ASME Conference Presenter Attendance Policy and Archival Proceedings

2014;():V04BT00A001. doi:10.1115/IMECE2014-NS4B.

This online compilation of papers from the ASME 2014 International Mechanical Engineering Congress and Exposition (IMECE2014) represents the archival version of the Conference Proceedings. According to ASME’s conference presenter attendance policy, if a paper is not presented at the Conference, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.

Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: General

2014;():V04BT04A001. doi:10.1115/IMECE2014-36096.

This paper discusses the work done on kinematic and dynamic analysis of Valve Train (VT) system of a diesel engine by Analytical method. Above said analysis was done as a part of verification of VT system design for an engine speed increase of 21 %. Kinematic analysis is carried out to study the change in valve motion characteristics such as cam contour radius, tappet contact eccentricity etc. Further to this, dynamic analysis is carried out to assess forces and stresses on valve train components. Effect of cam tappet contact stresses, buckling load on push rod, spring surge, ratio of spring force to inertia force, valve seating velocity at increased speed condition etc. are discussed in detail. The kinematic and dynamic analysis methodology adopted, was validated using GT-VTRAIN software for existing and increased speeds and the comparative results are also discussed.

Topics: Kinematics , Valves , Trains
Commentary by Dr. Valentin Fuster
2014;():V04BT04A002. doi:10.1115/IMECE2014-36157.

In this research, predictor-based system identification is recursively implemented to identify system in closed-loop, which has been connected with proper threshold setting for fault detection. The predictor-based system identification technique is based on the assumption that the process and measurement noise is white. This paper shows how recursive system identification is connected with fault detection, which can remove the influence of noise. The effectiveness is demonstrated for recursive system identification combined with proper threshold setting via Matlab simulation.

Topics: Flaw detection
Commentary by Dr. Valentin Fuster
2014;():V04BT04A003. doi:10.1115/IMECE2014-36451.

When agricultural machines are operated on pavements, the lug excitation force occurring on a rolling agricultural tire is primary cause of the vibration. Therefore, it is important to investigate the lug excitation force in order to clarify the vibration generation mechanism. In our previous study, it is considered that the dynamic behavior of a rolling agricultural tire is influenced by the vibration characteristics of the tire. Further, only the rigid modes among the natural modes could affect the rolling tire behavior. So, we modeled the tire as a circular rigid ring supported on an elastic foundation with contact model. This rigid ring model can be valid to investigate the lug excitation force, while it is necessary to measure forces acting on tire shaft in order to estimate the lug excitation force. In this study, the test equipment is modified to measure tire shaft forces at rolling, by improved supporting structure equipped with 6-component force transducers and the shaft force characteristics are investigated. It is confirmed that the vibration characteristics of the tire influence the shaft force characteristics.

Topics: Tires
Commentary by Dr. Valentin Fuster
2014;():V04BT04A004. doi:10.1115/IMECE2014-37971.

Bolted joints are widely used in the auto industry, energy field and Construction, and so on. Due to the wide use of the bolted joints, the degradation of bolts has significant effect on the performance of a whole machine. Under transversal vibration, the self-loosening of bolted joints, which is the biggest form of failure ranked only second to fatigue failure [1], will happen, due to the cyclic shear load. This paper is to study the mechanism of bolted joints’ self-loosening.

Aiming at analyzing the self-loosening mechanism of bolted joints under vibration, a three dimensional FEA model of bolted joints, which had taken thread into consideration, was built with the application of APDL, and the preload was applied on the bolted joints by dropping temperature, then FEA transient analysis of the bolted joints under transverse cyclic excitation was conducted. Effect of transverse cyclic excitation’s amplitude, initial preload, thread and bearing friction coefficients, the joints’ surface friction coefficient, the thread pitch and the hole clearance on self-loosening was investigated. The results show that the complete thread slip occurs prior to the complete bearing surface slip under transverse vibration; the smaller amplitude, the smaller thread pitch and the smaller hole clearance is, and the greater initial preload, thread and bearing friction coefficients are, the more difficult self-loosening is to happen; the joints’ surface friction coefficient has little relationship with self-loosening, however, the larger joints’ surface friction coefficient makes the needed shearing force, which induces the transversal vibration, larger. These are of great significance for understanding of fasteners’ self-loosening and designing of bolted joints’ anti-loosening.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A005. doi:10.1115/IMECE2014-37973.

The paper analyzes the influence on the stability of the remote pilot in pressure relief valves used for engine lubrication. Such valves are mainly used to discharge the excess flow generated by a fixed displacement pump, moreover they can also be used as pilot stage to control the displacement in the new generation of vane pumps. In the paper the transfer function that relates the pressure in the main gallery with the valve spool position is determined. It was found that, when the valve is provided with an external pilot, the interaction between the hydraulic inductance of the pilot pipe and the spool decreases by many times the mechanical frequency of the valve, leading to a reduction of the stability. The experimental procedure used to measure the frequency response of the valve is also described. The test rig was provided with a servovalve used to generate a sinusoidal excitation pressure with variable frequency. The valve frequency response was evaluated by means of two pressure transducers at the two ends of the pilot channel. Finally the influence on the stability of some geometric parameters is analyzed by means of a simulation model in the AMESim environment.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A006. doi:10.1115/IMECE2014-38156.

The goal of this paper is to estimate the mass and auxiliary power of a vehicle simultaneously. Auxiliary power is the portion of the load power that is consumed by any auxiliary devices such as A/C compressor which is connected to the engine directly. This estimation has many potential applications especially in power management control systems of hybrid and plug-in-hybrid vehicles to improve their efficiency.

The parameter estimation algorithm is based on power balance of the vehicle. That is, total generated power by the engine should be equal to the power required for moving the vehicle plus the power consumed by the auxiliary devices. After developing the system model, Kalman filter is applied for the estimation of the auxiliary power and vehicle mass.

The proposed estimation algorithm uses the signals available through the vehicle control area network (CAN), and no extra sensor is required. It is assumed that the road grade is provided by a Global Positioning System (GPS) installed in the car. Simulations are presented to show the performance of the estimation algorithm in both city and highway driving cycles. The estimated and actual results are in very good agreement.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A007. doi:10.1115/IMECE2014-38181.

Power management of a ship’s electrical system has become important due to increasing loads from manpower-reducing automation, greater power requirements of advanced weapons and sensors, introduction of all electric propulsion, and the increasing cost of oil-based fossil fuels. A coordinated power management strategy of the ship’s electric power grid is desired to optimally allocate power flows and minimize fuel consumption. This paper develops such an optimal power management system for an interconnected, supervisory-level ship power system model based upon a ship power system test bed developed for the Office of Naval Research. The ship power system consists of two electrical generators, one rated at 59 kW to represent a gas turbine engine-generator pair and the other rated at 11 kW to represent a diesel generator, an 8 kW pulsed power load that represents the discharge and charge of a capacitor bank for an electromagnetic railgun system, and 37 kW ship propulsion system comprised of an induction motor coupled to the propeller shaft. The ship propulsion system’s induction motor has switched operation with two modes of operation, propelling and generating; the latter mode means that excess kinetic energy during ship slowing can be used to charge the capacitor bank for loads such as pulsed power loads. Given the switched system model, the paper sets forth a hybrid model predictive control strategy based on a minimization of a performance index that trades off fuel consumption, velocity tracking error, and electrical bus voltage error. The optimization is performed using a relaxed representation of the control problem (termed the embedding method) and collocation for discretization with traditional numerical programming to compute the mode and continuous control inputs. The methodology avoids the computational complexity associated with alternative approaches, e.g., mixed-integer programming. Numerical optimization is performed with MATLAB’s sqpLineSearch. To demonstrate the power management approach, a scenario is simulated where the ship is to follow a changing desired velocity while simultaneously maintaining the bus voltage at a desired value, keeping the 11 kW generator at a fuel efficient operating point, and minimizing the fuel use of the 59 kW generator.

Topics: Ships
Commentary by Dr. Valentin Fuster
2014;():V04BT04A008. doi:10.1115/IMECE2014-39275.

Torsional couplings are used to transmit power between various rotating components of power systems while allowing for relatively small misalignments that may otherwise lead to equipment failure. When selecting a proper coupling type and size, one has to consider three important conditions: (1) maximum load applied to the coupling, (2) maximum operation speed and (3) amount of misalignment allowable for normal operation.

There are many types of flexible couplings that use various materials for the flexible element of the coupling on the market today. Design of the coupling and the materials used for the flexible elements determine the coupling’s operating characteristics. In this project, we study metal disk couplings. Benefits of this type of coupling include: ease of replacement or repair, clear visual feedback of element failure, and the absence of a need for lubrication. The torsional stiffness of a coupling is a major factor relative to the amount of misalignment allowable. Currently, flexible couplings are tested by manufacturers to experimentally determine the torsional stiffness; a process which requires expensive equipment and more importantly employee time to set-up and run. The torsional coupling lumped characteristics, such as torsional- and flexural stiffness, as well as natural frequencies are important for design of the entire power system and have to be as precise as possible. In this work, we have developed an accurate modeling framework for determining these parameters based on a full 3-D finite element model and model-order reduction procedure. Developed methodology was validated by available experimental data from one of the leading manufacturers of torsional couplings.

Topics: Design , Disks , Couplings
Commentary by Dr. Valentin Fuster
2014;():V04BT04A009. doi:10.1115/IMECE2014-40007.

This work examines the buckling behavior of constrained horizontal tubular in a cylinder subjected to axial compression force. Such configurations are of interest to coiled tubing (CT) and conventional hydrocarbon drilling. When compression force is applied beyond a critical value the coiled tubing (CT) will buckle forming sinusoidal wave and with increasing the load the CT ultimately goes into a helical configuration. The friction is introduced due to the contact between the CT and the borehole wall. Increasing the CT friction eventually leads to lock-up length beyond which the drilling cannot proceed further. Vibration is a well-known technique to reduce friction between contacting bodies in many engineering systems. An in-house experimental setup is developed to imitate the wellbore being drilled with the presence of drilling fluids and vibrating facility that has the capability to vibrate the CT axially. The setup is employed to examine the effects of amplitude and frequency of vibration on the axial force transfer and weight on bit (WOB) at normal and high temperature environments. Results show that both amplitude and frequency have significant effects in reducing the friction and they alter the buckling behavior on both normal and high temperature.

Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: Measurement and Analysis Techniques in Nonlinear Dynamic Systems

2014;():V04BT04A010. doi:10.1115/IMECE2014-36576.

Fast Fourier Transform (FFT) calculates integer harmonic components, but ignores other frequency components such as non-integer harmonics and non-harmonics. In a practical sampling problem, the length of a sampled signal is finite and the sampling time is minimized. Therefore, it is necessary for interpolation to improve the accuracy of frequency analysis considering 1/m harmonic components and zero-padding (ZP) technique. The proposed method was applied to a 3D RF profile measurement system and the resolution was improved to 1/m.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A011. doi:10.1115/IMECE2014-36577.

A parallel algorithm for a direct solution of customized Fourier transform was proposed using a general processing unit (GPU). The algorithm was derived from parallel addition and multiplication, and was applied to non-integer Fourier transform (NFT). The parallel NFT was targeted to improve the resolution in 3D RF profile measurement. The proposed algorithm was efficient in processing time through consideration of the amount of operation using recent parallel FFT (Radix-2).

Commentary by Dr. Valentin Fuster
2014;():V04BT04A012. doi:10.1115/IMECE2014-37559.

The present article deals with the processing of data obtained by non-invasive measurement methods of instantaneous displacement of lightweight structures. This data is necessary to evaluate tuning-up of characteristics of an electro-magnetic vibration energy harvester, which is used for energy harvesting from these ambient mechanical vibrations. The electro-magnetic vibration energy harvester is device for powering of low power consumption wireless sensors without any external source of energy. The primary source of energy is only mechanical vibrations in place of wireless sensor and the operation without primary batteries is required. These techniques of wireless measurement are commonly used in aeronautics applications. The knowledge of mechanical vibrations in place of wireless sensors with vibration energy harvester is used for development of vibration energy harvester design.

The major idea is to verify the use of non-invasive measurement using high-speed cameras with measurement obtained from the laser interferometer. The measurement using high-speed camera can provide very important information about resonance operation of the vibration energy harvester during the future development.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A013. doi:10.1115/IMECE2014-38562.

This paper presents the investigation of operational deflection shapes of vibration of a cantilever beam using a low-cost digital video camera, and by application of image processing techniques. The beam is uniform and under base excitation. The analytical model of the system is developed using dimensionless formulation. The analytical ODS’s are derived, and then compared with those found from experiment. The significance of this research is that it provides the researchers an inexpensive alternative tool for investigating the behavior of systems with low-frequency dynamics.

Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: Multi-Physics Dynamics and Control of Structures and Devices

2014;():V04BT04A014. doi:10.1115/IMECE2014-37366.

Gas turbine rotor works at high temperature, especially the turbine used to expand hot gas and generate power. For the F class heavy duty gas turbine, the inlet temperature of hot expanding gas of the first turbine stage can be as high as 1400°C. Temperature is not only the source of thermal stress of gas turbine rotors but also leads to the variation of elastic modulus. Both of these two factors can cause a local stiffness variation of the rotor and thus have an influence on the dynamic characteristics of the rotor. The rotor investigated in this paper is a circumferential distributed rod-fastened rotor which is made of several discs bolted together. A 3-D model of the combined rotor system considering contact effect is established. The steady-state temperature field of the combined rotor is obtained through a thermal analysis. The stress distribution due to restraint on free expansions of components of the rotor as well as the deformation under steady-state thermal load is derived from a static structural analysis. Then a pre-stress modal analysis is performed to calculate the lateral natural frequencies of the rotor-bearing system. Finally, based on modal results, unbalance response of the rotor-bearing system is calculated through a harmonic analysis. For all steady-state thermal related analysis, two kinds of elastic modulus are calculated, i.e., constant and temperature-dependent elastic modulus, corresponding to the effect of thermal stress and material degradation, respectively. Both two steady-state cases are compared with the room temperature results to evaluate the role of these two thermal factors.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A015. doi:10.1115/IMECE2014-37834.

The textbook Kalman Filter (LKF) seeks to estimate the state of a linear system based on having two things in hand: a.) a reasonable state-space model of the underlying process and its noise components; b.) imperfect (noisy) measurements obtained from the process via one or more sensors. The LKF approach results in a predictor-corrector algorithm which can be applied recursively to correct predictions from the state model so as to yield posterior estimates of the current process state, as new sensor data are made available. The LKF can be shown to be optimal in a Gaussian setting and is eminently useful in practical settings when the models and measurements are stochastic and non-stationary. Numerous extensions of the KF filter have been proposed for the non-linear problem, such as extended Kalman Filters (EKF) and ‘ensemble’ filters (EnKF). Proofs of optimality are difficult to obtain but for many problems where the ‘physics’ is of modest complexity EKF’s yield algorithms which function well in a practical sense; the EnKF also shows promise but is limited by the requirement for sampling the random processes. In multi-physics systems, for example, several complications arise, even beyond non-Gaussianity. On the one hand, multi-physics effects may include multi-scale responses and path dependency, which may be poorly sampled by a sensor suite (tending to favor low gains). One the other hand, as more multi-physics effects are incorporated into a model, the model itself becomes a less and less perfect model of reality (tending to favor high gains). For reasons such as these suitable estimates of the joint system response are difficult to obtain, as are corresponding joint estimates of the sensor ensemble. This paper will address these issues in a two-fold way — first by a generalized process model representation based on regularized stochastic non-linear networks (Snn), and second by transformation of the process itself by an adaptive low-dimensional subspace in which the update step on the residual can be performed in a space commensurate with the available information content of the process and measured response.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A016. doi:10.1115/IMECE2014-38389.

PolyVinyliDene Fluoride (PVDF) film is used in this work to develop surface displacement sensors for vibrating simply supported, clamped, and cantilever beams. The constant shape PVDF film is bonded to the surface of the beam spanning the entire beam length. Bands parallel to the width of the beam are etched on the film to create multiple separate sections of the sensor. The individual output charge of the sensor sections is proportional to the slope of the beam lateral displacement curve of that patch. The actual beam surface displacement curve is calculated from these slopes. Theoretical analysis and numerical simulation show that the proposed sensor can be used to effectively measure the lateral vibration displacements of prismatic beams with various boundary conditions. However the accuracy of the measurement is closely related to the number of sensor sections and thus, relatively large number of channels is required for accurate measurements.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A017. doi:10.1115/IMECE2014-38663.

There has been a growing interest in electroactive polymers (EAP) because of their ability to serve as artificial muscles for both macro and micro positioning tasks. Ionic Polymer Metal Composites (IPMC) are among the EAP materials that have been extensively studied in the last few years. Along with development of better manufacturing methods and increasing understanding of their mechanical properties, extensive studies have been geared towards controlling the actuation of these actuators. Despite many efforts, the one problem that has not been fully addressed is on electromechanical modeling and control of these actuators. This paper presents additional details on the model that was earlier proposed by the authors for positioning such actuators. Experimental data on Nafion IPMC specimens of various sizes indicated that the specimen has both resistive and capacitive properties that vary with time. By using this experimental data, electrodynamics and electrostatics principles were used in developing an electromechanical model that was experimentally validated on Nafion IPMC specimens of various sizes again. The resulting model was found to be nonlinear time varying that can be linearized and controlled by standard linear optimal control algorithms.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A018. doi:10.1115/IMECE2014-38714.

The dynamic response of an electro-magneto-mechanical coupled system excited by a harmonic voltage is addressed. The system mathematical model involves coupling quadratic nonlinearities due to the dependence of the inductance on the displacement of the metallic oscillator mass; as a result, a strongly nonlinear behavior characterizes the system’s dynamic response. The numerical analysis is carried out through Poincaré mappings and dynamic continuation. The initial periodic attractor is shown to evolve into higher order and quasi-periodic attractors as the forcing amplitude increases. The peculiar irregular dynamics involving a number of bifurcations characterized by dramatic qualitative changes of both the mechanical and electrical responses for high excitation amplitude is discussed.

Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: Multibody Dynamic Systems and Applications

2014;():V04BT04A019. doi:10.1115/IMECE2014-36807.

The fully intrinsic equations for plates (and analogous ones for shells), although equally as elegant as the corresponding beam equations, have neither been used for general-purpose finite element nor multi-flexible-body analysis. The fully intrinsic equations for plates have the same advantages of fully intrinsic equations for beams. These equations are geometrically exact, the highest order of nonlinearities is only of second order, and they do not include rotation parameters. We present a finite element formulation for these equations, and then investigate different possible boundary conditions and loading situations on simplified linear version.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A020. doi:10.1115/IMECE2014-37809.

Many numerical integration methods have been developed for predicting the evolution of the response of dynamical systems. Standard algorithms approach approximate the solution at a future time by introducing a truncated power series representation that attempts to recover an n-th order Taylor series approximation, while only numerically sampling a single derivative model. This work presents an exact fifth-order analytic continuation method for integrating constrained multi-body vector-valued systems of equations, where the Jacobi form of the Routh-Voss equations of motion simultaneously generates the acceleration and Lagrange multiplier solution. The constraint drift problem is addressed by introducing an analytic continuation method that rigorously enforces the kinematic constraints through five time derivatives. This work rigorously deals with the problem of handling the time-varying matrix equations that characterize real-world equation of motion models arising in science and engineering. The proposed approach is expected to be particularly useful for stiff dynamical systems, as well as systems where implicit integration formulations are introduced. Numerical examples are presented that demonstrate the effectiveness of the proposed methodology.

Topics: Dynamic systems
Commentary by Dr. Valentin Fuster
2014;():V04BT04A021. doi:10.1115/IMECE2014-38601.

A 3-RPR planar parallel robot is a kind of planar mechanisms, which can work at high speed, with high accuracy and high rigidity. In this paper, a multi-body bond graph system will be built for the 3-RPR planar parallel manipulator (PPM), along with 3 PID controllers which give commands to 3 DC motors respectively. The advantage of bond graphs is that they can integrate different types of dynamics systems, the manipulator, the control and the motor can be modelled and simulated altogether in the same process. Bond graph will be established for each rigid body with body-fixed coordinate’s reference frames, which are connected with parasitic elements (damping and compliance) to each other. The PID set-point signals are generated by the explicit inverse kinematic equations. The 3 prismatic lengths constitute the measured feedback signals. In order to make the end-effector reach the ideal position with target orientation, the three links should reach the target lengths simultaneously. In this study, the dynamics simulation of 3-RPR PPM is conducted after building the bond graph system. As the 3 motors are working simultaneously and independently, the end-effector will arrive to the expected position. Finally, the bond graph and control system are validated with the compiled results and 3D animation. Force plot and torque plot will be generated as dynamics performance. Moreover, kinematics of manipulators are also calculated using bond graph. Eventually, bond graphs are shown to be effective in solving not only dynamic but also kinematic problems.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A022. doi:10.1115/IMECE2014-39549.

Assembling and fitting parts together can be considered as one of the most practical but also challenging process in robotics. Various applications are conceivable such as spatial ones where accessibility is reduced or in construction fields where huge forces have to be dealt with in a meticulous manner. In this paper, the cooperation of two robots during the complete assembling process of two structural parts from the approaching phase to the fitting stage is investigated. In the approaching phase for taking the parts closer, the two large construction parts may collide due to the inertia of motion, causing considerable impact forces even with the slightest relative velocity. This issue presents important control challenges as the effects of this local impact may be transferred throughout the system’s frame, affecting all other elements and inducing instability. Finally after connection of these two parts is established, the whole frame is transported to any desired location by cooperative operation of the two robots. Each step requires a particular controller to deal with different system’s dynamics that occur during the whole process.

Topics: Robots
Commentary by Dr. Valentin Fuster
2014;():V04BT04A023. doi:10.1115/IMECE2014-39994.

This paper will investigate the use of large scale multibody dynamics (MBD) models for real-time vehicle simulation. Current state of the art in the real-time solution of vehicle uses 15 degree of freedom models, but there is a need for higher-fidelity systems. To increase the fidelity of models uses this paper will propose the use of the following techniques: implicit integration, parallel processing and co-simulation in a real-time environment.

Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: Nonlinear Dynamics, Control, and Stochastic Mechanics

2014;():V04BT04A024. doi:10.1115/IMECE2014-36009.

Based on linear damage accumulation law, this paper investigates the fatigue problem of drill-strings in time domain. Rainflow algorithms are developed to count the stress cycles. The stress within the drill-string is calculated with finite element models which is developed using Euler-Bernoulli beam theory. Both deterministic and random excitations to the drill-string system are taken into account. With this model, the stress time history in random nature at any location of the drill-string can be obtained by solving the random dynamic model of the drill-string. Then the random time history is analyzed using rainflow counting method. The fatigue life of the drill-string under both deterministic and random excitations can therefore be predicted.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A025. doi:10.1115/IMECE2014-36643.

In this analysis, we consider the dynamics of a pendulum under vertical excitation of a crank-shaft-slider mechanism. The nonlinear model approaches that of a classical parametrically excited pendulum when the ratio of the length of the shaft to the radius of the crank is very large. Numerical techniques are employed to investigate the results for different parameters and initial conditions. Lyapunov exponents, bifurcation diagrams, time histories and phase portraits are presented to explore conditions when the pendulum performs or not full rotations. Of special interest are the resonance regions. Rotations together with oscillations and chaos were observed in some resonance zones.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A026. doi:10.1115/IMECE2014-36647.

The Phase-Locked Loop (PLL) is a closed-loop control system that synchronizes a local oscillator to an oscillatory incoming signal. The PLL plays important roles in communication, computation and control systems, allowing the correct flow of information by efficiently generating and distributing clock reference signals. PLLs are also applied in motor speed control and in atomic force microscopy. Nevertheless, PLLs are inherently nonlinear devices, and behaviors such as bifurcations and chaos may arise. In this paper, the vibration control of an elastic beam is performed by a PLL control structure. Additionally, different designs for the PLL-beam control system are discussed.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A027. doi:10.1115/IMECE2014-37131.

Nonlinear vibrations of moderately thick functionally graded (FG) rectangular plates are investigated by considering a higher-order shear deformation theory that takes into account the thickness deformation effect. The geometrically nonlinear strain-displacement relationships are derived retaining full non-linear terms in the in-plane and transverse displacements and the three-dimensional constitutive equations are used by removing the assumption of zero transverse normal strain. The plate is assumed to have immovable boundary conditions at the edges. The equations of motion are obtained by using multi-modal energy approach. A code based on pseudo arc-length continuation and collocation scheme is utilized for numerical continuation and bifurcation analysis. Results show that higher-order thickness deformation theories yield a significant accuracy improvement for nonlinear vibrations of highly pressurized functionally graded plates.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A028. doi:10.1115/IMECE2014-37505.

This paper presents the position and vibration control of a single flexible slewing structure driven by a DC motor at the slewing axis. The position is controlled over the current applied to the DC motor armature. To control the vibration of the flexible structure Shape Memory Alloys (SMA) are applied to them. The control is made through the State Dependent Ricatti Equations (SDRE) technique which uses sub-optimal control and system local stability search. Numerical simulations and experimental results are presented which demonstrate the effectiveness of the proposed control strategy.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A029. doi:10.1115/IMECE2014-38294.

This paper utilizes Reduced Order Model (ROM) method to investigate the voltage-amplitude response of electrostatically actuated M/NEMS clamped circular plates. Soft AC voltage at frequency near half natural frequency of the plate is used. This results in primary resonance of the system. The effects of nonlinearities of the system including pull-in instability on the voltage-amplitude response are investigated. Namely, the effects of detuning frequency, damping, Casimir force, and van der Waals force on the voltage response of clamped circular plates are reported. Casimir and van der Waals forces are found to have significant effects on the response of clamped circular plates and must be considered to accurately model and predict the behavior of the system.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A030. doi:10.1115/IMECE2014-38500.

Flexible link systems are increasingly being used in the robotic and other applications. The dynamics of distributed parameter single flexible link system, especially in the vertical planes, is known to demonstrate chaotic behavior upon harmonic excitation. However, to the best of authors knowledge, chaotic dynamics of ultra-large deflection flexible systems with distributed and lumped parameters considered together has not been considered in the literature so far. Dynamics of a representative case, an inverted flexible pendulum with tip mass on cart system, is analysed in this paper. Experimental results on a custom built system consisting of link having 1. ultra large deformation (300 times thickness) as compared to thickness, 2. a tip mass, and 3. base fixed to a cart, under harmonic excitation under several frequencies were obtained. Poincaré maps with large set of data show successive progression with a small cluster of points to start with splitting into two clusters finally leading to butterfly figure of chaotic vibrations. Effect of variation of the excitation amplitude is also explored leading to interesting change in the patterns of Poincaré maps observed.

Topics: Chaos , Pendulums
Commentary by Dr. Valentin Fuster
2014;():V04BT04A031. doi:10.1115/IMECE2014-39223.

Super elastic alloy (SEA) has the characteristic of two-way deformation by heating and cooling under prestressed condition. The characteristic makes it possible to realize an actuator of flexible, compact, and quiet. Therefore, SEA can be applied to such robots for medical, assist, welfare, automatic door, and so on. However, there are many difficulties in its control as actuator because SEA shows strong non-linear behavior on its deformation process.

In this study, the measurement system of state quantities on the non-linear characteristics of SEA is constructed to control the deformation of it as practical actuator. Here, the actuator made by SEA is heated by electric current. And then, electrical systems are also developed to measure the state quantities of temperature, strain and electric resistivity of SEA during the Joule heating for its mechatronical control. In addition, the measurement of the electric resistivity on the process of heating and cooling is performed by applying pulse voltage for perform stable and accurate measurement even at a low voltage is applied.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A032. doi:10.1115/IMECE2014-39436.

In this article, the state estimation for Automotive Slip Angle considering the measurement noise in sensor is addressed. Real-time measurement of the slip angle is applicable to many active vehicle safety applications, such as rollover prevention and yaw stability control. As the sensors that measure slip angle directly are expensive, the method to extract slip angle from other available sensors in vehicle is considered. First from the simplified nonlinear dynamic system of vehicle, a Piecewise Affine (PWA) model with calculated uncertainties is obtained. The uncertainties are the result of nonlinear system deviation from PWA model. Then using the PWA model, a Stochastic Robust Hybrid Observer design is developed to estimate the slip angle. Design of the Observer is based on Linear Matrix Inequalities which gives bound on the estimation variance based on the sensor noise measurements. Finally, through simulation, the effectiveness and performance of this method is investigated.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A033. doi:10.1115/IMECE2014-39773.

The primary goal of this paper is to develop and test a new controller for an under-actuated bipedal robot. This controller handles adequately some limitations existing in other similar robot controllers. Fuzzy controller is used in this research in order to tuning the gain of controller adaptively. Tuning parameters lead to robust character and high performance for uncertain movements during the walking. Using adaptive fuzzy computed torque controller, it provide conditions through which i) adaptive fuzzy part adjusts parameters of the system and ii) computed torque part provide a nonlinear control simultaneously. Use of these two advantages lead to reduce uncertainty effects during walking. Finally the Matlab software is developed to evaluate the effectiveness for stability of proposed controller.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A034. doi:10.1115/IMECE2014-39950.

New formulas for obtaining the accurate amplitudes decay of the energy, velocity and displacement in the Duffing oscillator of odd-power stiffness components are derived here. The derivation is based on the new transformation proposed recently in the literature. These new formulas are found to be highly accurate in locating the decay envelopes of the energy, velocity and displacement regardless of the system physical parameters and the initial condition. In addition, the formulas are also found to be applicable to the damped double-well Duffing oscillator as long as the oscillation simultaneously occurs between the two stable equilibrium positions.

Topics: Stiffness
Commentary by Dr. Valentin Fuster
2014;():V04BT04A035. doi:10.1115/IMECE2014-39971.

An approach for accurate analytical solution of a two degree-of-freedom nonlinear dynamical system coupled with a strongly nonlinear restoring force is presented here. The approach is based on the application of the local equivalent linear stiffness method (LELSM) to linearize the nonlinear coupling stiffness in the system based on the nonlinear frequency calculation. Consequently, the system can be decoupled into two forced single degree-of-freedom subsystems by replacing the nonlinear coupling force with a forcing function where the solution can be analytically obtained. Different combinations of the positive and negative linear and cubic stiffness components are considered in the nonlinear coupling force. For all considered stiffness combinations, the obtained analytical solution strongly agrees with the numerical simulation of the system. In addition, the internal resonance is found not to significantly affect the accuracy of the analytical solution.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A036. doi:10.1115/IMECE2014-40055.

Rubbing between rotating and stationary surfaces in turbomachinery can result in catastrophic failures if not caught quickly. Removing the rub impact can then often require time consuming and expensive solutions including field balancing or magnetic bearing systems. However, simple changes in bearing dynamics via bearing and lubricant adjustment could provide for a faster and cheaper alternative. In this work, a three-disk rotor was examined analytically for nonlinear rotordynamic behavior due to an unbalance-driven rub. The rotordynamic solution was obtained using nonlinear and steady state finite element models to demonstrate the effect of the rub impact on the dynamic response of the machine. A thermoelasto-hydrodynamic (TEHD) model of tilting pad journal bearing performance was also used to study the possible removal of the rub impact by making minor adjustments to bearing parameters including preload, clearance, pad orientation, and lubricant properties. Gas-expanded lubricants, tunable mixtures of synthetic oil and carbon dioxide that have been proposed as a means to provide control in bearing-rotor systems, were also considered for their possible role in controlling the rub. The TEHD model provided a range of bearing inputs to the rotor models in the form of stiffness and damping coefficients. Results from the rotordynamic analyses included an assessment of critical speeds, peak rotor displacements, and vibration characteristics. Individual bearing parameter adjustments were found to have smaller, though still significant effects on the response of the machine. Overall it was found that by adjusting a combination of these bearing parameters that the peak displacement of the rotor could be reduced by large enough amounts to remove the rub impact in the machine, hence providing a simple approach to solving rub impact problems in rotating machinery caused by excessive vibration.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A037. doi:10.1115/IMECE2014-40118.

Robotic arms are becoming increasingly popular in industrial applications. However, improving the response and accuracy of robotic arms while reducing their cost has become challenging. The Kalman Filter (KF) has attracted a significant amount of research as it improves the control quality by filtering the feedback signal. On the other hand, KF solution becomes very challenging when the system under study is nonlinear. This work proposes a new online state estimation algorithm that combines the Smooth Variable Structure Filter (SVSF) with the Unscented Kalman Filter (UKF). The proposed method overcomes the limitations of SVSF and UKF in terms of stability and sensitivity to noise. A simulation study is conducted in this paper to demonstrate the results of the proposed method when applied to estimate the states of a PRRR industrial robotic arm.

Topics: Robotics , Filters
Commentary by Dr. Valentin Fuster
2014;():V04BT04A038. doi:10.1115/IMECE2014-40221.

This paper describes a new approach for ascertaining the stability of autonomous stochastic delay equations in their parameter space by examining their time series using topological data analysis. We use a nonlinear model that describes the tool oscillations due to self-excited vibrations in turning. The time series is generated using Euler-Maruyama method and then is turned into a point cloud in a high dimensional Euclidean space using the delay embedding. The point cloud can then be analyzed using persistent homology. Specifically, in the deterministic case, the system has a stable fixed point while the loss of stability is associated with Hopf bifurcation whereby a limit cycle branches from the fixed point. Since periodicity in the signal translates into circularity in the point cloud, the persistence diagram associated to the periodic time series will have a high persistence point. This can be used to determine a threshold criteria that can automatically classify the system behavior based on its time series. The results of this study show that the described approach can be used for analyzing datasets of delay dynamical systems generated both from numerical simulation and experimental data.

Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: Novel Control of Dynamic System and Design

2014;():V04BT04A039. doi:10.1115/IMECE2014-37363.

Permanent Magnet Synchronous Motor (PMSM) can behave chaotically for a certain range of its parameters. To improve its dynamical behavior and enable a robust control of the rotor angular speed, a novel method combining the wavelet transform with the filtered-x LMS algorithm is presented in this paper. Without linearizing the model so as to not advertently misinterpret the underlying dynamics, the method can identify the nonlinear PMSM model with adaptive filters in real-time and guarantee a comprehensive control in both the time and frequency domains. Firstly, the physical PMSM model is analyzed and its chaotic behavior without control is investigated. The wavelet-based filtered-x LMS is then applied to the nonlinear PMSM system subject to desired angular speeds that are constant and varying harmonically in time. Numerical studies show that chaotic behaviors are effectively mitigated and the system output matches the desired angular speed after the initial transient period, thus demonstrating the feasibility of the method for the control of PMSMs.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A040. doi:10.1115/IMECE2014-38118.

In this paper, a FTFC system is designed to handle a cosmic rays fault affecting actuator control signal. The geometric approach is used to design the fault diagnosis module. This module determines the gravity of the fault and calculates its parameters. Based thereon, a new reconfigurable Sliding Mode Control law is designed and applied on the longitudinal linear model of the F-16 aircraft. Simulations are performed using Matlab®/Simulink® to show the effectiveness of the proposed approach.

Topics: Cosmic rays , Flight
Commentary by Dr. Valentin Fuster
2014;():V04BT04A041. doi:10.1115/IMECE2014-38158.

Decision making of a vertebrate in response to the sensory signals from the environment is regulated by the neuromodulatory systems in its brain. A vertebrate’s behaviors like focusing attention, cautious risk-aversion and curiosity-seeking exploration are influenced by these neuromodulators. The paper presents an autonomous robotic control approach based on vertebrate neuromodulation and its implementation on multiple open-source hardware platforms. A simple neural network is used to model the neuromodulatory functions for generating context based behavioral responses to sensory signals. The neural network incorporates three types of neurons — attention focusing cholinergic and noradrenergic (ACh/NE), curiosity-seeking dopaminergic (DA), and risk aversive serotonergic (5-HT) neurons. The implementation of the neuronal model on multiple relatively simple autonomous robots is illustrated through the interesting behavior of the robots adapting to changes in the environment. The implementation is done in open-source, open-access robotics software framework of Robot Operating System (ROS).

Topics: Robots
Commentary by Dr. Valentin Fuster
2014;():V04BT04A042. doi:10.1115/IMECE2014-38281.

Impact oscillators are found in many applications. Some of the applications inadvertently experience the undesirable effect of vibro-impact called grazing bifurcation. For example, fitting joints are commonly considered in mechanical design. However, the grazing behavior of a loose fitting joint in response to the thermal variation of the working environment may cause unpredictable damage. In this paper, the Newtonian model of a vibro-impact system is investigated. The model system exhibits complex grazing dynamics that is highly nonlinear. The generation of grazing phenomena along with the corresponding periodic solution of the particular type of bifurcation is elaborated. The system is characterized using phase portraits. Since grazing and route-to-chaos are difficult to control, a novel concept capable of simultaneous control of vibration amplitude in the time-domain and spectral response in the frequency-domain is applied to develop a viable control scheme. The concept has been demonstrated working well for the control of dynamic instability including bifurcation and chaos in many engineering systems. The developed controller explores wavelet adaptive filters and filtered-x least mean square algorithm to the successful mitigation of the various states of dynamic instability of the vibro-impact system including grazing bifurcation and chaotic response. In addition, detail description is also given as to the setting of the control parameters such as control time step, sampling rate, wavelet filter vector, and desired targets.

Topics: Bifurcation
Commentary by Dr. Valentin Fuster
2014;():V04BT04A043. doi:10.1115/IMECE2014-38346.

The architecture of the electrical actuation module driving a magnetic-hydraulic bearing system is presented. The bearing is intended to be scaled for use in applications of all sizes in industries like shipboard for support of the engine-propeller shaft or in power-plants for the shaft through which the prime mover, e.g. steam or gas turbine, is driving the electric generator. The benefits of this new bearing is first and foremost its superb performance in terms of low down to practically no friction losses since there is no direct contact between the supporting bearing surface and the rotating shaft supported. Other benefits include the potential of active, inline, real-time balancing and alignment. To implement such concept of a magnetic-hydraulic bearing, the following tasks need to be carried out. First, identification of mechanical, electrodynamical and circuit properties of the bearing’s electromagnets in the system is necessary. Toward such identification, a series of experiments needed to be carried out. To be able to carry out these experiments, a specific power electronic converter is developed to drive each electromagnet. The power electronic drive is a quad MOSFET circuit based on full-bridge converter topology and outfitted with appropriate sensory instrumentation to collect and record measurements of all the physical variables of interest. Special care has been taken to compensate for magnetic hysteresis of the electromagnets, mitigate any induction heating effects and maintain operation within the material’s linear region i.e. without significant saturation occurring. The use of a power transistor bridge allows rapid changes to be applied on the electromagnet’s load force which could compensate disturbance or misalignment developed on the shaft supported. The data series from these experiments are useful for formulating a possibly nonlinear model of the electromagnetical and electromechanical processes involved in the bearing’s operation. Such a model can then be employed to help design a digital microcontroller system which could effectively drive the power electronics and electromagnets to perform their required tasks as part of the bearing. Besides, the model could also be used for the synthesis of the nonlinear, sampled-data (discrete-time) control law which will be programmed on the microcontroller system board.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A044. doi:10.1115/IMECE2014-38496.

In co-robotics applications, the robots must identify human partners and recognize their status in dynamic interactions for enhanced acceptance and effectiveness as socially interactive agents. Using the data from depth cameras, people can be identified from a person’s skeletal information. This paper presents the implementation of a human identification algorithm using a depth camera (Carmine from PrimeSense), an open-source middleware (NITE from OpenNI) with the Java-based Processing language and an Arduino microcontroller. This implementation and communication sets a framework for future applications of human-robot interactions. Based on the movements of the individual in the depth sensor’s field of view, the program can be set to track a human skeleton or the closest pixel in the image. Joint locations in the tracked human can be isolated for specific usage by the program. Joints include the head, torso, shoulders, elbows, hands, knees and feet. Logic and calibration techniques were used to create systems such as a facial tracking pan and tilt servomotor mechanism. The control system presented here sets groundwork for future implementation into student built animatronic figures and mobile robot platforms such as Turtlebot.

Topics: Robots
Commentary by Dr. Valentin Fuster
2014;():V04BT04A045. doi:10.1115/IMECE2014-38504.

In co-robotics applications, the robots must be capable of taking inputs from human partners in different forms, including both static and sequential hand gestures, in dynamic interactions for enhanced effectiveness as socially assistive agents. This paper presents the development of a gesture recognition algorithm for control of robots. The algorithm focuses on the detection of skin colors using monocular vision of a moving robot base where the inherent instability negates the effectiveness of methods like background subtraction. The algorithm is implemented in the open-source, open-access robotics software framework of Robot Operating System (ROS). The video feed from the camera is converted into several color spaces, including RGB and YCbCr. Pixels observed in the raw video feed as skin are randomly selected and their properties in each of the color spaces are recorded. A cylinder of infinite length is constructed out of the best fit line for both color spaces, and all points lying within both cylinders are accepted as a skin tone. The gesture recognition features are extracted from the filtered image and can be used for planning the motion of the robot. The procedure is illustrated using the on-board camera on an unmanned aerial vehicle (UAV).

Topics: Robots
Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: Poster

2014;():V04BT04A046. doi:10.1115/IMECE2014-36968.

Wireless sensor networks become increasingly important in modern life for structural health monitoring and other related applications. In these applications, due to their overall sensor populations and possible covered measurement areas, the replacement of batteries becomes a difficult and unrealistic task. As a result, energy harvesters to convert environment wasted vibration energy into electricity for powering those sensor nodes become important and many miniaturized device have been realized by using MEMS technology. In order to achieve optimal performance, the energy harvester must be operated at the resonance frequency. However, the vibration frequencies of environmental vibrations are usually much less than that of those miniaturizing energy harvesters and this fact could be a major barrier for energy harvesting performance. In this paper, a new piezoelectric energy scavenging concept is proposed and demonstrated to convert environmental vibrations into electricity. Unlike previous MEMS-based piezoelectric energy harvesters, which suffer from matching between environmental low frequency vibration and the much higher system natural frequency, this work proposes a novel beating design using polymer piezoelectric materials in collaborating with a beating mechanism. That is, by creating impact force via the low frequency vibration motion from the mechanism, it is possible to excite system natural frequency by the low frequency environmental vibrations and it is possible to operate the entire system at the natural frequency. This work contains details in presenting this idea, designing piezoelectric harvester systems with flexible PVDF elements, exploring their vibration characteristics, and energy accumulating strategies by using a capacitor with a full-bridged rectifiers or a boost conversion. By experimental characterization, the overall harvesting efficiency of the proposed design is much greater than that from the design without the beating mechanism. It indicates that the efficiency is significantly improved and the proposed translational design could potentially improve the future design approach for piezoelectric energy harvesters significantly. In summary, this preliminary study shows that it is a feasible scheme for the application of piezoelectric materials in harvesting electricity from environmental vibrations. Although this work is still in its initial phase, the results and conclusions of this work are still invaluable for guiding the development of high efficient piezoelectric harvesters in the future.

Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: Renewable Energy, Structural Health Monitoring, and Distributed Structural Systems

2014;():V04BT04A047. doi:10.1115/IMECE2014-36551.

A novel geared infinitely variable transmission (IVT) that can generate a continuous output-to-input speed ratio from zero to a certain value is studied for vehicle and wind turbine applications. The principle of changing the output-to-input speed ratio is to use a crank-slider mechanism; the output-to-input speed ratio is controlled by adjusting the crank length. Since the crank-slider mechanism can lead to relatively large variation of the output-to-input speed ratio in one rotation of the crank, the instantaneous input and output speeds and accelerations have variations and the corresponding forces exerted on each part of the IVT can have obvious changes in one rotation of the crank. Since forces on some parts of the IVT are critical and can cause failure of the IVT, a dynamic analysis of the IVT is necessary to simulate the input and output speeds and accelerations. A method that combines Lagrangian dynamics and Newtonian dynamics is developed in this work to analyze the motion of the IVT. The dynamic analysis results can be used to evaluate the design of the IVT.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A048. doi:10.1115/IMECE2014-37134.

There is a strong urge for advanced diagnosis method, especially in high power battery packs and high energy density cell design applications, such as electric vehicle (EV) and hybrid electric vehicle segment, due to safety concerns. Accurate and robust diagnosis methods are required in order to optimize battery charge utilization and improve EV range. Battery faults cause significant model parameter variation affecting battery internal states and output. This work is focused on developing diagnosis method to reliably detect various faults inside lithiumion cell using electrochemical model based observer and fuzzy logic algorithm, which is implementable in real-time. The internal states and outputs from battery plant model were compared against those from the electrochemical model based observer to generate the residuals. These residuals and states were further used in a fuzzy logic based residual evaluation algorithm in order to detect the battery faults. Simulation results show that the proposed methodology is able to detect various fault types including overcharge, over-discharge and aged battery quickly and reliably, thus providing an effective and accurate way of diagnosing Li-Ion battery faults.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A049. doi:10.1115/IMECE2014-37140.

Moving Horizon Estimation (MHE) has emerged as a powerful technique for tackling the estimation problems of the state of dynamic systems in the presence of constraints, nonlinearities and disturbances. In this paper, the Moving Horizon Estimation approach is applied in estimating the State of Charge (SoC) and State of Health (SoH) of a battery and the results are compared against those for the traditional estimation method of Extended Kalman Filter (EKF). The comparison of the results show that MHE provides improvement in performance over EKF in terms of different state initial conditions, convergence time, and process and sensor noise variations.

Topics: Algorithms , Batteries
Commentary by Dr. Valentin Fuster
2014;():V04BT04A050. doi:10.1115/IMECE2014-37157.

Nonlinear dynamic responses of an Euler-Bernoulli beam attached to a rotating rigid hub with a constant angular velocity under the gravity load are investigated. The slope angle of the centroid line of the beam is used to describe its motion, and the nonlinear integro-partial differential equation that governs the motion of the rotating hub-beam system is derived using Hamilton’s principle. Spatially discretized governing equations are derived using Lagrange’s equations based on discretized expressions of kinetic and potential energies of the system, yielding a set of second-order nonlinear ordinary differential equations with combined parametric and forced harmonic excitations due to the gravity load. The incremental harmonic balance (IHB) method is used to solve for periodic responses of high-dimensional models of the system and period-doubling bifurcation. The multivariable Floquet theory along with the precise Hsu’s method is used to investigate the stability of the periodic responses. Phase portraits and bifurcation points obtained from the IHB method agree very well with those from numerical integration.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A051. doi:10.1115/IMECE2014-37537.

The present work uses PolyVinyliDene Fluoride (PVDF) film to develop surface displacement sensors for vibrating plates with various boundary conditions. Two constant shape PVDF films are bonded together and to the surface of the plate covering the entire plate. The films are arranged such that the piezoelectric axis 1 of the top film is perpendicular to the piezoelectric axis 2 of the bottom axis. Right angle quadrilaterals patches are etched on the films to create multiple separate sections of the sensors. The output charges of sensor patches covering the same subarea are processed to compute the slopes of the lateral displacement surface of that subarea. The actual plate lateral displacement elevations are calculated from these slopes using forward difference equations. Theoretical analysis and numerical verification show that the proposed sensor can be used to effectively measure the lateral vibration displacements of plates with various boundary conditions. However the accuracy of the measurement is closely related to the number of sensor sections and thus, relatively large number of channels is required for accurate measurements. Furthermore, for non-zero slop conditions at the boundaries, additional point sensors are required.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A052. doi:10.1115/IMECE2014-37560.

The objective of this work is to design cantilever beams possessing close vibration modes to enable harvesting energy from variable frequency sources of base motion. In this context, the geometry of two-dimensional cantilever beams is designed to obtain closely spaced harvestable modes of vibration. A number of internal slits are made inside the beam, whose outer contour and mass distribution are altered in such a way to obtain the desired frequency spacing. The beam carries two permanent magnets that oscillate past stationary pickup coils in order to convert the mechanical motion into electric power. Optimum design results of the shape and geometrical parameters of the system are presented towards controlling the natural frequencies, their spacing and the output power. Simulations of the system dynamics are supported by experimental validation.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A053. doi:10.1115/IMECE2014-37640.

Energy harvesting devices are growing in popularity for their ability to capture the ambient energy surrounding a system and convert it into usable electrical energy. With an increasing demand for portable electronics and wireless sensors in a number of sectors, energy harvesting has the potential to create self-powered sensor systems operating in inaccessible locations. This paper discusses a torsion based piezoelectric energy harvester that utilizes superior shear mode piezoelectric properties to harvest energy from vibrations. Mathematical expressions are used to determine optimized geometry configurations for the harvester. Using these expressions, a harvester design is presented for use with wireless sensor networks.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A054. doi:10.1115/IMECE2014-38597.

In this paper, the propagation of lateral waves in a drill-string are studied by using a new numerical method and a stability monitoring scheme is proposed. The drill-string is modeled as a linear beam structure under gravitational field effects. An iterative wavelet-based spectral finite element method (WS-FEM) model is developed to obtain a high fidelity response. Numerical simulations of the lateral impact wave propagation at the bottom-hole-assembly (BHA) are conducted and a time-frequency analysis technique is applied to the response in order to identify the relationship between the position of the transition point between positive and negative strain and the dispersive properties of the lateral wave. Based on the results, a new monitoring scheme is proposed to monitor the stability of the drill-string based on a combination of lateral impact wave analysis at the BHA and the axial acoustic telemetry technique.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A055. doi:10.1115/IMECE2014-38684.

Hydraulic Pressure Energy Harvesters (HPEHs) use the direct piezoelectric effect to extract electrical power from the dynamic pressure ripple present in hydraulic systems. As with other energy harvesters, an HPEH is intended to be an enabling technology for powering sensor nodes. To date, HPEH devices have been developed for high-pressure, high-dynamic pressure ripple systems. High-pressure applications are common in industrial hydraulics, where static pressures may be up to 35 MPa. Other fluid systems, such as cross-country pipelines as well as water distribution networks operate at much lower pressures, e.g., from around 1 to 4 MPa, with proportionally lower dynamic pressures. Single-crystal piezoelectric materials are incorporated into the HPEH design, along with means to increase the load transfer into the piezoelectric material as well as increased output harvester circuits, so as to increase the power output of these devices. The load transfer from the pressurized fluid into the piezoelectric material is through an interface, where the interface area may be designed such that the area exposed to the fluid is greater than the cross-sectional area of the piezoelectric, yielding higher stress in the material than the pressure in the fluid. Furthermore, given the relatively large capacitance of the piezoelectric elements used in HPEH devices, inductive-tuned resonant harvester circuits implemented with passive elements are feasible. HPEH devices integrating these features are shown to produce viable power outputs from low dynamic pressure systems.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A056. doi:10.1115/IMECE2014-38686.

Wind turbines are renewable energy conversion devices that are being deployed in greater numbers. However, today’s wind turbines are still expensive to operate, and maintain. The reduction of operational and maintenance costs has become a key driver for applying low-cost, condition monitoring and diagnosis systems in wind turbines. Accurate and timely detection, isolation and diagnosis of faults in a wind turbine allow satisfactory accommodation of the faults and, in turn, enhancement of the reliability, availability and productivity of wind turbines. The so–called model-based Fault Detection and Diagnosis (FDD) approaches utilize system model to carry out FDD in real-time. However, wind turbine systems are driven by wind as a stochastic aerodynamic input, and essentially exhibit highly nonlinear dynamics. Accurate modeling of such systems to be suitable for use in FDD applications is a rather difficult task. Therefore, this paper presents a data-driven modeling approach based on artificial intelligence (AI) methods which have excellent capability in describing complex and uncertain systems. In particular, two data-driven dynamic models of wind turbine are developed based on Fuzzy Modeling and Identification (FMI) and Artificial Neural Network (ANN) methods. The developed models represent the normal operating performance of the wind turbine over a full range of operating conditions. Consequently, a model-based FDD scheme is developed and implemented based on each of the individual models. Finally, the FDD performance is evaluated and compared through a series of simulations on a well-known large offshore wind turbine benchmark in the presence of wind turbulences, measurement noises, and different realistic fault scenarios in the generator/converter torque actuator.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A057. doi:10.1115/IMECE2014-38755.

A modified generator, referred to as the variable electromotive-force generator, is developed to enhance fuel efficiency of hybrid vehicles and expand operational range of wind turbines. Obtaining a numerical model that provides accurate estimates on the generator output power at different overlap ratios and rotor speeds, comparable with those from experimental results, would expand the use of the proposed modified generator in different applications. The general behavior of the generated electromotive forces at different overlaps and rotor speeds is in good agreement with those from experimental and analytical results at steady-state conditions. Employing generator losses due to hysteresis and eddy currents in a three-dimensional model would generate more realistic and comparable results with those from experiment. In this work, electromagnetic analysis of a modified two-pole DC generator with an adjustable overlap between the rotor and the stator at transient conditions is performed using finite element simulation in the ANSYS 3D Low Frequency Electromagnetics package. The model is meshed with tetrahedral or hexahedral elements, and the magnetic field at each element is approximated using a quadratic polynomial. For a fixed number of coils, two cases are studied; one with constant magnetic properties and the other with nonlinear demagnetization curves are studied.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A058. doi:10.1115/IMECE2014-39124.

This paper presents an effective bearing fault parameter identification scheme based on evolutionary optimization techniques. Three seeded faults in the rotating machinery supported by the test roller bearing include inner race fault, outer race fault and a single ball defect. The fault related features are extracted experimentally by processing the acquired vibration signals in both the time and frequency domain. Techniques based on the power spectral density (PSD) and wavelet transform (WT) are utilized for feature extraction. The sensitivity of the proposed method is investigated under varying operating speeds and radial bearing load. In this study, the inverse problem of parameter identification is investigated. The problem of parameter identification is recast as an optimization problem and two well known evolutionary algorithms, differential evolution (DE) and particle swarm optimization (PSO), are used to identify system parameters given a system response. For online parameter identification, differential evolution outperforms particle both in terms of adaptability and tighter convergence properties. The distinction between the two methods is not distinctively obvious on the offline parameter identification problem.

Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: Smart Structures and Structronic Systems: Sensing, Energy Generation and Control

2014;():V04BT04A059. doi:10.1115/IMECE2014-36785.

This study aims to present a field dependent phenomenological model to characterize the Magneto-Rheological (MR) fluid in the pre-yield region under varying frequency and applied magnetic field. Systematic analytical and experimental studies are proposed to formulate a hybrid model for representing complex shear modulus of a typical MR fluid (MR 122EG from Lord Corporation) as a function of both applied magnetic field and frequency. Two fully treated MR based sandwich beams with aluminum and copper face layers and MR fluid as the core layer are designed and fabricated. Uniform magnetic flux across the sandwich beam is provided using two permanent magnets. The fabricated MR based sandwich beams are then tested on an electrodynamic shaker under sweep sine excitation and different applied magnetic field to realize the effect of external excitation frequency and applied magnetic field on the stiffness and damping properties of the structure. The finite element model based on classical plate theory is also developed to analyze vibration response of the designed MR based sandwich beams incorporated with MR fluid. Then, by correlating the finite element results with those of the experiment, the frequency and field dependent complex shear modulus of the MR fluid is identified.

Topics: Fluids
Commentary by Dr. Valentin Fuster
2014;():V04BT04A060. doi:10.1115/IMECE2014-37199.

Opto-mechanical actuators do not require hard-wired connections to control light source. Accordingly, the control commands will not be influenced by undesirable electric noises. Without accessorial devices and connecting wires, photonic control which conforms to the lightweight trend of space structure has great research value. PLZT photostrictive actuator can only induce actuation strain along its polarized direction, so it has the deficiency of one-way actuation. In this paper, the novel hybrid photovoltaic/piezoelectric actuation mechanism is proposed to remedy this deficiency. The ultraviolet light-driven PLZT induced voltages are used to drive piezoelectric actuator. Based on the equivalent electrical model, constitutive model is established to define the time history of actuation strain of piezoelectric actuator driven by photovoltage. Experimental platform is established to verify this established constitutive model. A logical switch is designed to realize positive and negative connection switch between PLZT photovoltaic generator and piezoelectric actuator. It is experimentally validated that the piezoelectric actuator can induce both positive and negative control forces.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A061. doi:10.1115/IMECE2014-37343.

Along with the rapid development of space exploration, communication and earth observation technology, the large space membrane structure gains its widely application. With poor stiffness and large flexibility, the surface accuracy of membrane structures can be easily interfered by the space environment variety, so precise shape control of in-orbit space membrane reflector becomes the focus in space technology area. As an object for this paper, the active control of the membrane reflector deformation under typical thermal disturbance in space is investigated. Considering of Von-Karman geometrical nonlinearity, the equilibrium equations of a circular membrane are firstly presented based on Hamilton’s Principle and Love’s thin shell theory. As a simplification for equilibrium equations, the nonlinear mathematical model for the circular membrane in a symmetrical temperature field is obtained. In the next place, an FE model for a circular membrane under thermal load is developed in Abaqus as an example. By contrasting the FEM deformation analysis with mathematical modeling solutions of circular membrane reflectors under typical thermal load, it is demonstrated that the theoretical model is capable of predicting the amplitude of membrane surface deformation. At last, a boundary actuation strategy for membrane shape control is proposed, which could effectively decrease the membrane wrinkle induced by thermal disturbance via precisely control to the tension of the SMA wire actuators. The simulation result indicates the effectiveness of boundary active control strategy on improving membrane surface accuracy with different temperature distributions. The conclusions of modeling and analysis in this paper will be an essential theoretical foundation for future research on active flatness control for in-orbit large space membrane structure.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A062. doi:10.1115/IMECE2014-37574.

Higher-order layerwise piezoelectric laminate mechanics are presented for predicting the low-velocity impact response of pristine composite and sandwich composite plates with piezoelectric transducers. The present formulation enables prediction of the global (temporal variation of impact force, deflection, strain and sensory potential) and local through-thickness (distribution of displacement, stress and strain) impact response of plates with piezoelectric layers or patches. Its enhanced capabilities include efficiency in terms of computational cost, since the system matrices are reduced by means of a Guyan scheme or by using the eigenvectors, thus leading to a plate-impactor system containing a single or two deflection amplitudes per vibration mode, depending on consideration of transverse compressibility. The transfer of the plate-impactor system to state-space enables investigation of the feasibility of real-time active control towards impact force reduction by using output feedback control laws.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A063. doi:10.1115/IMECE2014-37772.

Flexoelectric effect occurs in the solid crystalline dielectrics of symmetry or centro-symmetric crystals, which shows the electromechanical coupling of the polarization response and the strain gradient or the stress and the electric field gradient. Thus, a generic stress expression induced by the converse flexoelectric effect is established first in this study. The generic stress expression is simplified to a cantilever beam to evaluate the vibration control effect due to the converse flexoelectric effect. Flexoelectric fiber embedded with a metal core is placed into the cantilever beam to generate inhomogeneous electric field. When the flexoelectric fiber is actuated with the applied voltage, stress induced by the actuator is obtained with the electric field gradient, which results in a control bending moment to the beam. Static displacement control of the cantilever beam is established and the control effect is related to the fiber location and size of the flexoelectric fiber and the metal core. Cases show that the control effect is enhanced when the flexoelectric fiber is far away from the neural surface of the beam. Besides, the control effect can enhance with thinner fiber thickness. Since the piezoelectricity is similar to the flexoelectricity, comparison of the vibration control induced by the piezoelectric fiber is also discussed. The results show that the control effect of the flexoelectric fiber is more effective than the piezoelectric fiber in the cantilever beam.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A064. doi:10.1115/IMECE2014-37839.

Distributed sensing using piezoelectric sensors have been widely studied on shell-type structures. Usually, sensing signals by piezoelectric sensors are contributed by both membrane and bending strains which are always closely coupled so that either of them is not easy to be extracted from the physical output signal. Based on the direct flexoelectric effect, flexoelectric materials are promising transducers with capability of monitoring the structural vibration especially the bending behavior. In this study, a hybrid flexoelectric-piezoelectric configuration based on a cylindrical shell is proposed to separately monitor its membrane and bending behaviors. A five-layer composite cylindrical shell is established. A piezoelectric layer is embedded in the neutral surface of the shell and flexoelectric layers are laminated on the inner and outer surfaces. The piezoelectric layer and the flexoelectric layers are segmented into a number of patches serving as distributed sensors. Results show that for piezoelectric sensors, only the membrane strain component is detected while the flexoelectric sensing signals are only contributed by the bending strain component. In order to further obtain signal information respectively indicating the longitudinal and the circumferential bending strains, an orthogonal lamination scheme of flexoelectric layers was proposed. Signal modulate circuits with different flexoelectric material constants were also designed in order to directly achieve on-line monitoring. Spatial distributions of hybrid flexoelectric-piezoelectric sensing signals were evaluated and analyzed in case studies. Results show that by implementing the orthogonal lamination scheme, the flexoelectric sensors can individually predict the longitudinal and circumferential bending behaviors. Such a hybrid configuration is also applicable to other structures.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A065. doi:10.1115/IMECE2014-37850.

Conical shells have advantages such as light weight, higher stiffness and strength, its stiffness ratio between axial and transverse directions can be easily adjusted by changing its apex angle. Thus conical shell can be utilized as an isolator to protect precision payloads and equipment from severe dynamic loads. In this study, vibration isolation performance of a conical shell isolator laminated with piezoelectric actuators is investigated. The conical shell isolator is manufactured from epoxy resin. The payload is at the minor of the isolator. The major end of the isolator is fixed at a flange installed on a shaker. Macro fiber composite (MFC) is used as actuator, which is laminated on the outer surface of the conical isolator. The sensing signals from sensors on the isolator is transferred to a dSPACE system and the control voltage is transferred to a power amplifier and then to the MFC actuator. The control voltage is calculated in the Matlab/Simulink environment. Both negative velocity feedback and optimal controllers are employed in the active vibration control. The payloads are simplified to be a rigid cylinder, and two payloads with different weight are investigated in the study. Experimental results show that the proposed conical shell isolator is effective for vibration isolation of payloads, and vibration amplitude of the payload can be significantly reduced.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A066. doi:10.1115/IMECE2014-38481.

In this study the closed-loop vibrational behavior of aircraft wing is investigated. The wing is modeled as a thin-walled composite beam with a diamond shaped cross-section. This beam model incorporates a number of non-classical effects such as material anisotropy, transverse shear deformation and warping restraint. Moreover, the directionality property of thin-walled composite beams produces a wide range of elastic couplings. In this respect, an anti-symmetric lay-up configuration i.e. Circumferentially Uniform Stiffness (CUS) is employed to generate coupled motion of transverse-lateral bending and transverse shear. The active feedback control is performed by using adaptive materials. The piezoelectric layers are symmetrically embedded in the host structure and the piezoactuator is spread over the entire beam span. As a result of this a boundary moment is induced at the beam tip and in this case, the control is achieved via the boundary moment feedback control yielding an adaptive change in the dynamical characteristics of the beam. the cases of proportional and velocity feedback control procedures are applied and the effect of ply-angle orientation on the fundamental frequencies are investigated and discussed.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A067. doi:10.1115/IMECE2014-40319.

In this paper, a shape memory alloy wire is used as an actuator in a gripper. Additionally, a fuzzy controller is developed to control the force produced by the gripper. Fuzzy logic employed in the controller is used to tune the PID controller gains and improve the performance of the conventional PID controller. The performances of the proposed fuzzy PID controller and the conventional PID controller are compared with experiment tests. The experimental results verified the effectiveness of the proposed controller for the various command forces.

Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: Vibration, Noise Control and Damping Technologies

2014;():V04BT04A068. doi:10.1115/IMECE2014-36224.

This paper describes a vibration analysis system for a rider and two infants riding on a bicycle with two infant seats. To examine the vibrations of the rider and infants, a vibration model and a simulation system were designed for this bicycle–rider–infant system. The vibration characteristics in the analytical results were compared with the experimentally measured results. The effects of the vibrations on the occupants owing to the altered centroid of the bicycle were investigated. This investigation indicated that the analytical results corresponded with the measurement results for the occupants. When the centroid of the bicycle was moved forward, the root mean square (RMS) acceleration values for the front infant increased, whereas the maximum acceleration values decreased. In contrast, both the RMS and maximum values of acceleration for the rear infant increased when the centroid of the bicycle was moved forward. However, both the RMS and maximum values of acceleration for the rider increased when the centroid of the bicycle was moved backward. On the basis of these results, a relationship between the centroid of the bicycle and the transient response of the occupants was found by using the proposed vibration analysis system.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A069. doi:10.1115/IMECE2014-36242.

Mass imbalance is one of main vibration sources for rotating machine tool spindle, which has many negative effects on spindle bearing and work-piece surface. In order to reduce these harmful effects, an online automatic balancing system is investigated in this paper. The system proposed is composed of sensor, electromagnetic ring balancer and active controller. The electromagnetic ring balancer uses an annular coil to generate the pulsing drive magnetic field and uses the counterweight plate to obtain the required correction mass. When the spindle rotates, if unbalance occurs the proposed balancer will be driven to reach the predetermined angular position under the electromagnetic field to then realize balance, the balanced position can be determined according to the measured signals and the adaptive influence coefficient method. The new single-plane self-balancing motorized spindle and DSP-based controller were developed to validate design of the proposed online active balancing system. The experimental results show that the developed balancing system is effective for vibration suppression of rigid spindle.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A070. doi:10.1115/IMECE2014-37105.

In the past decade, beams that are made of functionally graded materials (FGM) have been employed in many engineering and biomedical application fields. In this paper, dynamic response of a FGM Timoshenko beam that is supported by an elastic foundation and is subjected to a moving mass, i.e., the effects of boundary flexibility, has been investigated. It is assumed that the material properties of the beam will change only in the thickness direction. The governing equations of motion are derived using Hamilton’s principles. The partial governing differential equations of motion are reduced to a set of ordinary differential equations by using Petrov-Galerkin method. Runge-Kutta numerical scheme is employed to solve the obtained set of ordinary differential equations. After verification of the results for some special cases with known sloutions the effect of various parameters such as the velocity of moving loads, the boundary flexibility, the power-law index on the vibration of the beam have been investigated. The special case of the solution of the problem was compared with the study of Mesut Simsek [2010] and H. P. Lee [1998] which showed excellent agreement. The results have also been compared to the similar beam without FGM and the advantages of FGM have been discussed.

Topics: Vibration
Commentary by Dr. Valentin Fuster
2014;():V04BT04A071. doi:10.1115/IMECE2014-37365.

This paper presents dynamic behaviors of a flexible rotor supported on nonlinear bearings and nonlinear squeeze film dampers. The nonlinear bearing and damper forces, which depend on instantaneous nodal displacements and velocities, are calculated at each time step through closed form solutions of Reynolds equation. Such combinations of fluid film bearings and squeeze film dampers are often used in industrial machines such as compressors and steam turbines to increase system damping. No previous works have studied the nonlinear time transient analysis of a fluid film bearing and damper combination. To describe the coupled motion of shaft, bearing and squeeze film damper, a method of assembling both the linear rotor and the nonlinear components is developed. The numerical transient analyses are applied to a 3-disk rotor supported with nonlinear short plain journal bearings and nonlinear short squeeze film dampers. Squeeze film dampers, introduced to the system, increase dynamic stability of the system under a wide range of system rotational speeds, and decrease the bearing forces under severe unbalance forces. Different nonlinear rotor dynamic behavior, such as sub-harmonic, super-harmonic and torus orbits are shown in transient analyses. This type of analysis can be employed to study whether a centering spring is required in the damper or not.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A072. doi:10.1115/IMECE2014-37646.

The natural frequency is the key performance parameters of a rubber materials damper, and it is determined by the static and dynamic shear properties of the rubber materials (rubber ring) and the moment of inertia of the inertia ring. The rubber ring is usually in compression state, and its static and dynamic shear properties are dependent on its sizes, compression ratio and chemical ingredients. A special fixture is designed and used for measuring static and dynamic shear performance of a rubber ring under different compression ratios in the study. To characterize the shear static and dynamic performances of rubbers, three constructive models (Kelvin-Voigt, the Maxwell and the fractional derivative constitutive model) are presented and the method for obtaining the model parameters in the fractional derivative constructive models are developed using the measured dynamic performance of a rubber shear specimen. The natural frequency of a rubber materials damper is calculated using the fractional derivative to characterize the rubber ring of the damper, and the calculated frequencies are compared with the measurements.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A073. doi:10.1115/IMECE2014-38177.

Condition monitoring and fault diagnosis for rolling element bearings is an imperative part for preventive maintenance procedures and reliability improvement of rotating machines. When a localized fault occurs at the early stage of real bearing failures, the impulses generated by the defect are relatively weak and usually overwhelmed by large noise and other higher-level macro-structural vibrations generated by adjacent machine components and machines. To indicate the bearing faulty state as early as possible, it is necessary to develop an effective signal processing method for extracting the weak bearing signal from a vibration signal containing multiple vibration sources. The ensemble empirical mode decomposition (EEMD) method inherits the advantage of the popular empirical mode decomposition (EMD) method and can adaptively decompose a multi-component signal into a number of different bands of simple signal components. However, the energy dispersion and many redundant components make the decomposition result obtained by the EEMD losing the physical significance. In this paper, to enhance the decomposition performance of the EEMD method, the similarity criterion and the corresponding combination technique are proposed to determine the similar signal components and then generate the real mono-component signals. To validate the effectiveness of the proposed method, it is applied to analyze raw vibration signals collected from two faulty bearings, each of which involves more than one vibration sources. The results demonstrate that the proposed method can accurately extract the bearing feature signal; meanwhile, it makes the physical meaning of each IMF clear.

Topics: Bearings , Vibration , Signals
Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: Vibrations of Continuous Systems

2014;():V04BT04A074. doi:10.1115/IMECE2014-37039.

Harnessing structural elements with strings, power cables, and signal cables increases the complexity in modelling the dynamic behaviour of such structures. Developing models capable of accurately predicting the dynamic behaviour of these systems is of great importance for space structures that cannot be tested prior to launch. The focus of this work is obtaining an equivalent continuum model for string-harnessed beam-like structures with periodic wrapping patterns. The tension in the string is assumed to vary as the beam deflects. The displacement field with second-order terms is determined and from which the Green-Lagrange strain tensor is obtained. After finding kinetic and potential energy expressions Hamilton’s principle is used to obtain the partial differential equation and boundary conditions. Numerical results for the shift in the natural frequencies are presented for various string properties to investigate their effects on the structure.

Topics: String , Modeling , Vibration
Commentary by Dr. Valentin Fuster
2014;():V04BT04A075. doi:10.1115/IMECE2014-37611.

The active vibration control of a rectangular sandwich plate by Positive Position Feedback is experimentally investigated. The thin walled structure, consisting of carbon-epoxy outer skins and a Nomex paper honeycomb core, has completely free boundary conditions. A detailed linear and nonlinear characterization of the vibrations of the plate was previously performed by our research group [1, 2]. Four couples of unidirectional Macro Fiber Composite (MFC) piezoelectric patches are used as strain sensors and actuators. The positioning of the patches is led by a finite element modal analysis, in the perspective of a modal control strategy aimed at the lowest four natural frequencies of the structure. Numerical and experimental verifications estimate the resulting influence of the control hardware on the modal characteristics of the plate. Experimental values are also extracted for the control authority of the piezoelectric patches in the chosen configuration. Single Input – Single Output (SISO) and MultiSISO Positive Position Feedback algorithms are tested and the transfer function parameters of the controller are tuned according to the previously known values of modal damping. A totally experimental procedure to determine the participation matrices, necessary for the Multiple-Input and Multiple-Output configuration, is developed. The resulting algorithm proves successful in selectively reducing the vibration amplitude of the first four vibration modes in the case of a broadband disturbance. PPF is therefore used profitably on laminated composite plates in conjunction with strain transducers, for the control of the low frequency range up to 100 Hz. The relevant tuning procedure moreover, proves straightforward, despite the relatively high number of transducers. The rigid body motions which arise in case of free boundary conditions do not affect the operation of the active control.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A076. doi:10.1115/IMECE2014-38239.

This paper deals with MEMS resonator sensors under double electrostatic actuation. The system consists of a MEMS cantilever between two parallel fixed plates. The frequencies of actuation are AC near natural frequency, and AC half natural frequency. The voltage response of the structure is investigated, and parameter influences reported.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A077. doi:10.1115/IMECE2014-39547.

The effects of spindles vibrational behavior on the stability lobes and the chatter behavior of machine tools have been established, and the service life has been observed to reduce the system natural frequencies. In this paper, a ‘calibrated’ FEM model of the spindle system, where the bearings are modeled as linear spring elements, is introduced. The numerical models of a sample spindle system are developed in ANSYS® software using BEAM188 and SOLID187 elements. COMBIN14 elements are used to model the bearings; by varying the spring constant value of these elements the spindle’s fundamental frequency is tuned to match the nominal value, also verified experimentally. The beam element-based model is observed to converge faster than the one based on solid elements. The uncalibrated frequencies resulting from latter model are also found to be lower than those obtained from the former one, which could be associated with the shear/rotary inertia effects present in the SOLID187 element.

Commentary by Dr. Valentin Fuster
2014;():V04BT04A078. doi:10.1115/IMECE2014-39841.

Flexible multistage rotating systems that are supported by water-lubricated rubber bearings (WLRB) have many engineering applications, including power generation, mining, water services, waste treatment, oil and gas industries, and industrial processes. Due to the flexibility of rotating shafts in these applications, dynamic modeling and vibration analysis is essentially important to optimal design and reliable operation of this kind of rotor systems.

This paper presents a new model of WLRBs, with the focus on determination of bearing dynamic coefficients. Conventional bearing models are normally of pointwise type, and are invalid for WLRBs that have a large length-to-diameter ratio. The bearing model proposed in this work considers spatially distributed bearing forces, and for the first time, addresses the issue of mixed lubrication, which involves interaction effects of shaft vibration, elastic deformation of rubber material and fluid film pressure. With the bearing model, the dynamic response of a flexible multistage rotating system with WLRBs is described by a Distributed Transfer Function Method (DTFM). The steady-state response of the rotor system due to unbalanced mass is then computed by the DTFM, and compared with experimental data, yielding the dynamic stiffness coefficients of WLRBs. It is shown that the proposed bearing model and DTFM formulation is useful in vibration analysis and optimal design of WLRB-supported flexible multistage rotor systems.

Topics: Rubber , Bearings , Modeling , Rotors , Water
Commentary by Dr. Valentin Fuster
2014;():V04BT04A079. doi:10.1115/IMECE2014-40247.

Typically, active resonators for vibration suppression of flexible systems are uniaxial and can only affect structure response in the direction of the applied force. The application of piezoelectric bender actuators as active resonators may prove to be advantageous over typical, uniaxial actuators as they can dynamically apply both torque and translational force to the base structure attachment point; this minimizes the likelihood that the attachment location is the node of a mode (rotary or translational). In this paper, Hamilton’s Principle is used to develop the equations of motion for a continuous two-beam system composed of a cantilevered, primary base beam with a secondary piezoelectric bender mounted to its surface. A disturbance force is applied near the fixture location of the base beam and the system response is estimated using a sufficient quantity of assumed eigenfunctions that satisfy the geometric boundary conditions. A theoretical study is performed to compared the continuous system eigenfunctions to a finite element model (FEM) of the two-beam structure and the required number of eigenfunctions required to yield a convergent solution for an impulse excitation is explored. In addition, the frequency response function for the dynamic system is presented and compared to that of a FEM.

Commentary by Dr. Valentin Fuster

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