Design of a high-precision clamping microgripper with a single actuator based on symmetrical half-bridge amplification mechanism

Abstract The parallelogram mechanism is commonly adopted as the final amplification stage of microgrippers due to its parallel clamping characteristics, which directly connects to the jaws. During rotation, the mechanism generates vertical parasitic displacement and angular deviation of the links due to uneven force distribution. To address this, a two-stage amplified microgripper with symmetrical half-bridge amplification mechanism is designed, actuated by a piezoelectric (PZT) actuator. The symmetrical half-bridge amplification mechanism configuration employs two first-stage mechanisms to simultaneously drive the second-stage mechanism, ensuring symmetric force distribution on both sides. This effectively mitigates the parasitic displacement generated by the parallelogram mechanism during operation. Through geometric parameter optimization, the mechanism’s amplification factor is significantly enhanced. Experimental results demonstrate that the closed-loop controlled PZT actuator alleviates hysteresis and creep in PZT ceramic output, enabling linear displacement output. The microgripper attains a displacement amplification factor of 50.6, with a parasitic displacement ratio standing at 0.22%.