Design and implementation of adaptive non-repetitive track-following disk file servos

This paper discusses the design, implementation and experimental verification of a new direct adaptive control scheme for disk file track-following servo systems. The adaptive controller acts as an add-on compensator to an existing fixed compensator, which stabilizes the feedback system. The control objective is to minimize the frequency weighted variance of the tracking position error signal in the presence of external random vibrations. The proposed adaptive control scheme was implemented on a TMS320C30 DSP board,and was tested on two different disk drives. The drives were subjected to stochastic input disturbances or random vibrations. Simulation and experimental results are in close agreement and show that the proposed adaptive scheme significantly improves the error rejection capabilities of the control system, without significantly increasing its bandwidth nor decreasing its open loop stability margins.