Research On The Exciting Methods And Experiments For Piezoelectric Actuator Using Bending Hybrid Modes

Piezoelectric actuator, with its large energy density, high positioning accuracy, fast response speed, as well as good electromagnetic compatibility, can be applied to some special occasions such as aerospace, precision machinery and so on. In multiple types of piezoelectric actuators, the piezoelectric actuator using bending hybrid modes can avoid the degeneration problem between the resonant frequencies of vibration modes by the combination of the orthogonal bending vibration modes. In order to make the p iezoelectric actuator using bending hybrid modes has higher electromechanical coupling efficiency and better mechanical output characteristic, five piezoelectric actuator s using bending hybrid modes are designed under different exciting methods, by which we can find out the exciting method with more excellent properties.Firstly, the new structure of piezoelectric actuator using bending hybrid modes was designed, which had sandwich type, and in which the d33 operating mode of the PZT elements was used to increase electromechanical coupling efficiency. It had circular cross-section, which can ensure that the two orthogonal bending vibration modes has the same resonant frequency. Then, the actuating principle of piezoelectric actuator using bending hybrid mode s was analyzed. The elliptical orbits of driving feet were deduced. The five exciting methods of this structure were proposed, which contained half piece PZT ceramics exciting method, whole piece PZT ceramics with two partitions and one electrode exciting method, whole piece PZT ceramics with two partitions and two electrodes exciting method, whole piece PZT ceramics with four partitions and two electrodes exciting method and whole piece PZT ceramics with four partitions and four electrodes exciting method. The materials of each part were determined according to the performance requirements. Finally, the equivalent circuit model was established, and the admittance circle was deduced to get the formulas of the equivalent circuit model’s parameters. They can refer to the theory guide of subsequent experiment part.Based on the theoretical analysis, the finite element parametric models of piezoelectric actuators using bending hybrid modes under five exciting methods were established by ANSYS software. The second order bending vibration modes were got by modal analysis, and the resonant frequencies were calculated to be about 35 k Hz by adjusting the structure parameters. So the final structure parameters were determined. It was verified that the symmetrical structu re makes horizontal bending and vertical bending have the same resonant frequency, and the thin ring between the fixed seat and the flange can reduce the changes of resonant frequencies and vibration modes when the flange was clamped. Then the electromechanical coupling efficiencies and driving feet ’s vibration paths of piezoelectric actuators using bending hybrid modes under five exciting methods were got by harmonic analysis and transient analysis. Finally, the effects of the no polarization parts of the whole PZT ceramics on the resonant frequencies, the electromechanical coupling efficiencies, the driving feet ’s amplitudes were studied. Simulation results show that the method using whole piece PZT ceramics with four partitions is the best.Piezoelectric actuators using bending hybrid modes under five exciting methods were fabricated according to the structure parameters which were determined by FEM calculation. The impedance-frequency curves and the admittance circles were measured by impedance analyzer i n impedance characteristics test. The equivalent circuit model ’s parameters were got, the impedance matching was accomplished. The vibration velocity curves, the second order bending vibration modes, and its resonant frequencies were measured by laser vibrometer in modal vibration shape test. When the five piezoelectric actuators were excited with no load, the temperature rising performances, the effects of temperature on driving feet ’ amplitudes and impedance characteristics were measured in thermal coupli ng characteristics test. Then we set up the experimental platform, and measured their mechanical output characteristics and the temperature rising performances under preloads. Finally, a special incentive power supply was designed and fabricated. Its outpu t waveforms, voltage and frequency values were measured by oscilloscope. And the five piezoelectric actuators’ mechanical output characteristics were measured by experimental platform when they were excited by the special incentive power supply.