Reseach On A Macro/micro Dual-drive Technology Based Precision Rotary System

With increasing demand of high precision mechanism system in high-tech fields such as aerospace,microelectronics,biomedical etc,precision mechanical system has attracted extensive attention.Because of its high precision in large range,which is difficult to achieve for traditional mechanical systems,the macro/micro technology has been widely used in precision mechanism systems as an importance way to realize the precision motion of precision systems.As one of the two basic motion forms in CNC equipment,rotary motion form has been widely adopted in the mechanical systems,such as CNC machine tool,high presicion weapon launch system,and medical microscope etc.However,compared with linear motion systems,the rotary motion is more complex,so studies of macro/micro rotary dual-drive technology are fewer and relative laggard.Based on studies of macro/micro dual-drive technology,a precision rotary system with macro/micro dual-drive is designed and its performance is studied.The main content of the dissertation include:(1)Motion guiding and transformation principles of flexure hinge is analyzed based on equivalent model of flexure hinge.Based on guiding and transformation principles of flexure hinge,a micro rotary mechanism with single DOF symmetric drive as well as guiding and motion transformation is designed and developed,which is able to accurate transform input of linear motion into output of rotary motion according to a certain relationship.And the mechanism has the function of balancing the additional force in the process of linear motion to rotary motion transformation,which can avoid the PZT to bear the horizontal force.The guiding and transformation performance of the mechanism is analyzed,experiment is carried out to validate accuracy of the transformation performance analyse and its results are basically consistent with the analysis,this show that the mechanism has good performance to transform linear motion to rotary motion.(2)The strength and modal analysis of the micro rotary mechanism is carried out by the finite element method,and the modal performance of the mechanism is tested by experiment,the analysis results show that the mechanism has high strength and good dynamic performance A high precision stiffness analysis method of flexure hinge is proposed:using stiffness equations of uniform beams derived from boundary element theory,the stiffness equations of straight circular flexure hinge is analyzed by exact discretization and rigid combination,then the stiffness of the mechanism is analyzed by rigid combination with coordinate transformation method,and the validity of the stiffness analysis is verified by following experiment.The method provide a new way to analyze stiffness of flexure mechanism(3)The precision rotary system with macro/micro dual-drive is designed and developed,among which,macro-drive part is actuated by direct-drive motor,and micro-drive part using piezoelectric actuator(PZT)to drive the micro rotary mechanism.A cross bearing is used as a rotary guiding rail.The motion error of macro-drive is compensated by micro-drive,and the total output displacement of the rotary table is detected and feed back by a circular grating,forming a closed-loop macro/micro motion control system.The macro/micro dual-drive rotary system have many advantages,such as continuous-large-travel,all-load bearing,high-precision(4)Base on dynamics modeling of the precision rotary system with macro/micro dual-drive which is accomplished by the Newton-euler method,dynamic transformation function of the system is obtained,and dynamic simulation of the system is finished by Simulink software.A continuous compensation method of positioning error for the precision rotary system with macro/micro dual-drives is proposed after the system motion error analysis was finished,and errors compensation of the macro/micro system is finished by closed-loop control method for macro/micro dual-drive system by distributing macro/micro motion proportionally and automatically.(5)The five experiments are finished,as following:positioning accuracy testing of the system,error direct compensation of the macro-drive,error manual compensation of the macro-drive,error compensation performance of the miro-drive part,and macro/micro compensation of the system.Results of the experiments show that the repeat position error and position error of the system is reduced by 78.8%and 95.2%respectively after the macro/micro compensation,the results also show that the error compensation method and the control method are correct and effective,and its positioning accuracy achieved sub-arc-second.