bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinematic Analysis of Brake-Induced Vehicle Steering Wheel Vibration
Authors: Loh Wei-Yi , Basch Rena , Dalka Tom
Published: June 2008

Vehicle steering comfort is strongly influenced by chassis system sensitivity to brake-induced vibration. If drivers feel vibration on the steering wheel during a braking event, it negatively impacts their satisfaction with a vehicle’s performance and quality. The suspension is the primary chassis sub-system that transmits vibration from the brakes to the rest of vehicle. Since the suspension system is directly linked with the brake, tire/wheel assembly, sub-frame and steering system, its coupled vibration is very complicated. The current paper presents a sensitivity study of chassis system vibration distribution, a vibration reduction proposal with traditional vibration approach and a vibration reduction proposal with a kinematic design strategy. A system integration approach is used to derive an improvement strategy that can potentially make a vehicle insensitive to the vibration caused by torque variation of the brakes. The approach links suspension, steering and sub-frame vibration characteristics, kinematics modeling and robust design principles in a systematic fashion. The concept and method have been successfully demonstrated on a typical mid-size passenger car.
From Off-Line to Real Time Simulations by Model Reduction and Modular Vehicle Modelling
Authors: Pankiewicz E. , Rulka W.
Published: June 2008

Over the last couple of years there has been a growing tendency in the automotive industry to use more active control systems with mechatronic components, realized by electronic control units (ECU). As the ECU is a highly complex system and also for reasons of safety and costs the ECU-test is not carried out in road tests, but at a much earlier time, i.e. in the laboratory, using Hardware-in-the-Loop (HiL) simulation. This requires real-time environmental models. This paper shows how the transition from offline multi-body-system (MBS) models to real-time simulation can be achieved automatically by using a component oriented reduction procedure for vehicle suspensions, which keeps the full component parameterization. This necessitates a transformation of the equations of motion from differential algebraic equations (DAE) into ordinary differential equations (ODE). For use in HiL-simulators the equations of motion with open interfaces of the applied forces and torques are provided to be integrated in a modular dynamic ride model.
Optimal Comfort Response of Road Vehicles Using Flexible Multibody Dynamics
Authors: Gonc¸alves Joa˜o P. C. , Ambro´sio Jorge A. C.
Published: June 2008

The design process of road vehicles, very often based in intuition and experience, can be greatly enhanced through the use of optimization techniques concurrently with multibody codes. The approach proposed here for flexible multibody models allows for the representation of complex shaped bodies using general finite element discretizations, which deform during the dynamic loading of the system, while the gross rigid body motion of these bodies is still captured using body fixed coordinate frames. Components of the system for which the deformations are relatively non-important are represented with rigid bodies. This methodology is applied to a road vehicle, where the flexibility plays an important role in its ride and handling dynamic behavior. The use of sparse matrix systems solvers and modal superposition, to reduce the number of flexible coordinates, in the computer simulation assures a fast and reliable analysis tool for the optimization process. The vehicle optimum design is achieved through the use of an optimization algorithm with finite differences sensitivities, where the characteristics of the vehicle components are the design variables to which appropriate constraints are imposed. The ride optimization is achieved finding the optimum of a ride index that results from a metric that accounts for the acceleration in several key points in the vehicle, weighted in face of their importance to the occupant comfort. Simulations with different road profiles are performed for different speeds accounting for various ride situations.
Edge Projected Planar Rectangular Element for Modeling Flexible Multibody Systems
Authors: Wasfy Tamer M.
Published: June 2008

A four-node planar rectangular element, suitable for modeling flexible multibody systems, is described. Linear interpolation is used for the element shape and normal stresses. The element normal stresses are projected to the element edges. The element shear strain is set to the average of the change of the element corners’ angles. The average shear strain is projected to torsional-springs at each of the element corners in order to model the element shear mode. The element is strategically designed to eliminate locking and spurious modes. Cartesian nodal coordinates are used as degrees-of-freedom. A total Lagrangian displacement formulation where the element deformations are measured relative to the unstressed element is employed. The equations of motion are integrated using an explicit temporal integration algorithm. Standard finite element and flexible multibody dynamics test problems are solved to demonstrate the accuracy and robustness of the element.
Vibration of an Euler-Bernoulli Uniform Beam Carrying Several Thin Disks
Authors: Naguleswaran S.
Published: June 2008

The Euler-Bernoulli uniform beam considered in this paper carry (n+1) thin disks, two of which are at the beam ends. For the analytical method used in the paper, n co-ordinate systems were chosen with origins at the disk locations. The mode shape of the portion of the beam between the jth and (j+1)th disk was expressed in the form Yj(Xj) = A Uj(Xj) + B Vj(Xj) in which Uj(Xj) and Vj(Xj) are ‘modified’ mode shape functions applicable to that portion but the constants A and B are common to all the portions. From the compatibility of moments and forces on the (n+1)th disk, the frequency equation was expressed in closed form as a 2nd order determinant equated to zero. Schemes are presented to compute the 4 elements of the determinant (from a recurrence relationship) and to evaluate the roots of the frequency equation. Computational difficulties were not encountered in the implementation of the schemes to beams carrying very large number of disks. The first three natural frequency parameters of 28 combinations of the boundary conditions (which includes classical clamped, pinned, sliding and free) are tabulated for beams carrying 6, 51, 201 or 1001 thin disks. The approaches in previous publications include those based on various approximate methods like finite element, Rayleighritz, Galerkin, transfer matrix etc. The results in the present paper may be used to judge the accuracy of values obtained by approximate methods. The theory developed in the paper will need modification if axial dimension of the disks are taken into account.
Robust Speed Control of a Low Damped Four Mass System Based on CRONE Control
Authors: Sabatier Jocelyn , Poullain Serge , Latteux Patrick , Oustaloup Alain , Thomas Jean Luc
Published: June 2008

In this paper, a robust speed control strategy is proposed for a low damped four mass system with backlash, in which the angular speed of the load to control cannot be measured by a sensor. This control strategy combines a Luenberger observer and a CRONE controller. The observer provides estimation of the load angular speed and of the disturbance torque applied on the load. Through the computation of only three independent parameters (as many as a PID controller), the CRONE controller permits to ensure the robust speed control of the load in spite of plant parametric variations and speed observation errors. The proposed control strategy is applied to a four mass experimental test bench.
The Time-Varying Fractional Order Difference Equations
Authors: Ostalczyk Piotr W.
Published: June 2008

In this paper we explore the linear difference equations with fractional orders being a function of time. A description of closed-loop dynamical systems described by such equations is proposed. In the numerical example a simple control strategy based on time-varying fractional orders is presented.
The Hydractive CRONE Suspension: Operation Principle and Stability Study
Authors: Altet Olivier , Moreau Xavier , Oustaloup Alain , Nouillant Ce´dric
Published: June 2008

Mechatronic subsystems have been extensively developed in automotive applications as they increase performance compared to passive components. The Hydractive CRONE suspension based on fractional differentiation is presented as a hybrid system undergoing an infinite sequence of autonomous switchings. The modelling and operation of Hydractive CRONE suspension as a hybrid system are presented. Finally the stability of Hydractive CRONE suspension is demonstrated using the maximum principle extended to hybrid systems.
A Local Fractional Derivative
Authors: Li Xiaorang , Essex Christopher , Davison Matt
Published: June 2008

A new definition of fractional order derivative is given and its basic properties are investigated. This definition is based on the Weyl derivative and is a local property of functions. It can be applied to non-differentiable functions and may be useful for studying fractal curves.
Numerical Simulations of Fractional Systems
Authors: Aoun Mohamed , Malti Rachid , Levron Franc¸ois , Oustaloup Alain
Published: June 2008

This paper deals with the design and simulation of continuous-time models with fractional differentiation orders. Two new methods are proposed. The first is an improvement of the approximation of the fractional integration operator using recursive poles and zeros proposed by Oustaloup (1995) and Lin (2001). The second improves the simulation schema by using a modal representation.
Modelling and Simulation of Fractional Systems Using a Non-Integer Integrator
Authors: Poinot Thierry , Trigeassou Jean-Claude
Published: June 2008

An original method for modelling and simulation of fractional systems is presented in this paper. The basic idea is to model the fractional system by a state-space representation, where conventional integration is replaced by a fractional one with the help of a non integer integrator. This operator is itself approximated by a N + 1 dimensional system composed of an integrator and of a phase-lead filter. This method is compared to other techniques like direct discretization of the fractional derivator and diffusive representation. Numerical simulations exhibit the general applicability and flexibility of this new approach to different types of fractional models and to non conventional non integer derivation with limited spectral range.
Implementation of Fractional Calculus Using Hierarchical Models: Application to the Terminal Transition of a Complex Polymer
Authors: Heymans Nicole
Published: June 2008

Hierarchical viscoelastic elements whose behaviour is intermediate between linear elasticity and Newtonian viscosity (springpots) are incorporated into classical analog models describing linear viscoelastic behaviour. This approach is extended in the present work to describe the terminal transition from self-similar viscoelasticity to pure flow. Tschoegl’s formulation of a finite Gross Marvin ladder model is generalized and applied to other models, and this approach is compared with Friedrich’s method based on application of an exponentiel cutoff to the relaxation function. The method is illustrated using dynamic mechanical measurements on a triblock adhesive in isothermal frequency sweeps. This material displays thermorheological complexity precluding application of time-temperature superposition. Tschoegl’s formulation affords a better description of this material than Friedrich’s approach. The method described here is a useful alternative to time-temperature superposition requiring a limited number of adjustable parameters.
Forced Vibrations of Continuous Rotor With Strong Geometrical Nonlinearity
Authors: Nagasaka Imao , Liu Jun , Ishida Yukio , Katou Kouta
Published: June 2008

When both ends of an elastic continuous rotor are supported simply by double-row self-aligning ball bearings, the geometrical nonlinearity appears due to the stiffening effect in elongation of the rotor if the movement of the bearings in the longitudinal direction is restricted. As the rotor becomes more slender, the geometrical nonlinearity becomes stronger. In this paper, we study unique nonlinear phenomena due to the strong nonlinear spring characteristics and an initial axial force in the vicinity of the major critical speed ωc and twice ωc. When the rotor is supported horizontally, the difference in support stiffness and the asymmetrical nonlinearity appear as a result of the rotor of the equilibrium position. By the influences of the internal resonance and the initial axial force, the nonlinear resonance phenomena become very complex. For example, a peak of resonance curves split into two peaks, these two peaks leave each other and then become a hard and a soft spring types, respectively, and almost periodic motions and chaotic vibrations appear. We clarified these phenomena theoretically and experimentally.
Non-Linear Dynamics of a Rotor-Bearing System Based on the Invariant Manifold Approach
Authors: Serra Villa Cristiano Viana , Sinou Jean-Jacques , Thouverez Fabrice
Published: June 2008

The invariant manifold approach is used to explore the dynamics of a non-linear rotor, by determining the non-linear normal modes, constructing a reduced order model and evaluating its performance in the case of response to an initial condition. The procedure to determine the approximation of the invariant manifolds is discussed and a strategy to retain the speed dependent effects on the manifolds without solving the eigenvalue problem for each spin speed is presented. The performance of the reduced system is analysed in function of the spin speed.
Experimental Investigation of a System With Multiple Nearly Identical Centrifugal Pendulum Vibration Absorbers
Authors: Nester Tyler M. , Haddow Alan G. , Shaw Steven W.
Published: June 2008

This paper presents experimental results from tests completed on a rotor system fitted with nearly-identical circular path centrifugal pendulum vibration absorbers. A brief review of theoretical background for the absorbers is given along with an overview of the test apparatus. The experimental results for one absorber and for four absorbers are presented and compared with theoretical predictions and expectations. To the best knowledge of the authors, this is the first time that systematic, controlled experiments that monitored both the response of the absorbers and the rotor have been undertaken.
Optimal Design in Flexible Rotor-Sliding Bearing System With Squeeze Film Damper
Authors: Lu Yong-Zhong , Liao Dao-Xun
Published: June 2008

A dynamic model of a flexible rotor-sliding bearing system with squeeze film damper (SFD) is established. In the model are oil film inertia force, damping force, clearance excitation force, interference force of different frequencies and static load considered, as opposed to the previous research. On the basis of this model, then optimal design of the system is deeply studied. Simulation shows that the system optimization design can effectively improve the system stability.
Investigation of Turbine Coolers Vibration Parameters
Authors: Simonov Vladimir L.
Published: June 2008

Aviation turbine coolers (TC) are the main units in airplane air conditioning system. In this paper described are investigations aiming to estimate turbine coolers’ technical state using analysis of vibration parameters. In order to do this, an optoelectronic vibration-measuring system was designed. This system was intended for measurements of linear and / or angular oscillations of various points on housing and rotor of the turbine cooler. Appropriate software for vibration specters procession was created. Experiments were conducted in laboratory and plant conditions.
Annulus Whirling Motion Analysis of the Rotary Drill String by the Action of Hydrodynamic Pressure and Friction Force
Authors: Xiao Wensheng , Zhang Yang , Zhong Yifang
Published: June 2008

This paper studied the annulus whirling motion of rotary drill string. The drill string whirling motion is caused by the perturbing pressure produced by both hydrodynamic pressure of drilling fluid and the bending deformation of the drill string. Here, hydrodynamic pressure comes form fluid both inside and outside drill string; the bending deformation is derived from the dynamic conditions which guarantee a regular drill string whirling. In this paper, we present a mathematics model describing the annulus whirling motion and derive a critical condition of unstable whirling of the drill string. Furthermore the paper discusses in detail the physical mechanism and operating laws of the drill strings whirling caused by the action of drilling fluid inside and outside the drill string, the whirling motion analysis of the drill string collision and friction the wall of the well.
Contact Pressure of Quadrupedal Animals
Authors: Marghitu Dan B. , Swaim Steven F. , Rumph Paul F. , Cojocaru Dorian , Gillette Robert L. , Scardino M. Stacie
Published: June 2008

In this study we determine the pressure on the central area of each of the weight bearing pads of the paws of dogs at the walk. Pressure signal data from stance phase during walking were analyzed. Within paws, there were significant pressure differences among pads on both fore and hind limbs. The coefficient of restitution, the embedding dimension, and the Lyapunov exponents were calculated. The ability to measure and analyze pressure on individual paw pads provides insight into soft tissue stresses on the palmar/plantar surface of the paw. Pressure at a wound site on the pads has a detrimental effect on wound healing and a better understanding these stresses will be of benefit when suturing and bandaging pad wounds. Such information is especially important in athletic and working dogs, e.g. search and rescue dogs.
Convergence Behaviors of Reduced-Order Models for Frictional Contacts
Authors: Deshmukh D. , Berger E. J.
Published: June 2008

Numerical models to simulate interface behavior of friction connections under cyclic loading are investigated. The question of validity of lower order models in successfully capturing response of friction joints under cyclic loading is addressed. Single-element macroslip models are not capable of capturing localized interface behavior prior to gross interfacial slip. This paper focuses the convergence behavior of a multi-point contact microslip model comprised of Iwan-type elements for different physical parameters such as system response amplitude and kinematic state of the friction joint. It is observed that system dynamics play a significant role in determining the convergence of frictional behavior, especially for tuned damper sets. This behavior is explored using simple linearized models. In addition, the interface kinematic behavior converges at a slower rate than the structural response and therefore requires a higher-order interface model.
Experimental Study of Nonlinear Effects in a Typical Shear Lap Joint Configuration
Authors: Hartwigsen Christian J. , Song Yaxin , McFarland D. Michael , Bergman Lawrence , Vakakis Alexander F.
Published: June 2008

Although mechanical joints are integral parts of most practical structures, their modeling and their effects on the structural dynamics are not yet fully understood. This represents a serious impediment to accurate modeling of the dynamics and to the development of reduced-order, finite element models capable of describing the effects of mechanical joints on the dynamics. In this work we provide an experimental study to quantify the nonlinear effects of a typical shear lap joint on the dynamics of two structures: a beam with a bolted joint in its center; and a frame with the bolted joint in one of its members. Both structures are subjected to a variety of dynamical tests to determine the nonlinear effects of the joints. The tests reveal several important effects on the effective stiffness and damping effects of the lap joints. The possibility of using Iwan models to model the experimentally observed joint effects is discussed.
The Nonlinear Vibration and Stability of Axially Traveling Thin Plates
Authors: Luo Albert C. J. , Hamidzadeh Hamid R.
Published: June 2008

Frequency and responses for the free vibration of traveling, nonlinear, elastic plates are obtained that are based on a nonlinear plate theory developed by Luo in 2000. The plate theory includes the in-plane inertial forces, the centrifugal forces, curvature effects and the in-plane Coriolis inertia. The critical speeds are obtained while the frequency of the prebuckled plate vanishes, and the critical speed for the mode (1,1) response is not always minimal.
Dynamic Characterization and Stability of a Large Size Multibody Tiltrotor Model by POD Analysis
Authors: Masarati Pierangelo , Quaranta Giuseppe , Lanz Massimiliano , Mantegazza Paolo
Published: June 2008

A great level of flexibility and accuracy can be gained by employing a multibody approach as the modeling strategy for servo-aeroelastic analyses of rotating wing aircraft. However, the resulting models are often large, in terms of degrees of freedom, and fully nonlinear, making the dynamic characterization phase cumbersome and computationally demanding. Moreover, nonminimal set formulations such as the one used here to express the equations of motion may cause the rise of spurious eigenvalues. This paper presents the application to a tiltrotor model of a technique which associates the POD (Proper Orthogonal Decomposition) methodology, to reduce the impact of the model large dimensions, with standard dynamic system identification methods, to efficiently circumvent the complexity usually associated with the development phase of flexible multibody models. The same technique is also employed to assess the periodic motion aeroelastic stability of the tiltrotor.
Frequency Shifting in Nonlinear Resonant Systems With Damping
Authors: Znider Abdelghani , Quinn D. Dane
Published: June 2008

The dynamical behavior of a three degree-of-freedom system is considered in the presences of a resonance between two modes with nonlinear coupling. One resonant frequency describes a translational oscillation and is a flxed quantity while the second characterizes an unbalanced rotational component and is allowed to slowly vary in time. When a system is attracted to a state of sustained resonance, the steady-state frequency of the sustained resonance shifts, depending on the parameter values of the system. As the applied torque increases, the resonant frequency shifts upward, approaching the natural frequency of the translational mode. If the applied torque is too large, the sustained resonance no longer exists and the system cannot be attracted to a long-term resonance motion. Likewise, increasing damping in the translational mode reduces the resonant frequency and the amplitude of the translational oscillations, as well as the critical torque for which sustained resonances exist. This frequency shifting, seen in both the simulations of the original system and verifled in a experimental system, is characterized through the analysis of a reduced-order model developed through the method of averaging.
Coupling of an Aircraft Landing Gear Simulation Strategy to Parameter Identification Techniques for Enhanced Fidelity
Authors: Rook Todd
Published: June 2008

Brake-induced vibration often involves strong coupling with the aircraft structure, thereby necessitating a system level understanding. However, testing a full system is both costly and impossible until late in the development cycle. To overcome these issues, it becomes necessary to utilize simulation tools to assess the system behavior at an earlier stage. This paper demonstrates a methodology which implements such simulations to guide appropriate brake component tests that are more tractable for the brake supplier. As a result of this combined simulation and testing, a reduction in actual testing can be achieved. However, the ultimate success of the methodology depends on how well the components and the various parameters are estimated. Consequently, means to improve these estimations are also addressed in this paper.
Structure Preserving Transformations and Isospectral Flows for Second Order Systems
Authors: Friswell Michael I. , Garvey Seamus D. , Prells Uwe
Published: June 2008

When the dynamics of any general second order system are cast in a state-space format, the initial choice of the state-vector usually comprises one partition representing system displacements and another representing system velocities. Coordinate transformations can be defined which result in more general definitions of the state-vector. This paper discusses the general case of coordinate transformations of state-space representations for second order systems. It identifies one extremely important subset of such coordinate transformations — namely the set of structure-preserving transformations for second order systems — and it highlights the importance of these. It shows that one particular structure-preserving transformation results in a new system characterised by real diagonal matrices and presents a forceful case that this structure-preserving transformation should be considered to be the fundamental definition for the characteristic behaviour of general second order systems — in preference to the eigenvalue-eigenvector solutions conventionally accepted. The regular λ-matrix λ2M + λD + K with M,D,K ∈ Rn×n defines a second-order system. A one-parameter trajectory of such a system {M(t),D(t),K(t)} is an isospectral flow (or more correctly an equivalence flow) if the eigenvalues and the dimensions of the associated eigenspaces are the same for all parameter values t ∈ R. This paper presents the general form for real isospectral flows of real-valued second order systems.
Aeroelastic Flutter of a Rotating Disk in an Unbounded Compressible Inviscid Fluid
Authors: Jana Anirban , Raman Arvind
Published: June 2008

The aeroelastic flutter of an unbaffled flexible disk rotating in an unbounded fluid is investigated, by modeling the disk-fluid system as a rotating Kirchhoff plate coupled to irrotational flow of a compressible inviscid fluid. The fluid motions are governed by the wave equation of linear acoustics. Fluid-structure coupling is achieved between the disk and the fluid by means of the fluid loading on the disk and the velocity matching boundary conditions on the disk surface. A perturbed eigenvalue formulation is used to compute systematically the coupled system eigenvalues. A series solution is presented for the dual integral equations, arising from the mixed boundary value problem governing the fluid motions. It is found that two distinct aerodynamic effects occur — radiation damping into the surrounding fluid and added fluid inertia effect. Provided the disk has zero material damping, the radiation damping causes the flutter speed to coincide with the critical speed. This flutter instability is a degenerate bifurcation with eigenvalues crossing into the right half plane through the origin with zero speed. The added fluid inertia effect modifies the frequencies of the traveling waves but does not affect the critical speed.
An Analytical Prediction of the Global Period-1 Motion in a Periodically Forced, Piecewise Linear System
Authors: Menon Santhosh , Luo Albert C. J.
Published: June 2008

The analytical solution for the period-1 motion of a periodically forced piecewise linear system is obtained that based on the Poincare mapping and the switch planes pertaining to the two constraints. The stability and bifurcation of the period-1 motion are investigated, and numerical simulations are carried out to check the analytical prediction of period-1 motion. The symmetric and unsymmetrical stable period-1 motion plus an irregular motion are illustrated, and the analytical and numerical results are in a good agreement. This system demonstrates the behavior of the twin-well Duffing oscillator instead of the single-well Duffing oscillator. The similar mapping technique is applicable for other non-smooth dynamical systems.
A Review of Optimal Shock Isolation
Authors: Zhao Yinglong , He Lin , Wang Yu
Published: June 2008

Non-contact underwater explosion is the main threaten for warships, especially for submarines. Because many shock protection means can be used to limit the rattlespace (i.e., the maximum displacement of the equipment relative to the base) and the peak acceleration experienced by the equipment. Taking shock protection means and choosing the equipment with best shock-resistant performance while designing the settings can assure the safety of the on board settings. The optimization design method can be used to design the on board shock-resistant equipments. This is a review of the investigations in the field of optimum shock isolation. This survey covers the literatures from the initial studies to the present.
Cutting Vibration Monitoring Using a Spindle Displacement Sensor in Turning
Authors: Kim IlHae , Jang Dong Young
Published: June 2008

Unwanted vibration in machining, chattering, is generated due to mode coupling or regenerative effect of the process. It has to be avoided for the stable machining operation and quality of machined products. And monitoring the process is also important for realizing an unmanned machining system. While many researches were done on this area, it is still a difficult job to detect very small amplitude amount of chattering. A monitoring system using a capacitive-type cylindrical displacement sensor (CCDS) was developed to monitor cutting vibration during turning in this research. The variance of the measured spindle displacement signals using the developed sensor was calculated and utilized to quantify the small vibration in machining. The results were compared with variance obtained using a tool dynamometer. The result showed that the developed system could be utilized in monitoring the subtle changes of cutting vibrations with high sensitivity and confidence.
Dynamic Response of Whole Body System Subjected to Walking Generated Excitation
Authors: Bhat Rama B.
Published: June 2008

A human body is subjected to periodic excitations when walking at a uniform rate. In this study, the whole body is modeled as a multi degree of freedom system. The excitation is strictly caused by the muscle action, however, in the present study it is modeled as a sinusoidal acceleration input to all the masses. In view of the changing boundary conditions at the alternating feet movements, the system under study is a time varying system. However, in order to simplify the study, the system is considered as piecewise time invariant for each half period when one foot is in contact with the ground. The natural frequencies, responses in the time and frequency domains are computed, presented and discussed.
Compliance Optimisation for Robotic Assembly
Authors: Sharf I. , Bykov A.
Published: June 2008

Robotic assembly is prone to jamming and wedging, however, both conditions can be alleviated if the manipulator has certain compliance properties. In this article, the problem of compliance optimization of robotic arms is investigated with the view to finding robot configurations that have optimal compliance properties in the end-effector frame. Planar manipulators are considered with joint compliance only, ranging from three-dof to kinematically redundant five-dof arms. Robot configurations are determined with some features of the optimal compliance, starting with decoupling of translational and rotational properties to full isotropy of endpoint compliance. Optimization results also account for small variations of joint stiffness values which can be achieved by adjusting the servo-loop proportional gains. Analysis and optimal solutions are validated with commercial simulation software MSC.ADAMS.
Vibration of a Flexible Manipulator Carrying Offset Payloads
Authors: Naguleswaran S.
Published: June 2008

Resonance is an important consideration in the design and performance of manipulators. A simple model of a manipulator consists of a beam carrying heavy bodies. Publications are available on the vibration of beams carrying thin disk at each end and up to two disks in-span. The problem has not been tackled taking the axial width of the disks into account. In this paper the vibration of an Euler-Bernoulli stepped beam carrying an axially wide rigid body at each end and one at the step is investigated. The centre of mass of the body is assumed to be on the beam axis but within or outside its width. The frequency equations are expressed as 4th order determinants equated to zero for 64 combinations of the ‘general’, degenerate and classical boundary conditions at the ends. Tables of the first three frequency parameters are presented for example sets of 15 system parameters. Some of the models considered in this paper are valid models of manipulators, space structures and the like. Designers often use numerical methods like finite element formulation to obtain natural frequencies. The tables presented in this paper may be used to judge the frequencies obtained by numerical methods.
Design of Extended Kalman Filter for a Shape Memory Alloy Manipulator
Authors: Elahinia Mohammad H. , Ashrafiuon Hashem , Ahmadian Mehdi , Baumann William T.
Published: June 2008

This paper presents an Extended Kalman Filter (EKF) for estimation of the state variables of a single degree of freedom rotary manipulator actuated by Shape Memory Alloy (SMA). A state space model for the SMA manipulator is presented. The model includes nonlinear dynamics of the manipulator, constitutive model of Shape Memory Alloy, and the electrical and heat transfer behavior of SMA wire. In the experimental setup, angular position of the arm is the only state variable that is measured. The other state variables of the system are arm’s angular velocity, SMA wire’s stress, temperature and the Martensite factor, which are not available experimentally due to measurement difficulties. Hence, a model-based state estimator that works with noisy measurements is presented based on the Extended Kalman Filter. This estimator predicts the state vector at each time step and corrects its prediction based on the angular position of the arm which can be measured experimentally. The state variables collected through model simulations are also used to evaluate the performance of the EKF. Several EKF simulations are presented that show accurate, and robust performance of the estimator for different types of inputs.
Multiple Cooperating Robot Dynamics and Fuzzy Logic Control for Internal Force Minimization
Authors: Kumar Manish , Garg Devendra P.
Published: June 2008

This paper presents formulation and application of a strategy for control of two six degree-of-freedom robots carrying a common object in a cooperative mode. The paper focuses on control of internal forces that are generated when two or more robots carry an object in coordination. A combined position-force control scheme based on fuzzy logic is proposed. The controller scheme developed has been implemented successfully on two six degree-of-freedom ABB industrial robots. The simulations and the experiments performed demonstrate that the proposed control strategy is able to considerably decrease the internal forces.
Nonlinear Dynamics of a Noncontacting Atomic Force Microscope in Ultra-High Vacuum
Authors: Gottlieb O.
Published: June 2008

In this paper we formulate a nonlinear boundary-value problem describing thermoelastic dynamics of a microbeam for noncontacting Atomic Force Microscopy (AFM) that is operating in an ultra-high vacuum environment (UHV). A modal Galerkin projection yields a strongly nonlinear dynamical system that is governed by a planar homoclinic structure describing escape from a potential well. This structure is perturbed by both thermoelastic damping and modulated periodic actuation and reveals existence of local and global bifurcations and sheds light on possible thermoelastic instabilities leading to aperiodic dynamics.
Passive Vibration Control Through Nonlinear Energy Pumping
Authors: Vakakis Alexander F. , McFarland D. Michael , Bergman Lawrence , Manevitch Leonid , Gendelman Oleg
Published: June 2008

We examine vibration control through passive energy pumping in a system of damped coupled oscillators. This is a one-way, passive and irreversible energy flow from a linear main system to a nonlinear attachment that acts, in essence, as a nonlinear energy sink (NES). Energy pumping is caused by 1:1 resonance captures on resonant manifolds of the damped systems. We show that the NES is capable of absorbing significant portions of the energies generated by transient, broadband external excitations. We present numerical simulations of single- and multi-mode energy pumping, that involve isolated resonance captures or resonance capture cascades, respectively. In addition, we discuss methodologies for enhancing the nonlinear energy pumping phenomenon by properly selecting the system parameters. The described technique of passively localizing and locally eliminating externally induced energy provides a new paradigm for vibration and shock isolation of mechanical oscillators.
Damping of Flexural Vibration by Low-Density Foams and Granular Materials
Authors: Varanasi Kripa K. , Nayfeh Samir A.
Published: June 2008

The damping of flexural vibration by introduction of a layer of low-density foam or powder into a structure is investigated. First, we report on experiments in which a layer of foam attached to an aluminum beam gives rise to significant damping at frequencies high enough to induce standing waves in the foam layer. Next, we provide a simple model for such vibration in which the foam is treated as a two-dimensional elastic continuum in which waves can propagate and find that the model is in good agreement with the experiments. Then the results of experiments in which aluminum beams are filled with a low-density powder are presented. The powder-filled beams exhibit behavior qualitatively like that of the foam-filled beams, but we find that the powder can be adequately modeled as an inviscid compressible fluid.
Characterization, Modeling and Vibration Control of a Flexible Rubber Beam With Embedded Piezoelectric Actuators and Sensors
Authors: Grier Matthew L. , Jalili Nader
Published: June 2008

A cantilever rubber beam with laminated piezoelectric actuators and sensors is initially tested to determine the properties governing the dynamic behavior of the beam. Various techniques are employed to estimate beam properties such as elastic stiffness, damping coefficient and natural frequencies, as well as piezoelectric actuator capabilities for vibration control purposes. A simplified Euler-Bernoulli model is proposed, which is validated using the properties previously discovered. A passive electric shunt circuit is then proposed for the beam vibration suppression, when subjected to external excitation forces. Simulation of a series resistor-inductor shunt circuit is used to demonstrate the capability of altering the beam’s dynamic behavior. Various methods for tuning the shunt circuit are explored in an effort to achieve optimal vibration suppression characteristics. Furthermore, experimental testing is conducted for validation of simulation results, which also yields similar information about passive shunting techniques for vibration damping.
Shunt Tuning of a Piezoelectric Cantilever Beam Resonator
Authors: Muriuki Muturi G. , Clark William W.
Published: June 2008

This paper presents the design and analysis of a cantilever beam resonator that is driven by a piezoelectric material. The beam is a bimorph structure with Lead Zirconate Titanate (PZT) and stainless steel or aluminum layers. The PZT layer is electroded in segments to form a sensor and actuator pair for feedback to drive the resonator. An additional PZT segment is used, in conjunction with a capacitive shunt circuit, to change the vibration frequency of the resonator. The study is based on an analytical model of the beam and experimental testing.
Stabilization of Active Magnetic Bearing System Subject to Base Motion
Authors: Kim Hyun-Sik , Kim Ha-Yong , Lee Chong-Won , Kang Tae-Ha
Published: June 2008

The active magnetic bearing (AMB) systems mounted in moving vehicles are exposed to the disturbances due to the base motion, often leading to malfunction or damage as well as inaccurate positioning of the systems. Thus, in the controller design of such AMB systems, robustness to base disturbances becomes an essential requirement. In this study, effective control schemes are proposed for the homo-polar AMB system, which uses permanent magnets for generation of bias magnetic flux, when it is subject to base motion, and its control performance is experimentally evaluated. The base motion of AMB system is modeled as the dynamic disturbances in the gravity and base excitation forces. To effectively compensate for the disturbances, the angle feed-forward controller based on the inverse dynamic model and the acceleration feed-forward controller based on the normalized filtered-X LMS algorithm and the inverse dynamic model are proposed. The performance test of the prototype AMB system is carried out, when the system is mounted on a six degrees-of-freedom motion platform. The experimental results show that the performance of the proposed controllers for the AMB system is satisfactory in compensating for the disturbances due to the base motion.
Power Flow Analysis for Complicated System
Authors: Sun Lingling , Song Kongjie
Published: June 2008

The generalized theoretical models for vibrating machines isolated by multiple elastic mounts or by a mount-raft-mount system from non-rigid foundation were proposed. The structural analysis method was developed based on the power flow control perspectives. The dynamic transmission equations were derived to predict the power flow characteristics between subsystems. Numerical calculations of power flow for practical isolation systems were carried out to explore the interaction between the mounting frequency and the flexibility of supporting structure. The effects of mounting frequency on the power transmitted to the foundation were discussed. It is shown that the power flow can be reduced effectively by reasonable choice of mounting frequency.
2:2:1 Resonance in the Quasiperiodic Mathieu Equation
Authors: Rand Richard , Guennoun Kamar , Belhaq Mohamed
Published: June 2008

In this work, we investigate regions of stability in the vicinity of 2:2:1 resonance in the quasiperiodic Mathieu equation: d2xdt2+(δ+εcost+εμcos(1+εΔ)t)x=0, using two successive perturbation methods. The parameters ε and μ are assumed to be small. The parameter ε serves for deriving the corresponding slow flow differential system and μ serves to implement a second perturbation analysis on the slow flow system near its proper resonance. This strategy allows us to obtain analytical expressions for the transition curves in the resonant quasiperiodic Mathieu equation. We compare the analytical results with those of direct numerical integration. This work has application to parametrically excited systems in which there are two periodic drivers, each with frequency close to twice the frequency of the unforced system.
Stability Analysis of Parametrically Excited Systems With Time-Delay
Authors: Butcher Eric A. , Ma Haitao , Bueler Ed , Averina Victoria , Szabo Zsolt
Published: June 2008

This paper presents a new technique for studying the stability properties of parametrically excited dynamic systems with time delay modeled by delay-differential equations (DDEs) with time-periodic parameters. By employing a shifted Chebyshev polynomial approximation in each time interval with length equal to the delay period, the dynamic system can be reduced to a set of linear difference equations for the Chebyshev expansion coefficients of the state vector in the previous and current intervals. This defines a linear map which is the “infinite-dimensional Floquet transition matrix U”. Two different formulas for the computation of the approximate U, whose size is determined by the number of polynomials employed, are given. The first one, which results in a numerical stability matrix, uses the direct integral form of the original system in state space form while the second, which can give a symbolic stability matrix in terms of parameters, uses a convolution integral (variation of parameters) formulation. An extension of the method to the case where the delay and parametric periods are commensurate is also available. Numerical and symbolic stability charts are produced for several examples of time-periodic DDEs, including the delayed Mathieu equation and a model for regenerative chatter in impedance-modulated turning. The results indicate that this method is a effective way to study the stability of periodic DDEs.
Links Between Disc Brake Squeal and Pad In-Plane Motion
Authors: Yang Fulun , Pilipchuk Valery , Tan Chin An
Published: June 2008

This paper is focused on links between disc brake squeal and in-plane vibration of pads. A special experimental setup is developed in order to determine correlation between squeal acoustical signals and longitudinal accelerations of both pads. A strong coherence between spectral properties of squeal and pad vibrations is found and quantified. In particular, the dominant frequency of the acoustical and mechanical responses appears to be same. Essentially unharmonic temporal mode shapes of the pad vibrations are detected. Such mode shapes reveal the information about multiple frequency friction forces applied to the disc and pads with a possibility of resonance with their coupled elastic modes. Experimental time history records also show a significant out-of-phase component in the pad motions, which is associated with a bending moment applied to the disc. Major experimental observations admit theoretical interpretation based on a two degrees of freedom model. Theoretical conclusions and experimental results are found to be in a good agreement.
Friction/Vibration Coupling Due to Viscoelastic Interaction of Rough Surfaces of Two Disks in Frictional Contact
Authors: Farhang Kambiz , Lim Aik-Liang
Published: June 2008

Approximate equations describing contact of rough surfaces are implemented in the equations of motion for frictional interaction of two disks in relative rotational motion. The approximate equations are nonlinear functions of the relative axial position of the two disks and provide coupling between their compressive and rotary motion. A set of two coupled nonlinear ordinary differential equations is obtained. The mathematical formulation propounded in this paper connects the tribological events at micron-scale and the macroscopic scale vibration response of the two-disk system. This is accomplished by a visco-elastic account of interaction at the micron scale, its statistical quantification through the approximate analytical representation of the statistical expectation of contact force and the introduction of the contact force into the macro-scale dynamics of the two-disk system. Steady-state analysis of the system supports observed behavior of many mechanical systems with friction. It is shown that, as a result of coupling of the macro-system’s dynamics and contact, there are combinations of parameters at the microand macro-scale that yield negative slope in friction force/sliding speed, a well known source of dynamic instability. This results in an effective negative damping that tends to reduce with decrease in the normal load and/or increase in structural damping of the system.