| Piezoelectric actuators are a kind of drive device,which can convert the electrical energy into the mechanical energy by using the converse piezoelectric effects of piezoelectric elements.Piezoelectric actuators have many advantages,such as high positioning accuracy,high response speed,no electromagnetic interference,low speed,high torque,etc.Compared with the traveling wave type and standing wave type piezoelectric actuators,the hybrid mode piezoelectric actuators have less structural constraints,more flexible design and larger torque or thrust force.It is of great significance to improve the theory and application of piezoelectric actuators to carry out the research on the configuration design,vibration characteristic analysis and motion control of the piezoelectric actuators.Firstly,the configuration of the multi-beams longitudinal vibration piezoelectric actuator is designed.Based on the requirement of processing and assembling,the advantages and disadvantages of different configurations are compared.Three longitudinal transducers,contains one vertical transducer and two horizontal transducers,are integrated in I-shape to form the proposed actuator.The driving feet are designed at the end of the horizontal transducers.The hybrid modes consist of two different mode: the longitudinal vibration on the horizontal transducers motivated by piezoelectric ceramics,the longitudinal vibration on the vertical transducers motivated by piezoelectric ceramics coupling with the bending vibration excited by the asymmetrical boundary conditions.Two excitating modes of resonance high frequency and stepping high frequency are planned,and the principle of actuation is analyzed,which can realize the fast driving and precision driving respectively.The vibration characteristics of the proposed piezoelectric actuator are analyzed by the simulation of the finite element parametric model.In view of the partial structural parameters,parametric sensitivity curves are drawn.The analysis of the feature frequency and vibration mode reveals the vibration characteristics of this kind of hybrid mode piezoelectric actuator.After that,frequency degeneration is realized through the adjustment of structural parameters.Based on transient simulation,the driving characteristics of piezoelectric actuators are analyzed,by which the elliptical driving trajectories of four actuators are verified.The characteristics of the hybrid piezoelectric actuator are discussed based on the design and simulation results.In order to meet the driving requirements of the multi-beams longitudinal vibration piezoelectric actuator,the corresponding high-power high-frequency driving power source is developed.Based on the low voltage operational amplifier chip OPA549,the overall scheme of driving power is established with targets of high frequency and high power.The output frequency of the designed piezoelectric driving power supply is 10 k Hz to 25 k Hz,the single output power can reach 100 W,and the output voltage can reach ±200 V.The driving power consists of power supply circuit,linear amplifier circuit and high frequency transformer.It can output the signal of resonance high frequency and stepping high frequency.The parameters of circuit and high frequency transformer are designed.Based on the simulation of Multisim,the primal test of the circuit is completed.After designing the PCB,the driving power supply is packaged.The closed-loop control system is constructed based on the driving power supply.Finally,the prototype of piezoelectric actuator is fabricated and tested.The impedance characteristic and vibration characteristics of the prototype are tested,and the differences between the prototype and the simulation model are compared and analyzed.In the resonance high frequency and stepping high frequency mode,the mechanical output characteristic are tested respectively.The results show that the maximum no-load output speed is 439.41 mm/s and the maximum thrust is 40 N,at the voltage peak value of 200 V,the excitation frequency of 18.5 k Hz,the signal phase difference of 60°.In the high frequency step mode,the minimum resolution of step distance is 2.83 ?m at 90 pulses per step,when the voltage peak value is 40 V.On the basis of the mechanical output characteristics,the speed responses of the step signal and sine signal under the open-loop system and closed-loop system are tested respectively.Compared with open-loop system,the speed stability has been greatly improved in closed-loop system,and the disadvantages of zero dead-zone,deviation of peak error and difference in positive and negative characteristics under sine signal are also improved. |
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