Miniaturized non-back-drivable mechanism for robotic applications

Small actuators and high efficiency transmissions are essential components in mechatronic and robotic systems, since their performances affect overall volume, weight and power consumption. An innovative miniaturized, low cost, clutching mechanism for robot applications, based on wedge phenomenon in eccentric non-eccentric cam coupling has been designed, developed and evaluated. It is embedded into a human-size, robot hand prosthesis, allowing it to efficiently produce powerful grasps, but it could be employed in all those applications where strict power and weight-size constraints exist and a self-braking mechanism is required. High efficiency, compared to conventional non-back-drivable mechanisms based on screw lead-screw coupling, is achieved by means of roll cylinders inside the clutch. The system has been integrated with a DC motor and a capstan on which a tendon is wound, and then finally connected to the hand fingers. Detailed kinematics, static and dynamic analysis are presented as well as finite-element-method simulations and experimental measurements showing successful fulfilment of requirements. Maximum efficiency is about 0.95 in a large load range, the critical torque at which the mechanism unlocks is about 1 Nm.