ON THE REDUNDANT-DRIVE BACKLASH-FREE ROBOTIC MECHANISMS

In this paper, we introduce a new and innovative concept for the contr ol of backlash in gear-coupled robotic mechanisms. The concept utilize s redundant unidirectional drives to assure positive coupling of gear meshes at all times. Based on this concept, a methodology for the enum eration of admissible redundant-drive backlash-free robotic mechanisms has been established. Some typical two- and three-DOF mechanisms have been sketched. Furthermore, actuator torques have been derived as fun ctions of either joint torques or end-effector dynamic performance req uirements. A redundantly driven manipulator has the fail-safe advantag e in that, except for the loss of backlash control, it can continue to function when one of its actuators fails. It does not have the compli ance problem associated with tendon-driven manipulators. A two-DOF bac klash-free experimental arm is currently under construction to demonst rate the principle.