Abstract:

In this paper,first,an error model of a robot is established via coordinates' homogeneous transformation and on the basis of the DH kinematic model. Next,in order to avoid the great change of the link distance due to small deviation of axes,another error model of parallel joints is set up via the homogeneous transformation and on the basis of the modified DH kinematic model. Then,the distance error of every two points in space is used to evaluate the absolute positioning accuracy of robot. Moreover,by the two above-mentioned models,a kinematic calibration model based on distance error,which avoids the complex coordinate transformation and simplifies the mea-surement process,is presented. Finally,the position of an end point of the self-developed 6-DOF industrial robot is measured by a three-coordinate measuring machine. The results indicate that,after the solving, compensation and correction of joint parameters,the average absolute distance error of the end point reduces by more than 50% and the positioning accuracy of the robot obviously improves.

Key words: industrial robots, distance error, kinematic parameter, calibration, accuracy