Journal of Vibration and Control recent issues

Vibration Control on a Pulse and Ramp Driven System with Friction

Shyu, K.-K., Lee, Y.-Y., Wu, R.-H. — Tue, 24 Nov 2009 03:29:17 PST

This paper investigates the sufficient stability condition of a three-phase proportional gain, pulse, and ramp (PPR) controller for pointing systems under the influence of friction. With the ramp and pulse schemes integrated, the PPR controller has been demonstrated to be an effective control strategy for fast and precise pointing applications. In this paper the LuGre model is used to derive the upper bounds of the ramp slope S_r for the sufficient stability condition to suppress vibrations around the [—0.5, +0.5] µm target region. Our study reveals that the frictional stiffness ₀ and the micro viscous damping coefficient ₁ in the LuGre model are required for the bounds of S_r . With the derived bounds of S_r , the Lyapunov direct method is applied to prove the stability of the PPR controller.

General-order Perturbation with a Skew-symmetric Approach for Structural Health Monitoring of a Modular Beam

Wong, C. N., Barhorst, A. A. — Tue, 24 Nov 2009 03:29:17 PST

A unique health monitoring method is formulated via a skew-symmetric approach in which the damage location and extent are estimated from the perturbation of a specific set of eigenparameters. The perturbed orthonormal equation is generated from the perturbation of the eigenvectors and eigenvalues to obtain the kth skew-symmetric coefficients. Meanwhile the perturbed eigenvalue equation is generated from the perturbation of the eigenparameters and linear expansion of the stiffness matrix to obtain other skew-symmetric coefficients. Throughout this process, specific permutation numbers and generalized Kronecker delta functions are manipulated. Then these skew-symmetric coefficients are simplified to obtain the symmetric coefficients. A finite element model of a modular beam is used as a test structure to investigate the applicability of the developed method. A fixed—fixed boundary condition is imposed on the two ends to approximate the actual operating situation. Different order perturbation algorithms are established based on the perturbation equations. Stiffness parameters are computed from these equations, inversely, using an optimization method. The algorithm is iterative in nature and terminates under certain criteria. Various small to large percentage systematic damaged cases are simulated under different perturbation orders. The results are compared and evaluated using health monitoring curves and estimation error manifolds, and their efficiencies and convergences are discussed.

Development of Adaptive Seat Mounts for Helicopter Aircrew Body Vibration Reduction

Chen, Y., Wickramasinghe, V., Zimcik, D. — Tue, 24 Nov 2009 03:29:17 PST

Helicopter aircrew are exposed to high levels of vibration and noise during flight. This paper presents the investigation of adaptive seat mount approaches to reducing vibration on the helicopter seat. A flight test on a helicopter with typical pilot configurations showed that the vibration spectra on the pilot’s helmet not only included the dominant N/rev harmonic peaks of the rotor speed, but also consisted of a low-frequency resonant peak in the frequency range of human abdominal and spine resonant frequencies. Long-term exposure to this vibration may lead to occupational health issues such as damage to the pilot’s spine and neck. In order to address this issue, a novel adaptive seat mount concept was developed to mitigate the vibration levels transmitted to the aircrew. As a proof-of-concept demonstration, a miniature modal shaker was installed between the cabin floor and the seat bottom as an adaptive mount that provided the actuation authority. The objective was to reduce the vertical vibration transmitted to the aircrew helmet in order to decrease aircrew neck and spine injuries that are caused by the transmitted vibration. Extensive closed-loop control tests have been conducted on a full-scale helicopter seat and a mannequin with varying physical properties. A 10,000 lb(f) mechanical shaker was used to provide representative helicopter vibration profiles to the seat. Significant vibration reductions on the N/rev vibration peaks were achieved1 the low-frequency resonant peak was also suppressed simultaneously.

Localization in the Vibration of an Axially Loaded Two-span Weakened Column

Challamel, N., Casandjian, C., Lanos, C. — Tue, 24 Nov 2009 03:29:17 PST

This paper is devoted to the dynamic analysis of two connected beam columns with a variation of the bending connection and minor perturbations of the length of each span. The point of reduced bending stiffness represented by a rotational spring may result from a crack. This rotational spring can also be associated with a semi-rigid connection in the field of steel or composite structures, for instance. The dynamics of this axially loaded two-span weakened column appears to exhibit strong localization for small values of stiffness of the rotational spring. The vibration mode shapes indicate a strong confinement of the vibration level to a fraction of the column. A quantitative criterion of localization is established and is correlated to well-known phenomena such as curve veering effect or close eigenvalues. Such a result is quite encouraging as localization is strongly associated with the flexibility values of the rotational spring. When considering the open crack analogy, localization only appears for severely damaged columns. It can then be understood as an indicator of the damage level of the global structure.

An Improved System of Active Noise Isolation Using a Self-sensing Actuator and Neural Network

Ji, H., Qiu, J., Zhu, K., Matsuta, K. — Tue, 24 Nov 2009 03:29:17 PST

In this paper we present an improved active noise isolation method, consisting of a self-sensing actuator, a neural network identifier and an adaptive feedback controller using a finite impulse response (FIR) filter and the Filtered-X LMS algorithm, in which no acoustical sensors were necessary to suppress the noise transmission through a plate structure. The structure is a composite plate with an embedded piezoelectric patch. Based on the self-sensing technique, the same piezoelectric element functions as both a sensor and an actuator. A bridge circuit was used to separate the sensor signal from the actuator signal on the piezoelectric patch and the obtained signal was used in the identification of the sound pressure of a point in the space. A neural network was used instead of the Rayleigh’s integral formula for the identification of the sound pressure as used in the former study. The results show that the proposed control approach using both a self-sensing actuator (SSA) and neural network identifier exhibited better noise control performance than using Rayleigh’s integral formula. It also exhibited similar noise control performance to the traditional control system using a microphone, although the new system used only one piezoelectric patch for both the sensor and actuator.

Simple Approaches to Improve the Performance of Noise Cancellation

Chang, C.-Y. — Tue, 24 Nov 2009 03:29:17 PST

In this paper we present a neural-based algorithm to cancel the nonlinear narrowband and broadband noise in an active noise control (ANC) system. The improved method, including the ways to decide the learning rate and optimal initial weighting values of the neural network (NN), are presented to enhance the noise reduction performance. The proposed approach does not need mathematical transfer functions of the duct plant and a method of avoiding the premature saturation problem of NNs is also provided. A comparison with conventional neural methods by simulation shows that the proposed method can effectively cancel the undesired noise very well. The proposed improved method is also versatile to the other applications in NN filter design.

Vibration Suppression Control of Beam-cart System with Piezoelectric Transducers by Decomposed Parallel Adaptive Neuro-fuzzy Control

Lin, J., Chao, W.-S. — Tue, 24 Nov 2009 03:29:17 PST

The main goal of this research is to develop a novel approach for achieving a high performance piezoelectric vibration absorber. Motion and control of a Bernoulli-Euler beam fixed on a moving cart will be analyzed in this study. The moving cart is mounted on the ball-screw mechanism system. Dynamic formulation for control purposes is first investigated for such a beam-cart system in this research. The controller has two separate feedback loops for positioning and damping, and the vibration suppression controller is independent of linear motion stage positioning control. The decomposed parallel fuzzy control with adaptive neuro-fuzzy concept has also been proposed for this research. An experimental device was constructed, constituted of a flexible cantilever aluminum beam type structure with piezoelectric patches symmetrically bonded on both sides to provide structural bending. Strip-bender type piezoelectric patches were attached to the surface of the beam to serve as actuators and sensor, respectively. Experimental validation for such a structure demonstrates the effectiveness of the proposed controller. The results of this study can be feasible to various mechanical systems, such as high tower cranes, ladder cars or overhead cranes.

An Intelligent Controller Design for Magnetorheological Damper Based on a Quarter-car Model

Tusset, A. M., Rafikov, M., Balthazar, J. M. — Tue, 24 Nov 2009 03:29:17 PST

This paper presents the control strategies of nonlinear vehicle suspension using a magnetorheological (MR) damper. We used two different approaches for modeling and control of the mechanical and electrical parts of the suspension systems with the MR damper. First, we have formulated and resolved the control problem in order to design the linear feedback dumping force controller for a nonlinear suspension system. Then the values of the control dumping force functions were transformed into electrical control signals by the application of a fuzzy logic control method. The numerical simulations were provided in order to show the effectiveness of this method for the semi-active control of the quarter-car suspension.

Optimization of Mechatronic Design Quotient Using Genetic Algorithm in Vibration Controllers for Flexible Beams

Sun, J., Poo, A.N., Chew, C.M., Ang, M.H., Hong, G.S., De Silva, C.W., Tan, K.K. — Mon, 26 Oct 2009 09:40:29 PDT

Due to their extensive utilization in engineering designs, various vibration controllers have been investigated with design specifications in mind. The optimization of vibration controller designs is a complicated multi-criteria problem. In this paper, the mechatronic design quotient (MDQ) approach and genetic algorithm (GA) are coupled together to determine this optimal design solution. The MDQ is presented to formulate an evaluation function for the passive vibration controller design of flexible beam structures, and the GA is then used to maximize this function so as to achieve a design solution with the highest MDQ value. For comparison, both the MDQ performance of passive vibration controller design using linear dampers and active vibration controller design using a linear quadratic regulator are provided. The latter is used as the performance benchmark to evaluate the optimal design solution of the former. Experimental results show that the linear dampers design with the proposed method can achieve similar performance to an optimal active controller.

Nonlinear Frequency Veering in a Beam Resting on an Elastic Foundation

Al-Qaisia, A.A., Hamdan, M.N. — Mon, 26 Oct 2009 09:40:29 PDT

In this work we present an investigation into nonlinear frequency veering of an elastic Euler— Bernoulli beam resting on a Winkler elastic foundation subjected to a static lateral load and hinged—hinged, with a torsional spring at one end. The beam is assumed to have an initial quarter-sine shape rise owing to a constant differential edge settlement. The beam static deflection is obtained by using a combined numerical—analytical procedure that accounts for the induced nonlinear axial force to mid-plane stretching. The harmonic balance method is used to solve for the nonlinear natural frequency of the associated nonlinear temporal problem obtained using the assumed mode method. The results are presented in the form of characteristic curves which show variation of the nonlinear natural frequency of the three modes of a selected range of system parameters. These results indicate that, depending on the system parameters, the nonlinear natural frequency of various modes can exhibit complicated behaviors not found using linear analysis.

Control of Lateral Vibrations and Slopes at Desired Locations Along Vibrating Beams

Foda, M.A., Alsaif, K. — Mon, 26 Oct 2009 09:40:29 PDT

In the present paper we develop an exact approach to annihilate lateral vibrations and slopes at chosen locations in a vibrating beam subjected to an external excitation. The proposed scheme allows certain chosen points anywhere along the beam to remain stationary with zero slopes without using any rigid supports. This is beneficial because it would allow sensitive instruments to be placed near or at these points where the transverse vibrations and tilting are eliminated. In addition, when the locations of these desired points are in the vicinity of one another, it is possible to specify a region of nearly zero amplitude and zero slope, thus drastically reducing the level of vibration in that segment of the structure and preventing its rotation. This will be achieved by attaching a set of translational and/or rotational oscillators with calculated parameters at arbitrary selected locations along the beam. The proposed procedure develops an exact analytical scheme for choosing the required oscillators’ parameters utilizing the dynamic Green’s functions. An experimental setup, in which the vibrations of a clamped—clamped beam are measured using a laser vibrometer, was designed and the experimental measurements are compared with the analytical results. Sample of illustrative examples has been considered to verify the proposed method.

Sliding Mode Control of a Three-dimensional Overhead Crane

Almutairi, N. B., Zribi, M. — Mon, 26 Oct 2009 09:40:29 PDT

This paper deals with the sliding mode control of a three-dimensional overhead crane. The model of the crane consists of five highly nonlinear second-order ordinary differential equations. The crane is an underactuated system, which makes the design of its controllers intricate. A sliding mode control scheme is proposed for the crane. This scheme, which guarantees the asymptotic stability of the closed-loop system, has two objectives: position regulation and anti-swing control. The performance of the closed-loop system is simulated using MATLAB. The simulation results indicate that the proposed control scheme works well. In addition, the robustness of the controller with respect to uncertainties in the crane parameters is investigated through simulations. It is found that the controller is robust to changes in the parameters. Moreover, since some of the states of the system are not measurable, a Luenberger-type observer is proposed. Simulation of the controlled system using the observer-based sliding mode controller produced good results.

Suppressing Resonant Vibrations Using Nonlinear Springs and Dampers

Zhang, B., Billings, S. A., Lang, Z.-Q., Tomlinson, G. R. — Mon, 26 Oct 2009 09:40:29 PDT

The transmitted force around the resonant region of a system can be significantly reduced by introducing designed nonlinearities into the system. The basic choice of the nonlinearity can be either a nonlinear spring element or a nonlinear damping element. A numerical algorithm to compute and compare the transmitted force reduction produced by these two types of designed elements is proposed in this study. Analytical results are used to demonstrate the procedure. The numerical results indicate that the designed nonlinear damping element produces low levels of higher-order harmonics and no bifurcations in the system output response. In contrast, the nonlinear spring-based designs induce significant levels of harmonics in the transmitted force and can produce bifurcation behaviour. The conclusions provide an important basis for the design of nonlinear materials and nonlinear engineering systems.

Discrete Time Sliding Mode Flow Controller for Multi-source Single-bottleneck Connection-oriented Communication Networks

Bartoszewicz, A., Zuk, J. — Mon, 26 Oct 2009 09:40:29 PDT

In this paper, we propose a sliding mode flow controller for connection-oriented, multi-source, single-bottleneck communication networks. For that purpose, we model the networks as discrete time systems with the available bandwidth acting as the disturbance. The proposed control algorithm is designed in such a way that the closed-loop system stability and finite time error convergence are ensured. Moreover, we demonstrate that the proposed controller guarantees no bottleneck link buffer overflow and full utilization of its available bandwidth. Furthermore, transmission rates generated by the controller are always bounded and nonnegative.

The Control and Optimization Design of the Fish-like Underwater Robot with the Aid of the Giant Magnetostrictive Material Actuator

Xu, X.S., Sun, F.M., Wang, G.P. — Tue, 22 Sep 2009 03:55:15 PDT

In this paper, the mechanism of the underwater fish-like robot, which is controlled by the giant magnetostrictive material actuator, is studied. A mechanical model of the robot is presented based on the relationship between the driving force and frequencies, which is controlled by external magnetic fields. At the same time, a new design project is given by optimizing structures and a two-tail fish-like robot is devised, in which the robot can swim directly forward and backward.

Nonlinear Dynamic Response and Vibration Active Control of Piezoelectric Elasto-plastic Laminated Plates with Damage

Tian, Y., Fu, Y., Wang, Y. — Tue, 22 Sep 2009 03:55:15 PDT

Based on the elasto-plastic mechanics and continuum damage theory, a yield criterion that is related to the spherical stress tensor is proposed to describe the mixed hardening of damaged orthotropic materials, the dimensionless form of which is isomorphic with the Mises criterion for isotropic materials. Furthermore, the incremental elasto-plastic damage constitutive equations and damage evolution equations of orthotropic materials are established. The electric potential distribution along the thickness direction of the piezoelectric sensor layer is determined by adopting the quadratic Lagrange interpolation, and the incremental electric charge equilibrium equation is built according to the Maxwell equation. In addition, by using the classical nonlinear plate theory, the incremental nonlinear dynamic governing equations of the piezoelectric elasto-plastic laminated plates with damage are obtained. Meanwhile, an analytical model for the vibration control of the system is proposed by introducing the negative velocity feedback control algorithm coupling the direct and converse piezoelectric effects. The finite difference method and the Newmark-β method are adopted to make the undetermined variables discretized in the space and time domains, respectively, and the whole problem is solved by the iterative method. In the numerical examples, the effects of damage, piezoelectricity, feedback control gain and the piezoelectric position on the nonlinear vibration of piezoelectric elasto-plastic laminated plates are discussed in detail, and the differences between the piezoelectric elastic laminated plates and piezoelectric elasto-plastic laminated plates are analyzed.

Optimal Control of a Flexible Beam with Multiple Time Delays

Long-Xiang, C., Guo-Ping, C. — Tue, 22 Sep 2009 03:55:15 PDT

In this paper, active control of a flexible cantilever beam with multiple time delays is studied, where a controller is designed using a discrete optimal control method and piezoelectric patches are used as actuators. Firstly, the state equation of controlled modes of the system with multiple time delays is obtained using modal orthogonality. Then, the state equation is discretized and transformed into a standard form without any explicit time delay by a particular augmenting for state variables. A continuous performance index is also discretized into a standard discrete form that is a function of the augmented states. So, the discrete controller may be designed based on the augmented system. In every step of computation for the controller, it contains not only the current step of state feedback but also a linear combination of some former steps of controls. Simulation results indicate that the system may suffer from instability at a small time delay if the time delay is not treated. It may be well compensated by the proposed controller and good control effectiveness may be obtained simultaneously. In addition, the proposed controller may possibly obtain better control effectiveness than the controller with no time delay.

Dynamic Mechanical Properties and Weight Optimization of Vibrated Ground Recycled Rubber

Chettah, A., Ichchou, M.N., Bareille, O., Chedly, S., Onteniente, J.P. — Tue, 22 Sep 2009 03:55:15 PDT

The aim in this paper is first and foremost to present an experimental method for measuring the dynamic characteristics of granular rubber. Dynamic measurements on recycled granular rubbers are performed here using dynamic mechanical thermal analysis. The Young’s modulus and loss factor of these materials are estimated by using the frequency—temperature equivalence introduced by Williams—Landel—Ferry. It allows us to describe the dynamic properties over a wide range of frequencies. An increase in the wave speed and a decrease in the loss factor were observed with an increase in the frequency for ground tire rubber (GTR) and compound particles obtained by extrusion of GTR—ethylene vinyl acetate blend. However, for recycled polyurethane particles, the loss factor increases with increasing frequency. Then, we investigate the damping efficiency of granular rubbers introduced into a metallic tube, which was subjected to vibrating bending loads. A numerical model is presented to predict the frequency response for the displacement—force function of the tube—particles system. Model prediction is hence validated through a comparison with experimental results. Second, this paper also aims at calculating the optimum weight of granular material with maximum allowable damping effects on tube subjected to bending vibrations. For this purpose, a technique is proposed from the model developed by optimizing the apparent mass of granular material and the dissipation energy of the tube—particles system. Optimization is achieved by a nondominated storing genetic algorithm (NSAG-II). From the results, this technique can be successfully used to optimize the frequency dependence of wave speed and the loss factor of granular rubber with optimized weight.

A New Algorithm for Crack Localization in a Rotating Timoshenko Beam

Masoud, A. A., Al-Said, S. — Tue, 22 Sep 2009 03:55:15 PDT

In this paper a new crack localization algorithm based on a mathematical model describing the lateral vibration of a rotating cracked Timoshenko beam is proposed. The Lagrange equation and the assumed mode method are used to derive the model. The localization algorithm utilizes the variation in a single natural frequency of the beam versus a few rotor speed values to detect and localize a crack. The algorithm has different means of checking/reconfirming its crack estimate. This may be used to improve the accuracy of the decision. Also, the effect of rotational speed and crack location on the system’s dynamical characteristics is investigated using the derived mathematical model. The results are compared with those obtained from a three-dimensional finite-element analysis. Good agreement is observed between the two sets of results. Finally, the reliability of the identification algorithm is established using the data obtained from the finite-element analysis.

Experimental Identification of Nonlinearities under Free and Forced Vibration using the Hilbert Transform

Feldman, M., Bucher, I., Rotberg, J. — Tue, 22 Sep 2009 03:55:15 PDT

In this paper we discuss the experimental identification of a nonlinear vibrating mechanical system. The system under test incorporated several spring and damping related nonlinearities. Indeed, in this paper we use data from a real laboratory device thus increasing the confidence in the proposed methods that have been previously applied mostly to simulated data. A unique feature of the identified model is that it shows the dependency of the estimated parameters on the vibration amplitude. The provided measurements of free and forced vibration motion, together with the unique signal processing, based on the Hilbert transform analysis, yield an accurate estimation of nonlinear spring and friction parameters of the vibration model. The obtained natural frequencies and friction parameters are functions rather than scalars that describe the system’s behavior under different operating conditions. This paper complements previously published Hilbert transform analytical methods with experimental and numerical results.

Slow Passage through Multiple Parametric Resonance Tongues

Bridge, J., Rand, R., Sah, S. M. — Tue, 22 Sep 2009 03:55:15 PDT

This work concerns linear parametrically excited systems that involve multiple resonances. The property of such systems is that if the parameters are fixed and lie inside a resonance tongue, the motion becomes unbounded as time goes to infinity. In this work we consider what happens when the parameters are not fixed, but rather are constrained to vary slowly in time, passing into and out of the resonance tongues. One might expect that during the time in which the motion lies inside a tongue the solution grows, and that the slower the passage through the tongue the more time is spent inside the tongue, and the larger the resulting growth. We show that this is not always the case. In particular we investigate the effect of initial conditions and relative forcing amplitudes on the growth or amplification of the solution. We address the problem of how to choose these parameters so as to minimize growth (i.e., to de-amplify the solution) after passage through multiple tongues.

Effects of Nonlinearities on the Steady State Dynamic Behavior of Electric Actuated Microcantilever-based Resonators

Jazar, R.N., Mahinfalah, M., Mahmoudian, N., Rastgaar, M.A. — Thu, 20 Aug 2009 07:23:21 PDT

This paper presents the dynamic behavior of microcantilever-based microresonators and compares their steady state behavior for polarized and nonpolarized systems at different levels of nonlinearities. A microcantilever, equipped with a time-varying capacitor, makes the microresonator system. The capacitor is activated by a constant polarization voltage, and an alternative actuating voltage. The partial differential equation of motion of the vibrating electrode can be reduced to a highly nonlinear parametric second order ordinary differential equation. The steady state behavior of the microresonator has been analyzed with and without polarization voltage. The main characteristic of the non-polarized model is explained by the stability of the system in parameter plane. A set of stability chart is provided to predict the boundary between the stable and unstable domains. Furthermore, the main characteristic of the polarized model is determination by the period-amplitude relationship of the system. Applying perturbation methods, analytical equations are derived to describe the frequency response of the system, which are suitable to be utilized in parameter study and design.

Magnetic Bearing Application by Time Delay Control

Xuan, D.J., Kim, Y.B., Kim, J.W., Shen, Y.D. — Thu, 20 Aug 2009 07:23:21 PDT

In this paper a magnetic bearing system is designed for the suppression of rotor vibration. Magnetic bearing is able to support the shaft without mechanical contacts, and it is also able to control the rotational vibration. Magnetic bearing is composed of position sensors, a digital controller, actuating amplifiers, and electromagnets. In order to control the vibration of a magnetic bearing system effectively, Time Delay Control (TDC) is utilized. It proposes the design skill of an optimal controller when the system has the uncertainty, i.e. it has a difficulty in extracting the exact mathematical expressions, as well as it has external disturbances. The observer with the position information is utilized as a feedback signal for regulating the rotor whirling motion. Simulation is performed first to check the validation of the proposed controller in suppressing the rotor whirling. Experiments are followed to guarantee its usefulness in the rotor rig with a magnetic actuator. The vibrating suppression is confirmed with TDC and its effect is compared with proportional and derivative controller’s one.

Vold-Kalman Filter Order Tracking in Vibration Monitoring of Electrical Machines

Wang, K.S., Heyns, P.S. — Thu, 20 Aug 2009 07:23:21 PDT

This paper presents a simplified simulation model of electrical rotating machinery and an experimental test rig for applying the Vold-Kalman filter order tracking technique (VKF-OT). The effectiveness and advantages of VKF-OT for condition monitoring are demonstrated on both the simulation model and the experimental test rig through time domain analysis, using crest factor and kurtosis. The choice of the Vold-Kalman filter bandwidth is considered in the context of the simulation model, based on two different damping ratios. Several observations are made regarding the choice of Vold-Kalman filter bandwidth for the different damping ratios. Three different filter bandwidths are subsequently considered in a study of the experimental data, to confirm the conclusions made during the simulation study.

Rolling Bearing Fault Classification Based on Envelope Spectrum and Support Vector Machine

Lei Guo, , Jin Chen, , Xinglin Li, — Thu, 20 Aug 2009 07:23:21 PDT

Based upon Hilbert envelope spectrum and support vector machine (SVM), a method for the fault diagnosis of rolling bearing is proposed in this paper. Targeting the modulation characteristics of rolling bearing fault vibration signals, the Hilbert transform based envelope spectrum analysis is used to extract fault bearing features. In the envelope spectrum, character frequencies are quite clear and can be used as a reliable source of information for bearing diagnosis. Basic SVM is originally designed for two-class classification problem, while bearing fault diagnosis is multi-class case. A new bearing fault diagnosis system based on "one to others" SVM algorithm is presented to solve the multi-class recognition problems. Practical vibration signals measured from rolling bearings with ball fault, inner race fault and outer race fault are analyzed by the proposed method. The results show that the proposed method provides accurate diagnosis and good diagnostic resolution.

An Active Identification Method of Rotor Unbalance Parameters

De Queiroz, M.S. — Thu, 20 Aug 2009 07:23:21 PDT

This note presents a new method for identifying the unknown unbalance parameters of a rotor. The active feedback method asymptotically learns the unbalance-induced disturbance forces. From the resulting disturbance estimates, we show how to identify the unbalance parameters. Simulation results illustrate the proposed identification method.

Modeling and Robust Control of Horizontal Vibrations for High-speed Elevator

Yonghui Feng, , Jianwu Zhang, , Yane Zhao, — Thu, 20 Aug 2009 07:23:21 PDT

Modeling and robust controller design of horizontal vibrations for high-speed elevators are presented in this paper. Based on the theory of rigid body dynamics, the model of the horizontal vibrations about the elevator cage is developed. The motion of the elevator cage is resolved into translation and rotation round the mass center of the cage. Taking account of the characteristics of nonlinearity, parameter uncertainties and external disturbances of the elevator cage, robust controller is designed using Lyapunov’s method. To simplify the controller design, the position controller and the attitude controller are designed based on the translation model and the rotation model, respectively. Placement, velocity and acceleration feedback and the Lyapunov method are used to design the position controller; input/output feedback linearization approach, pole placement and the Lyapunov method are used to design the attitude controller. Simulation results demonstrate the effectiveness of the proposed controller.

Hybrid Vibration Control of a Circular Cylindrical Shell Using Electromagnetic Constrained Layer Damping Treatment

Hongpan Niu, , Shilin Xie, , Xinong Zhang, — Thu, 20 Aug 2009 07:23:21 PDT

This paper investigates hybrid vibration control of a circular cylindrical shell through electromagnetic constrained layer damping (EMCLD) treatment, which consists of an electromagnet layer, a permanent magnet layer and a sandwiched viscoelastic damping layer. A mathematical model is developed based on the equivalent current method to calculate the electromagnetic control force produced by EMCLD. The governing equations of the shell system are established using Hamilton’s principle and then reduced with the assumed-mode method. The vibration control of a clamped-free circular cylindrical shell is simulated with velocity-proportional feedback to demonstrate the energy dissipation capability of EMCLD. Also, parametric studies are performed to examine the influences of geometry and physical properties of EMCLD on control performance. The results show the distinct energy consumption function of EMCLD in the passive way. The hybrid way provides much better control performance than the passive way in the concerned frequency range. It is also indicated from parametric studies that increasing the value of any one of the physical parameters, such as the loss factor of the viscoelastic material, the thickness of the permanent magnet and the area of EMCLD, has a contribution to the improvement of hybrid control performance. In contrast, increasing the thickness of the viscoelastic layer deteriorates both passive and hybrid control effects.

Fuzzy Logic Control of Vibrations of a Light Rail Transport Vehicle in Use in Istanbul Traffic

Guclu, R., Metin, M. — Thu, 20 Aug 2009 07:23:21 PDT

A high standard service must be provided in rail transportation for passenger safety and comfort. With this need in mind, data are collected on vibration problems in rail systems and control. In this study, a rail vehicle system in use in Istanbul traffic is studied and a physical model in the form of a 22-degrees-of-freedom half light rail transport vehicle and differential equations created for analyzing vibrations. A computer simulation is also been carried out. In the simulation, real parameters for the modeled vehicle are employed. In an effort to minimize displacement and acceleration of the vibrations obtained in the end of simulations based on time and frequency domains, a fuzzy logic controller is used to actively control vibrations in the simulation environment.