This paper describes a piezo-based "moving-suspension" secondary actuator (called milliactuator) which provides increased servo bandwidth and reduced track-misregistration in a hard disk drive. The milliactuator comprises a pair of piezo-elements driving a relatively thick loadbeam that is partially etched in selected areas to form a honeycomb like structure. Partial etching allows more freedom in optimizing mass and stiffness to enhance the milliactuator dynamics. For a 18 mm (swage to dimple) milliactuator head gimbal assembly (HGA) with load/unload tab, we were able to achieve a first torsion frequency (T1) of 6 kHz. In a prototype drive populated with milliactuators, a new dual stage servo algorithm resulted in 60 higher bandwidth (0 dB open-loop crossover) compared to without the milliactuator. Further modifications to the milliactuator along with improvements in sampling rate and computational time could allow up to 100 higher servo bandwidth. The benefits and limitations of milliactuators are also discussed. The milliactuator provides a low cost, enhanced performance solution for high track densities.
展开▼
