VCM design to improve dynamic performance of an actuator in a disk drive

Position error signal (PES) design margin of a current hard disk drive is getting smaller as the track density of high-capacity disk drives increases. In the present work, a new actuator design concept is introduced for suppressing one of the actuator vibration modes, the so-called butterfly mode, that normally limits the expansion of servo bandwidth. The new actuator has a single coil with four sections having respective particular directions. By adjusting the length and inclined angle of the sections of the voice coil motor (VCM) coil, the forces perpendicular to track-seeking direction can be balanced with each other. Consequently, the butterfly mode is not excited by the resultant force of the VCM. Contribution of the proposed actuator design for the PES management is verified by numerical simulations. Our results show that the servo bandwidth can be increased from 1207 to 1680 Hz so that the PES can be decreased by 27% due to the use of the improved actuator.