Time optimal seek control for a coupled dual stage disk drive actuator

A unified expression and three typical kinds of seeking trajectories of the time optimal control of a dual stage disk drive actuator with passive coupling between the two stages are presented. Necessary conditions for finding the optimal control for the problem with state-variable constraints are applied to derive the solution. Numerical calculations and computer simulations were performed to get the trajectories. The experimental trajectories of 1/3 full stroke for a disk drive are also presented. A DSP (Digital Signal Processor) based control system is used to implement the optimal control. The time optimal seek control features cooperative control of the two stages of the actuators, and seek time can decrease as compared with one-stage seeking when the fine actuator locked onto the coarse actuator.