Head positioning control for low sampling rate systems based on two degree-of-freedom control

To enhance formatting efficiency in high density hard disk drives, it is desirable to decrease the number of embedded servo signals. As a consequence, the sampling rate of servo systems has been becoming lower. In this situation, it is difficult to attain fast track seeking by using only a feedback controller. This paper presents a high-speed track seek technique, based on two degree-of-freedom control. A new reference model is developed by focusing on the attainment of fast track seeking through the effective use of a voice coil motor, which functions as a disk head actuator. The model generates reference trajectories, allowing high-speed movement. Also, in order to quickly settle the disk head to a target track under various disturbances, an initial value compensation (IVC) method to minimize a quadratic performance index is developed. Experimental results, using a 3-1/2 inch hard disk drive, confirm the validity of the proposed method.