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A novel stick-slip type piezoelectric rotary actuator is proposed in this paper. The actuator equips with a parallelogram driving mechanism to generate a pair of variable force couple to drive the rotor. Two piezo-stacks are used to deform the parallelogram driving mechanism to realize large range motions with high resolution in both forward and backward directions. By utilizing pseudo-rigid-body method, geometric model of the parallelogram driving mechanism is established to analyze the motion of the actuator. Finite element analysis is conducted to simulate the deformation of the driving mechanism. A prototype is fabricated and a series of experiments are carried out. The experimental results indicate that the actuator prototype can achieve various angular velocities by changing the driving voltage and frequency and it can output large range rotary motions in both forward and backward directions. The driving resolutions are 0.75 μrad in forward direction and 0.82 μrad in backward direction and the maximum loading capacities are 74 N and 78 N, respectively. The angular displacement outputs under various driving voltages and frequencies show good linear relationships with the time in both forward and backward motions.

A major deficiency of piezoelectric actuators is that their open-loop control accuracy is seriously limited by hysteresis. In this paper, a novel mathematical model is proposed to describe hysteresis precisely and a new parameter called turning voltage is introduced. It was found experimentally that the shapes of hysteresis curves are decided by the value of the turning voltage. A computer-based inverse control approach under open-loop operation based on the mathematical model was applied to suppress the inherent hysteresis to within ±1% full span range of a stack piezoelectric actuator and the performance of the piezoelectric actuator is noticeably improved.

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