Singularities of the Typical Collaborative Robot Arm

Abstract

In this paper, the singularities of the typical 6R collaborative robot (such as the cobots made by Universal Robots) are analytically and geometrically described. Since the axes of the last three joints in such a cobot are not concurrent, the singularities are slightly different from those of the PUMA-style manipulator. It is shown that the determinant of the Jacobian matrix of the typical cobot splits into four factors, three of which can vanish. As in the typical PUMA-style manipulator, the three vanishing factors correspond to shoulder, elbow and wrist singularities. However, in a wrist singularity, the redundant motion associated with no end-effector movement is more complex.