Piezoelectric stick-slip actuator integrated with ultrasonic vibrator for improving comprehensive output performance

In this paper, a novel compact piezoelectric stick-slip actuator integrated with ultrasonic vibrator based on ultrasonic anti-friction effect is proposed. Based on inverse piezoelectric effect, the piezoelectric stack generates the axial vibration under the excitation of asymmetric sawtooth wave, the ultrasonic vibrator is composed of a brass block and four piezoelectric plates, which is used to excite the ultrasonic longitudinal vibration mode in the fast deformation phase of piezoelectric stack. Due to ultrasonic anti-friction effect, the backward displacement of the actuator is effectively suppressed, and the bidirectional comprehensive output performance is improved. The prototype is fabricated and the operating principle of hybrid excitation is introduced, then the frequency of the first-order longitudinal vibration mode is explored by finite element analysis and impedance test, and the systematic experimental test is conducted. The test results show that when the sawtooth frequency is 300 Hz, comparing with the traditional sawtooth excitation mode, the proposed hybrid excitation mode can improve the velocities of the forward and backward directions by 30% and 26.7%, and the bidirectional maximum vertical mass loads are increased by 44.4% and 50%. This work provides a design concept that uses ultrasonic vibrator to improve the bidirectional comprehensive output performance of the piezoelectric stick-slip actuator.