Positioning error calibration of six-axis robot based on sub-identification space

A novel subspace-based positioning error calibration method is proposed for six-axis industrial robots. This method divides the entire workspace of the robot into two sub-identification spaces to achieve error dimensionality reduction. A spherical S-shaped trajectory with multi-axis linkage is proposed by using a double ball bar (DBB). The error measurement mode combining three-axis and six-axis linkage is adopted to effectively simplify the error identification process and improve the calibration accuracy. In order to evaluate the influence of various errors on the positioning error of the robot end-effector, based on the robot kinematics calibration model, the sensitivity analysis of each axis error is carried out by uniaxial and multi-axis linkage. Compared with the last three axes, the error of the first three axes has a greater impact on the positioning error of the robot end-effector. The installation error of the DBB is eliminated by fitting three orthogonal plane circular trajectories. Compared with the general six-axis linkage calibration method, the calibration accuracy of the proposed subspace calibration method is improved by 15.52%.