Research Of Calibration Method For Industrial Robot Based On Error Model Of Position And Orientation

With the wide application of industrial robots,people have higher and higher requirements for their accuracy.However,the absolute positioning accuracy of industrial robots is generally not high at present.Therefore,it is particularly important to carry out the research on the methods to improve the absolute positioning accuracy of industrial robots.Robot calibration can make up for the errors caused by the inconsistency between the robot body structure and the kinematics model parameters in the controller at the minimum cost and improve the robot end pose accuracy which is the main method to improve the robot end pose accuracy at present.In this paper,the industrial robot is taken as the research object from the aspcects of robot modeling,robot end pose measurement,parameter identification and error compensation,a set of relatively universal robot calibration scheme is proposed and the feasibility of the scheme is verified by experiments.This paper mainly focuses on the following aspects:This paper presents a general scheme of robot end pose measurement including DCP(Dection Center Point)calibration and base coordinate system measurement.Then the MDH modeling method is used to establish the kinematics model of the robot.Based on differential kinematics,the mathematical model between the robot link parameters error and the robot end pose error is established.From the actual measurement point of view,DCP coordinate system error and robot base coordinate system error are added to the model and the complete error model is established.Simulation results show that the model can approximately reflect the actual pose error of the end of the robot under the premise of small error.The redundancy analysis of different joint parameters in robot error model is carried out and the method of identifying redundancy parameters of robot model is given.The least square method is used as the identification algorithm of the parameter error and the off-line calibration program is developed by combining Matlab software.The model of the given error is successfully identified in the simulation.Based on the differential method and Newton iteration method,a joint space compensation algorithm is proposed.The joint angle is used to compensate the robot's end pose error and simulation and experiments show the effectiveness of the method.The calibration method of industrial robot is verified by experiments.ABB IRB 120 is used as the experimental object and Leica laser tracker is used to measure the end pose of the robot.Based on the robot end position error and the robot end pose error,the error identification is respectively carried out and the compensation effect of the two results is compared.The conclusion is that the robot pose accuracy can be effectively improved based on the robot position error calibration,the robot pose error calibration and the latter can better improve the robot pose accuracy.At the same time,comparing the two results on the same space compensation effect,it is found that in a certain workspace,the larger the calibration points distribution,the better the space calibration effect.