Journal of Vibration and Control

Published by SAGE Publications
Online ISSN: 1077-5463
Publications
Conference Paper
Dynamic vibration absorbers are passive devices that have the appealing quality that, once properly designed, built, and installed, they generally operate without further attention or energy input. However, for additional flexibility, virtual absorbers have been introduced. A virtual absorber emulates the effect of a physical absorber by sensing the motion of the primary structure, utilizing a dynamic compensator to simulate the motion that a physical absorber would undergo, and computing and applying the reaction force that the physical absorber would apply to the primary structure. The computed reaction force is then implemented by means of a suitable actuator. Thus, the implementation of a virtual absorber requires the availability of sensors and actuators as well as processors and power supplies. One advantage of virtual absorbers over passive absorbers is that the parameters of the virtual absorber can be adjusted online
 
Conference Paper
This paper proposes a neural network approach for the identification and control of a benchmark flexible structure, i.e. a thin simply-supported plate with bonded piezoelectric film actuators and sensors. A specific linear differential inclusions (LDI) model is developed for a class of multilayer feedforward networks. With the technique, the plant model identified by the neural network can be represented as a linear time-invariant system so that the linear control theory can be applied to design the stabilizing flexible structure controller.
 
Conference Paper
An adaptive controller known as the self-tuning regulator (STR) is employed for actively controlling an actuator for vibration isolation. Numerical simulations of the developed STR for active vibration isolation of a simple mass-spring-damper system of two-degree-of-freedom subject to external disturbances are carried out. Experimental studies of vibration isolation by using a magnetostrictive actuator with a Terfenol-D rod are also presented. Both studies demonstrate the validity and effectiveness of the STR for active vibration isolation when the system is disturbed by a pure harmonic, two-modes harmonic, random, or even band-limited white noise excitation. In addition, the results are shown to be superior in terms of faster convergence and more vibration attenuation to those obtained by using a previously developed adaptive plant disturbance canceler
 
Conference Paper
A hybrid seismic control system for building structures is considered, which combines a class of passive nonlinear base isolator with an active control system. The objective of the active control component applied to the structural base is to keep the base displacement relative to the ground, the interstory drift and the absolute acceleration within a reasonable range according to the design of the base isolator. We use the adaptive backstepping approach for the control design. The base isolator device exhibits a hysteretic nonlinear behavior which is described analytically by the Bouc-Wen model. The control problem is formulated representing the system dynamics in two alternative coordinates: absolute (with respect to an inertial frame) and relative to the ground. A comparison between both strategies is presented by means of numerical simulations.
 
Conference Paper
Tall, slender structures and long bridges that inherit numerous uncertainties due to model errors, stress calculations, material properties, and load environments, may undergo large forces from natural hazards such as earthquakes and strong wind events. The paper develops a robust active control approach with parametric uncertainties in the system and control input, and unstructured uncertainties in disturbance input matrices based on an uncertain structural system. Special single valued decomposition (SVD) is applied to structured uncertain structures. The robust control law provides robust relative stability, an H<sub>∞</sub>-norm disturbance attenuation and H<sub>2</sub> optimality. The H<sub>∞</sub> norm of the transfer function from the external disturbance forces (e.g., earthquake, wind, and etc.) to the observed system states is restricted by a prescribed attenuation index δ. Preservation of robust H<sub>2</sub> optimality of uncertain structural systems is discussed. Considered uncertainties are both structured uncertainties and norm-bounded unstructured uncertainties. Numerical simulations that use the robust controller show significant reduction in vibrations. The resulting approach to robust control may be applied to analysis and design of practical structural systems
 
Conference Paper
This paper focuses on the design of optimal passive controllers for rest-to-rest manoeuvres of flexible structures. The parameters of the passive controller are determined by formulating an optimization problem to minimize the integral of the time absolute error, subject to control constraints. Appropriate outputs are selected which result in a passive input-output transfer functions for the plant. The design technique is first illustrated on the benchmark floating oscillator problem. This technique is then used to design dissipative controllers for models of overhead cranes. The crane is modeled with the wave equation used to represents the dynamics of the cable. Numerical results illustrate the effectiveness of the proposed technique
 
Conference Paper
One of the principal objectives of vibration isolation technology is to isolate sensitive equipment from a vibrating structure or to isolate the structure from an uncertain exogenous disturbance source. In this paper a dynamic observer-based active isolator is proposed that guarantees closed-loop asymptotic stability and disturbance decoupling between the vibrating structure and isolated structure. The proposed active isolator is applied to a uniaxial vibrational system and compared to an optimal linear-quadratic design
 
Article
We extend the second Noether theorem to fractional variational problems which are invariant under infinitesimal transformations that depend upon $r$ arbitrary functions and their fractional derivatives in the sense of Caputo. Our main result is illustrated using the fractional Lagrangian density of the electromagnetic field.
 
Article
Free, out of plane vibration of a rotating beam with nonlinear spring–mass system has been investigated. The nonlinear constraint is connected to the beam between two points on the beam through a rigid rod. Formulation of the equation of motion is obtained starting from transverse/axial coupling through axial strain. Solution is obtained by applying method of multiple time scale directly to the nonlinear partial differential equations and the boundary conditions. The results of the linear frequencies match well with those obtained in open literature. Subsequent nonlinear study indicates that there is a pronounced effect of spring and its mass. The influence of rigid rod location on frequencies is also investigated on nonlinear frequencies of rotating beam.
 
Article
This paper concerns stochastic perturbations of piecewise-smooth ODE systems relevant for vibro-impacting dynamics, where impact events constitute the primary source of randomness. Such systems are characterised by the existence of switching manifolds that divide the phase space into regions where the system is smooth. The initiation of impacts is captured by a grazing bifurcation, at which a periodic orbit describing motion without impacts develops a tangential intersection with a switching manifold. Oscillatory dynamics near regular grazing bifurcations are described by piecewise-smooth maps involving a square-root singularity, known as Nordmark maps. We consider three scenarios where coloured noise only affects impacting dynamics, and derive three two-dimensional stochastic Nordmark maps with the noise appearing in different nonlinear or multiplicative ways, depending on the source of the noise. Consequently the stochastic dynamics differs between the three noise sources, and is fundamentally different to that of a Nordmark map with additive noise. This critical dependence on the nature of the noise is illustrated with a prototypical one-degree-of-freedom impact oscillator.
 
The combustion curve ∆m(λ) for the constant fresh air feed δm a = 200 mg. 
Constants and variables of the model. 
Bifurcation diagrams: ∆m f against a residual gas fraction α for various fresh fuel amounts δm f . 
Article
We examine a simple, fuel-air, model of combustion in a spark ignition (si) engine with indirect injection. In our two fluid model, variations of fuel mass burned in cycle sequences appear due to stochastic fluctuations of a fuel feed amount. We have shown that a small amplitude of these fluctuations affects considerably the stability of a combustion process strongly depending on the quality of air-fuel mixture. The largest influence was found in the limit of a lean combustion. The possible effect of nonlinearities in the combustion process has been also discussed.
 
Article
We present a unified treatment to control problems on an arbitrary time scale by introducing the study of forward-backward optimal control problems. Necessary optimality conditions for delta-nabla isoperimetric problems are proved, and previous results in the literature obtained as particular cases. As an application of the results of the paper we give necessary and sufficient Pareto optimality conditions for delta-nabla bi-objective optimal control problems.
 
Article
We prove a necessary optimality condition for isoperimetric problems under nabla-differentiable curves. As a consequence, the recent results of [M.R. Caputo, A unified view of ostensibly disparate isoperimetric variational problems, Appl. Math. Lett. (2008), doi:10.1016/j.aml.2008.04.004], that put together seemingly dissimilar optimal control problems in economics and physics, are extended to a generic time scale. We end with an illustrative example of application of our main result to a dynamic optimization problem from economics. Comment: This is a preprint of an article whose final and definitive form will be published in the Journal of Vibration and Control. Date Accepted: November 21, 2008
 
The reduced Green function U(x) = 1 2 M β 0 /2 (x)) versus x (in the interval |x| ≤ 5), for β 0 = 0, 1/4, 1/2, 3/4, 1.
The fundamental solution versus x (in the interval |x| ≤ 5), for the double-order distribution {β 1 = 1/4, β 2 = 1} at times t = 0.1, 1, 10. Top: R-L form; Bottom: C form.
The fundamental solutions versus x (in the interval |x| ≤ 5), for the uniform order distribution in R-L and C forms compared with the solutions for some cases of single order. Top: t = 1; Bottom: t = 10.
Article
The partial differential equation of Gaussian diffusion is generalized by using the time-fractional derivative of distributed order between 0 and 1, in both the Riemann-Liouville (R-L) and the Caputo (C) sense. For a general distribution of time orders we provide the fundamental solution, that is still a probability density, in terms of an integral of Laplace type. The kernel depends on the type of the assumed fractional derivative except for the single order case where the two approaches turn to be equivalent. We consider with some detail two cases of order distribution: the double-order and the uniformly distributed order. For these cases we exhibit plots of the corresponding fundamental solutions and their variance, pointing out the remarkable difference between the two approaches for small and large times.
 
Article
The first-order differential equation of exponential relaxation can be generalized by using either the fractional derivative in the Riemann-Liouville (R-L) sense and in the Caputo (C) sense, both of a single order less than 1. The two forms turn out to be equivalent. When, however we use fractional derivatives of distributed order (between zero and 1), the equivalence is lost, in particular on the asymptotic behaviour of the fundamental solution at small and large times. We give an outline of the theory providing the general form of the solution in terms of an integral of Laplace type over a positive measure depending on the order-distribution. We consider with some detail two cases of fractional relaxation of distributed order: the double-order and the uniformly distributed order discussing the differences between the R-L and C approaches. For all the cases considered we exhibit plots of the solutions for moderate and large times.
 
Convergence of x(t) for the TIP for α = 0.75 (∆ : N = 8, O : N = 16, + : N = 32, X : N = 64, ∇ : N = 128, ⋆ : N = 256)  
Article
This paper presents a modified numerical scheme for a class of Fractional Optimal Control Problems (FOCPs) formulated in Agrawal (2004) where a Fractional Derivative (FD) is defined in the Riemann-Liouville sense. In this scheme, the entire time domain is divided into several sub-domains, and a fractional derivative (FDs) at a time node point is approximated using a modified Gr\"{u}nwald-Letnikov approach. For the first order derivative, the proposed modified Gr\"{u}nwald-Letnikov definition leads to a central difference scheme. When the approximations are substituted into the Fractional Optimal Control (FCO) equations, it leads to a set of algebraic equations which are solved using a direct numerical technique. Two examples, one time-invariant and the other time-variant, are considered to study the performance of the numerical scheme. Results show that 1) as the order of the derivative approaches an integer value, these formulations lead to solutions for integer order system, and 2) as the sizes of the sub-domains are reduced, the solutions converge. It is hoped that the present scheme would lead to stable numerical methods for fractional differential equations and optimal control problems.
 
Road roughness values classiied by ISO. Degree of Roughness S(() 10 ?6
Article
: An analytical investigation of a half-car model including passenger dynamics, subjected to random road disturbances is performed, and the advantage of active over conventional passive suspension systems are examined. Two different performance indices for optimal controller design are proposed. The performance index is a quantification of both ride comfort and road handling. Due to practical limitations, all the states required for the state-feedback controller are not measurable, and thus must be estimated with an observer. Stochastic inputs are applied to simulate realistic road surface conditions, and statistical comparisons between passive system and the two controllers, with and without state estimator, are carried out to gain a clearer insight into the performance of the controllers. The simulation results demonstrate that an optimal observer-based controller, when including passenger acceleration in the performance index, retains both excellent ride comfort and road handling ch...
 
Article
The paper addresses dynamic and control issues related to a dynamical model we call the classical shimmying wheel. The classical shimmying wheel models the rolling dynamics of many physical rolling systems such as aircraft nose wheels, motorcycles, automotive systems and tractor--trailer systems. Such system can exhibit undesirable unstable rolling motion, i.e. shimmying, which can often lead to disastrous results. Prior work with this particular model has focused on the stability of the system as well as an analysis of the qualitative nature of its dynamics, including numerical observation of chaotic behavior. Such chaotic behavior is observed when the rolling element is allowed to slip under certain conditions, which is intended to realistically model real physical rolling systems. We present a slightly different, but more realistic, condition for the rolling element to switch from pure rolling to a slipping state and observe similar chaotic behavior. Additionally, we present a contr...
 
Article
In this work, we present a third-order, semi-discrete, central-upwind scheme for computing approximate solutions of 1D systems of conservation laws. We combine the third-order CWENO reconstruction proposed in Levy et al., the semi-discrete central-upwind numerical flux proposed in Kurganov et al. and the third-order TVD Runge—Kutta method, proposed in Shu and Osher. We are interested in the behavior of the total variation of the approximate solution obtained with this scheme. Also we test our scheme on both scalar and gas dynamics problems. We observe that the total variation of computed solutions is close to the total variation of the exact solution or a reference solution.
 
Article
This paper investigates the multi-objective optimization of active control systems for vibration control of three-dimensional (3D) high-rise buildings under a variety of earthquake excitations. To this end, a novel multi-objective genetic algorithm is developed through the integration of the best features of a non-dominated sorting II (NS2) genetic algorithm (GA) and an implicit redundant representation (IRR) GA. The proposed NS2-IRR GA finds not only minimum distributions of both actuators and sensors within structures, but also minimum dynamic responses of 3D structures. Linear quadratic Gaussian controllers, hydraulic actuators and accelerometers are used for implementation of active control systems within the 3D buildings. To demonstrate the effectiveness of the proposed NS2-IRR GA, two 3D building models are investigated using finite element methods, including low- and high-rise buildings. It is shown that the proposed NS2-IRR GA is effective in finding not only optimal locations and numbers of both actuators and sensors in 3D buildings, but also minimum responses of the 3D buildings. The simulation also shows that the control performances of the proposed approach significantly enhance those of the engineering judgment oriented benchmark layout, which is validated by comparisons of each performance using the same number of actuators.
 
Article
Heat pumps are typically controlled by a programmable logic controller (PLC). However, PLCs are generally expensive and large. This work uses an MCS-51-based controller to control a heat pump, so that the size of the controller of a heat-pump system can be reduced markedly. Moreover, the proposed MCS-51-based controller can detect the status of each heat pump’s sensor automatically, so that a user can know whether a sensor is normal or abnormal, thereby protecting the heat-pump compressor. Knowing the number of a faulty sensor also helps during maintenance. Experimental results demonstrate that the proposed MCS-51-based controller can replace a PLC-based controller and control a heat pump successfully, achieving an inexpensive and effective solution for controlling heat pumps.
 
Article
In this paper the authors have extended their work on active stabilization of rotors with circulatory force arising from linear viscous dissipation in a frame rotating with the rotor to an active stabilization of the rotor with face grinding or abrasive tool tip for surface processing of brittle materials like inorganic glasses or thin strata or wafers of semiconducting materials for production of optoelectronic or integrated circuit devices. The dynamics and stabilization of such systems turned out much more complex than one that was addressed earlier due to the complex nature of dry friction forces. To analyze the dynamical nature of dry friction forces in rotating frames four vector operators are proposed. The operators provide a rational basis for creation of paradigms and algorithms (gain switching scheme) for stabilization. The efficacy of the proposals is established by simulation studies.
 
Article
This paper investigates the effects of mass ratio, clearance, and excitation amplitude on system dynamics and impact vibration absorber (IVA) effectiveness. The experimental studies were carried out for both free and forced vibrations. For free vibrations, the effects of system parameters on the rate of decay of vibrations were shown. Constant frequency and frequency sweep experiments were conducted to study the dynamics of the system under forced vibration. Optimum system parameters were extracted, for which the vibration absorption and absorber efficiency is greatest. It was also shown that phase plots and coherence, between the forcing function and the primary system response, offered an insight in the effectiveness of the IVA.
 
Article
The authors investigate theoretically and experimentally the performance of a recently developed quadratic vibration absorber that is based on the saturation phenomenon. They consider the problem of con trolling the vibrations of a single-degree-of-freedom plant, develop the equations governing the response of the closed-loop system, and obtain an approximate solution. They investigate the strategy by studying its steady-state characteristics and comparing its performance with that of a linear tuned absorber. Then, they implement both techniques experimentally using a digital signal processing device. The authors develop a software algorithm that allows for automatic real-time tracking of the system response. They use both tech niques to control high-amplitude responses of a cantilever beam fitted with piezoceramic actuators. When each absorber's frequency is tuned properly, they show that both schemes possess similar suppression band widths. In addition, they demonstrate that the power requirement of the quadratic absorber can be reduced by judicially modifying its control signal.
 
Article
The geometric filtering phenomenon is first analyzed with a simplified vertical vehicle model. Analytical solutions obtained with this model show that geometric filtering phenomenon consists of ‘wheelbase filtering’ and ‘bogie spacing filtering’ effects. The wheelbase filtering effect occurs when there is neither car body bounce nor pitch response at certain track wavelengths, whereas the bogie spacing filtering effect occurs when there is a null in either the car body bounce or pitch response at particular track wavelengths. Then, the correlated frequency response function for railway vehicles is defined to assess the effect of geometric filtering upon the resonant frequencies of a flexible car body. It is found that if the car body’s first bending frequency coincides with the peak values of bounce acceleration transmissibility, that is, it is near the null pitch response frequencies, resonant vibration of the flexible car body will happen. Finally, to suppress the resonant vibration of the flexible car body, it is proposed to use a dynamic vibration absorber (DVA) suspended under the car body underframe. The DVA parameters are optimized according to car body bending frequency and the null pitch frequency. The optimal DVAs show very good performance and robustness in suppression of the car body resonant vibration.
 
Article
Torsional rotor vibrations are undesirable phenomena which are very difficult to control in rotating systems. A common method for reducing vibrations involves the use of dynamic absorbers. However, if their physical parameters are constant, the frequency range of efficiency of dynamic absorbers is tight, making them unsuitable for systems with variable speeds. The use of smart materials, due to their variable and controllable mechanical properties, may be a powerful tool for increasing the frequency range. Electrorheological (ER) fluids are attractive materials that undergo very fast reversible changes in their rheological properties upon the application of an electric field. In this study, an electrorheological dynamic torsional absorber, called the Smart ER Dynamic Absorber, has been designed in order to reduce torsional rotor vibrations. Under shear mode, the ER absorber can exhibit various torsional damping and stiffness characteristics when an electric field is applied. A nonlinear empirical model of the dynamic behavior of ER materials has been developed. An On-Off control strategy has been applied and absorber efficiency measured. The results show that the ER dynamic absorber exhibits very good performances.
 
Article
In this paper the averaging method is used to research the approximately analytical solution of a semi-active on-off dynamic vibration absorber (DVA). At first the approximately analytical solutions for the two existing semi-active on-off DVAs, named as velocity-velocity based ground-hook control and displacement- velocity based ground-hook control, are established by the averaging method. Then two other new semi-active on-off DVAs, named as velocity-displacement based ground-hook control and displacement-displacement based ground-hook control, are presented for the first time in this paper and also researched analytically. Moreover, all the optimal parameters of the four semi-active DVAs, including the stiffness and the maximum and minimum damping ratio of the subsystem, are optimized to make the peak of the displacement transmissibility curve minimum, based on the amplitude-frequency equations from approximately analytical solutions. The comparisons of the displacement transmissibility obtained from the approximate solutions and the numerical ones are fulfilled, and the results certify that the approximate solutions have satisfactory precision. At last, the statistical results of the stochastic responses of the primary systems, including the original single degree-of-freedom system, the optimally passive DVA system, and the four semi-active on-off DVA systems, are obtained when subject to random excitation. The results show that the two new semi-active DVAs presented in this paper are almost as excellent as the existing two semi-active DVAs, and all of the four semi-active DVAs have better control performance than the optimally passive DVA.
 
Article
All rotating systems are subjected to residual unbalance forces that are proportional to speed squared. Systems that operate close to the critical speed and have low damping can generate destructive vibrations. Dynamic vibration absorbers are simple devices attached to a mechanical structure (the primary system) to reduce vibrations and noise levels and are extensively used in non-rotating systems. This study addresses the design of viscoelastic vibration absorbers for rotating systems. The primary system is modeled using modal parameters obtained in the frequency domain of the state-space representation. Using a methodology that has a more general application, the compound system (the primary system and absorbers) is represented in a modal subspace of the primary system state space. In this modal subspace, the optimal design of the dynamic viscoelastic absorbers is performed using an optimization algorithm. The objective function to be minimized is defined as the Euclidean norm of the vector composed of the maximal absolute values of the principal coordinates. The absorbers are attached to a floating bearing located away from a nodal point. Numerical and experimental results are presented and discussed.
 
Article
In this paper we deal with the boundary control of the Euler–Bernoulli beam by means of wave-absorbing feedback. Such controls are based upon the reduction of reflected waves and involve long memory non-rational convolution operators resulting from specific properties of the system. These operators are reformulated under so-called diffusive input–output state-space realizations, which allow us to represent the global closed-loop system under the abstract form dX/dt = AX with A the infinitesimal generator of a continuous semigroup. So, well-posedness and stability of the controlled system result from classical semigroup theory. Finite-dimensional approximations of the diffusive realizations are then studied, with the aim of providing implementable controls close to the ideal ones. Finally, significant numerical simulations are presented.
 
Article
In order to improve the low-frequency acoustic performance, a composite sound absorption coating made by embedding another viscoelastic material into the viscoelastic substrate of the traditional sound absorption coating, has been developed. Compared to the substrate, the transverse wave speed of the embedded-layer is lower. Accounting for the symmetry, the unit cell of the traditional sound absorption coating or the composite sound absorption coating could be approximately regarded as a viscoelastic single-layer cylindrical tube or a viscoelastic double-layer cylindrical tube, respectively. The plane wave normally impinging on the sound absorption coating only excites the axisymmetric wave propagating in the axial direction of the viscoelastic cylindrical tube. If the complex axisymmetric wave number and the effective impedance of the viscoelastic cylindrical tube are obtained, the acoustic performance of the sound absorption coating could be evaluated by using the transfer matrix method, which is suitable for both the single-layer cylindrical tube and the double-layer cylindrical tube. Numerical results show that the peak frequency of the sound absorption coefficient is shifted to the lower location as the proportion of the embedded-layer increases, or the transverse wave speed of the embedded-layer decreases.
 
Article
Accelerated testing involves testing a product at a level higher than the normal usage level. This is important because test time and expenditure for testing can be greatly reduced by accelerated testing. This study involves aluminum beams (bare as well as coated with sprayable damping material) subjected to random vibration. Since most materials fail in fatigue and because accelerated testing is becoming more important due to economic considerations, this paper addresses applicability of various theories for estimation of time failure in normal usage and accelerated condition. Another issue addressed was whether application of damping material makes any difference because many automotive and aerospace applications involve damped materials. Experimentally observed failure time in random vibration for both bare and damped beams under random vibration are compared with various fatigue failure theories. Next the exponent for accelerated testing isobtained for bare and damped beams. This exponent has been studied in terms of both G2/Hz and Grms. Even though different failure theories predicted different failure times, the exponent correlated with all theories for undamped beams and in general with Dirlik theory for damped beams.
 
Article
For an electro-hydraulic servo shaking table, there are nonlinearities, which cause acceleration harmonic distortion when they corresponds to a sine acceleration excitation signal. The work here is to develop an acceleration harmonic identification algorithm by using the normalized least-mean-square (LMS) adaptive algorithm, whose weights are updated by the error between the acceleration response and the estimated acceleration signal. The input vector is generated by the reference harmonics and the phase shift. When the identification algorithm converges, the amplitude and phase of each harmonic can be computed from the weight vector. Experimental results show that the proposed harmonic identification has good real-time performance and a fast convergence rate, and it can identify harmonics on-line with high precision both in amplitude and in phase.
 
Article
The shaking table is an important experimental apparatus for mechanical environment tests. This work is focused on an electro-hydraulic shaking table, which has a single degree of freedom. Its configuration and working principle are described. A three-variable controller composed of feed-forward and feedback is applied to achieve iso-acceleration control. The acceleration excitation signal is filtered by an input filter to obtain input variables for the three-variable controller. From the sinusoidal shaking results, harmonic distortion exists in the acceleration response. The frequencies of harmonics are integer multiples of the fundamental frequency. Different harmonic distortion and harmonic distribution occur in the acceleration response excited by different acceleration excitation signals. The acceleration harmonic distortion is decreased as the amplitude and frequency of the excitation signal are increased.
 
Article
The acceleration output of an electro-hydraulic servo system corresponding to a sinusoidal input contains higher harmonics besides the fundamental input, because of complex nonlinearities occurring in the system. This causes harmonic distortion of the acceleration signal. The method for harmonic elimination based on adaptive notch filter is proposed here. The task is accomplished by generating a reference signal with a frequency that should be eliminated from the output. The reference input is filtered in such a way that it closely matches the harmonic. The filtered reference signal is added to the fundamental signal such that the output harmonic is cancelled leaving the desired signal alone. The weights of the adaptive filter are adjusted by the error between the input and the feedback acceleration to eliminate acceleration harmonic, creating an adaptive notch filter. The above concept is used as a basis for the development of an acceleration harmonic cancellation algorithm. Results of simulation and experiment on an electro-hydraulic servo shaking table demonstrate the efficiency and validity of the proposed control scheme.
 
Article
Contact and impact dynamics modeling of rigid bodies continues to be an intensive research area, as new applications of contact dynamics simulation develop in engineering practice. Yet, relatively few studies are dedicated to the experimental investigation of rigid-body impacts and associated issues. In this manuscript we report our findings for a sphere to flat impact experiments conducted for a range of low impact velocities, such as those that may be encountered in multibody systems. A unique feature of our investigation is that the impact forces between the impacting objects are reconstructed from force and acceleration measurements, the latter obtained from an accelerometer mounted on the impacted surface body. It is noted that when the impacted body is free to move during impact, it may experience high accelerations which must be taken into account. The reconstructed impact force responses are compared to those predicted with the dynamics model of the experimental scenario, which in turn is based on a nonlinear compliant model of the impact force. The experiments, in addition to generating novel impact measurements, provide a number of insights into both the study of impacts and the impact response.
 
Article
In this paper, the deflection of a two-link flexible manipulator has been modeled with each point on the flexible link being described by both axial and lateral displacement variables instead of lateral displacement variable only. This has been possible by including the shortening of the projection effect on the deformed link. A control law based on computed-torque formulation has been utilized to expose the difference between the responses of the two models, and thus the impact of the shortening of projection effect due to the flexible link deformation on following the desired trajectory is presented.
 
Article
The main purpose of this paper is to study the attenuation of the jump phenomena associated with the Sommerfeld Effect introduced by the nonlinearities of a magnetic rheological damper (MRD) in a non-ideal vibrational system, excited by a DC motor modeled as limited power source. Numerical simulations of the nonlinear vibrations of the system are carried out for different values of the MRD control parameter in order to show the amplitude reduction of the vibrations close to the system resonance introduced by the nonlinear damping effect of the MR system.
 
Article
In this paper, an exact analytical solution is obtained for free flexural vibration of a cantilever piezoelectric panel carrying a rigid mass. The cantilever piezoelectric panel, commonly used in vibrational energy harvesting, may consist of a single layer of piezoelectric material (unimorph), two layers of piezoelectric material with or without a center core (bimorph), or multiple layers of piezoelectric material (multimorph). For an immediate application to a class of piezoelectric energy harvesting devices, the analytical procedure is presented for vibration modes, which are symmetric with respect to the panel major centerline. Numerical results and comparisons of several example applications show that the proposed scheme is accurate and convergent.
 
Article
It is a well known fact that system parameters of flexible structures keep on changing because of several reasons. Ordinary controllers lose their effectiveness in changed situations and do not guarantee the stability of the closed loop (CL) system. However, controllers designed based on robust control theory not only maintain the CL stability of the perturbed system for a large variation in system parameters but also maintain best performance. In this work, optimization based controllers are designed and implemented experimentally on a flexible beam with active constrained layer damping treatment. It is observed that loop shaping design procedure based controllers outperform linear quadratic Gaussian and standard controllers both in terms of robust stability and robust performance. Relative merits and demerits of the controllers designed using - synthesis technique are also discussed. It has also been observed that time domain results also explain some of the important facts. Certain time domain parameters of the CL system prove the relative superiority of these controllers in terms of control energy utilization and robust performance.
 
Article
Modal models are developed for vibro-acoustic response computation of fluid-structure interaction problems on the basis of modal frequencies and modal damping ratios. The uncoupled equations are built using in vacuo mode shapes and fluid-loaded undamped real mode shapes and are solved for the coupled response of the fluid-loaded structures. Conventional modal analysis techniques are used to obtain the response of the coupled fluid-structure systems from a reduced-order modal model. The accuracy and efficiency of the technique is demonstrated with examples of computing the vibro-acoustic response of a baffled thin plate and a baffled thick stiffened plate. The comparisons in terms of mean-square normal velocity and sound power between the present models and the conventional coupling method show a good agreement. The present modal models for computing the vibro-acoustic response of the fluid-loaded structures have the advantages of constructing a model from modal parameters that could be obtained from either numerical computation or experimental measurement; a small dimension of using only a very small number of modes; and of being applicable to conventional modal analysis techniques. These features may make the present technique a powerful tool for dynamics and the control of fluid-loaded structures.
 
Article
This paper proposes designing a static output feedback controller for a structural-acoustics coupling system using piezoelectric actuators. The system consists of a rectangular cavity with two flexible plates, one at the top of the cavity and the other at the bottom, and four other rigid boundaries. Piezoelectric pair patches are considered to be bonded to the top plate, and each pair is assumed to produce a pure moment actuation. The top plate is exposed to an external pressure excitation due to a planar wave generated by a sound source mounted above the cavity. The series solution is assumed for the displacements of the plates and the pressure inside the cavity. The responses of the coupled system are obtained using Galarkin’s method. In the control scheme, the controller gains have been optimally tuned using genetic algorithms. The proposed static output feedback controller shows an acceptable performance with simple implementation requirements compared to the linear quadratic Gaussian state feedback controller.
 
Article
This work deals with the dynamics of a levitated rotor, which is also rotated by a fluid squeeze film created by a vibrating cylinder type stator. The model, which describes the transient behavior of the rotation of a rotor, by means of the squeeze film generated by a traveling flexural wave of the stator surface, is presented. In such problems, the control equations of fluid in the squeeze film are firstly simplified on the basis of several reasonable assumptions. These equations, together with control equation of the rotor, are solved by using explicit finite difference methods. Then, the vibration mode of pressure at the stable time and the transient rotating speed of the rotor with time are evaluated. Finally, the rotating speeds, with different parameters of vibration of the stator, the squeeze film and inertial moment of the rotor, are compared in order to study how to effectively increase and control the rotating speed. This paper will provide the foundations to study the driving technology of squeeze film and will be helpful in the design and application of non-contact ultrasonic actuators.
 
Article
High magnetic field strength and high-speed gradient coil current switching are becoming ever more commonplace in magnetic resonance imaging scanners. These and other factors are combining to yield high acoustic sound pressure levels (SPLs) in and around magnetic resonance imagers. Studies have already been conducted which partially characterize this sound field, and various methods have been investigated to attenuate the noise generated. In order to predict the vibration and acoustic response of a gradient coil inside a scanner, finite element analysis (FEA) was carried out. The model was based on specific internal and external structural dimensions and the material physical properties of a gradient coil. The FEA results were verified through experimental modal testing of the same gradient coil. It was found that the experimental modal analysis results were in good agreement with the FEA results. The Lorentz force distribution on the gradient coil caused by the time varying current in the coil windings was then applied to the FEA model to obtain the velocity distribution of the coil surface as a function of time. A vibro-acoustic computational model was then developed based on the verified FEA model. The surface velocity distribution was then used to predict the sound field inside the gradient coil. The vibro-acoustic model was verified using experimental noise measurements with swept sinusoidal waveform inputs to the gradient coil conductors. The numerical methods developed in this study could provide a guide and virtual testing platform for the designer of gradient coils to predict the vibration and acoustic behavior of new designs and thereby offer the opportunity to redesign and/or optimize the design to reduce SPLs.
 
Article
With the combination of the near-field acoustic holography (NAH) and pattern recognition technique, a NAH-based diagnosis technique is proposed and applied to diagnose gearbox faults by analyzing the sound field distribution information first. After visualizing the sound fields under different working conditions by NAH, the spatial gray level co-occurrence matrices based textural features can be obtained from the NAH images. Then, the support vector machine is employed to identify different working conditions and diagnose the faults. Two gearbox experiments with different gear faults and fault severity are studied in a semi-anechoic chamber to verify the NAH-based diagnosis technique. The experimental results demonstrate that the NAH-based diagnosis method is feasible and effective, and can be anticipated as a choice for gearbox fault diagnosis.
 
Article
A nonlinear six degree-of-freedom dynamic model is presented for a marine surface vessel. The formulation closely follows the current literature on ship modeling. It considers the effects of inertial forces, wave excitations, retardation forces, nonlinear restoring forces, wind and current loads along with linear viscous damping terms. The capability of the model is shown through its prediction of the ship response during a turning-circle maneuver. The ship model is used herein as a test bed to assess the performance of the proposed controller. The present study assumes that the ship is fully actuated and all state variables of the system are available through measurements. A nonlinear robust controller, based on the sliding mode methodology, has been designed based on a reduced-order version of the ship model. The latter accounts only for the surge, sway and yaw motions of the ship. The initial simulation results, generated based on the reduced-order model of the marine vessel, demonstrate robust performance and good tracking characteristics of the controller in the presence of structured uncertainties and external disturbances. Furthermore, they illustrate the adverse effects of the physical limitations of the propulsion system on the controlled response of the ship. Next, the same controller is implemented on the six degree-of-freedom model of the ship. The simulation results reveal tracking characteristics of the controller that are similar to those observed in the initial results, in spite of significantly larger modeling uncertainties.
 
Article
In 2013 the Editor of Journal of Vibration and Control and SAGE became aware of a peer review ring involving assumed and fabricated identities that appeared to centre around Peter Chen at National Pingtung University of Education, Taiwan (NPUE). SAGE and the Editor then began a complex investigation into the case during the rest of 2013 and 2014. Following an unsatisfactory response from Peter Chen, NPUE was notified. NPUE were serious in addressing the Journal and SAGE’s concerns. NPUE confirmed that the institution was investigating Peter Chen. SAGE subsequently uncovered a citation ring involving the above mentioned author and others. We regret that individual authors have compromised the academic record by perverting the peer review process and apologise to readers. On uncovering problems with peer review and citation SAGE immediately put steps in place to avoid similar vulnerability of the Journal to exploitation in the future. More information may be found at www.sagepub.co.uk/JVC_Statement_2014 . The Journal and SAGE understand from NPUE that Peter Chen has resigned his post at NPUE. The following articles are retracted because after thorough investigation evidence points towards them having at least one author or being reviewed by at least one reviewer who has been implicated in the peer review ring and/or citation ring. All authors have had an opportunity to respond to the allegations and proposed actions. OnlineFirst articles (these articles will not be published in an issue) Chen CY, Chen T-H, Chen Y-H, Yu S-E and Chung P-Y (2013) Information technology system modeling an integrated C-TAM-TPB model to the validation of ocean tidal analyses Journal of Vibration and Control Epub ahead of print 7 May 2013. doi: 10.1177/1077546312472924 Chang R-F, Chen CY, Su F-P and Lin H-C (2013) A two-step approach for broadband digital signal processing technique Journal of Vibration and Control Epub ahead of print 26 April 2013. doi: 10.1177/1077546312472925 Chen TH, Chang CJ, Yu SE, Chung PY and Liu C-K (2013) Nonlinear information analysis and system management technique: the influence of design experience and control complexity Journal of Vibration and Control Epub ahead of print 12 April 2013. doi: 10.1177/1077546312473321 Chen CY, Shih BY, Chen YH, Yu SE and Liu YC (2013) The exploration of a 3T flow model using vibrating NXT: II. Model validation Journal of Vibration and Control Epub ahead of print 10 April 2013. doi: 10.1177/1077546312470481 Chen CY, Shih BY, Chen YH, Yu SE and Liu YC (2013) The exploration of 3T flow model using vibrating NXT: I. model formulation Journal of Vibration and Control Epub ahead of print 6 February 2013. doi: 10.1177/1077546312467360 Lin M-L and Chen C-W (2013) Stability analysis of fuzzy-based NN modeling for ecosystems using fuzzy Lyapunov methods Journal of Vibration and Control Epub ahead of print 6 February 2013. doi: 10.1177/1077546312466687 Chen CY, Chen TH, Chen YH and Chiu J (2012) A multi-stage method for deterministic-statistical analysis: a mathematical case and measurement studies Journal of Vibration and Control Epub ahead of print 20 December 2012. doi: 10.1177/1077546312466579 Shih BY, Lin MC and Chen CY (2012) Autonomous navigation system for radiofrequency identification mobile robot e-book reader Journal of Vibration and Control Epub ahead of print 13 December 2012. doi: 10.1177/1077546312466578 Chang RF, Chen CY, Su FP, Lin HC and Lu C-K (2012) Multiphase SUMO robot based on an agile modeling-driven process for a small mobile robot Journal of Vibration and Control Epub ahead of print 13 December 2012. doi: 10.1177/1077546312464993 Shih B-Y, Lin Y-K, Cheng M-H, Chen C-Y and Chiu C-P (2012) The development of an application program interactive game-based information system Journal of Vibration and Control Epub ahead of print 12 December 2012. doi: 10.1177/1077546312464682 Chen C-Y, Chang C-J and Lin C-H (2012) On dynamic access control in web 2.0 and cloud interactive information hub: technologies Journal of Vibration and Control Epub ahead of print 12 December 2012. doi: 10.1177/1077546312464992 Shin BY, Chen CY and Hsu KH (2012) Robot cross platform system using innovative interactive theory and selection algorithms for Android application Journal of Vibration and Control Epub ahead of print 13 November 2012. doi: 10.1177/1077546312463757 Articles published in an issue Chen C-W (2014) Applications of neural-network-based fuzzy logic control to a nonlinear time-delay chaotic system Journal of Vibration and Control 20 (4): 589-605. Epub ahead of print 5 November 2012. doi: 10.1177/1077546312461370 Chen C-W (2014) A review of intelligent algorithm approaches and neural-fuzzy stability criteria for time-delay tension leg platform systems Journal of Vibration and Control 20 (4): 561-575. Epub ahead of print 5 November 2012. doi: 10.1177/1077546312463759 Chen C-Y, Chang C-J and Lin C-H (2014) On dynamic access control in web 2.0 and cloud interactive information hub: trends and theories Journal of Vibration and Control 20 (4): 548-560. Epub ahead of print 5 November 2012. doi: 10.1177/1077546312463762 Lin M-L and Chen C-W (2014) Stability conditions for ecosystem modeling using the fuzzy Lyapunov method Journal of Vibration and Control 20 (2): 290-302. Epub ahead of print 23 October 2012. doi: 10.1177/1077546312451301 Chen C-H, Kuo C-M, Hsieh S-H and Chen C-Y (2014) Highly efficient very-large-scale integration (VLSI) implementation of probabilistic neural network image interpolator Journal of Vibration and Control 20 (2): 218-224. Epub ahead of print 22 October 2012. doi: 10.1177/1077546312458822 Chen C-Y (2014) Wave vibration and simulation in dissipative media described by irregular boundary surfaces: a mathematical formulation Journal of Vibration and Control 20 (2): 191-203. Epub ahead of print 22 October 2012. doi: 10.1177/1077546312464258 Chen C-H, Yao T-K, Dai J-H and Chen C-Y (2014) A pipelined multiprocessor system- on-a-chip (SoC) design methodology for streaming signal processing Journal of Vibration and Control 20 (2): 163-178. Epub ahead of print 16 October 2012. doi: 10.1177/1077546312458821 Lin M-L and Chen C-W (2014) Fuzzy neural modeling for n-degree ecosystems using the linear matrix inequality approach Journal of Vibration and Control 20 (1): 82-93. Epub ahead of print 8 October 2012. doi: 10.1177/1077546312458533 Chen C-H, Wu W-X and Chen C-Y (2013) Ant-inspired collective problem-solving systems Journal of Vibration and Control 19 (16): 2481-2490. Epub ahead of print 18 September 2012. doi: 10.1177/1077546312456231 Chen C-H, Yao T-K, Kuo C-M and Chen C-Y (2013) Evolutionary design of constructive multilayer feedforward neural network Journal of Vibration and Control 19 (16): 2413-2420. Epub ahead of print 12 September 2012. doi: 10.1177/1077546312456726 Chen C-W (2013) Applications of the fuzzy-neural Lyapunov criterion to multiple time-delay systems Journal of Vibration and Control 19 (13): 2054-2067. Epub ahead of print 16 August 2012. doi: 10.1177/1077546312451034 Chung P-Y, Chen Y-H, Walter L and Chen C-Y (2013) Influence and dynamics of a mobile robot control on mechanical components Journal of Vibration and Control 19 (13): 1923-1935. Epub ahead of print 20 July 2012. doi: 10.1177/1077546312452184 Chen C-W (2013) Neural network-based fuzzy logic parallel distributed compensation controller for structural system Journal of Vibration and Control 19 (11): 1709-1727. Epub ahead of print 22 June 2012. doi: 10.1177/1077546312442233 Chen C-W, Yeh K, Yang H-C, Liu KFR and Liu C-C (2013) A critical review of structural system control by the large-scaled neural network linear-deferential-inclusion-based criterion Journal of Vibration and Control 19 (11): 1658-1673. Epub ahead of print 18 June 2012. doi: 10.1177/1077546312443377 Chen C-H, Kuo C-M, Chen C-Y and Dai J-H (2013) The design and synthesis using hierarchical robotic discrete-event modeling Journal of Vibration and Control 19 (11): 1603-1613. Epub ahead of print 27 June 2012. doi: 10.1177/1077546312449645 Chang CJ, Chen CY and Chou I-T (2013) The design of information and communication technologies: telecom MOD strength machines Journal of Vibration and Control 19 (10): 1499-1513. Epub ahead of print 27 June 2012. doi: 10.1177/1077546312449644 Shih B-Y, Chen C-Y, Li K-H, Wu T-Y, Chen G-Y (2013) A novel NXT control method for implementing force sensing and recycling in a training robot Journal of Vibration and Control 19 (10): 1443-1459. Epub ahead of print 1 June 2012. doi: 10.1177/1077546312446361 Chen C-W, Chen P-C and Chiang W-L (2013) Modified intelligent genetic algorithm-based adaptive neural network control for uncertain structural systems Journal of Vibration and Control 19 (9): 1333-1347. Epub ahead of print 31 May 2012. doi: 10.1177/1077546312442232 Chen C-Y, Shih B-Y, Shih C-H and Wang L-H (2013) Enhancing robust and stability control of a humanoid biped robot: system identification approach. Journal of Vibration and Control 19 (8): 1199-1207. Epub ahead of print 26 April 2012. doi: 10.1177/1077546312442947 Chang C-J, Chen C-Y and Huang C-W (2013) Applications for medical recovery using wireless control of a bluetooth ball with a hybrid G-sensor and human-computer interface technology Journal of Vibration and Control 19 (8): 1139-1151. Epub ahead of print 24 April 2012. doi: 10.1177/1077546312442948 Hsu W-K, Chiou D-J, Chen C-W, Liu M-Y, Chiang W-L and Huang P-C (2013) Sensitivity of initial damage detection for steel structures using the Hilbert-Huang transform method Journal of Vibration and Control 19 (6): 857-878. Epub ahead of print 29 February 2012. doi: 10.1177/1077546311434794 Chen C-Y, Shih B-Y, Shih C-H and Wang L-H (2013) Human–machine interface for the motion control of humanoid biped robots using a graphical user interface Motion Editor Journal of Vibration and Control 19 (6): 814-820. Epub ahead of print 23 February 2012. doi: 10.1177/1077546312437804 Chen C-Y (2013) Internal wave transport, nonlinear manifestation, and mixing in a stratified shear layer - technical briefs Journal of Vibration and Control 19 (3): 429-438. Epub ahead of print 18 January 2012. doi: 10.1177/1077546311429337 Chen C-W (2013) Delay independent criterion for multiple time-delay systems and its application in building structure control systems Journal of Vibration and Control 19 (3): 395-414. Epub ahead of print 17 January 2012. doi: 10.1177/1077546311429341 Chen C-Y, Shih B-Y, Shih C-H and Wang L-H (2013) Design, modeling and stability control for an actuated dynamic walking planar bipedal robot Journal of Vibration and Control 19 (3): 376-384. Epub ahead of print 17 January 2012. doi: 10.1177/1077546311429476 Liu K-C, Liu Y-W, Chen C-Y and Huang W-C (2013) Nonlinear vibration of structural deterioration in reinforced concrete columns: experimental and theoretical investigation Journal of Vibration and Control 19 (3): 323-335. Epub ahead of print 17 January 2012. doi: 10.1177/1077546311429477 Chen C-Y, Shih B-Y and Ma J-m (2013) Development for low-cost and cross-platform robot control environment Journal of Vibration and Control 19 (2): 228-233. Epub ahead of print 11 January 2012. doi: 10.1177/1077546311430107 Shih B-Y, Chang H and Chen C-Y (2013) Path planning for autonomous robots – a comprehensive analysis by a greedy algorithm Journal of Vibration and Control 19 (1): 130-142. Epub ahead of print 17 January 2012. doi: 10.1177/1077546311429841 Liu T-Y, Chiang W-L, Chen C-W, Hsu W-K, Lin C-W, Chiou D-J and Huang P-C (2012) Structural system identification for vibration bridges using the Hilbert–Huang transform Journal of Vibration and Control 18 (13): 1939-1956. Epub ahead of print 14 December 2011. doi: 10.1177/1077546311428347 Chen C-W (2012) Applications of the fuzzy Lyapunov linear matrix inequality criterion to a chaotic structural system Journal of Vibration and Control 18 (13): 1925-1938. Epub ahead of print 14 December 2011. doi: 10.1177/1077546311428346 Chen C-W (2012) Applications of linear differential inclusion-based criterion to a nonlinear chaotic system: a critical review Journal of Vibration and Control 18 (12): 1886-1899. Epub ahead of print 14 December 2011. doi: 10.1177/1077546311428345 Shih B-Y, Chen C-Y and Chou W (2012) An enhanced obstacle avoidance and path correction mechanism for an autonomous intelligent robot with multiple sensors Journal of Vibration and Control 18 (12): 1855-1864. Epub ahead of print 14 December 2011. doi: 10.1177/1077546311426734 Chen C-W, Yeh K, Liu KFR and Lin M-L (2012) Applications of fuzzy control to nonlinear time-delay systems using the linear matrix inequality fuzzy Lyapunov method Journal of Vibration and Control 18 (10): 1561-1574. Epub ahead of print 18 October 2011. doi: 10.1177/1077546311410765 Chen C-Y (2012) A critical review of internal wave dynamics. Part 2 – Laboratory experiments and theoretical physics Journal of Vibration and Control 18 (7): 983-1008. Epub ahead of print 21 September 2011. doi: 10.1177/1077546310397561 Chen C-Y and Huang P-H (2012) Review of an autonomous humanoid robot and its mechanical control Journal of Vibration and Control 18 (7): 973-982. Epub ahead of print 21 September 2011. doi: 10.1177/1077546310395974 Shih B-Y, Chen C-Y, Chang H and Ma J-m (2012) Dynamics and control for robotic manipulators using a greedy algorithm approach Journal of Vibration and Control 18 (6): 859-866. Epub ahead of print 25 August 2011. doi: 10.1177/1077546311407649 Yeh K, Chen C-W, Lo DC and Liu KFR (2012) Neural-network fuzzy control for chaotic tuned mass damper systems with time delays Journal of Vibration and Control 18 (6): 785-795. Epub ahead of print 15 August 2011. doi: 10.1177/1077546311407538 Chen C-Y, Shih B-Y, Shih C-H and Chou W-C (2012) The development of autonomous low-cost biped mobile surveillance robot by intelligent bricks Journal of Vibration and Control 18 (5): 577-586. Epub ahead of print 21 April 2011. doi: 10.1177/1077546310371349 Chen C-Y (2012) A critical review of internal wave dynamics. Part 1 – Remote sensing and in-situ observations Journal of Vibration and Control 18 (3): 417-436. Epub ahead of print 13 July 2011. doi: 10.1177/1077546310395971 Tseng C-P, Chen C-W and Liu KFR (2012) Risk control allocation model for pressure vessels and piping project Journal of Vibration and Control 18 (3): 385-394. Epub ahead of print 13 July 2011. doi: 10.1177/1077546311403182 Lin M-L and Chen C-W (2011) Stability analysis of community and ecosystem hierarchies using the Lyapunov method Journal of Vibration and Control 17 (13): 1930-1937. Epub ahead of print 9 December 2010. doi: 10.1177/1077546310385737 Chen C-Y, Shih B-Y, Chou W-C, Li Y-J and Chen Y-H (2011) Obstacle avoidance design for a humanoid intelligent robot with ultrasonic sensors Journal of Vibration and Control 17 (12): 1798-1804. Epub ahead of print 26 November 2010. doi: 10.1177/1077546310381101 Chen C-W (2011) Fuzzy control of interconnected structural systems using the fuzzy Lyapunov method Journal of Vibration and Control 17 (11): 1693-1702. Epub ahead of print 23 November 2010. doi: 10.1177/1077546310379625 Shih B-Y, Chen C-Y and Chou W-C (2011) Obstacle avoidance using a path correction method for autonomous control of a biped intelligent robot Journal of Vibration and Control 17 (10): 1567-1573. Epub ahead of print 22 November 2010. doi: 10.1177/1077546310372004 Tang J-P, Chiou D-J, Chen C-W, Chiang W-L, Hsu W-K, Chen C-Y and Liu T-Y (2011) A case study of damage detection in benchmark buildings using a Hilbert-Huang Transform-based method Journal of Vibration and Control 17 (4): 623-636. Epub ahead of print 8 November 2010. doi: 10.1177/1077546309360053 Liu TY, Chiang WL, Chen CW, Hsu WK, Lu LC and Chu TJ (2011) Identification and monitoring of bridge health from ambient vibration data Journal of Vibration and Control 17 (4): 589-603. Epub ahead of print 12 November 2010. doi: 10.1177/1077546309360049 Lin JW, Huang CW, Shih CH and Chen CY (2011) Fuzzy Lyapunov Stability Analysis and NN Modeling for Tension Leg Platform Systems Journal of Vibration and Control 17 (1): 151-158. Epub ahead of print 25 August 2010. doi: 10.1177/1077546309350477 Lee WI, Chen CY, Kuo HM and Sui YC (2010) The Development of Half-circle Fuzzy Numbers and Application in Fuzzy Control Journal of Vibration and Control 16 (13): 1977-1987. Epub ahead of print 22 April 2010. doi: 10.1177/1077546309349849
 
Article
This paper investigates a nonlinear controller designed to stabilize a single-degree-of-freedom rotary shape memory alloy (SMA) actuated robotic arm. To this end, a bias-type robotic arm was built using 150 pm Flexinol SMA wire. This robot is designed to lift and position lightweight objects. Upon complete phase transformation, the SMA wire actuates the robot to rotate up to 1350. A linear spring is used to extend the wire to its original length because the SMA wire can only apply force in one direction. To measure the angular position of the robotic arm, an optical rotary encoder was used. To stabilize the robot, a model-based controller was developed. The controller incorporates the SMA actuated robot model with nonlinear control techniques. The model consists of three parts: the dynamics/kinematics of the arm, the thermoruechanical behavior of SMA wire, and the heat transfer model of the wire. The model-based backstepping controller determines the applied voltage to the SMA wire for positioning the arm at the desired angle by first calculating the wire's stress to stabilize the arm. The voltage to the SMA wire is then calculated based on the desired stress and the SMA's thermomechanical and heat transfer models. A series of simulations were performed to investigate stabilizing performance of the controller. Moreover, other issues such as robustness of the control design was evaluated. The results show that the control algorithms is able to globally and asymptotically stabilize the robot. The results further indicate that the sliding mode control has better robustness properties.
 
Article
Passivity-based control of under-actuated mechanical systems with nonlinear friction effects in the generalized coordinates of motion is analyzed in this paper. Nonlinear friction is modeled with a modified LuGre dynamic friction model. The internal states of the dynamic friction model are incorporated as generalized coordinates in a port-controlled Hamiltonian formulation for the complete mechanical system in such a way that all passivity properties of this formulation are preserved for the extended generalized coordinates system. Interconnection and damping assignment passivity-based control laws are developed for the models of two case studies: a building with a magneto-rheological damper and a double pendulum. Simulation results are also presented.
 
Schematic of a symmetric spatial parallel mechanism (SSPM) with 2p struts.
8-8 redundant parallel mechanism.
Location of compliance center when r a ¼ 0:707r b , ¼ ¼ 0 .
Article
In this paper, we study dynamic isotropy using natural frequency analysis for a class of symmetric spatial parallel mechanisms (SSPMs) with 2p (p≥3) struts. This kind of dynamic isotropy has been defined as the square roots of the eigenvalues of the equivalent mass-spring systems formed via the interactions between rigid-body mechanical systems and their driving systems. Analytic expressions for these eigenvalues are then derived in the task space, which is linearly dependent on p. Furthermore, a general compliance center was found for all the SSPMs in which the parallel mechanisms are fully decoupled. Based on the dynamically decoupling, then, dynamic isotropy for the SSPM is discussed which shows that though taking the inertial parameters into consideration, the SSPM can not attain complete dynamic isotropy and the optimal dynamic isotropy index is the quartic root of two. At the end of the paper, to demonstrate these results, an example is given.
 
Top-cited authors
Ali H. Nayfeh
  • Virginia Polytechnic Institute and State University
Dumitru Baleanu
  • Institute of Space Sciences
José A. Tenreiro Machado
  • Polytechnic Institute of Porto
Ziyad N. Masoud
  • German Jordanian University
Eihab M. Abdel-Rahman
  • University of Waterloo