Motion mechanism of two-degree-of-freedom spherical motor using single PZT vibrator

A two-degree-of-freedom piezoelectric spherical ultrasonic motor using only one piezoelectric element to drive the rotator was proposed based on two vibration modes of a rectangular plate type piezoelectric vibrator. The motion mechanism of the motor was verified by simulation and experiment. The vibration modes and resonance frequencies of the motor's plate type piezoelectric vibrator were calculated by finite element method. The simulation results show that the piezoelectric vibrator can produce clear vibration shapes in B32 and B23 modes, and their modal frequencies are 49.127 kHz and 49.756 kHz, respectively. The motion trajectories of four contact points between the protrusion and the spherical rotor were analyzed with computer simulation, and prototype test was carried out to verify the simulation results. The results indicate that the four contact points can form elliptical trajectories with reasonable timing, which can be used to drive the spherical rotor to form rotation with two-degree-of-freedom, and the deformation of protrusions which act as support feet is 30% of that of protrusions that act as drive feet. The simulation and experimental results confirm the formation of two-dimensional motion mechanism of the two-degree-of-freedom spherical motor.