State space disturbance compensation for robust fast servo track writer seek control

Abstract

Unknown and uncertain bias significantly affects the servo performance of servo track writers. Such bias has motivated the design and application of a state space disturbance observer for robust fast seek control. In contrast to some existing methods that employ an explicit model for disturbance or adjust the sensitivity using a filter, the proposed method effectively compensates for bias even during track seek, which is not possible when an integrator or a frequency domain disturbance observer is used. The experimental results presented here demonstrate the utility of the robust fast seek controller. The proposed servo track writer control scheme is shown to yield a very fast track seek in the presence of unknown and uncertain bias.