Mechanism And Experimental Research Of Piezoelectric Stick-slip Smooth Driving Assisted By The Inertial Block

Piezoelectric stick-slip actuators have the advantages of fast response within milliseconds,nano-nanometer positioning accuracy,simple structure,self-locking when power off,immunity to electromagnetic interference,etc.,which have become one of the mainstream technologies in the field of precision drive.However,the friction in the slip stage will seriously deteriorate the performance of the actuators,resulting in bottleneck problems such as backward motion and velocity fluctuation.To overcome the above problem,the design idea of piezoelectric stick-slip actuators assisted by the inertial block is proposed in this paper.Using the inertia block to generate different inertias under asymmetric excitation,it can dynamically change the normal pressure between the stator and mover to realize the dynamic regulation of friction;during the slip stage,the driving foot produces a deflection away from the mover,thereby eliminating the normal pressure,so that the impulse of the friction on the mover can be almost reduced to zero,and the smooth motion of the piezoelectric stick-slip actuator can be realized.Firstly,the basic theory of piezoelectric stick-slip actuators is expounded in this paper,including the introduction of the piezoelectric effect,the development of piezoelectric materials,and the composition of the piezoelectric stacks;at the same time,the working principle of piezoelectric stick-slip actuators is analyzed.Additionally,the classification of flexure hinges is summarized,and the calculation methods of the right circular and the straight beam flexure hinges are introduced.Secondly,the rotary and linear piezoelectric stick-slip actuators assisted by the inertial block are proposed,and the working principles of the actuators are analyzed.The pseudo-rigid body method is used to establish the dynamic model of two actuators,and the mathematical expression of the normal pressure between the stator and the slider and the piezoelectric element under asymmetric excitation is deduced,which reveals the mechanism of piezoelectric stick-slip smooth driving assisted by the inertial block.Then,the finite element simulation analysis of the stator is carried out to guide the parametric design of the structure,a dynamic model considering the dynamic change of the normal pressure is built based on MATLAB/Simulink,and the single-step displacement characteristics from the backward motion to displacement surge are simulated,which verifies the feasibility of the designed scheme.Finally,the prototypes of the rotary and linear piezoelectric stick-slip actuators assisted by the inertial block are developed,the corresponding test systems are built,and the output characteristics of the actuators are experimentally studied.The linear fitting correlation coefficient R² of the displacement curves of the developed rotary and linear actuators both can reach 0.9999.Among them,the displacement curve of the rotary actuator still has good smoothness under a load of 2.0 kg,with an R² of 0.9998;under the excitation of 100 V_P-Pand 700 Hz,the velocity of the actuator was 231320μrad/s;the resolution is 1.56μrad.For the linear actuator,the maximum velocity is 101.76 mm/s;even at low voltage(5 V_p-p)and low frequency（10 Hz）,R² can reach 0.9991;in addition,the positioning accuracy of the actuator can achieve 27 nm under a PID closed-loop control system.In this paper,the design scheme of dynamic adjustment of the normal pressure is proposed;the linear and the rotary actuators are proposed by decoupling the inertia block and the flexure hinge mechanism,which realize the smooth driving under different working conditions of low voltage,low frequency,high frequency and heavy load for piezoelectric stick-slip actuators excited by only a piezoelectric element.