The design and development of a bio-mechanical robotic hand for remote maintenance of the ITER reactor

Abstract

To try and recreate the human hand. one of nature’s most sophisticated system that is designed from both powerful grasping and precise manipulation, is an incredible challenge. Mimicking functionalities using robotics and mechatronics in a hazardous environment that is the ITER nuclear fusion reactor is what this thesis was set out to do. Presenting a design of a biomimetic, tendon-driven robotic hand for remote maintenance applications in the ITER. The study is set out to answer questions addressing functional requirements, application of biomimetic principles and the final performance of the proposed design. These are achieved through extensive biomechanical analysis of the human and review of existing robotic hands.

The result is a five-digit, 20 degrees-of-freedom tendon-driven, underactuated robotic hand. Finger actuation is managed by two servos for each of the four fingers apart the thumb, one for the flexion one for abduction/adduction while a torsion spring is responsible for a passive extension mechanism. The thumb is actuated by 3 servos to achieve true opposition. 4 servos are placed under each finger for shorter mechanical paths (higher accuracy) for the side-to-side movement. The remaining 8 servomotors are placed in a box in place of the forearm that houses all internal electronics. The design prioritised low friction through ball bearings and modularity for the ease of repair and protection of parts. The prototype is under construction while the model was created in SolidWorks.

Initial testing shows great promise and confirms the feasibility of the tendon-driven approach and the effectiveness of the thumb mechanism. There are multiple identified limitations like, spring calibration, high tendon friction or limited control system. The design serves more of a proof of concept than the final iterations to validate the biomimetic approach.