sudden disturbance reject

Fig. 6.11 sudden disturbance rejection

Fig. 6.12 control loop model

Fig. 6.11 and Fig. 6.12 shows the simulation results of the sudden disturbance (initial time 0.02 second and final time 0.03 second 100 amplitude step function in VCM actuator)for comparing the characteristics of the new control (solid line), robust control (dotted line), and conventional PID control (dashed line) at a dual stage servo system. Each control methods design to minimize the sudden disturbance.

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In each compensator, the sudden disturbance of the new control is obvious within the tolerance level at this PZT focusing. The simulation results thus confirmed that the new control loop may allow precise control at very high speed focusing.

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VI. CONCLUSION

ZPET-FF robust design in 2DOF of dual-stage system is proposed for high speed focusing in miniaturized ODD. The high-bandwidth micro-actuator working in the path can greatly improve the output response of reference focusing. The 2DOF construction of dual-stage actuator provides a fine focusing solution to overcome the signal actuator coarse motion. The feed-forward control signal should be injected to the VCM and PZT input in addition to the usual servo signal, which would guarantee that the primary actuator PZT can arrive the target eventually. This paper proposes a new robust focusing servo system for dual-stage mechanical system, which detects and suppresses the both periodic disturbance and sudden disturbance. The experimental results point out that the proposed sudden disturbance observer well estimate by robust controller. Moreover, in order to suppress the periodic disturbance, this paper designs the ZPET feed-forward servo system with prediction of focusing error. The experimental result confirms that the proposed robust tracking servo system reduces the focusing error and the influence of sudden disturbance.

Acknowledgment

Research supported by TDPA project 95-EC-17-A-07-S1-011, MOEA, Taiwan, ROC.

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