Gabriel Buche

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 Suppression of Multiple Time-Varying Unknown Vibrations Using an Inertial Actuator

An active vibration control system using an inertial actuator for suppression of multiple unknown and/or time-varying vibrations will be presented. 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 in real-time information upon the disturbances. A direct feedback adaptive regulation scheme for the suppression of multiple unknown and/or time-varying vibrations will be used and evaluated in real time. It uses the internal model principle and the Youla-Kucera parametrization. In the Appendix, a comparison with an alternative indirect adaptive regulation scheme is presented.

Design and Tuning of Reduced Order H-Infinity Feedforward Compensators for Active Vibration Control

This brief presents a procedure for design and tuning of reduced orders H∞ feedforward compensators for active vibration control systems subject to wide band disturbances. The procedure takes in account the inherent “positive” feedback coupling between the compensator system and the measurement of the image of the disturbance. It also takes advantage of the availability of reliable models obtained by system identification. A controller order reduction technique is proposed for reducing the complexity of the nominal H∞ controller without degrading the performance. Experimental results obtained on an active vibration control system for a flexible mechanical structure will illustrate the procedure.

Subnanometer Positioning and Drift Compensation With Tunneling Current

This paper introduces tunneling current as a sensor to detect and control the displacements of micro- and nanoelectromechanical systems. Because of its extremely small magnitude, the tunneling current cannot be used without an appropriate control strategy. A control methodology involving two feedback loops is proposed to control displacements with an accuracy of 40 pm while also compensating the sensor drift. With this strategy, controlling displacements with an amplitude is possible, extending the predicted capabilities of tunneling current by the literature. The overall approach is a solution for the control of macro to nano systems and may be embedded in positioning applications requiring a very high degree of accuracy.

Direct adaptive suppression of multiple unknown vibrations using an inertial actuator

An active vibration control system using an inertial actuator for suppression of multiple unknown and/or time-varying vibrations will be presented. 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 in real time information upon the disturbances. A direct feedback adaptive regulation scheme for the suppression of multiple unknown and/or time-varying vibrations will be used and evaluated in real time. It uses the internal model principle and the Youla- Kucera parametrization.

Robust and Adaptive Feedback Noise Attenuation in Ducts

In this brief, the attenuation of sound propagation in an air-handling duct using robust and adaptive feedback active noise control (ANC) strategies is investigated. The case of multiple narrow-band disturbances located in distinct frequency regions and the interference occurring in the presence of disturbances with very close frequencies are considered. The active control uses a loudspeaker as a compensatory system. The objective is to minimize the residual noise at the end of the duct segment considered. The system does not use any additional sensors for receiving real-time information upon the disturbances. This brief illustrates the application of the techniques for active vibration control presented by Landau et al. to this problem. A hierarchical feedback control approach will be used. At the first level, a robust linear controller will be designed taking advantage of the knowledge of the domains of variation of the frequencies of the noise disturbances. To further improve the performance, a direct adaptive control algorithm will be added. Its design is based on the use of the internal model principle combined with the Youla–Kučera parameterization of the controller. Guidelines for the design of the baseline (central) controller are provided. Both robust and adaptive controls require the knowledge of the discrete-time model of the compensation path, which is obtained by identification from experimental data. Experimental results on a relevant duct ANC test bench will illustrate the performance of the proposed methodology.