Singularity-Free Inverse Kinematics by Cyclic Coordinate Descent of A 6 DOF Robotic Manipulator

This paper presents forward and inverse kinematics analysis for a 6 degree-of-freedom robotic manipulator. Cyclic Coordinate Descent (CCD) is chosen to be the framework of inverse kinematics. The limitation of the existing CCD is identified in this paper, where the robot can be locked at the singular conditions and fails to reach the target. After analyzing and categorizing the singular conditions, an unlock mechanism is developed by adding a small angle disturbance to a robot joint. The unlock mechanism can be implemented on top of the conventional CCD. It is shown that the singularity-free CCD is valid and the desired properties of the algorithm are illustrated by numerical simulation, experiments and digital twin visualization.