Research On A Piezoelectric Actuator Based On Bending Vibration Modes

Piezoelectric actuators(also called ultrasonic motor)is one of the key component of precision drive system,which has been widely used in robot systems,micro mechanical system,and the ultra-precision measuring instruments,etc.The composite piezoelectric actuator based on the bending mode works on the composition vibration of the oscillator in the direction of the two or more bending vibration,which has the advantages of simple structure and easy processing.However,there are few studies on composite bending modes piezoelectric actuators,and there are generally poor driving performance.In this thesis,a dynamic model is established to evaluate the dynamic characteristics of cantilevered piezoelectric actuator,then,the boned-type of piezoelectric actuator with composition of bending vibration is designed,and the structure parameter,response characteristics and mechanical performance of the piezoelectric actuators are analyzed.The main contents of this thesis are given as follows:1.Based on the Euler-Bernoulli beam theory and the piezoelectric constitutive equation,a dynamic model of piezoelectric actuator is established to evaluate the dynamic characteristics of piezoelectric actuators.The segmented electrodes vibrator is designed to investigate the effect of strain node on the dynamic performance of piezoelectric actuator.Then,the dynamic performance of the segmented electrodes vibrator is comparative studied with the traditional continuous electrode vibrator.The results shown that the segmented electrodes structure can effectively improve the output performance of actuator under high vibration modes.2.Based on the cantilevered piezoelectric actuator,a boned-type of piezoelectric actuator with composition of bending vibration is designed,which constituted two symmetrical cantilever beam and two groups of piezoelectric ceramic patched on the cantilever beam.The two groups of piezoelectric ceramic can actuate the beam generate the direction of the horizontal and vertical two bending vibration,and then to generate the driving action by composited the two direction vibration.Then,the actuation principle of the piezoelectric actuator is explained theoretically,and the elliptic trajectory equation is derived.3.A finite element model of the piezoelectric actuator is established by the finite element software ANSYS.The effect of the modal frequency of the piezoelectric actuator on the structure parameter is analyzed by the finite element model,then,the final structure parameter is determined to match the first bending mode of the vertical direction and second bending mode of the horizontal direction.It is found that when the frequency of the driving voltage equal to 21.072 kHz,the piezoelectric actuators generate driven motion in the plane.Then,the response characteristics and mechanical performance of the piezoelectric actuators are also analyzed,the results shown that the output of the piezoelectric actuators is maximum torque of 0.11 Nm and maximum power of 0.73 W.