Research On The Longitudinal-bending Coupling Vibration Standing Wave Piezoelectric Actuators

In recent years, more attentions for piezoelectric actuator is transferred from rotary type to the linear type gradually, which mainly adopts hybrid modes to realize the driving. There are longitudinal-bending hybrid modes, bending-torsion hybrid modes, bending-bending hybrid modes and longitudinal-torsion hybrid modes, etc.For traditional linear piezoelectric actuator using longitudinal-bending vibration mode, independent piezoelectric(PZT) ceramic groups were used to generate the longitudinal vibration and bending vibration respectively, which made the piezoelectric actuator has complicated structure. Some piezoelectric actuators use only one group of bending PZT plates to generate the longitudinal-bending hybrid modes with different electric signals, which need a complicated ultrasonic power.In this study, a novel L-B hybrid piezoelectric actuator using vibration coupling is proposed. In this new design, the longitudinal-bending hybrid vibrations are excited synchronously by only one group pf longitudinal PZT elements. Fixed boundary condition is applied on one side surface of the flange to obtain the vibration coupling effect of the longitudinal and bending modes.Firstly, the vibration equations of the longitudinal vibration mode and bending vibration mode were established. Motion equation of the piont at the end of composite beam was analyzed and oblique ellipse trajectory was got. Equivalent circuit of the piezoelectric actuator was also analyzed. Based on the theoretical analysis, the structure of piezoelectric actuator was designed. Modal analysis, harmonic analysis and transient analysis were developed to verify the feasibility of the proposed design. The relationship between unsymmetric boundary condition and actuator property was analyzed by finite elements method(FEM).Based on the result of FEM, a prototype was fabricated and the experimental platform was establiched. The design and analysis work was verified by impedance Analyzer and scanning laser Doppler vibrometer. The relationship between unsymmetric boundary condition and actuator property was analyzed by experiment. The proposed standing wave linear piezoelectric actuator achieves maximum no-load speed and thrust force of about 891.3mm/s and 39.2 N under voltage of 400 VP-P under working frequency of 39.2 k Hz. Moreover, two kinds of bi-directional driving solutions were studied.