Research On Foot Linear Piezoelectric Actuator And Driving Power Supply For A Deployable Mechanism

Deployable mechanism is a type of structure widely used in the aerospace field,which is usually required to have the performances of fast response,high position precision and simple structure.With the advantages of high torque density,fast response speed,easy to achieve linearmotion,the piezoelectric actuator is more and more widely used in the field of aerospace,precision positioning equipment and so on.According to the performance requirements of the deployable mechanism,a piezoelectric actuator with dual operation mode under high and low frequency is developed.The developed actuator can take advantage of the resonant and non-resonant piezoelectric actuators to meet the fastness and location accuracy requirements of the deployable mechanism in the deploying process.In this paper,the structure of a deployable mechanism driving by piezoelectric actuators is designed on basis of an existing deployed structure consisting of linkages.And a single foot linear piezoelectric actuator with dual operation mode of high and low working frequency is proposed according to the structure and motion performance requirements of the deployable mechanism.Three exciting methods of impact low frequency,resonance high frequency and stepping high frequency are discussed.Then,static analysis,modal analysis and transient analysis under three different excitation methods is carried out respectively by using SNSYS software to determine the structural parameters,the resonant frequency and the vibration state on driving foot of the piezoelectric actuator,which provide the theoretical guidance for the follow-up experiments.According to the exciting signals requirement under three differenct exciting methods of the proposed actuator,a driving power supply which can output corresponding waveform sginals is designed.The design of the drive power is based on the principle of switching power supply,using half-bridge inverter circuit to chop DC voltage,which can output square wave voltage.The driving power supply with three working modes,four channels of signals is developed.The amplitude,frequency,phase and duty cycle of the output signals are independently adjustable.The amplitude and frequency asjustment error of the power supply are less than 1% and 0.5%,respectively.According to the structural parameters of the single-foot linear piezoelectric actuator,the prototypes are fabricated.The vibration modes of the prototypes are measured by using a scanning laser Doppler vibrometer,and the resonant frequencies of the prototypes are obtained.An experimental platform was set up,on which the mechanical output performances of the proposed actuator under three exciting methods of impact low frequency,resonance high frequency and stepping high frequency are measured.The test results show that the maximum thrust force of the proposed actuator under three exciting methods are 17 N,48 N and 27 N,respectively.The maximum output velocity under resonance high frequency excitation is 1104 mm/s,and the minimum displacement resolution under impact low frequency and stepping high frequency excitation are 0.416 ?m/s and 0.21 ?m/s,respectively.Finaly,the proposed piezoelectric actuator is used to drive the deployable mechanism.The experimental results show that when the deployable mechanism is placed horizontally or vertically,the fastest unfolded time is about 0.2 s or 0.5 s.The minimum step displacements of the push rod is measured as about 0.258 ?m.