Repetitive control of hard disk drives based on switching scheme: experimental verification for multiple mode disturbance

Because the record density of hard disk drive (HDD) increased very rapidly, the required servo accuracy is getting dramatically severe. In this paper, novel feedforward (FF) control is proposed to reject the periodic disturbance based on switching scheme and open-loop observer. The advantages of proposed method are verified by several experiments. First, the proposed FF method is compared with the conventional feedback (FB) control in the case of single-mode disturbance rejection. Second, multiple-mode disturbance is considered in high-frequency region, which cannot be rejected by conventional technologies. The final experiments show that the proposed control algorithm eliminates 20.4 [%] tracking error compared with a conventional method.