Error Analysis And Compensation Of 2-DOF Spherical Parallel Pointing Mechanism

With the development of China's aviation industry,more and more attention has been paid to directing mechanism with the characteristics of heavy load and high accuracy.Spherical parallel mechanism has the characteristics of heavy load and good reliability.However,the problem of accuracy has always restricted its application in pointing mechanism.Therefore,this paper takes the prototype of 2-DOF spherical parallel pointing mechanism as the research object,carries out theoretical analysis and Research on error modeling,error analysis,error parameter identification and error compensation of the mechanism,and finally carries out error calibration and compensation of the prototype through experiments.Firstly,kinematics analysis of the pointing mechanism is carried out,position and attitude description considering error parameters is established,and kinematics inverse solution and kinematics forward solution of the mechanism are obtained.The error model of single branch chain is established by differential method and the error model of spherical parallel pointing mechanism is built by loop increment method.Secondly,the error sources of parallel pointing mechanism are classified and analyzed.In static error analysis,the corresponding relationship between each error parameter and actual error source is obtained,and the influence of error parameter on end-pointing accuracy is obtained according to error model,and the sensitivity of each error parameter is obtained.In the dynamic error analysis,the model of rotating pair with clearance is simplified,and the influence of clearance in mechanism motion on end-pointing accuracy is analyzed by means of Adams software.Then,based on multiple collinearity detection,a grouping regression analysis method is designed,and the correlation between the correlation coefficient vector and the corresponding error parameters in the identification model is obtained;a succession search method is designed to optimize the pointing configuration based on the matrix condition number;and the parameter identification simulation research is carried out based on least square method and genetic algorithm.The compensation methods based on kinematic error parameters and non-kinematic error parameters are studied.Finally,zero-position rough calibration of the pointing mechanism is carried out by inclinometer and optical platform;a pointing error measurement method based on position measurement is put forward,and the pointing error of spherical parallel pointing mechanism is calibrated by means of position measurement function of laser tracker,and the endpointing error data is obtained;the feasibility of the two compensation methods is verified by experiments.