| 摘要 |
PURPOSE:To shorten time required for centering and to improve positioning accuracy by varying the gains of a signal in proportion to a position signal in the middle of centering and after the centering in terms of PID control. CONSTITUTION:When a head seeks around a target track and a switching position detector operates, switches SW1, SW3 and SW4 are turned on, and the operation enters a PID control mode 1. After that, a timer counts time. The switches SW2, SW3 and SW4 are turned on and the operation enters a mode 2. Compared with the mode 1, only the gain of the signal in proportion to the position signal changes in the mode 1 and it is halved. There are a large phase margin and a small error amplification, thereby positioning the head at high accuracy. Thus the centering time is shortened, and the positioning accuracy is improved.
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