Active high-frequency vibration rejection in hard disk drives

This paper presents an active vibration rejection (AVR) control technique to reject actuator arm resonance modes using a piezoelectric sensor attached to the actuator arm to detect high-frequency off-track actuator vibration. The voice coil motor (VCM) is used as an actuator, while the piezoelectric sensor is used as a sensor only. A multirate digital implementation is proposed for high-frequency AVR over the sector-induced sampling frequency. The vibration control signal can be synchronized with the slow-state feedback control input such that the two control signals are summed and applied to the VCM. Throughout an application example the proposed AVR scheme, using the VCM as an actuator while the piezoelectric sensor as a sensor, is shown to be very prospective for high-frequency vibration rejection, provided a good vibration sensing scheme is used.