Micro-actuators for high density disk drives

An electrostatic actuator for use in a dual-stage disk-drive servo has been fabricated using the HexSil process. A 2.6 mm diameter device has been shown to be capable of producing 0.23 mN-mm of output torque at a predicted bandwidth of 1.6 kHz. This actuator has been fabricated through a low-cost process using reusable mold wafers. Initial continuous-time control designs for the dual-stage servo have been designed and simulated using Matlab´s μ-tools. Single-input/single-output (SISO) and multi-input/multi-output (MIMO) control design methods have been shown to be capable of meeting specified uncertainty and performance specifications. Uncertainty models have included bearing effects in the disk drive arm as well as high frequency dynamics not included in the system model. Simulations using a linearized system model with the SISO design achieved a low frequency disturbance rejection of 53 dB with a bandwidth of 1.5 kHz. The MIMO design achieved a low frequency disturbance rejection of 60 dB with a bandwidth of 2.0 kHz