Research On Kinematic Calibration And Accuracy Compensation Of Flexible Manipulator

As a kind of flexible automation equipment with high environmental adaptability and flexibility,manipulator has been widely used in industrial production,medical service,emergency rescue,space exploration and other fields.However,accuracy of manipulator is affected by many factors such as manufacturing assembly error,joint clearance,joint encoder error,and changes of environment,which limits applications of manipulators in fine operation tasks.At the same time,to improve load-to-weight ratio and flexibility,manipulators are developing in the direction of light weight.However,weight reduction of manipulator's structure leads to an increase in flexible deformation of joints and links,and the existence of flexible error increases difficulty of improving manipulator's accuracy.Based on the demands of project of intelligent sensing and control of light and small manipulator,the kinematic calibration and accuracy compensation technologies are studied for flexible manipulator in this paper.Specifically,this paper includes analysis of the factors affecting the accuracy of flexible manipulator,the research on kinematic calibration method of flexible manipulator,the optimization method of calibration configurations,the development of manipulator compensation software and related experiment.Firstly,research is conducted on related factors that affect the accuracy of flexible manipulator.Five error sources affecting the accuracy of flexible manipulator are summarized.By establishing models between error sources and end position/attitude errors of flexible manipulator,the sensitivity of the error source to the accuracy of manipulator is analyzed.A simulation of 8-DOF(degrees of freedom)manipulator shows the change laws of end position/attitude errors caused by different error sources with manipulator's configuration,and the proportion of each error source in end position/attitude errors.Secondly,aiming at the problem of misalignment of kinematic parameters,this paper studies kinematic calibration method of flexible manipulator.Based on MDH(modified Denavit-Hartenberg)model,a geometric error model is established.Based on force analysis of joint and link,a flexible error model is established.Then,kinematic error model is established by the geometric error model and flexible error model,and a kinematic calibration method for flexible manipulator is designed.The proposed calibration method can accurately solve kinematic parameters under the influence of flexible error.Thirdly,in order to solve the problem of poor calibration result due to random calibration configurations,we study optimization method of calibration configurations.On the basis of analyzing the factors affecting calibration accuracy,the quality index which can comprehensively reflect observation ability and globality of configuration set is established.Then,a calibration configurations optimization model is established and an optimization algorithm is designed.The configuration set obtained by the proposed optimization method can effectively improve calibration accuracy.Finally,a manipulator accuracy compensation software is developed,and experiments based on an 8-DOF modular manipulator is carried out.The designed software can apply the algorithms proposed in this paper to calibration of an actual manipulator,and the experiments verify the practicality of the proposed method and the developed software.