Tsai, Lung-WenChang, Sun-LaiIn this paper, a novel concept for the control of backlash in geared servo-mechanisms is demonstrated with a prototype manipulator. The concept utilizes unidirectional redundant drives to assure positive coupling of gear meshes at all times and, thereby, eliminates backlash completely. To establish a proof of concept, a two-DOF prototype manipulator with three unidirectional drives is designed and tested. Dynamic model based on Lagrange's formulation is established. a PID controller using computed torque control technique is developed. Two experiments, one with redundant drives and the other without redundant drives, are conducted. The experimental results demonstrate that use of unidirectional redundant drives improves the repeatability of a manipulator by an order of magnitude.en-USkinematicsoptimal controlroboticsintelligent servo: backlash controlIntelligent ServomechanismsTechnical Report