Design of seek control of hard disk drive using discrete-time sliding mode control

We present a modified improved time-optimal sliding-mode control of hard disk drives. A second order velocity reference profile is used with a linear region as the conventional proximate time-optimal servomechanism. In a nonlinear velocity region, time varying sliding surface is used while in a linear region, a fixed time invariant sliding surface is used. We have obtained improved seek performance over the previous results using discrete-time sliding mode proximate time-optimal seek control. We show that it is applicable in the presence of unmodeled dynamics and parameter variations. Its effectiveness is verified with simulation results.