The paper presents a new proximate time optimal seek control approach with discrete- time variable structure control theory for a hard disk drive (HDD) servo. It incorporates the time optimal control idea into the time-varying sliding mode control design and derives a class of proximate time optimal control algorithms with robustness. The proposed approach provides one unified framework for both track seeking and track following controller design, it achieves smooth transition from seek control to track-following control naturally, and it eliminates the common chattering and overshoot problem as well. A systematic method is developed for the choice of controller parameters. Simulation results are demonstrated to show the robustness of the proposed method to disturbances, unmodelled dynamics and parameter variations with near time optimal performance.
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