The RIC Arm-A Small Anthropomorphic Transhumeral Prosthesis

Recent advances in motor and gear designs have accelerated the development of multi-degree of freedom prosthetic limbs controlled by novel electromyographic signal processing techniques. Most of these new devices have focused on improved performance at the expense of other critical factors for clinical use, such as weight and bulk, which significantly affect cosmesis and comfort. This paper presents the mechatronic design of an anthropomorphic transhumeral prosthetic arm-the Rehabilitation Institute of Chicago (RIC) arm-that is small enough for a 25th percentile female and weighs only 1518 g. Specifically, we describe the design of the RIC arm, including the integration of custom external rotor motors, cycloid transmissions, nonbackdrivable clutches, and custom pattern recognition control. Mechanics and control performance of the RIC arm were evaluated within the laboratory, and clinical viability was preliminary evaluated during a take-home field trial by an individual with a transhumeral amputation.