A miniature longitudinal-bending hybrid linear ultrasonic motor inspired by the planar hinged five bar mechanism

Inspired by the double crank planar hinged five bar mechanism, a longitudinal-bending hybrid linear ultrasonic motor with compact miniature is proposed and tested. In order to realize miniaturization, it adopts a bonded-type structure. Four lead zirconate titanate (PZT) piezoelectric ceramics are distributed equally into two groups and bonded to the two ends of the metal frame, and then, two voltages with a phase difference of 90° are applied to each of the two groups of PZT ceramics. Subsequently, the first-order longitudinal vibration and second-order bending vibration generated by the motor combine with each other at the tip of the driving foot to form an elliptical motion trajectory. According to the theoretical kinematic analysis of the free beam, the initial structural dimensions of the motor were designed. Then, the initial dimensions of the motor were optimized, and the zero-order optimization algorithm was used to achieve the purpose of longitudinal and bending resonance of the motor, and finally, the optimal dimensions of the motor were obtained. A prototype of the designed motor was made, followed by experimental tests on the performance of the prototype, including mechanical output. The maximum motor speed without load at 69.4 kHz is 134.57 mm s-1. Under 200 Vpp voltage and 6 N preload, the output thrust of the motor is about 0.4 N at the maximum. The actual mass of the motor is about 1.6 g; therefore, the thrust-to-weight ratio was calculated as 25.