Singularity coupling in robotic manipulators

The existence of singular positions inside the robot workspace is an inherent problem for task planning and robot control. Identifying the singularities in the robot workspace is not always an analytically tractable problem, except for manipulators with opportune placement of the joint axes. Typically, it is easier and more informative to evaluate the robot ´arm´ and ´wrist´ singularities which reflect the limitations of the lower-order robot subsystems responsible for positioning and orienting, respectively, the end-effector in space. The objective of this paper is to present a general formula that defines manipulator singularities in terms of the subsystem singularities. The analysis leads to a novel, efficient method for identifying the singularities of six-axes manipulators. The contributions of the paper are then illustrated through an example.<>