| Stick-slip piezoelectric actuators are commonly used in precision actuator.They have the characteristics of small size,high precision,easy control and fast response,and is widely used in precision manufacturing,optical engineering,biological cell engineering,micro-nano technology and other scientific and technological fields.Focus on the problems of existing stick-slip piezoelectric actuators,such as the difficulty in measuring the contact force,the unclear relationship between the contact force and the stepping characteristics,the poor linearity over large stroke,and the inconvenience in the active control of the stepping characteristics.In this paper,a stick-slip piezoelectric actuator with contact force measurement function is proposed.Based on the measured contact force,the relationship between the contact force and the stepping characteristics is analyzed,the active control of the stepping characteristics is realized.The motion stability of the actuator is improved and stepping displacement could be predicted.It provides a reference for the design and development of high stability,miniaturization,and self sensing piezoelectric actuators.The main research work is as follows:(1)A stick-slip piezoelectric actuator with contact force measurement function is proposed,and the contact force measurement principle and movement principle of the actuator are analyzed.The influence of the sensing unit size on its stress distribution is studied by finite element simulation,so size parameters are determined.Through theoretical calculation,the relationship between the input voltage and the change of the contact force is established.After the prototype is developed,the calibration of the sensing unit and the noise level test are carried out.(2)The test platform is built to test the output performance of the actuator under different contact forces,and the dynamic simulation model is established.The frequency output characteristics,voltage output characteristics,load output characteristics and resolution of the actuator under different contact forces are studied.The results show that the output characteristics of the actuator are affected by the contact force.The greater the contact force,the smaller the driving speed,the stronger the load capacity,and the greater the starting voltage.Furthermore,the influence of contact force,driving frequency and driving voltage on the output performance of the actuator is analyzed through dynamics simulation.(3)Based on the above research,a method of active control of contact force to control the stepping characteristics is proposed.It is to control the maximum contact force to be constant during the movement.Under different contact forces and contact surfaces,the stability of the actuator under active and non-active control conditions is studied,and the influence of contact force evolution on the output characteristics is analyzed.The results show that the stepping characteristics of the actuator are related to the size and change trend of the contact force.Through active control of the contact force,the active control of the stepping characteristics can be achieved,and the stability and repeatability of the actuator over large stroke motion can be improved.(4)Based on the relationship between the change of the contact force and the stepping displacement,a method for predicting the displacement of the actuator is proposed.Under different voltage conditions,the influence of whole section and subsection calibration on the prediction displacement accuracy is studied.The results show that the error of subsection calibration is smaller.On this basis,the influence of frequency and load on the accuracy of displacement prediction by subsection calibration is studied.The results show that the error of displacement prediction by this method is within 5%.Furthermore,the program of contact force prediction displacement is written,which realizes the real-time display of the output displacement of the actuator. |
