Pose error compensation based on joint space division for 6-DOF robot manipulators

Abstract

This paper introduces a pose error compensation method performed in joint space to improve both position and orientation accuracy of industrial robots. Joint space division is proposed to achieve dimension reduction to reduce the workload of pose error sampling. The six-dimensional joint space is divided into two three-dimensional subspaces by the wrist center. Each subspace is discretized by a sequence of grid elements of which grid vertices are considered as sample points. Based on point set registration, two spatial databases of pose errors are built in the two subspaces respectively using a laser tracker. For a given robot posture, the pose errors generated in the two subspaces can be separately estimated using spatial interpolation based on inverse distance weighting algorithm. Formed by the estimated values, two transformation error matrices are introduced to compensate for the pose errors of the two subspaces. A Comau NJ370–3.0 manipulator was employed as an experimental platform to evaluate the effectiveness of the proposed method. Experimental results demonstrated the maximum position error was reduced by 96.06% to below 0.334 mm, and the maximum orientation errors have decreased to below 0.027° after compensation was performed.