Tudor-Bogdan Airimitoaie

Benchmark on adaptive regulation—rejection of unknown/time-varying multiple narrow band disturbances

Abstract Adaptive regulation is an important issue with a lot of potential for applications in active suspension, active vibration control, disc drives control and active noise control. One of the basic problems from the “control system” point of view is the rejection of multiple unknown and time varying narrow band disturbances without using an additional transducer for getting information upon the disturbances. An adaptive feedback approach has to be considered for this problem. Industry needs to know the state of the art in the field based on a solid experimental verification on a representative system using currently available technology. The paper presents a benchmark problem for suppression of multiple unknown and/or time-varying vibrations and an associated active vibration control system using an inertial actuator with which the experimental verifications have been done. The objective is to minimize the residual force by applying an appropriate control effort through the inertial actuator. The system does not use any additional transducer for getting real-time information about the disturbances. The benchmark has three levels of difficulty and the associated control performance specifications are presented. A simulator of the system has been used by the various contributors to the benchmark to test their methodology. The procedure for real-time experiments is briefly described. 1 The performance measurement methods used will be presented as well as an extensive comparison of the results obtained by various approaches. 2

Adaptive feedforward compensation algorithms for active vibration control with mechanical coupling

Adaptive feedforward broadband vibration (or noise) compensation is currently used when a correlated measurement with the disturbance (an image of the disturbance) is available. Most of the active vibration control systems feature an internal positive mechanical feedback between the compensation system and the reference source (a correlated measurement with the disturbance). Such systems have often also a feedback control loop for reducing the effect of disturbances. Therefore the adaptive feedforward compensation algorithms should take into account this structure. For stability reasons the adaptation algorithms requires the implementation of a filter on observed data or a filtering of the residual acceleration in order to satisfy some passivity conditions. The paper proposes new algorithms for the adaptive feedforward compensation in this context with both filtering of data and of the residual acceleration and using an Integral + Proportional (IP) adaptation as a means for accelerating the transients as well as for relaxing the positive real conditions required by the stability analysis. The paper also shows that the main interest in filtering the residual acceleration is to shape in the frequency domain the power spectral density (PSD) of the residual acceleration. The algorithms have been applied to an active vibration control (AVC) system and real time results illustrating the advantages of the proposed algorithms are presented.

Indirect Adaptive Attenuation of Multiple Narrow-Band Disturbances Applied to Active Vibration Control

In this brief, an indirect adaptive control methodology for attenuation of multiple unknown time varying narrow-band disturbances is proposed. This method is based on the real time estimation of the frequency of narrow-band disturbances using adaptive notch filters followed by the design of a controller using adjustable band-stop filters for the appropriate shaping of the output sensitivity function. A Youla-Kučera parametrization of the controller is used for reducing the computation load. This approach is compared on an active vibration control system with the direct adaptive control scheme based on the internal model principle proposed. Real time experimental results are provided.

IIR Youla–Kucera Parameterized Adaptive Feedforward Compensators for Active Vibration Control With Mechanical Coupling

Adaptive feedforward broadband vibration (or noise) compensation requires a reliable correlated measurement with the disturbance (an image of the disturbance). The reliability of this measurement is compromised in most of the systems by a “positive” internal feedback coupling between the compensator system and the correlated measurement of the disturbance. The system may become unstable, if the adaptation algorithms do not take into account this positive feedback. Instead of using classical infinite impulse response (IIR) or finite impulse response (FIR) feedforward compensators, this paper proposes and analyses an IIR Youla-Kucera parametrization of the feedforward compensator. A model-based central IIR stabilizing compensator is used, and its performance is enhanced by the adaptation of the parameters (Q-parameters) of an IIR Youla-Kucera filter. Adaptation algorithms assuring the stability of the system in the presence of the positive internal feedback are provided. Their performances are evaluated experimentally on an active vibration control system. Theoretical and experimental comparisons with FIR Youla-Kucera parameterized feedforward compensators and IIR feedforward compensators are provided.

A Youla-Kucera parametrized adaptive feedforward compensator for active vibration control

Abstract Adaptive feedforward broadband vibration (or noise) compensation is currently used when an image of the disturbance (i.e. a correlated measurement) is available. However, in most of the systems there is a “positive” feedback coupling between the compensator system and the measurement of the image of the disturbances. This may lead to the instability of the system. The paper proposes a new Youla-Kucera parametrization of the compensator. The central compensator assures the stability of the system and its performances are enhanced in real time by the adaptation of the Q-parameters. An analysis of the resulting system is provided. The algorithm has been applied to an active vibration control (AVC) system and real time results are presented.

Identification of mechanical structures in the presence of narrow band disturbances - Application to an active suspension

The objective of this paper is to provide an insight into the performances of available identification algorithms for estimating the model of an active suspension system in the presence of narrow band disturbances. Various algorithms from the general class of SISO systems are compared. Furthermore, a new method is proposed that combines the use of an output error algorithm for the estimation of plant dynamics and a prediction error algorithm for disturbance dynamics. The methods have been tested on an active suspension using an inertial actuator.

A general adaptive feedforward compensation algorithm for active vibration control with mechanical coupling and local feedback

Adaptive feedforward broadband vibration (or noise) compensation is currently used when a correlated measurement with the disturbance is available. Most of the active vibration control systems feature an internal “positive” mechanical feedback between the compensation system and the reference source (a correlated measurement with the disturbance). Such systems have often also a feedback control loop for reducing the effect of disturbances. For stability reasons the adaptation algorithms require the implementation of a filter on observed data or a filtering of the residual acceleration in order to satisfy some passivity conditions. Recently the use of the “Integral + Proportional” (IP) adaptation has been proposed. The paper provides a general algorithms for the adaptive feedforward compensation which includes as particular cases the various algorithms presented in the literature. The algorithm has been applied to an active vibration control system.

An indirect adaptive feedback attenuation strategy for active vibration control

From a control point of view, active vibration control requires attenuation of unknown and/or time varying multiple narrow band disturbances. Internal Model Principle (IMP) is currently used for building adaptive active vibration control systems. IMP leads to asymptotic suppression of the disturbances but often introduces in the case of multiple narrow band disturbances a strong ”water bed” effect on the output sensitivity function (unwanted amplification). In this paper, an indirect adaptive control methodology for attenuation of multiple unknown time varying narrow-band disturbances is proposed. The method is based on the real time estimation of the frequency of narrow-band disturbances using adaptive notch filters (ANF) followed by the design of a controller using adjustable band-stop filters (BSF) for the appropriate shaping of the output sensitivity function. A Youla-Kučera parametrization of the controller is used for reducing the computation load. This approach is compared on an active vibration control (AVC) system with the direct adaptive control scheme based on the internal model principle (IMP) proposed in [1]. Real time experimental results are provided.

An IIR Youla-Kucera parametrized adaptive feedforward compensator for active vibration control with mechanical coupling

Adaptive feedforward broadband vibration (or noise) compensation is currently used when a measurement correlated with the disturbance is available. However, in most of the systems there is a “positive” feedback coupling between the compensator system and the disturbance correlated measurement. This may lead to the instability of the system. The paper proposes a new Youla-Kucera (YK) parametrization of the compensator. The central compensator assures the stability of the system and its performances are enhanced in real time by the adaptation of the parameters of an IIR Youla-Kucera filter. An analysis of the resulting system is provided. The results of this paper on one hand generalize previous results obtained for FIR Youla-Kucera adaptive filters and on the other hand lead to a significant reduction of the number of parameter to be adapted for the same level of performance. The algorithm has been applied to an Active Vibration Control (AVC) system and real time results are presented.

Direct and indirect adaptive regulation strategies for rejection of time varying narrow band disturbances applied to a benchmark problem

The paper will compare the performances which can be obtained using a direct adaptive regulation scheme based on the Youla-Kučera (YK) parametrization of the controller and using an adaptive finite impulse response (FIR) filter for implementing the internal model of the disturbance with a new indirect adaptive regulation scheme. The main features of this new scheme are: (i) the use of adaptive Band-stop Filters (BSFs) tuned at the frequencies of the disturbance instead of the Internal Model Principle (IMP) and (ii) a procedure for direct identification of frequencies contained in the disturbance. The use of adaptive BSFs allows to introduce the desired attenuation of the disturbance (instead of total rejection) and allows to get a much better shaping of the output sensitivity function (to meet the specification for the tolerated amplification outside the frequencies of the disturbance). The two approaches are comparatively evaluated on the benchmark simulator and on the benchmark active vibration control system.