Research On Modeling And Compensation Of Geometric Error For 3-PRS Parallel Bonnet Polishing Machine Tool

In recent years, optical technology has get great development. As core elements, curved optical parts have been more and more widely used in aerospace, military reconnaissance and many civilian products fields, which gives a higher request to surface precision and quality of curved optical parts.3-PRS parallel bonnet polishing machine tool combines low cost, high precision, high efficiency of bonnet polishing technology and great rigidity, high operating speed, low inertia of parallel mechanism. It has broad application prospects in the field of curved optical parts processing. However, its low positioning accuracy can not meet the processing requirements of curved optical parts. Considering geometric error is the main error source of 3-PRS parallel bonnet polishing machine tool, research on modeling and compensation of machining geometric error for the machine tool to improve its positioning accuracy, has an important application value.Process of error compensation includes analysis of error sources, error modeling, error detection, error identification, error compensation and compensation evaluation. In order to simplify error identification and error compensation, this thesis used a better algorithm to improve inverse solution of 3-PRS parallel mechanism, defined the range of error compensation by analyzing the machining space. Establishing an appropriate geometric error model is the basis for error identification and error compensation. Considering independence of machine structure, established geometric error model of 3-PRS parallel mechanism by closed-loop vector method, established simplified geometric error model of serial mechanism, and analyzed the influence of position and orientation error on shape of polishing contact area. Established identification model on the basis of geometric error model of 3-PRS parallel mechanism and verified its feasibility. Measured position and orientation bonnet polishing spindle with Laser Tracker and simulation showed that measurement accuracy meet the requirements of the machine. In the beginning of error compensation, completed position error measurement and compensation of series mechanism, measured the original position and orientation error of machine and then identified parameter errors, achieved error compensation of 3-PRS parallel bonnet polishing machine tool by modifying the parameters of the CNC machine tool. Finally verified the influence of position and orientation error on shape of polishing contact area by bonnet polishing experiments before and after error compensation. Verified the practical effect of geometric error compensation.By research on modeling and compensation of geometric error for 3-PRS parallel bonnet polishing machine tool, position error decreased 93.86% from 6.1mm to 0.4mm, orientation error decreased 95.88% from 4.9 ° to 0.2 °. The positioning accuracy of 3-PRS parallel bonnet polishing machine tool has been greatly improved, which laid the foundation for polishing processing of curved optical parts, has an important application value.