High-Speed Positioning Control for Hard Disk Drives Based on Two-Degree-of-Freedom Control

We present a high-speed track seeking technique based on two-degree-of-freedom (2DOF)control. 2DOF control, which simultaneously uses feedback and feed-forward control, specifies loop performance and response performance independently. Therefore, conventional mode-switching from velocity control to positioning control becomes unnecessary. Focusing on how to effectively use a voice coil motor (VCM), that is, a head actuator, for fast track seeking, a new reference model is also proposed. In this 2DOF control system, a reference model plays an important role in shortening of seek times. Considering the VCM dynamics, this reference model generates a reference trajectory allowing high-speed movement and fast settling to target tracks. Experimental results using a typical hard disk drive indicated the validity of the proposed method, especially for short stroke seeks.