consists of a series of experiments including a simulated microgravity test onboard the NASA JSC Reduced Gravity aircraft in order to accurately simulate an environment similar to a flying satellite in orbit.

Topics: Robotics , Testing
Commentary by Dr. Valentin Fuster
2008;():617-628. doi:10.1115/IMECE2008-66664.

Advances in vehicle modeling and simulation in recent years have led to designs that are safer, easier to handle, and less sensitive to external factors. Yet, the potential of simulation is adversely impacted by its limited ability to predict vehicle dynamics in the presence of uncertainty. A commonly occurring source of uncertainty in vehicle dynamics is the road-tire friction interaction, typically represented through a spatially distributed stochastic friction coefficient. The importance of its variation becomes apparent on roads with ice patches, where if the stochastic attributes of the friction coefficient are correctly factored into real time dynamics simulation, robust control strategies could be designed to improve transportation safety. This work concentrates on correctly accounting in the nonlinear dynamics of a car model for the inherent uncertainty in friction coefficient distribution at the road/tire interface. The outcome of this effort is the ability to quantify the effect of input uncertainty on a vehicle’s trajectory and the associated escalation of risk in driving. By using a space-dependent Gaussian process, the statistical representation of the friction coefficient allows for consistent space dependence of randomness. The approach proposed allows for the incorporation of noise in the observed data and a nonzero mean for inhomogeneous distribution of the friction coefficient. Based on the statistical model considered, consistent friction coefficient sample distributions are generated over large spatial domains of interest. These samples are subsequently used to compute and characterize the statistics associated with the dynamics of a nonlinear vehicle model. The information concerning the state of the road and thus the friction coefficient is assumed available (measured) at a limited number of points by some sensing device that has a relatively homogeneous noise field (satellite picture or ground sensors, for instance). The methodology proposed can be modified to incorporate information that is sensed by each individual car as it advances along its trajectory.

Commentary by Dr. Valentin Fuster
2008;():629-636. doi:10.1115/IMECE2008-66815.

Zero dynamics of a helicopter system is modeled in this study with respect to the control point’s tracking path. The derivation is comprehensive and has been done for the most general flying maneuvers. The approach is based on a six Degree of Freedom (DoF) model of the helicopter’s body, the configuration of the aerodynamic traction, and the geometrical and inertial parameters of the helicopter. Considering the vast grows in the field of Autonomous Aerial Vehicle (UAV), this study can be utilized both for improving the design parameters of an aerial platform, deriving the feasible maneuvering scenarios and working regimes for available systems. Also, the study provides a platform to test the performance and stability of the control strategies for autonomous helicopter systems and other aerial vehicles.

Commentary by Dr. Valentin Fuster
2008;():637-645. doi:10.1115/IMECE2008-66821.

In this article, investigations into the nonlinear asymmetric vibrations of a pressure sensor diaphragm under initial tension are presented. A comprehensive mechanics model based on a plate with in-plane tension is presented and the effect of cubic nonlinearity is studied on the nonlinear asymmetric response when the excitation frequency is close to the natural frequency of an asymmetric mode of the plate. The obtained results show that in the presence of an internal resonance, depending on the initial tension, the response can have not only the form of a standing wave but also the form of a traveling wave. The results of this work should be relevant to diaphragm-type structures used in micro-scale sensors including pressure sensors.

Commentary by Dr. Valentin Fuster
2008;():647-653. doi:10.1115/IMECE2008-66937.

This paper presents a noise reduction technique for vibration signal analysis in rolling bearings, based on local geometric projection (LGP). LGP is a non-linear filtering technique that reconstructs one dimensional time series in a high-dimensional phase space using time-delayed coordinates, based on the Takens embedding theorem. From the neighborhood of each point in the phase space, where a neighbor is defined as a local subspace of the whole phase space, the best subspace to which the point will be orthogonally projected is identified. Since the signal subspace is formed by the most significant eigen-directions of the neighborhood, while the less significant ones define the noise subspace, the noise can be reduced by converting the points onto the subspace spanned by those significant eigen-directions back to a new, one-dimensional time series. Improvement on signal-to-noise ratio enabled by LGP is first evaluated using a chaotic system and an analytically formulated synthetic signal. Then analysis of bearing vibration signals is carried out as a case study. The LGP-based technique is shown to be effective in reducing noise and enhancing extraction of weak, defect-related features, as manifested by the multifractal spectrum from the signal.

Commentary by Dr. Valentin Fuster
2008;():655-664. doi:10.1115/IMECE2008-66960.

We consider a four dimensional Hamiltonian system representing the reduced-order (two-mode) dynamics of a buckled beam. The system has a saddle-center equilibrium point, and we pay attention to the existence and detection of the stable-unstable nonlinear manifold and of homoclinic solutions, which are the sources of complex and chaotic dynamics observed in the system response. The system has also a coupling nonlinear parameter, which depends on the boundary conditions, and is zero, e.g., for the hinged-hinged beam and different from zero, e.g., for the fixed-fixed beam. The invariant manifold in the latter case is detected assuming that it can be represented as a graph over the plane spanned by the unstable (principal) variable and its velocity. We show by a series solution that the manifold exists but has a limited extension, not sufficient for the deployment of the homoclinic orbit. Thus, the homoclinic orbit is addressed directly, irrespective of its belonging to the invariant manifold. By means of the perturbation method it is shown that it exists only on some curves of the governing parameters space, which branch from a fundamental path. This shows that the homoclinic orbit is not generic. These results have been confirmed by numerical simulations and by a different analytical technique.

Commentary by Dr. Valentin Fuster
2008;():665-672. doi:10.1115/IMECE2008-66997.

A parallel combination of oil cycle and fossil fuel boiler is utilized in the integrated solar power plant (ISPP) to achieve better efficiency and reduce cost of electricity generation. There are two cycles, oil and steam, in an ISPP. To enhance performance and achieve control optimization more precise simulation for power plant dynamics are needed. In this paper, a dynamic simulation of an ISPP was developed using the HYSYS software. To enhance efficiency and reduce damage to turbine due to flow rate variations of produced steam by oil cycle, the prime control requirement is to maintain the inlet steam temperature and flow rate of the turbine at a constant value. In this paper, to control the complete oil cycle, two fuzzy controllers are proposed: continuous controller and a switching controller. In steam cycle three controllers are proposed for boiler and reboiler heat exchanger. These controllers are used to maintain constant the inlet steam temperature and flow rate to turbine. Simulation results of the integrated solar power plant and the control systems show that the applied control systems can manage the oil and steam cycles in different situations.

Commentary by Dr. Valentin Fuster
2008;():673-682. doi:10.1115/IMECE2008-67109.

This study applies a discontinuous systems theory by Luo (2005) to an approximate machine-tool model. The machine-tool is modeled by a two-degree of freedom forced switching oscillator. The switching of the model emulates the various types of dynamics in a machine-tool system. The main focus of this study is the loss of effective chip contact and boundaries of this motion. The periodic motions will be studied through the mappings developed for this machine-tool. The periodic motions will be numerically and analytically predicted via closed form solutions. The phase trajectory, velocity, and force responses are presented.

Topics: Machine tools , Motion
Commentary by Dr. Valentin Fuster
2008;():683-689. doi:10.1115/IMECE2008-67131.

This paper discusses the enhancement of gripping efficiency of a gripping mechanism for miniature grippers. This gripping mechanism employs a displacement enlarging mechanism utilizing an elastic buckling of the flexible gripping fingers. Miniature grippers have been realized by the flexible gripping fingers acting as the displacement enlarging mechanism. However, there is a trade-off relation between the enlarged displacement and gripping force of the gripping mechanism. For this reason, the enhancement of gripping efficiency of the gripping mechanism has been experimentally attempted by constraining an elastic deformation of the flexible gripping fingers. The flexible gripping fingers are largely deformed due to elastic buckling after gripping an object. This elastic deformation is constrained by supports. Experiments have been conducted for some different cases of placement of the supports. The driving force, driving displacement and gripping force of the gripping mechanism have been measured. From experimental results, it has been confirmed that the enhancement of gripping efficiency of the gripping mechanism is feasible by controlling deformation of the flexible fingers passively.

Commentary by Dr. Valentin Fuster
2008;():691-697. doi:10.1115/IMECE2008-67146.

In this paper, H∞ identification is performed in frequency domain for the longitudinal pitch and speed channels of a commercial Boeing 747 transport aircraft flying at a particular flight condition. The plant (i.e. the longitudinal pitch and speed transfer functions) to be identified is a causal, bounded-input/bounded-output (BIBO) stable, single-input/single-output (SISO), linear time-invariant (LTI) discrete-time system. The frequency response data is generated by simulation of the plant transfer functions and is corrupted by unknown but bounded measurement noise. An identification algorithm is used to map the experimental data into an identified model such that the worst case identification error converges in a particular sense. In this paper, untuned linear algorithm and two-stage nonlinear algorithm are used respectively for computing the identified models for the pitch and speed transfer function of the aircraft. Different window sequence (rectangular, triangular, traperzoidal, etc.) are used in these algorithms. The error response and worst case error bound computed by these two algorithms are also compared. The paper demonstrates the effectiveness of the two algorithms for computing the identified model. Unlike classical identification which is inadequate for robust control, the results of H∞ identification can be used for designing the H∞ robust controllers.

Commentary by Dr. Valentin Fuster
2008;():699-705. doi:10.1115/IMECE2008-67473.

Invariant manifolds provide important information about the structure of flows. When basins of attraction are present, the stable invariant manifold serves as the boundary between these basins. Thus, in experimental applications such as vibrations problems, knowledge of these manifolds is essential to understanding the evolution of phase space trajectories. Most existing methods for identifying invariant manifolds of a flow rely on knowledge of the flow field. However, in experimental applications only knowledge of phase space trajectories is available. We provide modifications to several existing invariant manifold detection methods which enables them to deal with trajectory only data, as well as introduce a new method based on the concept of phase space warping. The method of Stochastic Interrogation applied to the damped, driven Duffing equation is used to generate our data set. The result is a set of trajectory data which randomly populates a phase space. Manifolds are detected from this data set using several different methods. First is a variation on manifold “growing,” and is based on distance of closest approach to a hyperbolic trajectory with “saddle like behavior.” Second, three stretching based schemes are considered. One considers the divergence of trajectory pairs, another quantifies the deformation of a nearest neighbor cloud, and the last uses flow fields calculated from the trajectory data. Finally, the new phase space warping method is introduced. This method takes advantage of the shifting (warping) experienced by a phase space as the parameters of the system are slightly varied. This results in a shift of the invariant manifolds. The region spanned by this shift, provides a means to identify the invariant manifolds. Results show that this method gives superior detection and is robust with respect to the amount of data.

Commentary by Dr. Valentin Fuster
2008;():707-717. doi:10.1115/IMECE2008-67498.

In this work, the nonlinear coupled dynamics of a sandwich structure with hexagonal honeycomb core are characterized in terms of Proper Orthogonal Decomposition modes. A high fidelity nonlinear finite element model is derived to describe geometric nonlinearity and displacement and rotation fields that govern the coupled dynamics. Contrary to equivalent continuum models used to predict vibration properties of lattice and sandwich structures, a high fidelity finite element model allows for a quite detailed description of the distributed complicated geometric nonlinearity of the core. It was found that the free dynamics excited by a blast load and the forced dynamics excited by a harmonic force posses POD modes which are localized in space and time. The processing of the simulated dynamics by the Time Discrete Proper Transform forms a means to study the nonlinear coupled dynamics of sandwich structures in the context of nonlinear normal modes of vibration and reduced order models.

Commentary by Dr. Valentin Fuster
2008;():719-724. doi:10.1115/IMECE2008-67727.

Subharmonic resonances of nonlinear forced bending vibrations in the case of moderately large curvature of nonuniform cantilever beams of rectangular cross section and a sharp end are reported. Cantilevers of constant width and parabolic thickness variation are considered in this research. The method of multiple scales is directly applied to the governing partial-differential equation of motion and boundary conditions. Two problems, zeroth- and first-order, result. Using factorization method, the linear modes of the zeroth-order problem are obtained in terms of hypergeometric functions. The first-order problem provides the amplitude and phase evolution equation and consequently the regions where subharmonic responses exist.

Topics: Vibration
Commentary by Dr. Valentin Fuster
2008;():725-734. doi:10.1115/IMECE2008-68122.

The contact problems between the rigid conductor line and the pantograph in a current railway system are studied from the viewpoint of nonlinear dynamics. It is assumed that there are impact oscillations between the rigid conductor line and the pantograph under the state of contact loss. The rigid conductor line pantograph system is modeled with a spring-supported beam excited by an oscillating body. First, we approached as an impact problem and theoretically examined by using this model. As a result, periodical impact oscillations were shown in low moving velocities of body. Second, we employed the method of mapping to clarify impact problems, and we obtained the relationship of the state of the system at the arbitrary impact to that at the next impact. Finally, the experiments are conducted with the simple experimental model using dimensionless parameters which are equal to the one of the analytical model.

Commentary by Dr. Valentin Fuster
2008;():735-742. doi:10.1115/IMECE2008-68226.

In this research, primarily designing and manufacturing of Double Acting Pick and Place robot (DAP) mechanism, along with its kinematic and dynamic analysis aiming at elimination of human force usage in contaminated industrial environment such as coating process shops is introduced and analyzed. Simulations of the robot’s movement and control procedure via nonlinear adaptive-robust and inverse dynamic controllers are applied in order to overcome to their uncertainties. The main function of this robot is coating epoxy powder on “Hawel” gate valves at temperatures up to 200°C. The results obtained in this study can greatly fulfill the need to resolve industrial uncertainties in such combinational processes.

Commentary by Dr. Valentin Fuster
2008;():743-748. doi:10.1115/IMECE2008-68401.

A FLOATING bush bearing is a kind of bearing which has a thin bush floating freely between journal and fixed bush. In recent years considerable attention has been paid to the “vibration suppressing effect” of floating us bearing. It is reported that floating bush bearing are, if properly designed, effective in suppressing both resonant vibrations at the critical speed and self excited vibration call oil whip. This study deal with performance of dynamically loaded floating ring journal bearing and investigates their feasibility for two for one textile machine application. A mathematical model is developed and its analysis for performance of floating bush journal bearing with flexible shat in flexible anisotropic bearing is conducted. The potential contribution of the floating bush journal bearing design concept to reduce vibration is assessed and its compliance with current bearing durability criteria is evaluated. The result indicates that the adoption of floating bush design concept has potential for reducing power loss and vibration in two for one (TFO) textile machine bearing. It is shown that this can be accomplished without violating minimum film thickness constraints currently accepted as criteria for successful machine bearing operation.

Topics: Textiles , Bearings
Commentary by Dr. Valentin Fuster
2008;():749-755. doi:10.1115/IMECE2008-68497.

Torsional instabilities in a single-degree-of-freedom system having variable inertia are investigated by means of Lyapunov exponents. Linearised analytical model is used for the purpose of stability analysis. Numerical schemes for simulating the top Lyapunov exponent for both deterministic and stochastic systems are established. Instabilities associated with the primary and the secondary sub-harmonic resonances have been identified by studying the sign of the top Lyapunov exponent. Predictions for the deterministic and the stochastic cases are compared. Instability conditions have been presented graphically in the excitation frequency-excitation amplitude-top Lyapunov exponent space. The effects of fluctuation density as well as that of damping on the stability behaviour of the system have been examined. Predicted instability conditions are adequate for the design of a variable-inertia system so that a range of critical speeds of operation may be avoided.

Commentary by Dr. Valentin Fuster
2008;():757-765. doi:10.1115/IMECE2008-68567.

An algorithm is developed that generates statistically optimal flight trajectory to a best landing site after occurrence of an in-flight distress condition using an abort probability model. The approach developed increases overall survivability by minimizing the expected flight path distance, given the abort probability model. An airport grouping strategy that clumps the airports logically prior to path derivation is also developed. The performance of this newly developed probabilistic trajectory algorithm is evaluated using numerical simulations that include variable failure rates to simulate different in-flight distress conditions, and multiple turns to accommodate realistic trajectories. The results show that it is possible by using this algorithm to increase aircraft survivability.

Commentary by Dr. Valentin Fuster
2008;():767-774. doi:10.1115/IMECE2008-68571.

This work describes the development and analysis of nonlinear adaptive based control algorithms for composite structures/systems operated with Shape Memory Alloy (SMA) actuators. A mathematical model charactering the motion of the composite systems is established, and by using Lyapunov stability theory, algorithms for linear displacement tracking control are derived. Actuation and control is achieved by adjusting the supply current to the SMA actuators. It is shown that with the proposed strategy for both linear displacement and velocity requires that the desired trajectory is tracked precisely. The novelty of the proposed approach also lies in the fact that it is fairly easy to set up and the computation involved as compared with other strategies. An example is used to verify the validity of the proposed approach. Simulation results using Matlab are presented.

Commentary by Dr. Valentin Fuster
2008;():775-784. doi:10.1115/IMECE2008-68766.

This paper provides the design of a simple robotic arm for pick and place operations as well as other material handling operations. The movements of the arm are anthropometric i.e. resembling the human arm with respect to degrees of freedom so as to provide a human touch in industrial and space operations. This system operates using controlled motion of DC geared motors along with a microcontroller based system (8051 or PIC based). Use of PWM (Pulse Width Modulation) can be used to control the RPM of DC geared motors. This system has the advantage of being simple and low cost with a varied flexibility of operation. A collective array of sensors viz. voice sensor, infrared light sensors, proximity sensors etc. can be incorporated to form a feedback induced closed loop system. Whereas for tasks of picking and placing at a fixed location from another location the system can be operational at open-loop. The material for the robotic arm can be polypropylene or acrylic or aluminium to reduce weight without compromising on the strength and lifting capacity of the robotic arm, such that the torque of the DC geared motors (actuators) at each joint are sufficient to lift the arm along with the weight at the end effector. Clutch and gear shifting mechanism can be used to increase the degrees of freedom per actuator. The driving circuit mainly consists of the microcontroller and H-bridge drivers using an 8-bit port to control 4 DC geared motors per port simultaneously or one at a time using delay commands. DC geared motors are quite cheaper than stepper motors and RC Servos thus reducing the total cost of the system drastically. Plus being light weight, DC geared motors reduce the total weight of the system. This paper will also throw light on the programming aspects for the microcontroller (8051 or PIC based) along with the compatible flash programmers and HEX code generators. This project will further explain on the approach followed in the mechanical design of the robotic arm (motion, work volume etc.) as well as the possible future applications of the robotic arm. Also the design of the robotic arm on CAD tools like Solidworks will be discussed in brief along with the modeling and simulation of the various links of the arm as well as the whole assembly of the system. With increasing popularity of Automation, robotic arms are the present and future of all industrial operations. Finally the paper concludes on the further improvements in design and technology.

Topics: Motors , Design , Robotics , Delays
Commentary by Dr. Valentin Fuster
2008;():785-790. doi:10.1115/IMECE2008-68886.

With daily growth of using microcantilevers in microelectromechanical systems, comprehensive analysis on their dynamical behavior is necessary since they are mostly utilized as the main sensing device. In this paper, the out-of-plane vibrations of the piezoelectrically actuated microcantilever are experimentally investigated. The microcantilever is covered with a piezoelectric layer on its top surface through which it can be excited by applying the voltage to the piezoelectric actuator. The nonlinear frequency response of the microcantilever is studied and shift in natural frequency due to nonlinearity is examined. By observing the subharmonics of the fundamental frequencies at 2X and 3X, it is experimentally shown that there exist cubic and quadratic nonlinearities in the microcantilever. A mathematical model based on these experimental tests is then proposed and verified. The out-of-plane measurements provide the ability to observe both transversal and torsional modes. In addition, the modes in which the microcantilever acts like a plate are observed.

Commentary by Dr. Valentin Fuster
2008;():791-798. doi:10.1115/IMECE2008-68974.

This paper presents an investigation into the nonlinear dynamics of a carbon nanotube (CNT) actuated electrically by a DC force and an AC harmonic load. The CNT is described by an Euler Bernoulli beam model that accounts for the system nonlinearities due to mid-plane stretching and electrostatic forcing. A reduced-order model based on the Galerkin method is developed and utilized to simulate the static and dynamic response of the CNT. The static deflection of the CNT and its pull-in voltage are calculated and validated by comparing them to published results. It was found that mid-plane stretching has a major impact on the pull-in prediction of CNT. Dynamic analysis is conducted to explore the nonlinear oscillation of the CNT near its fundamental natural frequency (primary resonance) and near one half, twice, and three times its natural frequency (secondary resonances). The nonlinear analysis is carried out using a shooting technique combined with the Floquet theory to capture periodic orbits and analyze their stability. The results show that these resonances can lead to complex nonlinear dynamics phenomena such as hysteresis, dynamic pull-in, hardening and softening behaviors, and frequencies bands with an inevitable escape from a potential well.

Commentary by Dr. Valentin Fuster
2008;():799-805. doi:10.1115/IMECE2008-69104.

This paper presents an optimal algorithm to enhance the performance of an On-demand All Wheel Drive (ODAWD) vehicle by traction improvement through regulation of wheel slip. A “Minimum Fuel Problem” is developed with a cost function minimizing the slip error and the control action which is the ratio of the torque transmitted to the non driven wheels (rear wheels) to the total torque from engine. A simplified vehicle model (bicycle model) is used for the derivation and the system produces a Two Point Boundary Value Problem (TPBVP) once the Hamiltonian is formed and Pontryagin minimum Principle is used. An iterative algorithm based on the “Shooting Method” is then used to arrive at the optimal control action. The proposed controller optimally reduces the wheel slip error by engaging and dynamically controlling a hydraulic clutch which transmits the optimal torque to the rear wheels, thus reducing the vehicle longitudinal slip and enhancing vehicle traction. The controller was simulated in two phases where the first phase was an open loop simulation for a desired vehicle speed profile and the second phase, a closed loop system where the controller was integrated on a validated 14 degree-of-freedom detailed vehicle model in SIMULINK. The two phased simulation results provide high promise of the controller performance on low friction coefficient surfaces with enhanced traction and reduced vehicle longitudinal slip in an acceleration event.

Commentary by Dr. Valentin Fuster
2008;():807-814. doi:10.1115/IMECE2008-69247.

XY-positioning is an important task in industrial applications. The improvement of the speed of positioning while keeping good accuracy can increase productivity and is therefore highly desirable. The studied H-frame system is a parallel XY-positioning device that uses a timing belt to transmit motion from two stationary motors. As a result, the system is capable of fast acceleration due to lower number of moving parts. However, the flexibility of the timing belts poses a problem when trying to move the positioning system at high speed. A dynamic model of the H-Frame system that accounts for the non-linear friction present in the system was developed and verified experimentally. This model was further used in simulation to develop a controller for the system. A collocated PD controller with friction compensation was designed and implemented experimentally on the system. Furthermore, results of the previous controller were compared to an adaptive PD controller. The adaptation algorithm involves changing the controller gains as a function of the tracking error without sacrificing the stability of the system. It was found that the adaptive PD controller is more suitable for positioning applications.

Commentary by Dr. Valentin Fuster
2008;():817-826. doi:10.1115/IMECE2008-66008.

Rotorcraft dynamics represents a major analytical challenge to aeronautical industry and research centres. Complexities arising from large rigid motions, body elasticity, aerodynamic loads and control systems have to be taken into account in order to ensure the accuracy of a comprehensive analysis. Architected for the nonlinearities associated with large motion in three-dimensional space, the ADAMS general-purpose multibody code allows to automatically formulate and integrate the equations of motion for a wide range of mechanisms, including rotary wing systems (once provided with an aerodynamic force field description). However, the ADAMS simulation system lacks the capability to calculate periodic motions, as required in the helicopter trim analysis and stability evaluation. The prediction of the trimmed periodic motions of the rotor system implies the numerical solution of differential-algebraic boundary value problem. In this work we present a new approach to perform this task inside the ADAMS numerical environment. Thia approach is based on the perturbation of the minimal set of Ordinary Differential Equations (ODEs), being equivalent to the original system of Differential Algebraic Equations (DAEs) which defines the rotorcraft equation of motion. The transformation of DAEs to ODEs is based on the linearization of the local constraint manifold defined by the algebraic constraint equations, as suggested by Maggi in his work [1–3]. The proposed method is quite general and can be used to drive the ADAMS integration scheme within the periodic motion analysis of mechanical systems. The algotithm is adopted to simulate the wind tunnel trim test of a ECD BO105 machscaled model (EU HeliNOVI project [4]). Comparisons between numerical and experimental results are provided.

Commentary by Dr. Valentin Fuster
2008;():827-831. doi:10.1115/IMECE2008-66041.

Among the irregular responses of nonlinear dynamic systems, chaotic responses of nonlinear systems are probably the most attractive phenomena along with the new observations in the last decades. A nonlinear deterministic system may behavior chaotically under regular such as periodic excitations. Regular motion of a system subjected to periodic exertions is usually periodic. In contrast with regular motions, final states of chaotic vibrations are extremely nonperiodic. This research is to analyzing the irregular behavior of dynamic systems with implementation of a newly developed criterion named Periodicity-Ratio. The development of a methodology for diagnosing the irregular motions from the regular motions of a dynamic system is presented. The Periodicity-Ratio describes the degree of periodicity of motion and can be conveniently used to distinguish a nonperiodic motion from a regular vibration or oscillation and to diagnose whether or not a motion is chaotic and the other irregular responses of the nonlinear dynamic systems, without plotting any figures. The analyses on the irregular behavior of nonlinear dynamic systems with the implementation of the Periodicity-Ratio will be demonstrated.

Commentary by Dr. Valentin Fuster
2008;():833-840. doi:10.1115/IMECE2008-66088.

Conventional nonadjustable four-bar linkages can only generate the desired continuous paths approximately. With one link length adjustment, the whole desired continuous path can be generated precisely. In this paper, the length of the driven side link or coupler is adjusted to generate the desired continuous paths precisely. The linkage feasibility conditions and path generation flexibilities of the adjustable four-bar linkages are analyzed. The optimal synthesis model of adjustable four-bar linkages is established based on the required optimal link length adjustment when the desired continuous path is precisely generated. The global optimal solution is searched by a real-valued genetic algorithm in which the involved constraints are handled using the function penalty method. The effectiveness of the optimal synthesis approach proposed in the paper is verified by the demonstrated examples.

Topics: Linkages
Commentary by Dr. Valentin Fuster
2008;():841-851. doi:10.1115/IMECE2008-66127.

This paper presents an analysis on the nonlinear dynamics and multi-pulse chaotic motions of a simply-supported symmetric cross-ply composite laminated rectangular thin plate with the parametric and forcing excitations. Firstly, based on the Reddy’s three-order shear deformation plate theory and the model of the von Karman type geometric nonlinearity, the nonlinear governing partial differential equations of motion for the composite laminated rectangular thin plate are derived by using the Hamilton’s principle. Then, using the second-order Galerkin discretization approach, the partial differential governing equations of motion are transformed to nonlinear ordinary differential equations. The case of the primary parametric resonance and 1:1 internal resonance is considered. Four-dimensional averaged equation is obtained by using the method of multiple scales. From the averaged equation obtained here, the theory of normal form is used to give the explicit expressions of normal form. Based on normal form, the energy phase method is utilized to analyze the global bifurcations and multi-pulse chaotic dynamics of the composite laminated rectangular thin plate. The results obtained above illustrate the existence of the chaos for the Smale horseshoe sense in a parametrical and forcing excited composite laminated thin plate. The chaotic motions of the composite laminated rectangular thin plate are also found by using numerical simulation. The results of numerical simulation also indicate that there exist different shapes of the multi-pulse chaotic motions for the composite laminated rectangular thin plate.

Commentary by Dr. Valentin Fuster
2008;():853-859. doi:10.1115/IMECE2008-66133.

Because of errors in the geometric parameters of the parallel robots, it is necessary to calibrate them to improve the positioning accuracy for accurate task performance. Traditionally, to perform system calibration, one needs to measure a number of robot poses using an external measuring device. However, this process is often time-consuming, expensive and difficult for robot on-line calibration. In this paper, a methodical way of self-calibrating of Hexaglide parallel robot is introduced. This method is performable only by measuring input joint variables and errors of positioning relative to the desired position in some sets of configurations where in each set the desired position is fixed, but orientations of the moving platform are different. In this method, measurements are relative, so it is performable by using a simple measurement device. Simulations give us an idea about the number of desired points, the number of orientations in each point and the effect of noise on the calibration accuracy.

Commentary by Dr. Valentin Fuster
2008;():861-867. doi:10.1115/IMECE2008-66162.

In the application of parallel robots, it is necessary to calibrate the geometric parameters and improve the positioning accuracy for accurate task performance. Traditionally, to perform system calibration, one needs to measure a number of robot poses using an external measuring device. However, this process is often time-consuming, expensive and difficult for robot on-line calibration. In this paper, a methodical way of self-calibrating of Hexaglide parallel robot is introduced. This method is performable only by measuring input joint variables in some sets of configurations where in each set center of the end-effector is fixed, but orientations are different. Simulations give us an idea about the number of points that must be measured, the number of orientations in each point and the effect of noise on the calibration accuracy.

Commentary by Dr. Valentin Fuster
2008;():869-872. doi:10.1115/IMECE2008-66264.

This paper deals with the problem of the waveform distortion in the output of a bistable stochastic resonance system. The waveform recovery formula is proposed by observing the movement track of a particle in the bistable system and the suggested recovery system. The recovery mechanism and rules with and without noise are revealed. Moreover, a novel explanation about pulse distortion caused by the particle’s transitions occurring at the wells’ inflexions is put forward. Under the stochastic influence of the noise in subthreshold stochastic resonance, we develop a method via cascaded-bistable stochastic resonance and the recovery system with tuned system parameters to restore the output waveform. The numerical simulation has presented that it can recover the waveform containing weak information submerged in noise effectively. The method is applicable to both periodic and aperiodic signals.

Topics: Resonance , Signals
Commentary by Dr. Valentin Fuster
2008;():873-877. doi:10.1115/IMECE2008-66265.

Bistable stochastic resonance (BSR) can change the image signal’s histogram distribution. In this paper, the influence of bistable system parameters on the contrast of the output image is investigated through the observation of histograms. An image-processing method of BSR via tuning parameters is proposed. The experiment on the treatment of an image plus noise has proved that it can improve the quality of the image effectively.

Commentary by Dr. Valentin Fuster
2008;():879-886. doi:10.1115/IMECE2008-66328.

Parallel manipulators are closed-loop multi-degree-of-freedom linkages, which have the merits of high stiffness, load-bearing, operation speed and precision positioning capabilities that are required in many industrial applications. The main challenges for parallel manipulators are the limited workspace and singularity-free path generation capability. This paper is focused on the singularity-free path generation of five-bar double-slider two-DOF parallel manipulators. The linkage feasibility conditions are derived based on the elimination of dead point position within the workspace. The workspace is generated using the curve-enveloping theory. The singularity characteristics and linkage configurations are presented. The singularity-free path generation capability is analyzed. The performance index contours within the workspace are produced using the condition number of the manipulator Jacobian matrix. This paper shows that five-bar double-slider two-DOF parallel manipulators can be used as effective singularity-free path generators if properly designed. The results of this paper provide a useful map for the proper design of this type of parallel manipulator.

Topics: Manipulators
Commentary by Dr. Valentin Fuster
2008;():887-892. doi:10.1115/IMECE2008-66393.

Advances in electronic and consumer technology are increasing the need for smaller, more efficient energy sources. Thus vibration-based energy harvesting, the scavenging of energy from existing ambient vibration sources and its conversion to useful electrical power, is becoming an increasingly attractive alternative to traditional power sources such as batteries. Energy harvesting devices have been developed based on a number of electro-mechanical coupling mechanisms and their design must be optimized to produce the maximum output for given environmental conditions. While the role of nonlinearities in the components has been shown to be significant in terms of the overall device efficiency, few studies have systematically investigated their influence on the system performance. In this work the role of a nonlinear piezoelectric relationship is considered on the performance of a vibration-based energy harvester. Using a Poincaré-Lindstedt perturbation analysis the response of the harvesting system is approximated, including mechanical damping, stiffness nonlinearities, and the above mentioned nonlinear piezoelectric constitutive relationship. The predicted behavior is then compared against numerical simulations of the original system, focusing on the relationship between the power generated by the device, the ambient vibration characteristics, and the nonlinearities in the system.

Commentary by Dr. Valentin Fuster
2008;():893-901. doi:10.1115/IMECE2008-66521.

Optimal control schemes are usually employed to minimize different performance criteria of active suspension system of a vehicle such as, ride comfort and road safety. These factors are usually combined into a single quantity using proper weighting parameters that depend on the designer’s preferences. Generally, the selection of these weighting parameters is based on trial and error, which can be a time-consuming and computationally-intensive process. This paper proposes the use of an approach based on nested optimization loops to automate the selection process of these weighting parameters. The objective of the inner optimization loop is to minimize of the quadratic performance index associated with the original active suspension problem while the objective of the outer optimization loop is to minimize driver’s acceleration, for ride comfort, while maintaining both tire deflection and suspension deflection within acceptable limits. The design variables are the weighting parameters associated with the quadratic performance index used in the optimal control of active suspension. A modified form of Hooke-Jeeves algorithm is used to handle this problem while the penalty function method is used to handle the constraints. Simulation results show that this approach can improve the design process for active suspension of vehicles.

Commentary by Dr. Valentin Fuster
2008;():903-907. doi:10.1115/IMECE2008-66558.

This research focuses on the optimal design of the transformer oil tank shield of an electrical locomotive which has the operating speed of 160km/h. The analysis of 3-D eddy current loss in the magnetic leakage field of the tank shield is performed in the research. The optimization of the three-dimensional geometry of the tank shield is also carried out. Based on the analysis of 3-D eddy current loss in the magnetic leakage field of the tank of the main transformer for 200km/h electrical locomotive, an optimal model of the tank shield of the transformer is developed and optimized by using the algorithm of sub-problem approach. The research results show that it is efficient to combine the optimized algorithm with the FEM analysis in optimizing the design of electromagnetic equipment.

Commentary by Dr. Valentin Fuster
2008;():909-914. doi:10.1115/IMECE2008-66560.

Porous pavement materials such as asphalt rubber concrete (ARC) have attracted attentions from the researchers and practitioners in road science in the recent years due to their durability and environmental advantages. The porous pavements also show advantages in traffic noise reduction. This research concentrates on an investigation of the effects of the permeability of porous and other pavement materials on the response of the noise generated by the interaction between tire and the pavement surface. Experimental tests are carried out in the field to acquire tire/road noise data for difference pavement materials with implementation of the Close-Proximity CPX method. Lab experiments are performed for examining the permeability of the pavement materials. Empirical relationship between the noise level and permeability of the pavement materials is established. Comparison for the responses of the pavement materials with different permeability is also presented. The research results provide guidance for optimal design of the microstructure of porous pavements to be used for reducing traffic noise.

Commentary by Dr. Valentin Fuster
2008;():915-919. doi:10.1115/IMECE2008-66609.

It is shown in the present paper, on the basis of numerical simulations, that in some Hamiltonian systems with two degrees of freedom the transition to chaos takes place not through the destruction of two-dimensional tori of the unperturbed system in accordance with the Kolmogorov-Arnold-Moser (KAM) theory but, on the contrary, through the generation of complicated two-dimensional tori around cycles of the approximating expanded nonlinear dissipative system and through an infinite cascades of bifurcations of generation of new cycles and singular trajectories in accordance with the universal Feigenbaum-Sharkovskii-Magnitskii (FSM) theory developed initially for dissipative nonlinear systems.

Commentary by Dr. Valentin Fuster
2008;():921-926. doi:10.1115/IMECE2008-66811.

Micromachined beams are widely used as resonant structures. The electrostatic interdigitated comb-drives are commonly utilized for exciting/detecting the vibration of these resonators. Recent investigations into the analytical model of the resonator have shown that the added mass due to the comb-drive not only alters the natural frequencies of the resonator, but also changes the mode shapes of vibration. In this paper, the analytical model is extended to include the nonlinear effects due to the stretching of the beam. The generalized orthogonality condition along with the method of assumed-modes summation and the method of multiple scales has been used to study the primary and internal resonance of micro-beam resonators.

Commentary by Dr. Valentin Fuster
2008;():927-939. doi:10.1115/IMECE2008-66849.

The lateral force created by a tire necessary for a vehicle to change direction is generated by slip and camber angles. Camber angle may be defined as the angle between a vertical line passing through a wheels’ center and the horizontal projection of this line onto the wheel. If the axis which the tire turns about is not parallel to the vertical axis, a change in camber will be induced as a result of the change in steer angle. This axis is called the steering axis and can be determined by the caster and lean angles relative to the wheel position in a body coordinate frame. The relation between the steer and camber angles may favor or detract from the lateral force being generated by the tire. This paper describes a method for determining the induced camber angle with respect to steer angle. In this method the wheel is defined throughout the steering range as a circle. The lowest point of the circle with respect to the global coordinate frame may then be defined via a method for determining maxima and minima. This point is then used to determine camber angle with respect to steer angle throughout the steering range. The lowest point of the tire may also be used in finding ride height and body roll due to change in steer angle. A sensitivity analysis reflects the suspension behavior for a variety of different suspension parameters. The relative difference between the induced steer angle about the steering axis and the actual steer angle with respect to the body coordinate frame are relevant in developing more accurate vehicle dynamics models.

Commentary by Dr. Valentin Fuster
2008;():941-947. doi:10.1115/IMECE2008-67100.

Recently, a remarkable shortening of the development and design period becomes possible by the development of CAE and the optimization technologies, and efficient improvement of design quality in the detailed design stage has been achieved. Nevertheless, it is thought that there is a limit to for this kind of improvement in the near future, no matter how much the upgrade of the detailed design stage will be attempted. Therefore, the technology requested in the next step should be a new approach that can improve the quality of design concept and the efficiency of the concept design processes. For the engineers to improve concept design efficiency, they are requested that they should have very good understanding about the physics of their objectives and special experience about know-how for forming the answers to a very complicated problems. Thus, it is necessary to know the complicated physical relation between the design factors and the evaluation characteristic values to upgrade the concept design stage. It is thought that it can make a further improvement on the efficiency of design process if the technique, which can help the engineers to grip this relation, is established. However, it is very difficult for the engineers to understand a real complicated problem by few experiences. There are a lot of reasons for this kind of problems. For example, there will be a various patterns of design factors that achieve the similar design results, if the design factors have strong interacting relation between each other. In this study, the authors proposed a design support method for extracting the relation between the design factors and the evaluation characteristic values by using the results obtained by simulation models, and it was applied to the vehicle design problems in considering the interaction among the multi-variables by using a hierarchical cluster analysis and a graphical model. It was shown that the results given by the proposed approach can help the engineers to find and understand the essence of the phenomena involved.

Topics: Design
Commentary by Dr. Valentin Fuster
2008;():949-954. doi:10.1115/IMECE2008-67200.

This paper addresses the application of the perturbation/correlation method to optimizing the torque output of internal combustion engines. This application was inspired by observations of the limitations in current techniques of the automotive performance tuning industry. The engine simulated is the Cooperative Fuel Research Engine, which is an industry standard testing engine. Issues such as selection of parameter perturbation frequency and amplitude are addressed as well their effect on input parameter stability. Based on these parameters, a basis for correlation multiplication terms will be chosen. Performance issues to take into consideration are errors from true optimum spark timing and fuel injector pulse width values as well as convergence. The ability of the system to deal with engine cycle to cycle variations and its effect on input parameters is also analyzed.

Commentary by Dr. Valentin Fuster
2008;():955-964. doi:10.1115/IMECE2008-67319.

The paper presents a gradient-based numerical algorithm for optimal control of nonlinear multivariable systems with control and state vectors constraints. The algorithm has a backward-in-time recurrent structure similar to the backpropagation-through-time (BPTT) algorithm, which is mostly used as a learning algorithm for dynamic neural networks. This paper presents an enhancement of the basic optimization algorithm. Our enhanced algorithm uses high-order Adams time-discretization schemes instead of the basic Euler discretization method, and a numerical calculation of Jacobians as an alternative to analytical Jacobians. Two examples are considered to illustrate the algorithm and its performance. The first example is that of a tubular reactor, for which an analytical solution is available, which can be readily used for validation of our approach. The second example is related to controlling vehicle dynamics based on a realistic high order model.

Commentary by Dr. Valentin Fuster
2008;():965-970. doi:10.1115/IMECE2008-67983.

In order to give a comprehensive view about the essential relationship between vegetation and erosion, we employ an analysis of systemic dynamic stability based on vegetation-erosion equation raised by Thornes, and the further simulation about the equilibriums (fixed points) of the dynamic system can be given. We get four different types of the real equilibriums of the system. As well as this, the stability about all equilibriums is determined by systematic differential equation qualitative theory -Jacobi method. As a development of the original work of J.B.Thornes, this theoretical study highlights the insight to the interactive competition between vegetation and erosion.

Topics: Erosion
Commentary by Dr. Valentin Fuster
2008;():971-978. doi:10.1115/IMECE2008-68480.

We consider an age-maturity structured model arising from a yeast cell proliferation problem. This model is a new study in the filed of analysis of cell kinetics and cell division using mathematical modeling and optimized by Genetic Algorithm. We use our mathematical analysis in conjunction with experimental data from the division analysis of primitive cells to characterize the maturation/proliferation process.

Commentary by Dr. Valentin Fuster
2008;():979-987. doi:10.1115/IMECE2008-68854.

One of the simple, fast, and economical methods for controlling the condition of a weld is checking its superficial appearance. In this paper a method, based on the composition of Image Processing and CAD algorithms is presented for controlling different welding defects. The main purpose of this project is omission of the human interference in Visual Test of the weld. The main core of this system is a computer which analyses the captured images of a CCD camera and extracts the parameters of the weld such as size, position, surface smoothness and etc. By putting the results of analyses executed on the images captured from different sections of the weld next to each other, a continuous, 3D model of the weld is achieved. By comparison of this model with the standard samples, the probable defects on the weld and the type of each recognized defect is defined. Omission of human mistakes, decrease in the costs, higher speed of the control line and coincidence with the new production standards are the advantages of this method. The presented method has been implemented on the automobile rings manufactured in Mashhad Wheel Manufacturing Co.

Commentary by Dr. Valentin Fuster
2008;():989-991. doi:10.1115/IMECE2008-66187.

Phononic crystals (PC) are structures with periodic variations in their elastic properties. PC structures with complete phononic band gaps (CPBGs) are of special interest as they can be used to add new functionalities and make improvements to the conventional acoustic/elastic wave based devices. Recently, there has been a growing interest in PC structures with two-dimensional (2D) periodicity and a finite thickness in the third dimension, called PC plates (or slabs). PC slabs are interesting as the elastic waves are manipulated by the PC structure in the plane of periodicity while it is confined within the finite thickness of the slab structure in the third dimension, preventing the loss of energy out of the plane of periodicity. Although there have been a few reports on the implementation of PC plates with partial band gaps at low frequencies (below 5 MHz), the possibility of utilizing PC structures with high frequency CPBGs which can be used in wireless communication and sensing systems is still unverified. In this paper, we fist show (to the best of our knowledge) the first experimental proof for the existence of large high frequency (119MHz–150MHz) CPBGs in Si-based PC plates, and then using this CPBG, we create a waveguide by introducing a line defect in the PC structure. The structure is made by etching a hexagonal lattice of air holes in a free standing silicon plate by the use of a CMOS-compatible fabrication procedure. The transmission of elastic waves through the PC structure is measured by the use of a network analyzer and embedded interdigitated transducers. More than 30 dB attenuation in transmission through eight layers of PC structure is observed in the frequency range of the CPBG (119MHz–150MHz) with very good agreement with theoretical predictions of the CPBG. By adding a line defect to the PC structure, a PC waveguide with low loss propagation characteristics is formed and experimentally demonstrated. This result adds a new powerful functionality to micro/nano-mechanical devices that can lead to new high-performance, high-frequency devices with possible use in various wireless communication and sensing systems.

Commentary by Dr. Valentin Fuster
2008;():993-996. doi:10.1115/IMECE2008-67428.

We proposed an approach to construct a 2D Fresnel lenses by acoustic network. This lens is composed of an array of Helmholtz resonators. The resonance at individual resonators results in effective focusing even the plate has subwavelength thickness. The FEM simulation results presented the ultrasonic wave propagation through the lenses together with the resulting diffraction pattern.

Commentary by Dr. Valentin Fuster
2008;():997-1001. doi:10.1115/IMECE2008-67480.

Metamaterials are materials with manmade microstructures. Recently, researchers have looked at a class of metamaterials whose microstructures contain internal degrees of freedom that are different from those of the macro-medium. These metamaterials exhibit unusual dynamic behavior and if modeled as homogeneous solids then their effective mass densities would become negative in certain frequency range. Specifically, a new stop band in the vicinity of the local resonance frequency of the internal mass in the microstructure would result. In this paper, a one dimensional metamaterial is employed to investigate the meaning of the negative mass density in the material and the energy flow in and out of the microstructure. In addition, numerical solutions are used to illustrate the phenomenon.

Topics: Metamaterials
Commentary by Dr. Valentin Fuster
2008;():1003-1009. doi:10.1115/IMECE2008-68246.

We propose a hierarchical approach for the design of NEMS components with favorable dynamical characteristics. The approach consists of two steps: (i) design of several defect-engineered crystalline materials through intentional introduction of uniformly distributed defects, and in doing so altering precisely the frequency band structure of these materials, and (ii) allocation of patches of these designed materials to various regions in the component. Through this multiscale dispersive design approach, NEMS components can be designed to act as filters forbidding the transmission of vibrations at certain frequencies or waveguides confining the flow of energy to predetermined paths. Case studies are presented for 1D and 2D nanostructures.

Commentary by Dr. Valentin Fuster
2008;():1011-1018. doi:10.1115/IMECE2008-68257.

Recent advances in the fabrication of nanoscale material systems have made it possible to alter precisely the atomic structure in ways that enhance the properties and allow for certain functions to be realized. This work is concerned with two-dimensional periodic structures and emphasizes the effects of intentional defects on their wave propagation characteristics. In this draft paper, investigations are limited to a two-dimensional spring-mass lattice, composed of “super-cells” where mass inclusions are added to alter band-gap properties, as well as low frequency directionality. The presented results will then be extended to two-dimensional nanostructures, such as graphene nanosheets, in order to investigate their application as nanoscale acoustic waveguides, where engineered defects, uniformally distributed across the entire sheet, are introduced by design with the objective of rendering the medium anisotropic. Such anisoptropy leads to acoustic directionality, which can be exploited for waveguiding or acoustic-focusing purposes.

Commentary by Dr. Valentin Fuster
2008;():1019-1028. doi:10.1115/IMECE2008-68381.

The design of thermoelectric materials led to extensive research on superlattices with a low thermal conductivity. Indeed, the thermoelectric figure of merit ZT varies with the inverse of the thermal conductivity but is directly proportional to the power factor. Unfortunately, as nanowires, superlattices cancel heat conduction in only one main direction. Moreover they often show dislocations owing to lattice mismatches, which reduces their electrical conductivity and avoids a ZT larger than unity. Self-assembly is a major epitaxial technology to design ultradense arrays of germanium quantum dots (QDs) in silicon for many promising electronic and photonic applications as quantum computing. Accurate positioning of the self-assembled QD can now be achieved with few dislocations. We theoretically demonstrate that high-density three-dimensional (3-D) arrays of self-assembled Ge QDs, with a size of only some nanometers, in a Si matrix can also show an ultra-low thermal conductivity in the three spatial directions. This property can be considered to design new CMOS-compatible thermoelectric devices. To obtain a realistic and computationally-manageable model of these nanomaterials, we simulate their thermal behavior with atomic-scale 3-D phononic crystals. A phononic-crystal period (supercell) consists of diamond-like Si cells. At each supercell center, we substitute Si atoms by Ge atoms to form a box-like nanoparticle. Since this phononic crystal is periodic, we compute its phonon dispersion curves by classical lattice dynamics. Non-periodicities can be introduced with statistical distributions. From the flat dispersion curves, we obtain very small group velocities; this reduces the thermal conductivity in our phononic crystal compared to bulk Si. However, owing to the wave-particle duality at very small scales in quantum mechanics, another reduction arises from multiple scattering of the particle-like phonons in nanoparticle clusters. At room temperature, the thermal conductivity in an example phononic crystal can be reduced by a factor of at least 165 compared to bulk Si or below 0.95 W/mK. This value, which is lower than the classical Einstein limit of single crystalline Si, is an upper limit of the thermal conductivity since we use an incoherent-scattering approach for the nanoparticles. Because of its very low thermal conductivity, we hope to obtain a much larger ZT than unity in our atomic-scale 3-D phononic crystal. Indeed, this silicon-based nanomaterial is crystalline with a power factor that can be optimized by doping using CMOS-compatible processes. Future research on the phononic-crystal electrical conductivity has to be performed in order to compute the full ZT with a good accuracy.

Commentary by Dr. Valentin Fuster
2008;():1029-1035. doi:10.1115/IMECE2008-69219.

In this paper, we discuss the mechanism of focusing airborne ultrasound using heated wires. The heated wire generated a radially stratified temperature field surrounding the wire. The temperature field subsequently caused both the sound speed in the air and the mass density of the air to become radially stratified. This radial profile causes the impinging plane ultrasonic wave to form two strong beams in the forward direction, with a very strong shadow region. When multiple such wires are placed into a grid, the beams from adjacent wires form a sharply focused region. In this paper, experiment details are discussed. The analysis of single and multiple scattering of a planar acoustic wave by such fields are performed using experimentally measured temperature field, and compared with the experimentally measured acoustic field.

Topics: Sound , Wire
Commentary by Dr. Valentin Fuster

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