Research On Micro-displacement Compliant Amplification Mechanisms Actuated By Piezoelectric Actuator

As one of the key technologies of precision machinery and precision instruments,micro-displacement technology plays an important role in microelectronic technology,aerospace,and biological engineering.Compliant mechanisms have high precision,no friction,free assembly and integral processing advantages.Piezoelectric actuators have the advantages of high resolution,quick response,high precision,high stiffness,large output force and compact structure.Therefore,the current nanoscale precision micro-displacement positioning and movement are generally achieved by piezoelectric ceramic actuators driven compliant mechanisms.However,the output displacement of piezoelectric actuators is very small,usually only a few tens of microns,so the output displacement of piezoelectric actuators needs to be amplified.At present,the research on compliant amplification mechanisms with micro-displacement amplification function have become the focus and hot spot at home and abroad.Aiming at the problems of small displacement amplification ratio and low load capacity in the current compliant amplification mechanisms,two novel micro-displacement compliant amplification mechanisms based on piezoelectric actuators are designed in this paper.The specific research work is as follows:(1)Aiming at the problems of small displacement amplification ratio and low load capacity in the current compliant amplification mechanisms,two novel micro-displacement compliant amplification mechanisms are proposed.The first compliant amplification mechanism is a compound bridge-type amplifier combining the bridge-type mechanism and scott-russell mechanisms.The output stiffness and load capacity of the amplifier are improved by embedding scott-russell mechanisms inside the bridge-type mechanism.The second kind of compliant amplification mechanism adopts L-type lever mechanisms and half-bridge mechanism to form a two-stage symmetrical amplification mechanism.Through two-stage displacement amplification,the displacement amplification ratio of the amplifier is greatly improved.(2)The static and dynamic analytical models of the two kinds of amplifiers are established by stiffness matrix method.Firstly,the flexure hinges of the compliant amplification mechanisms are regarded as a flexure element with three DOF in the plane,and the rest as rigid bodies.Through the coordinate transformation of the displacement of the rigid bodies and their forces,the stiffness matrix model reflecting the static characteristics of the overall structure of the mechanisms are obtained.Based on the matrix model,the displacement amplification ratio,input and output stiffness of the designed mechanisms are studied.Finally,the dynamic characteristics of the designed mechanisms with and without piezoelectric actuators are studied by using Lagrange equations.(3)Through finite element simulation and experimental analysis,the static and dynamic characteristics of the two amplifiers,such as displacement amplification ratio,input and output stiffness,and natural frequency,are verified and compared with the analytical model.Firstly,the static and dynamic characteristics of the mechanism such as displacement amplification ratio and natural frequency are obtained by using the finite element simulation software ANSYS Workbench.The experimental prototypes of the amplifiers are processed,and the open-loop experimental system is built by using Labview virtual instrument software to verify the performances of the amplifiers.The results show that the load capacity of the compound bridge-type amplifier is 285% higher than that of the bridge-type amplifier,and the displacement amplification ratio of the two-stage symmetrical amplifier is as high as 27.5.The results of analytical model,simulation analysis and experimental verification are consistent,which indicates the feasibility of the designed mechanism and the reliability of analytical model.(4)The compound control method based on dynamic inverse model feedforward control and PID feedback control is used to realize high-precision and high-speed control of the amplifier.The inverse model feedforward control,PID feedback control and the compound control based on dynamic inverse model feedforward control and PID feedback control are studied,and the real-time simulation experiment control system of piezoelectric actuator hardware in the loop is built by using x PC Target.The step signal localization experiment under PID feedback control and the sinusoidal signal trajectory tracking experiment under compound control are carried out for the compound bridge-type amplifier.The results show that compared with the PID controller alone,the compound bridge-type amplifier can achieve better tracking accuracy by using the method of dynamic inverse model feedforward combined with PID feedback control.