Research On Design And Control Method Of A Six-DoF Magnetic Levitation Positioning Platform

In recent years,with the development of semiconductor manufacturing,ultraprecision machining,and aerospace,modern positioning platforms have put forward higher requirements for their positioning accuracy,response speed,application environment,travel range and other aspects.The traditional positioning platform has limited the development of related fields due to serious mechanical wear,poor accuracy,and limited travel range.The positioning platform system using magnetic levitation technology has attracted widespread attention in the field of ultra-precision manufacturing because of its advantages of non-contact operation,high positioning accuracy,fast dynamic response,and compatibility with vacuum environment.In this thesis,the structure of the maglev positioning platform and its control strategy are mainly studied,and a six-degree-of-freedom magnetic levitation system based on repulsive levitation force is proposed.The stator structure of the magnetic levitation system is composed of four circular air core coils and four square air core coils,which are used to generate levitation force and driving force respectively,reducing the coupling degree of electromagnetic force to achieve higher precision sixdegree-of-freedom motion;the mover structure consists of a square stage and four permanent magnets embedded in it;the sensing system consists of eight laser displacement sensors symmetrically distributed to measure the six-axis position of the mover stage.Secondly,the electromagnetic characteristics of stator coil and mover permanent magnet are analyzed by MAXWELL software,and a nonlinear mathematical model of single-degree-of-freedom maglev platform is established,and on this basis,the dynamic model of six-degree-of-freedom maglev system with electromagnetic force decoupling and position decoupling is derived,which lays the model foundation for the design of subsequent maglev platform system controllers.Finally,a sliding mode-controlled magnetic levitation platform system based on exponential approximation law is designed,and the influence of different approximation parameters on the dynamic performance of the system is analyzed.For the single-degree-of-freedom(taking the z-axis direction as an example)and sixdegree-of-freedom maglev platform,sliding mode control and traditional PID control were used to simulate experiments,and the experimental results showed that the system had fast response and excellent robust performance under sliding mode control,which verified its feasibility and advantages for magnetic levitation platform system.