Anti-shock controller design for optical disk drive systems with a nonlinear controller

This paper presents a modified nonlinear controller design for optical disk drive systems to improve antishock performance. It was proposed in previous work that a nonlinear anti-shock controller is added parallel to the original linear servo control loop to improve its tracking performance in the presence of external shock. In the previous work, a dead-zone type nonlinear element is used for the nonlinear controller and a PID control method is used for the linear controller. Although this parallel structure improves anti-shock performance, it has a relatively low stability bound. In this paper, a dead-zone with saturation is proposed for the nonlinear controller. Since this nonlinear element improves the stability margin, we can use a higher gain for the dead-zone than the previous one. In addition, we found that the overall controller with a lead-lag type linear controller has an improved stability margin over that with the PID type linear control in this application. Numerical simulation results and experimental results confirm that the proposed method provides better performance against external shock than the previous method