Tendon Drawn Pronation/Supination Actuation Concept for a Rigid Assistive Forearm Exoskeleton

Pronation and supination of the forearm and wrist in the human body is permitted by a combination of movements from the carpal bones and the constrained relative motion between the radius and the ulna. Despite being crucial to completion of tasks involving the hand and arm, this degree of freedom is lesser explored with mobile and rigid exoskeleton designs for the upper limb. This paper presents the design, preliminary modelling, and prototype construction of a compact, robust, 1 degree of freedom rigid exoskeleton which circumvents these challenges by reframing a soft exoskeleton-based method of actuation - providing a structure on which to bear the forces created by the device, instead of transferring it through the body as a typical soft exoskeleton would. The design actuates wrist pronation/supination with tendons that directly power the motion through tension, actuating interlocking segments that progressively slide along each other in a cylindrical pattern. The exoskeleton essentially provides rigid support and utilises actuation principles of a soft robotics exoskeleton without suffering from the drawbacks.