This paper describes a micro-actuator for high-bandwidth tracking servo, where a micro-actuator is attached between slider and suspension, and moves the slider relative to the suspension. The micro-actuator frequency response measurement proved that this micro-actuator can be modeled as an ideal spring-mass-damper system up to 80 kHz, so that very high bandwidth servo system can be easily designed. The maximum servo bandwidth of 6.4 kHz was achieved in a drive level experiment, which is the highest bandwidth ever demonstrated as a drive level. A rapid step response time of 0.2 mS for 0.6 /spl mu/m step was also achieved. The experimental bandwidth was not limited by the micro-actuator's resonance mode, but the saturation of the micro-actuator driver.

A micro-actuator which can largely improve the capacity and performance of current hard-disk drives (HDDs) was investigated. This micro-actuator is located between a slider and a suspension, and moves the magnetic head (attached on the edge of the slider) with very high speed and accuracy. As a result, extremely high data-track density (thus, high capacity) and fast access time can be achieved. First, requirements for this actuator were investigated, and new design methods and fabrication technologies were developed, including area-efficient electrode design, "integrated traces", 20:1 (40 /spl mu/m thick, 2 /spl mu/m resolution) high-aspect ratio polymer etching, and multi-layer metal structure. The micro-actuator was successfully fabricated and assembled. A servo experiment was carried out by using a commercially available 3.5 inch HDD. High servo bandwidth of 2.4 kHz, high track-following accuracy of 0.0275 /spl mu/m (one sigma) which enables 25 kilo track-per-inch (TPI), and fast P move time of 0.5 mS for 9.8 /spl mu/m- seek were demonstrated.

Reports on the design, fabrication, and testing of an electrostatic microactuator for a magnetic hard disk drive (HDD) tracking servo. The design requirements for a microactuator are investigated. These include high Z-directional stiffness, low in-plane stiffness, high structural aspect ratio, large output force, high area efficiency, low cost, and mass batch production. An area-efficient rotary microactuator design was devised, and microactuators were successfully fabricated using innovative processing technologies. The microactuator has a structural thickness of 40 /spl mu/m with a minimum gap/structure width of approximately 2 /spl mu/m. Its frequency response was measured and it was determined that it can be modeled as a second-order linear system, up to the 26-kHz frequency range. Moreover, the microactuator will enable the design of a servo system that exceeds a 5-kHz servo bandwidth, which is adequate to achieve a track density of more than 25 kilotrack per inch (kTPI). The microactuator/slider assembly was also tested on a spinning disk, with its position controlled by a PID controller using the magnetic position error signal written on the disk. An accuracy of about 0.05 /spl mu/m was observed when the servo controller was turned on. Continuous-time dual-stage servos were designed and simulated using the /spl mu/-synthesis technique. A sequentially designed SISO and a MIMO control design method have been shown to be capable of meeting prescribed uncertainty and performance specifications.