3 kHz servo bandwidth demonstration by HDD tracking microactuator

Abstract

A demonstration of a closed loop system with a 3 kHz 0 dB open loop crossover using a microactuator in an HDD is reported. An electrostatic rotational microactuator is placed between the suspension beam and the slider, and moves the slider relative to the suspension. A new suspension with extra leads that provide signal to the microactuator was also developed. These leads are electrically connected by a microscale solder-ball reflow process. The dual-stage servo experiment was carried out in an HDD and a 3 kHz servo bandwidth was achieved, which is more than twice as high as a conventional servo system. The error rejection function also shows that this dual-stage servo system has superior error rejection capability over the conventional VCM-only servo system. Simulation shows that the bandwidth can be as high as 44 kHz, if a continuous-time servo is used.