Design And Experimental Research Of Friction-control Stick-slip Piezoelectric Actuator

Piezoelectric actuators which are part of precision driving technology are wildly used in the fields,such as in-situ testing of micro-mechanical properties of materials,precision optics,biomedicine and aerospace engineering,owing to characteristics of simple structures,no interference of electromagnetic,rapid resoponse,large stoke,high positioning accuracy and so on.Compare with the direct drive type,the ultrasonic type and the inchworm type,the stick-slip piezoelectric actuator has advantages of low energy consumption,high resolution,compact structure,large stoke and so on.Hence,the stick-slip piezoelectric actuator is wildly used in micro/nano indentation and scratch testing,aerospace engineering,positioning platforms,micromanipulation under SEM and some other precision systems.The drawback of the existing stick-slip piezoelectric actuator is the backward motion which reduces the displacement/load resolution of the actuator and decreases its output performances.The following essay will propose two measures to promote the characteristics of the actuator:1)Controlling the contact force between the stator and slider by the centrosymmetric-type flexure hinge mechanism is beneficial to improve the output performances of the actuator.2)A composite flexible hinge is designed to actively control the contact force between the stator and the slider of a stickslip piezo-driven linear actuator.It is helpful to solve the problems of backward motion and low loading capability.A stick-slip actuator with a centrosymmetric-type flexure hinge mechanism was designed and manufactured.To study the output characteristics,the experimental system was established and the actuator was tested under various experimental conditions.The results showed that the better working condition was the driving frequency of 360 Hz and the driving voltage of 100 V.The maximum speeds of the positive and negative motions were 2.893mm/s and 2.747 mm/s respectively,the maximum load was 3.8 N for both the positive and negative motions.It is proved that the feasibility of using a centrosymmetric-type flexure hinge mechanism to achieve stick-slip drive and suppress the backward motion by its structure.According to the first stick-slip actuator with a centrosymmetric-type flexure hinge mechanism,the paper also proposed the stick-slip piezo-driven linear actuator whose flexible hinge mechanism has been optimized by using the finite element method(FEM)of ANSYS to output bidirectional motion.An experimental system was established to evaluate the output performances of the actuator,mainly analysing the factors of the stepping displacement and the ratio of backward motion,such as driving voltage,driving frequency and vertical load.The experimental results indicated that the optimal working conditions of the actuator were a driving frequency of 220–300 Hz and a constant driving voltage of 100 V.When the driving frequency was >220 Hz,the actuator eliminated the backward motion under no load and the step efficiency of the actuator reached 100%.The maximum speeds of the forward and reverse motions were 2.01 mm/s and 2.34 mm/s,respectively.The maximum vertical load was 380 g.It is proved that the backward motion was suppressed effectively by the actuator with the structure optimization.Additionally,a novel stick-slip piezo-driven linear actuator with a composite flexible hinge which could actively control the contact force during the working process was proposed.The main parameters of the flexible hinge were determined and optimised by the simulation results of FEM.To confirm the validity,the effects of the driving frequency and horizontal load on the output characteristics of the actuator were tested and discussed by experiments.The results of experiments showed that the actuator accomplishes the maximum speed of 1.39 mm/s at 100 Hz and 2.18 mm/s at 200 Hz without load and no actively controlling the contact force.With actively controlling the contact force,the maximum speed of 1.74 mm/s at 100 Hz and 4.1 mm/s at 370 Hz were achieved without load.Moreover,the maximum horizontal loads of the actuator under 100 Hz and 200 Hz with no actively controlling the contact force were 25 g and 50 g,respectively.With actively controlling the contact force,the maximum horizontal loads at 100 Hz and 200 Hz upgraded to 40 g and 70 g.The results of experiments illustrated that actively controlling the contact force between the stator and the slider could improve the performances and reduce the backward motion of the actuator effectively.The paper proposed two types of stick-slip actuators based on the stick-slip driving principle and they could effectively develop the performances of the actuator,such as the large stoke,high speed and resoluion.The research about improving the performances of the actuator by actively controlling the contact force could promote the development of the stick-slip actuator.