A Gated Two-Frequency Two-Mode Method for Piezoelectric Motorization

Abstract

In this study, we present a new driving method to generate traveling waves in a finite plate for application to piezoelectric motors. Due to resonant modes which dominate the vibration of finite structures, methods to reduce resonant effects such as using an electric sinker or driving at a non-resonant frequency have been reported. To take advantage of natural resonance and to increase driving efficiency, a new method entitled gated two-frequency-two-mode (G-TFTM) was developed. A piezoelectric bimorph of 1.1 g weight with two rectangular actuators was implemented to verify the design concept. One actuator was operated at a first bending mode and the other actuator operated at a second bending mode with a phase difference. The driving signal was gated to generate an intermittent excitation to provide the periodic propulsion. To determine the profile of the induced traveling wave, an analytical solution was derived and a numerical model was used. Using these design tools, we experimentally verified that traveling waves can be generated using a G-TFTM method. A 0.1-g object can be moved at a speed of 3.31 mm/s under the condition of a 70-to-20 voltage ratio and a 137 deg phase difference. The moving direction was found to be reversed by changing the phase to −43 deg. The experimental and numerical data are detailed in this paper to demonstrate the feasibility of this G-TFTM method.