Compensation for Disk-Flutter Vibrations of Head-Positioning Control Systems in Hard Disk Drives

Abstract

In a head-positioning control system of a hard disk drive, the head-positioning accuracy is worsened because of the airflow-induced vibration of disks (called “disk flutter”). Therefore, the control system must compensate for the disk-flutter-induced positioning error. In this paper, we propose a new framework of the head-positioning control system using a resonant filter to suppress the disk-flutter-induced positioning error. The control system uses resonant filters with variable gains that depend on the cylinder number of the head position and the modal shape of the flow-induced vibration of disks. The resonant filter can obtain a circular vector locus that recedes from the unstable point on the Nyquist diagram and can decrease the sensitivity function's gain at a specific frequency. The variable gains are optimized depending on the cylinder number of the head position. As a result, the resonant filter is able to improve the transient response after track-seeking control. The result of track-seeking simulations showed that the proposed method was effective in decreasing the positioning error caused by the disk-flutter-induced vibration and improving the seek time of the hard disk drive.