| 摘要 |
PROBLEM TO BE SOLVED: To actualize stable, high-precision follow-up performance even if disturbance is applied. SOLUTION: An error compression part 13 performs a read lag filter process for a focus error signal 17. A nonlinear controller part 21 switches a gain according to the states of a position and a speed, when the deviation from a target state is large, the control is performed with a high gain, but when the deviation is small, a dead zone is provided and the control is performed so as to stably converge on the target. A disturbance observer part 20 estimates the state of the disturbance from a focus error signal 17 and a control signal 24. A composing unit 19 obtains the control signal 24 by putting together the outputs of the error compression part 13, nonlinear controller part 21, and disturbance observer part 20 so as to compress a focus error and also suppress the disturbance.
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