Active control for reducing disk flutter induced track misregistration

This paper shows that the disk vertical vibration signal picked from the slider has a fixed phase and amplitude relationship with the position error signal at a few disk flutter frequencies. A differential type feedforward control, which is additional to the usual hard disk drive servo loop and with the disk vertical direction velocity as input, is proposed to reduce the disk flutter induced position error. The proposed control can reduce the disk flutter induced track misregistration considerably.