Modeling And Compensation Of Friction Characteristics Of Precision Mechanical Platform

This topic is derived from the national science and technology major projects‘greatly scale integrated circuit manufacturing equipment and complete sets of technology',subproject ‘variable slit system'.Variable slit system is the important part in the process of lithography exposure.In the process of its exposure,the subassembly of the vertical direction needs to compensate for gravity.This topic ues the cylinder to be the gravity compensation device.The friction of the cylinder movement process is small,but considering the accuracy of the platform,to compensate the friction is necessary.This topic for the friction of the slit scanning system in gravity compensation cylinder,makes a thorough inquiry.Firstly,according to the practical engineering background,pull out the gravity compensation part of the variable slit system vertical.And then,according to the requirements of the project indicators,do the selection of components,and complete the part of the actual platform structures.After that,to verify the feasibility of the platform,do the preliminary simulation and the experiment on it.In the process,put forward the friction of the cylinder movement process affects the precision of the platform.Secondly,to explore the main object of this topic,the gravity compensation cylinder.First of all,with the mechanical structure of the cylinder,discuss the composition and the working process of the gravity compensation cylinder.And then derive the mechanism model of the selected cylinder by theoretical derivation,Finally,the model is simulated.In the case of external disturbance,explore the cylinder position,internal pressure,internal flow and other changes of the model,obtain the simulation results.Then,analyze the advantages and disadvantages of several kinds of friction models with high versatility,and by comparing the various aspects,finally get a better mathematical model of the friction force-LuGre friction model.Thirdly,in view of the LuGre friction model simulation,the influence of each parameter to be evaluated on the LuGre friction model is discussed.The simulation conclusions to lay a good foundation for later parameter identification process,the purpose is that if the identification result is not ideal,adjust the parameters by fine tuning.Then,the least squares method,the nonlinear least squares method and the genetic algorithm are used to identify the friction parameters,and the identification results obtained by different methods are compared,the advantages and disadvantages of different identification methods are analyzed.Finally,the method proposed above is verified by experiment,and the friction ofthe actual system is compensated by experiment.The applicability of the friction model proposed above to the actual system and the identification accuracy of the identification method proposed above are verified.And then,through comparison,select the feedforward control method,which owns the high practicability and better control effect.At last,the compensation of the frictional force existing in the part of the actual system gravity compensation cylinder is completed,and the control precision of the system is improved and the initial index requirement is completed.