Short seeking control with minimum jerk trajectories for dual actuator hard disk drive systems

This paper is concerned with short seeking control for hard disk drives with a dual actuation servo system consisting of a coarse actuator (voice coil motor, VCM) and a fine actuator (piezoelectric actuator, PZT). Short seeking refers to moving the recording head over a few tracks. The primary elements in short seeking control are the feedback controller, the feedforward controller and the reference input. These elements must be determined for each of the coarse and fine actuators. The unique feature of the proposed short seeking control scheme is on the use of two minimum jerk trajectories as reference inputs: one with a seek time typical for VCM and the other with a shorter seek time. The first one is used as the reference input for VCM and the difference between the two is used as the reference input for PZT, which makes the second faster trajectory set the actual seek time of the dual actuator system. Single rate and multi rate implementations of the proposed scheme are presented along with experimental results. The motivation for multi-rate implementation is saving of computation.