Control and dynamic releasing method of a piezoelectric actuated microgripper

This paper proposes the control and dynamic releasing method of a symmetric microgripper with integrated position sensing. The microgripper adopted in this micromanipulation system is constructed by two L-shaped leverage mechanisms and the fingers of the microgripper is machined much thinner than the gripper body. A combined feedforward/feedback position controller is established to improve the motion accuracy of the microgripper in high frequency. The feedforward controller is established based on rate-dependent inverse Prandtl-Ishlinskii (P-I) hysteresis model. The inertial force generated in dynamic based releasing process is analyzed through MATLAB simulation. Open-loop experimental tests have been performed, and the results indicate the first natural frequency of the microgripper is 730 Hz. Then experiments in high frequency based on the developed combined controller are carried out and the results show the tracking error of a superimposed sinusoidal trajectory with the frequency of 100 Hz, 120 Hz and 130 Hz is 6.4%. Finally, the tiny objects releasing experiments are conducted where the combined controller is used to control the motion amplitude and frequency to achieve inertial force controllable to improve operation accuracy. And the results show that the dynamic releasing strategy is effective.