Coordinated System with Tracking-position and Fiying-height Controls for Magnetic Heads in HDDs

摘要

To improve positioning accuracy of a magnetic head in hard disk drives (HDDs), a triple-stage-actuator system was proposed with a thermal-positioning actuator for a magnetic-head-positioning system. This positioning system has three types of actuators: a voice coil motor (VCM), piezoelectric (PZT) actuators, and the thermal-positioning actuator. The thermal actuator systems have simple characteristics without mechanical resonant modes even in a high-frequency range. However, the thermal-positioning actuator causes flying-height fluctuations of the magnetic head that could lead to fall of magnetic recording performances. To compensate for the flying-height fluctuations of the magnetic heads caused by the thermal-positioning actuator, this paper presents a magnetic-head-positioning system that employs a two-degree-of-freedom control on the thermal flying-height control system. Simulation results showed that the proposed method was able to compensate for the flying-height fluctuations during the track-following control by about 89 % against the plant perturbations.