Research On Modeling And Compensation Method Of Friction Characteristics For Precision Variable Slit System

As a subsystem under the lithography equipment,the precision variable slit system has a vital role,and its performance directly affects the exposure quality of the silicon wafer.The precision variable slit system completes the opening and closing of the light-blocking window by controlling four blades in two directions,and cooperates with other systems of the lithography machine to complete the lithography task.It has the features of high acceleration and high precision,and has extremely high motion control performance index requirements.In this paper,based on the precise variable slit system,the friction modeling and compensation for the frictional force problem existing in the Y direction of the system are used to improve the tracking precision and rapidity of the system.First of all,this article begins with the whole system of precision variable slits,and analyzes the mechanical structure and electrical system components of the system.Lists the movement indicators in both directions of the system and decomposes the indicators to provide a theoretical basis for the syst em bandwidth design.In order to reduce the mechanical impact of the platform and make the system move smoothly from the starting point to the end point,this paper plans the S-curve motion trajectory for the Y-direction movement index.According to the mechanical characteristics of the Y direction,the reasons for the existence of friction were analyzed,and interference force acquisition schemes were designed to perform data acquisition and preprocessing.Secondly,this paper selects the Lu Gre friction model for parameter identification according to the characteristics of the system.The parameter identification of Lu Gre friction model can be divided into two parts: static parameter identification and dynamic parameter identification.In static parameter identification,the least square method and particle swarm optimization algorithm parameter identification scheme are designed,and the advantages and disadvantages of both are analyzed and the parameters are identified.Select the degree of convergence.Thirdly,the driver,linear motor and motion platform are taken as general controlled objects.The frequency domain identification scheme is designed to obtain the frequency domain response of the controlled object and the transfer function of the controlled object is obtained.Using the established friction model,a feedforward compensation control scheme based on the friction model was designed.The effectiveness of the method was verified by simulation and experiment,and higher tracking accuracy and rapidity were obtained.Finally,this paper considers the uncertainty of the friction model parameters caused by the change of working conditions such as mechanical wear in the actual system,designs a backstepping adaptive controller,and compares the backstep ping adaptive control with the friction based model through simulation.It validates the superiority of backstepping adaptive control in overcoming such problems.