Basic Theory And Experimental Research On Asymmetric Friction Impact Inertial Piezoelectric Drives

Precision driving technology plays a vital role in supporting and promoting the development of cutting-edge high-tech fields,and the actuator with precision output performance is the core device of precision driving technology.Piezoelectric actuators are a kind of precision actuators that can convert electrical energy into mechanical energy based on the inverse piezoelectric effect of piezoelectric materials.According to the different driving principles,piezoelectric actuators include many types.Among them the impact inertial piezoelectric actuator has been widely concerned because of its simple control and structure,large stroke,high resolution and small backward motion.However,traditional impact inertial piezoelectric actuators still have some disadvantages such as the low bandwidth and driving speed,the output performance degradation caused by the overturning moment,the contradictions between the structural size and output performance,and the poor compatibility between the speed and load.Based on the comprehensive analysis of the causes of the above problems,this paper proposed an asymmetric friction driving principle by replacing the main mass block and inertial mass block with asymmetric friction on the left and right sides.Focusing on the theoretical analysis and dynamics model of this driving principle,the structural design and performance test analysis of the piezoelectric actuator,the main research work carried out in this paper is as follows.The structure and driving principle of the traditional impact inertial piezoelectric actuator were deeply analyzed.Based on the comprehensive analysis of the causes of the disadvantages,the asymmetric friction driving principle was proposed,and a general kinetic model of asymmetric friction driving was established.The kinetic simulation revealed the motion process of this driving principle,verified its feasibility,and provided a theoretical basis for the subsequent research.Based on the two methods of friction tuning,two actuator implementation methods of positive pressure tuning and friction coefficient tuning were proposed.A positive pressure tuning actuator was proposed by using an asymmetric complaint mechanism(ACM)to realize positive pressure tuning on both sides.The structural design of the ACM was carried out.The deformation of the ACM,the influence of the driving feet thickness and the surface friction coefficient on the driving process were simulated and analyzed.The feasibility of the positive pressure tuning piezoelectric actuator was verified.According to Newton’s second law,the dynamics model of the positive pressure tuning piezoelectric actuator was established,and the motion process of the actuator was further revealed,which provides theoretical support for the subsequent experimental work.A prototype of the positive pressure tuning piezoelectric actuator was manufactured,and an experimental system was built.The experimental analysis of output performances such as the stepping displacement,driving speed were carried out.The results showed that both thin end(stick-slip inertial drives)and the thick end(impact inertial drives)of the actuator can achieve stable bidirectional steeping motion(the maximum speed of 7311μm/s,the resolution of 221 nm,vertical and horizontal loading capacities being over 20 N and 1.4 N,respectively).Based on the analysis of the causes of the difference between their stepping characteristics,the thick end was selected as the output end.The scratch test based on the positive pressure tuning piezoelectric actuator was carried out,and a relatively smooth residual scratch morphology was obtained.Furthermore,by removing the rail slider of the positive pressure tuning piezoelectric actuator,the simplified structure design of the piezoelectric actuator was carried out,and the prototype was developed.The output performances under different working gaps were tested and analyzed.The experimental results showed that the simplified piezoelectric actuator could still achieve stable large stroke bidirectional motion.Aiming at the problem of many design parameters caused by the ACM,based on the friction coefficient tuning,the structure design of the friction coefficient tuning piezoelectric actuator was carried out by using symmetric complaint mechanism(SCM).Four basic microstructures were manufactured on the surface of the driving feet by laser texturing,and the surface friction characteristics were compared and tested.Two microstructures(strip convex,T_a microstructure and square convex,T_b microstructure)were selected,and the driving speed,resolution and wear resistance of the T_a and T_bmicrostructure microstructure actuators were compared and analyzed.The results showed that the T_b microstructure actuator performed better in the motion stability,driving speed and load capacity(the maximum speed of 2523μm/s,the resolution of 188 nm,vertical and horizontal loading capacities being 2 N and 0.6 N,respectively),and the T_amicrostructure actuator had relatively high motion resolution(75 nm).Compared with the positive pressure tuning piezoelectric actuator,the friction coefficient tuning piezoelectric actuator could also achieve better comprehensive output performances.In summary,this work proposed the asymmetric friction driving principle,and two kinds of asymmetric friction impact inertial piezoelectric actuators(positive pressure tuning and friction coefficient tuning)were designed and developed.The dynamic simulation and output performance were carried out.The research work enriches the design theory of impact inertial piezoelectric actuators and provides a reference for the design,analysis,and application of the high-performance impact inertial piezoelectric actuators.