Study on Singularity Passing Method for Large Industrial Robot Based on Proper Element Improvement of Inverse Matrix

Abstract

Singularity has become a limitation to the expected diversification of industrial robot applications in production. Here, we propose a novel solution for the inverse kinematics of a 6-DOF manipulator that suppresses rapid joint rotation when passing through a singularity. The proposed method is based on the optimization of the inverse Jacobi cofactor matrix utilized in the inverse kinematics calculation. By optimizing only the elements related to the four and six joints of the cofactor matrix in the inverse matrix, we were able to suppress the divergence of the joint velocities and achieve smooth robot motion when the robot entered a singular posture at the wrist. The developed system application range and tuning gain that minimize the position and orientation error were also determined. Hence, the position and orientation errors were improved by approximately 76%, and rapid rotation of the joints was almost completely suppressed. The method did not require consideration of tools attached to the hand tip, and the hand tip position, orientation, and velocity were all maintained.