Layer-Jump Control of a Focus Servo System and Periodic Disturbance Compensation of a Track-Following Servo in Optical Disk Drives

• Main Authors: Yueh-Tsang Li, 李岳蒼
• Other Authors: Lu, Yu-Sheng
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/mmk5j5

碩士 === 國立雲林科技大學 === 機械工程系碩士班 === 95 === This paper proposes an improved design of the Internal Model Control (IMC) controller for lightly damped plants suffering from periodic exogenous signals.The Traditional IMC (T-IMC) system for lightly damped plants would have oscillatory output responses. Moreover, when being subjected to periodic exogenous signals, the T-IMC system could not achieve asymptotic tracking performance or complete disturbance rejection. To solve these problems in the traditional IMC, this paper proposed an improved IMC design by incorporating a lowpass filter and several band pass filters into the controller block in the IMC structure. The bandpass filters are tuned according to the resonant frequencies of the plant and the frequencies of periodic exogenous signals. In addition, this paper proposes a sliding repetitive control based on sliding disturbance observer, called SRC with SDOB, for repetitive tracking control tasks. The proposed control consists of the pole-placement feedback control, the SDOB-based feedback compensation, and the learning feedforward compensation to improve system robustness. Both proposed schemes have been applied to the track-following servo. Layer-jump control of the focus servo system is the SONY layer-jump control for multilayer-recording optical disk. In addition, this paper proposes Zero-Overshoot PID (ZOPID) to alleviate overshoot and achieve fast responses for layer-jump process. The experimental system consists of a commercially available 12Xs DVD-ROM drives and a DSP/FPGA system that is the control kernel and replaces the servo chip on the original drive. We use C language and hardware description language (VHDL) as tools for developing servo control systems for optical disk drives.