Triple-Stage-Actuator System of Head-Positioning Control in Hard Disk Drives

In this paper, we propose a triple-stage actuator system with a thermal actuator to increase a servo bandwidth of a head-positioning control system in hard disk drives. The thermal actuator is good for control in high frequency range because it has little negative impact caused by mechanical resonances. Therefore, the proposed system with a thermal actuator can control the head position beyond the major mechanical resonances caused by a voice coil motor (VCM) or piezoelectric (PZT) actuator. As a result, the servo bandwidth of the proposed triple-stage actuator system can be higher than that of the conventional dual-stage actuator system which consists of the VCM and the PZT actuators. Simulation results of sensitivity functions showed that the disturbance-compensation performance below 2 kHz will be improved by 6 dB with proposed control system.