Error Analysis And Calibration Of A 5-DOF Hybrid Mechanism

In this dissertation,the analyzed hybrid mechanism,a five degrees of freedom mechanism,is composed of serial mechanism and parallel mechanism.Not only does the hybrid mechanism have the advantages of high rigidity,excellent stability and bearing capacity,but also possess relatively large workspace.In order to improve the accuracy of the hybrid mechanism,this dissertation does some research surrounding three contents about the kinematics,error sensitivity and calibration of the hybrid mechanism in the following aspects:First of all,the constitution of the hybrid mechanism is introduced in detail;the degree of freedom of the hybrid mechanism is analyzed by using the screw theory,and the result indicates that the degree of freedom of the mechanism is five;the positive and inverse solution of the hybrid mechanism is found by using analytical method and vector method respectively,and a group of the array is used to verify the effectiveness of the solution,and the result confirms that the correctness and validity of the positive and inverse solutions;the reachable workspace of the mechanism is determined via search method.Secondly,each error source of the parallel and serial parts is determined by using vector method and DH method respectively;according to the establishment of the error probability model,each error of the parallel part is analyzed by using the sensitivity analysis,which clarifies the error impacting on precision of the parallel part;the sensitivity of the error parameters is presented,and the influence of the error of the parallel part on the end precision is analyzed;in the serial part,the error impacting on precision of the serial part is analyzed by using the error sensitivity analysis;the influence of the different actuation on the end of the mechanism is determined in the same error condition.Thirdly,a principle about calibrating parallel part and serial part is proposed for the mechanism separately;in the parallel part,the error model is established by using vector chain method,and the least squares method is used to do parameter identification,and the way to modify geometric parameters is used to compensate error;in the serial part,the error model is established by using D-H method,and the least squares method is used to do parameter identification,and the way to modify geometric parameters is used to compensate error.Finally,the correctness of the calibration is verified by computer simulation,and the validity of the calibration principle is confirmed by analyzing the simulation results.