Research on interactions between different operating modes of piezoelectric motors

This paper explores interactions between multiple operating modes of piezoelectric motors. The developed motor can operate in the second-order in-plane bending modes (I), the third-order in-plane bending modes (II) and the first-order out-of-plane bending modes (III). These working modes excited separately and simultaneously, can be manipulated electronically. Each of the vibrational modes can both be driven by applying single-phase and two-phase voltages to piezoelectric ceramic plates. In order to produce all the vibration states, the structural parameters of stator were strictly designed to harmonize two eigenfrequencies of each type of vibrational modes by using finite element software ANSYS. Displacement characteristics of stator driving particles under all vibration states were calculated to evaluate mutual effects of different operating modes. Simulation results reveal that the superposition of I and II corresponds to a mode with lower resonance frequency and larger vibration amplitude in stator body. For the designed motor, the conjunction of modes I and II actually forms the first-order in-plane vibrational mode B01. Therefore, the response displacement of stator driving points reaches the maximum value when modes I and II are conjointly actuated by supplying single-phase excitation voltage under the premise of undistorted three-dimensional motion trajectory. The motor performances under that condition were also investigated experimentally. The dimension of the fabricated prototype motor is 10 mm x 10 mm x 20 mm. The stall torque is 0.2 N center dot m under 200 V single-phase excitation, when the motor operates in modes I and II simultaneously. The maximum no-load speed is 74 r min-1. Compared with separate actuation of vibrational modes I and II, mechanical properties of the prototype motor are significantly improved.