Design and development of a compliant piezoelectric microgripper based on three-stage amplification

Abstract

This work presented the design and test of a double-arm actuated compliant piezoelectric microgripper based on three-stage amplification mechanism, which can also perceive the gripping displacement and force simultaneously. Developing a proper structure for the microgripper to achieve large amplification ratio in a compact space and to ensure sufficient natural frequency is a fundamental and challenging task. Firstly, the structure of piezoelectric microgripper was designed and the kinematic principle of the amplification mechanism was analyzed. Meanwhile, theoretical and simulation analysis of the statics and dynamics were carried out. Then, the calibration methods for both force and displacement sensors are presented. The calibration coefficients are 0.163 $\text {mN/mV}$ and 0.040 $\mu \!\!\text { m/mV}$, respectively. Finally, a series of experiments were performed to verify the performance of the designed microgripper. The test results show that the displacement amplification ratio of the microgripper is 16.8, and the maximum output displacement of 102.30 $\mu \!\!\text { m}$ and the maximum gripping force of 227.70 $\text {mN}$ can be reached when applying a sinusoidal input voltage with the frequency of 0.10 Hz and the amplitude of 100 $\text {V}$. The closed-loop experiment shows that the peak-to-valley errors of both gripping displacement and force are less than 0.49 $\mu \!\!\text { m}$ and 3.74 $\text {mN}$ respectively. The obtained natural frequency of 215.1 Hz. The micro-gripper achieves excellent static and dynamic performance in clamping accuracy, natural frequency, clamping range, and dual finger independence.