Journal of Vibration and Control current issue

Analysis of Narrowband Active Noise and Vibration Control Systems Using Parallel Adaptive Notch Filters

Yang, F., Gupta, A., Kuo, S.M. — 2008-06-20

This paper analyzes narrowband active noise and vibration control (ANVC) systems using multiple second-order adaptive filters configured in parallel form with the filtered-x least mean square algorithm. Theoretical analysis of convergence of the algorithm is based on the autocorrelation and crosscorrelation matrices of the overall parallel structure. Analysis results show that extra harmonics are induced in the residual error because of using a single error signal to update all adaptive filters with different sinusoidal reference signals. An optimized filter-adapting method which uses bandpass filters to split the error signal into multiple bandlimited error signals according to frequencies of reference signals is proposed to improve the performance of narrowband ANVC systems in steady state. Computer simulations are conducted to verify analysis results and performance of the optimized narrowband ANVC system.

Modified Fuzzy Variable Structure Control Method to the Crane System with Control Deadzone Problem

Chang, C.-Y., Hsu, K.-C., Chiang, K.-H., Huang, G.-E. — 2008-06-20

This paper proposes a modified fuzzy based variable structure control to achieve the position and swing control of the 3-D nonlinear overhead crane system. One derives the control power according to the variable structure controller and feedback signals-trolley position and payload swing angle. Compensating algorithm for the deadzone problem is provided in this paper and the heuristic sliding factors are also tuned automatically by the proposed fuzzy method to enrich the system performance without plant information of crane. Several experiments for the position and swing control of the nonlinear overhead crane system demonstrate the effectiveness of the proposed scheme.

Application of Genetic Algorithms to Observer Kalman Filter Identification

Schoen, M. P. — 2008-06-20

In this paper several applications of genetic algorithm (GA) as an aid to the system identification process are presented. First, GAs are used in a set of covariance-based optimum input signal algorithms using a proposed architecture suitable for online system identification. The optimal signals are computed recursively using a predictive filter. The efficiency of these algorithms are compared based on a set of simulations. Second, a novel input design for a two-step identification scheme is presented. Constraint systems, such as commonly found in structural and biomedical engineering applications, are considered for the input design algorithm. This paper presents a novel approach that induces a learning scheme into the input design computation and allows for considerations of the given constraints of the system. The optimization of the new input signal is accomplished using a simple elitism based genetic algorithm. Simulation results indicate the proposed piecewise adaptive input design algorithm performs well compared to the general white-noise-based estimation results. In the third portion of this paper proof is given that no dynamic controller can reduce the noise influence in linear system identification. A new selection scheme of the corresponding singular values is proposed for the eigensystem realization portion of the Observer Kalman filter IDentification algorithm in noisy systems. The selection is done using a GA. Simulation results of the proposed algorithm in comparison with the traditional used method are presented. The results indicate an improved ability to extract system models from highly noise corrupted data.

Simulation of Tool Vibration Control in Turning, Using a Self-Sensing Actuator

Freyer, B.H., Theron, N.J., Heyns, P.S. — 2008-06-20

Besides reducing the restricting effects of tool vibrations on productivity, work-piece surface finish and tool life, it is desirable to handle lack of space for sensors at the tool tip and the cost of control systems in turning processes in an effective way. This work considers these two aspects by exploiting the concept of a self-sensing actuator (SSA) in the simulation of tool vibration control. The tool holder structure, in its passive as well as active state, is modeled as a supported cantilever. A feedback filtered-x least-mean-square (LMS) algorithm is chosen to compute the control action. A known technique, which consists of pre-filtering the inputs to the LMS-algorithm maintains the stability of the control system. The self-sensing path is modeled and illustrated. It consists of the transmission of the tool tip displacement to the SSA where it is sensed by converting it into a voltage signal. A considerable reduction of 93% of the displacement r.m.s. values of the tool tip, was obtained when simulating this control system.

Parametric Identification and Health Monitoring of Complex Ground Vehicle Models

Metallidis, P., Stavrakis, I., Natsiavas, S. — 2008-06-20

A systematic methodology is applied for performing parametric identification and health monitoring in the suspension substructures of complex vehicle models. The equations of motion are derived by applying a finite element method. As a consequence, they involve quite a large number of degrees-of-freedom (DOF). In addition, they include strongly nonlinear terms. In particular, the main nonlinearities arise due to the function of the suspension dampers and springs. Moreover, the action of the bushings connecting the suspension subsystems to the vehicle body is also strongly nonlinear. Since the resulting number of DOF is large, an appropriate coordinate condensation technique is applied first. This drastically reduces the dimension of the original system and allows the application of a statisticcal system identification methodology, which is effective for dynamical systems with relatively small dimension, in order to perform parametric identification and fault detection studies in the suspension subsystems of an example vehicle model. In the second part of this study, the methodology developed is applied and yields numerical results related to parametric identification and fault detection in the suspensions of the vehicle model examined. The results are found to be sufficiently accurate even in the presence of considerable measurement noise and model errors.

Suppression of Vehicle-induced Bridge Vibration Using Tuned Mass Damper

Xiaomin Shi, , Cai, C.S. — 2008-06-20

This paper focused on a numerical model for vehicle-induced bridge vibrations controlled with a tuned mass damper (TMD) system, taking road surface conditions into account. A computer program was developed to study the possible effectiveness of the TMD for suppressing the vibration of bridges under vehicle loads. Then, a comprehensive investigation was conducted on different bridges under two vehicle load patterns, i.e. two trucks moving side by side or several trucks passing over the bridge in a traffic flow. It was found that the additional damping provided by the TMD results in a reduction of the maximum dynamic displacement for both free and forced vibrations. On the other hand, for all the bridges investigated in this study, the reduction of acceleration is also significant. More generally speaking, it can be concluded that for the same TMD installed on the same bridge, it is more effective for cases with trucks passing over the bridge in traffic flow than for cases with only one truck. Such a study is helpful in evaluating the control performance before the real control devices are designed in practice.

An Experimental Study on Semi-active Seismic Response Control of a Large-span Building on Top of Ship Lift Towers

Tu, J.-W., Qu, W.-L., Jing Chen, — 2008-06-20

A vertical ship lift under earthquake excitation may suffer from a violent whipping effect due to the sudden change of building lateral stiffness at the top of ship lift towers. This paper presents an experimental investigation to explore the validity of using a magnetorheological (MR) isolation system to prevent the whipping effect manipulated by neuro-fuzzy control algorithm. The two-story building was constructed as a ship lift model, in which the first story was much stiffer than the second story and the plates of the second story were divided into two mass pieces. MR isolation systems were used to link those two mass pieces. The dynamic characteristics of the model with rigid connection and with only seismic isolator connection were first identified. The models with those two connections and with MR isolation system connection were then tested under the scaled Three Gorge artificial ground motion and the scaled El Centro 1940 north-south ground motion. Finally, the seismic responses of the ship lift model were recalculated with the modified structural parameters through measured natural frequencies and were compared with the experimental seismic responses. The experimental results show that an MR isolation system manipulated by neuro-fuzzy control algorithm can achieve a significant reduction in seismic whipping effect on the building model. The comparison consequences indicate that the theoretical simulation results are accurately consistent with the experimental results.

Energy Recovering in Active Vibration Isolation System -- Results of Experimental Research

Kowal, J., Pluta, J., Konieczny, J., Kot, A. — 2008-06-20

Studies of systems with energy regeneration have been carried out for years, because they primarily cover the assemblies with electrodynamic actuators. This paper addresses the issue of active reduction of mechanical vibration using an electrohydraulic actuator. The testing procedure aims to assess the potential use of those assemblies in a different frequency band and force range than in electrodynamic actuators. The paper explains the operating principle of the system, and the findings of laboratory tests are presented. The tested vibration reducing system is the physical model of a 2 degree-of-freedom (DOF) suspension. An initial analysis has been conducted to explore the potential use of the energy produced by the vibration of unsprung mass in the first degree of the suspension system, for power supply to the active component incorporated in the second suspension degree.

The energy recuperated from the first suspension DOF is transferred by a dedicated hydraulic system and stored in an accumulator. Results of the experiments revealed that the mechanical parameters of the system can be selected in such a way that for specific interfering signals the accumulated energy should be at least equal to the energy used up by the system.