Research On Evolution Process And Mechanism Of Stepping Characteristics Induced By Initial Contact Gap Of The Stick-Slip Piezoelectric Actuator

The modern high-end field is mainly developing towards high-precision and miniaturization.As an important part of the key technology,precision drive technology has also been given more requirements.The advantages of traditional actuators are mainly reflected in their large stroke,high load-carrying capacity,and high driving speed,but they are not satisfactory in terms of micro-nano precision and lightweight requirements in high-end fields.As a new type of precise actuator,the piezoelectric actuator has many advantages such as high precision,fast response,light weight,small size,low energy consumption,stable operation,and immunity to electromagnetic interference.It has been widely used in modern medicine,biological cell engineering,micromanipulation,ultra-precision machining and assembly,precision optical engineering and other fields.The stick-slip piezoelectric actuator,with friction as the main driving force,converts the microscopic deformation of piezoelectric elements into macroscopic linear or rotary output with large stroke by means of steps.Owing to the fact that it can achieve high speed,high precision accurate positioning,and has the characteristics of small size,convenient processing,simple assembly,etc.,it has received strong attention from industry researchers.In previous studies,researchers mainly focused on the structural design and optimization of the flexure hinge mechanism in the actuator,but ignored the influence of the initial contact gap between the flexure hinge mechanism and the mover on the output performance.Therefore,this paper focuses on evolution process and mechanism of stepping characteristics induced by initial contact gap of the stick-slip piezoelectric actuator.First of all,a piezoelectric actuator with adjustable initial contact gap is designed based on stick-slip principle,and its driving principle,structure composition and theoretical single step maximum displacement are analyzed.On this basis,a test system is built to test its stepping characteristics under different initial contact gaps.The results show that with the increase of the initial contact gap,the backward motion in the stepping characteristic of the actuator decreases gradually until it disappears;with the increase of the initial contact gap,a new phenomenon of displacement increment opposite to the backward motion is found.Furthermore,the mechanism of the evolution of the stepping characteristics with the initial contact gap is revealed through the analysis.Based on the evolution process and mechanism of the above stepping characteristics,the theoretical assumption of driving mode transition induced by initial contact gap is proposed.In order to prove the assumption,this paper designs a stick-slip piezoelectric actuator with lever amplification structure and adjustable initial contact gap.The output end of the driving mechanism has certain flexibility and large secondary deformation can be generated during contact.Based on the theoretical and finite element simulation analysis of the driving mechanism,a prototype test is carried out to test the stepping characteristics of the actuator under different initial contact gaps.The test result shows that the initial contact gap can induce the driving mode of the actuator to change from parasitic motion mode to self-deformation mode.In addition,in order to explore whether the flexibility of the output end of the driving mechanism will further aggravate the influence of the initial contact gap on the stepping characteristics and output performance,an additional flexure hinge is introduced at the output end of the lever amplification structure.The performance test results show that the peak speed of the actuator is increased by increasing the flexibility of the output end at the same driving voltage,but the selflocking of the actuator is reduced.In order to explore the influence of initial contact gap on stepping characteristics and output characteristics of stick-slip piezoelectric actuator working in self-deformation mode,a stick-slip piezoelectric actuator working in self-deformation mode is designed,and then a prototype of the actuator is manufactured and its stepping characteristics are tested in detail.The results show that the stepping characteristics of the self-deformable stick-slip piezoelectric actuator are also affected by the initial contact gap,and the actuator can realize reverse driving when the driving voltage of reverse waveform is applied.The stepping characteristics under different initial contact gaps show that the self-deformable stick slip actuator has excellent large stroke motion stability.Finally,based on the stick-slip principle and Lu Gre friction model,the dynamic model of the self-deformation stick-slip piezoelectric actuator with adjustable initial contact gap is established.Through MATLAB/Simulink simulation,the influence of the initial contact gap on the stepping characteristics and driving mode of the stick-slip piezoelectric actuator is analyzed.The simulation results show that changing the initial contact gap will have a significant influence on the stepping characteristics of the stick-slip piezoelectric actuator,and also can induce the driving mode of the actuator to change,which is consistent with the previous experimental results.