Error Modeling and Calibration of a Novel 6-DOF Robot for Cross-scale Assembly

This paper proposes a six-degree-of-freedom (6-DOF) robot for cross-scale assembly. The end motion of the robot can achieve decoupling of three translational degrees of freedom and two rotational degrees of freedom around the X-axis and Y-axis, and also enable the large-stroke workstation switching. For this 6-DOF robot, a segmented error calibration method is employed. First, local error parameter identification is carried out for the motion transmission chain containing the worm gear mechanism, and then error parameter identification for the remaining transmission chain is performed based on full-joint motion. The 29 selected error parameters include the worm gear ratio error and the installation error between the end effector and the sixth j oint. Experimental results show that, after error compensation, the position errors in the three directions are 0.004 mm, 0.0614 mm, and 0.0165 mm, respectively, and the average error in each direction is less than 0.1 mm. The attitude errors in the three directions are <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.049^{\mathrm{o}_{2}}0.039_{)}^{\mathrm{o}}$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.023^{\mathrm{o}}$</tex>. respectively, and the average error in each direction is less than 0.05ɗ. These results verify that the proposed calibration method improves the accuracy of this 6-DOF robot in cross-scale assembly.