Design and control of a dual-stage disk drive servo system with a high-aspect ratio electrostatic microactuator

Dual-stage servo systems have been proposed as a method for attaining increased bit densities from computer hard disk drives. To aid in controller operation, the second-stage microactuator used in a dual-stage system should operate at low voltages, feature relative position sensing, and have dynamics that interact well with the dynamics of the original drive servo. This paper describes a high-aspect ratio electrostatic microactuator modified to improve dynamic interactions, relative position sensor performance, and device yield. A multi-rate, multivariable control design technique was used to evaluate the closed- loop performance of a disk drive system with a microactuator and relative position sensing. Closed-loop simulations reveal that the proposed configuration can reduce off-track position error. Addressing both hardware design and control design, this paper demonstrates the success of an integrated mechatronic approach to hard disk drive servo control.