External vibration compensation via loop shaping and H∞ feedforward control design for hard disk drives in mobile applications

This paper focuses on compensation for external vibration effect on the positioning accuracy of hard disk drives. A feedforward controller is designed to attenuate the effect with the aid of a sensor to detect external vibrations. Loop shaping in frequency domain and H_∞ method in state space are used to design the feedforward controller. The application results in a 1.8-inch disk drive with an accelerometer to measure acceleration signal show that 70% and 97% reduction of the position error signal can be achieved with the feedforward control designed by the loop shaping and H_∞ method respectively. The robustness of the two methods is also evaluated and compared for external vibrations with amplitude variations.