Design And Analysis Of A Multi-driven Large Stroke Flexible Positioning System

With the development of "Submicron-nano" technology,traditional mechanical transmission methods cannot meet the requirements for positioning accuracy in high-precision machining,semiconductor fabrication,optical precision engineering,aerospace and other high-precision fields.In order to meet the requirements of micro-nano scale precision positioning,there is an urgent need for a high-precision positioning system with multi-degrees of freedom,large stroke,?m/nm positioning accuracy,ms response speed,easy control and manufacturing.The flexible positioning system driven by piezoelectric actuator has the advantages of high motion accuracy,fast response,compact structure,easy control,and easy implementation of the lightweight and miniaturization of the positioning system.It has potential application value in many high-precision fields and has become a hot research at home and abroad.Therefore,it is of great significance to carry out the flexible positioning systems with large-scale work range,multi-degrees of freedom,and high-precision to promote the development of high-precision fields,such as the micro/nano processing,manufacturing,measurement,and so on.This article is based on the project of State Key Laboratory of Mechanical Transmission of Chongqing University and Shanghai Key Laboratory of Spacecraft Mechanism.To achieve the design goals of multi-degree of freedom,large work stroke,and high precision positioning,a five-degree of freedom flexible positioning platform is designed innovatively.The structural design,work principle,static and dynamic characteristic,coupled motion,hysteretic modeling,closed-loop control,testing and comprehensive evaluation of positioning stage are carried out.The main research contents are summarized as follows:(1)The design and working principle of the flexible positioning system are studied.The construction and working principle of flexible positioning system are discussed by using the theory of flexible mechanism,mechanical principle and innovative structure design.Based on the design principle of system,the flexible hinge,displacement amplifier,and actuator are determined,and the flexible positioning system with five-degrees of freedom is innovatively designed.(2)The static and dynamic characteristics and coupling motion of the flexible positioning platform are studied.The pseudo-rigid body model method,energy method,Lagrange's equation and geometric method are used to explore the deformation relationship between the input and output of the positioning platform,and the static and dynamic index,the coupling error of the positioning platform are deduced.The finite element simulation is implemented based on the software of Ansys Workbench,the simulation results of the platform performance are obtained,which reveal the correctness of the theoretical model for positioning platform.(3)The hysteresis,parameter identification and closed-loop control strategy of flexible positioning system are studied.Bouc-Wen hysteresis mathematical model is used to describe the hysteresis characteristics of the positioning system,and the system hysteresis model is obtained.By means of the on-line parameter identification method,the hysteresis parameters of the Bouc-Wen model is obtained,and the accuracy of hysteresis model is evaluated.The feed forward closed-loop control strategy of the system is designed innovatively by using the inverse Bouc-Wen model combining with PID controller,and the open-closed loop simulation is performed by Matlab/Simulink.(4)The evaluation and experiment of the flexible positioning platform are studied.A flexible positioning experimental system is built,and the hysteresis characteristics,displacement resolution,repetitive positioning accuracy,linearity,decoupling,dynamic response,working stroke,and so on are respectively performed.The experimental results verify the correctness and feasibility of the theory,and the expected design goals are achieved.