Integrated Design of a Controller and a Structure for Head-positioning in Hard Disk Drives

In head-positioning systems of hard disk drives, the negative effects of a primary resonant mode are serious problems for positioning accuracy. In order to improve positioning accuracy, the primary resonant frequency should be increased because the effects of the primary resonant mode limit the servo bandwidth. An integrated design of a controller and structure for the head positioning system was developed to solve this problem. We showed that the servo bandwidth is limited not only by the peak frequency of the primary resonance but are also its residue. The proposed method decreases the negative impact of the primary resonant mode through a newly designed modal shape, and increases the servo bandwidth without the addition of any sensors or actuators. The effectiveness of this method was verified by designing an actual servo control system and experimentally measuring its bandwidth, demonstrating that the method increases the servo bandwidth without increasing the production cost.