Development And Contol System Of A Linear Stepping Piezoelectric Actuator With Adjustable Friction Forces Of The Driving Feet

Precision motion platform has become a research hotspot of precision manufacturing with the rapid development of the precision manufacturing industry in recent years.In addition to the conventional electromagnetic induction actuator,novel actuators adopting the piezoelectric effect,magnetostrictive effect,and shape memory effect have emerged.The piezoelectric actuator has potential application value in the field of precision manufacturing,as it has the merits of simple structure,fast response,high resolution,and strong electromagnetic compatibility.Piezoelectric actuators can be divided into four groups: ultrasonic motors,direct-drive piezoelectric actuators,inchworm piezoelectric actuators,and inertial piezoelectric actuators,according to their operating principles.Compared with the other piezoelectric actuators,the inertial piezoelectric actuator has a simpler structure,longer stroke,fewer exciting signals,etc.Thus,it has attracted the attention of many scholars in recent years.The operating principle of the inertial piezoelectric actuator is based on the "stick-slip" motion between the driving foot and the runner.During the "stick" motion,the driving foot slowly pushes the runner forward with the static friction.During the "slip" motion,the driving foot rapidly moves backward and the relative slip between the drive foot and the runner is obtained.Thus,the relative sliding displacement between the driving foot and the runner is accumulated as the output of the runner by repeating t he "stick-slip" motion process successively.It can be recognized from the operating principle that the forward motion of the runner is inevitably followed by its backward motion(rollback phenomenon exists),which is an intolerable drawback for its applic ation in the fields of cell puncture,microinjection,and fiber docking.Aiming to suppress the rollback motion of the inertial piezoelectric actuator,its operating principle is analyzed and modified in this work.A novel stepping piezoelectric actuator w ithout rollback motion is developed and its motion control system is built up.The conventional operating principle of the inertial piezoelectric actuator is analyzed,and the model of the output displacement of the actuator is established.The reasons for the rollback motion are discussed and the factors affecting the magnitude of the rollback are analyzed.A modified operating principle of the inertial piezoelectric actuator is proposed,in which the friction forces of the driving foot and the auxiliary friction foot are adjustable.Based on this concept,a non-rollback inertial piezoelectric actuator and a motion platform composed driven by it are developed.The analytical model of the piezoelectric unit is established,its key dimensions are optimized,and a prototype is performed.A high-power high-voltage linear power amplifier is designed and fabricated to inmprove the working frequency of the actuator and the output speed of the linear motion platform.Performances of the power amplifier are tested by experiments and the measured results shows that: the voltage nonlinearity errors are 0.0037% and 0.0038%,the full-scale drifts are 0.0074% and 0.007%(FS/8hours),the maximum frequencies of the full-scale output are 5 k Hz and 500 Hz,under the conditions of no-load and 3?F capacitive load,respectively.The ripples of the output voltage are both less than 10 m V under the no-load and 3 ?F load conditions.The average output current of the amplifier is 1.5 A and the peak current is 2.25 A when charging the 3 ?F capacitive load.A high-power high-voltage linear power amplifier is designed and fabricated to improve the working frequency of the actuator and the output speed of the linear motion platform.Performances of the power amplifier are tested by experiments and the measured results show that: the voltage nonlinearity errors are 0.0037% and 0.0038%,the full-scale drifts are 0.0074% and 0.007%(FS/8hours),the maximum frequencies of the full-scale output are 5 k Hz and 500 Hz,under the conditions of no-load and 3?F capacitive load,respectively.The ripples of the output voltage are both less than 10 m V under the no-load and 3 ?F load conditions.The average output current of the amplifier is 1.5 A and the peak current is 2.25 A when charging the 3 ?F capacitive load.The output performances of the proposed stepped piezoelectric actuator are tested with the developed motion control system,which contains the displacement-time characteristics,voltage-speed characteristics,frequency-speed characteristics,load-speed characteristics,and resolution characteristics.The test results show that the displacement rollback can be reduced effectively and even eliminated by adjusting the frictional force of the friction foot.The motion platform driven by the developed actuator achieves a maximum speed of 4.76 mm/s under the sawtooth wave of 150 Vp-p and 250 Hz.Its carrying load is is not less than 1.3 kg.The optimal resolution of the motion platform is about 20 nm.The stepping piezoelectric actuator presented in this paper eliminates the ro llback motion that is the common defects of the inertial piezoelectric actuator,and the developed prototype has significant superiorities in output speed,load capacity,and displacement resolution.