Accuracy Analysis And Optimization Design Of Precision Docking Platform

Based on the technical specifications of experiments,the assembling and calibration task is put forward by a facility.Moreover,due to the variety of modules,the precision of manufacturing and the complexity of alignment interface,the method to ensure and improve the accuracy of alignment has become the main problem of module calibration.Based on the key projects for precision calibration of the module.A precision docking platform that is suitable for the pose adjustment of the module is introduced in the paper.By studying the kinematics performance of the platform,analyzing its precision and optimizing its design,the quality and efficiency of the module calibration are improved,which is of great significance to ensure the operation reliability of the facility.The content of this paper is as follows:Through a comprehensive analysis of the characteristics of the module and the requirements of calibration,the technical scheme of the precision docking platform was determined.The precision docking platform was proposed,which was composed of 3-PSS/PU spatial parallel mechanism(horizontal adjustment unit)and 4-PPR planar parallel mechanism(plane adjustment unit).The DOF of the adjustment units is calculated by the helical theory,meanwhile,the corresponding constrained helical system is obtained,which lays a foundation for kinematics analysis.The closed vector method is used to obtain the mapping relation between the input of each driver and the end-pose of the platform.By the analytic method,the inverse kinematic can be obtained,then,the mathematical model of velocity and acceleration is derived.The correctness of the kinematics model is verified by comparing the simulation results with the theoretical calculation values.The reachable workspace of the horizontal adjustment unit is drawn by the integral search method,which indicates that the horizontal adjustment unit meets the kinematic performance index.Through the analysis of main error sources involved in manufacturing and driving control of the horizontal adjustment unit,the total error transfer relationship of pose accuracy can be given by introducing the matrix differential method.According to the performance index and error boundary conditions,the simulation of the maximum endpose error is conducted under any angle.Meanwhile,the global mean sensitivity analysis of each error source parameter is obtained,the main error and directions that affect the motion accuracy of the horizontal adjustment unit are clarified.Based on sensitivity analysis and calculation,the boundary value of manufacturing and assembling errors of moving joints is optimized,which made the distribution of errors more reasonable.Meanwhile,with the simulation of the error transfer function,the influence of the structure parameters on platform end-pose is obtained.Taking the comprehensive error as the objective function,the global optimization of the platform structural size is carried out,which indicated that the optimized structural parameters significantly improve the motion precision of the horizontal adjustment unit.