Study On Control Strategy Of Parallel Module Of Large Mirror Processing Equipment

With the continuous development of information technology,modern processing equipment is developing from CNC machine tools to industrial processing robots,and is playing an increasingly prominent role in the new field of optical system processing platforms.In modern optical processing,as the requirements for the accuracy and resolution of optical components continue to increase,the requirements for processing equipment are also getting higher and higher.At present,the mirror processing equipment in the optical system is developing rapidly in the direction of high precision and high efficiency.Modern processing equipment can bring greater economic benefits while promoting the development of technology.Therefore,it is of great significance to study the mirror processing equipment in the optical system.In order to improve the processing accuracy of optical mirror processing equipment,it is necessary to enhance its control performance and study its control strategy further.Parallel mechanism has a series of advantages such as stronger load-bearing capacity,larger working space,no cumulative error and higher precision,and the hybrid mechanism combining series mechanism and parallel mechanism,becomes the best choice for machining equipment under the condition of large-scale optical mirror machining.However,the parallel mechanism has strong nonlinearity,and the existence of multiple drive branches makes the kinematics and dynamics of the parallel mechanism more complicated,which increases the control difficulty of the parallel mechanism.This paper takes the largescale mirror processing equipment of the five-degree-of-freedom hybrid mechanism as the research object,and mainly conducts in-depth research on the kinematics,dynamics,virtual prototype and control strategy of the parallel mechanism modules.The main research contents are as follows:1)To solve the problem of inverse motion and forward motion analysis of the parallel module of large mirror processing equipment,firstly,the vector cosine method is adopted to establish the spatial coordinate system of the parallel module and the series module,and the inverse kinematics solution of the parallel module is derived according to the vector geometric relationship,so as to obtain the movement trajectory of the displacement change,axial velocity and acceleration of the driving branch chain.Solve the positive kinematics of the parallel modules by the Newton-Raphson method,and obtain the motion trajectory of the center point of the moving platform through the simulation analysis based on the positive kinematics,so as to meet the control accuracy requirements.In the case of considering the side-effect force of motion,the dynamic model of the parallel module of the mirror processing equipment is constructed by using the Newton-Euler method,and the driving force change curve of the driving branch chain is obtained.The results show that the side-effect force of motion(namely contact force and friction force)has a significant impact on the driving force of the drive branch.Finally,the obtained dynamic model of parallel modules is transformed into an explicit dynamic model that is convenient for control strategy research.2)Import the physical model of the mirror processing equipment established in the 3D modeling software Solidworks into Adams,and use Adams’ virtual simulation function to build the motion simulation model of the parallel module mechanism of the processing equipment.The consistency between the kinematics and dynamics results and the ideal calculated values is verified by simulation analysis,and the reliability of the established kinematics and dynamics models are further verified.Use MATLAB’s Simulink toolbox to establish a simulation model of permanent magnet synchronous motor servo system based on FCS-MPCC,and compare it with traditional FOC control.This servo control model has the advantages of fast response,strong anti-interference,and high control accuracy.Finally,through the joint simulation of Adams and Simulink,the simulation experiment platform of the entire control system of the processing equipment is built,which lays a good foundation for the follow-up research of control strategy.3)From the perspective of kinematics and dynamics,the control strategy of the parallel module of mirror processing equipment is studied.Three spatial multi-input and multi-output controllers are designed on the basis of considering the dynamic characteristics of the parallel mechanism.These three kinds of controllers are nonlinear PD controller,augmented nonlinear PD controller and calculated torque controller based on nonlinear PD control.The closed-loop stability of these controllers are analyzed,and a simulation model of the parallel module controller is constructed.The simulation results show that,compared with traditional PD controllers,all these controllers have stronger trajectory tracking during the entire operation process and can make the parallel modules of processing equipment run smoothly.Among them,the calculated torque control based on the nonlinear PD control has a strong tracking ability and a small tracking error of the motion trajectory.4)Based on the established dynamic model of the parallel module,from the perspective of dynamics,the control system model of the parallel module is established,and a new synchronous control method is proposed by using synchronous control technology.Firstly,introduce the fractional calculus PID control theory;secondly,expand the expected trajectory point of the center point of the moving platform in the parallel module of the processing equipment according to the Taylor formula;then deduce the tracking error of the central point of the parallel module moving platform and the synchronization error between its movements;finally,the total trajectory tracking error of the center point of the moving platform of the parallel module is obtained by calculation,and combined with the fractional order control technology,the synchronization control strategy of the parallel module control system of the mirror processing equipment based on the workspace is constructed.The reliability of the designed controller and better trajectory tracking performance is proved by simulation and analysis.