Long-Span Seek Control System for Hard Disk Drive without Mode-Switching

Abstract

In Hard Disk Drive (HDD), there are two control modes. One is a head positioning control mode, the other is a seek control mode. In the head positioning control mode, a feedback controller is optimally designed to suppress a disturbance. In the long span seek mode, a velocity feedback control system is applied in order to move a head fast. Thus, a HDD has plural control systems, and the head is moved to the target position while changing from one control system to the other. However, the changing of the control system causes a discontinuous control signal, which activates the resonance mode of an actuator. The past methods only can decrease the discontinuous control. Therefore, a single control system that can be used for both a seek control mode and a head positioning control mode is necessary for narrow track pitch. In the proposed method, the feedback controller is decomposed to an integrator and a phase compensator. The VCM model is updated by the output of the phase compensator, and the integrator and the output of the velocity feedback controller control the VCM. The validity of the proposed method was confirmed by numerical and experimental results using a miniature 2.5-inch Hard Disk Drive.