Multirate Adaptive Compensation of Uncertain Resonances Beyond the Nyquist Frequency

Abstract

In this paper, an add-on multirate adaptive control scheme is proposed for compensation of uncertain mechanical resonant modes beyond the Nyquist frequency in mechatronic systems. A polynomial transformation technique is applied to obtain the mixed-rate model of the control system that is suitable for multirate adaptive control design. To preserve the performance of the pre-designed nominal controller, an auxiliary error is utilized in the parameter estimation process instead of tracking error. The proposed multirate adaptive control combined with a Recursive Least-Squares (RLS) algorithm and a dead-zone ensures boundedness of all the closed-loop signals and convergence of the auxiliary error. Our simulation results on the model of the Voice Coil Motor (VCM) actuator in a commercial Hard Disk Drive (HDD) demonstrate the effectiveness of our proposed compensation scheme in attenuating the mechanical resonances beyond the Nyquist frequency.