Research On Sliding Mode Control Method Of Vertical Precision Worktable With Three Degrees Of Freedom

The work table is one of the core subsystems of the lithography machine,and it plays a very important role in the ope rations of alignment,leveling,focusing,and scanning exposure of the silicon wafer.The six-degree-of-freedom micro-motion stage is the core component of the workpiece stage,and its tracking and positioning accuracy directly affects the resolution of th e lithography machine.The six degrees of freedom of the micro-motion stage can be divided into two groups,the horizontal direction and the vertical direction.The horizontal direction includes three degrees of freedom X,Y,and Rz,which mainly complete the alignment and step scanning of the silicon wafer,and the vertical direction includes three degrees of freedom Rx,Ry,and Z,which mainly complete the leveling and focusing.This paper mainly studies the control of vertical three degrees of freedom.(1)Analyze the overall structure and work flow of the lithography machine,analyze in detail the leveling and focusing technology of the single work stage and the double work stage,analyze the control accuracy index of the work stage,and plan the single degree of freedom movement trajectory It is a third-order S curve.(2)The dynamic modeling and decoupling control of the vertical three degrees of freedom of the workpiece table are carried out,the dynamic model of the vertical three degrees of freedom o f the workpiece table is established through the Kaldan angle transformation,and the decoupling of the vertical three degrees of freedom is studied.problem.The co-simulation of Simulink and Adams verifies the correctness of the established model.(3)According to the design method of sliding mode control,the sliding mode controller is designed using the reaching law method,and the reason of its chattering is analyzed,and then the boundary layer sliding mode controller and the super spiral sliding mode are designed from the consideration of weakening the chattering.Controller.Then,in order to suppress the interference,an extended state observer is introduced to observe the disturbance of the system,and the observation result is fed forward to compe nsate,which improves the ability of the system to suppress the disturbance and reduces the chattering to a certain extent.The control effects of these controllers are compared through simulation.(4)The principle of fuzzy control and the composition of the fuzzy system are analyzed,and several methods of combining sliding mode control and fuzzy control are discussed.Then an adaptive fuzzy sliding mode controller was designed,and the relevant parameters of the controller were optimized by the particle swarm algorithm.Finally,a controller with high tracking accuracy and low chattering was obtained,and the control effect was verified by simulation.