The Design and Control of a Low-Power, Upper-Limb Prosthesis

Control moment gyroscopes (CMGs) offer a unique approach to address power consumption issues that currently limit the design of prosthetic limbs. CMGs generate large output torques while requiring less power than conventional actuators. This advance is possible because CMGs conserve angular momentum without increasing the kinetic energy of the system, providing high-agility, low-power movements. We have designed a novel, three degree-of-freedom prosthetic arm actuated with small-scale CMGs. Each of the three segments contains one CMG scissored pair, which allows precise control over joint torques and accelerations. The prototype arm will have a workspace of 360 degrees of rotation about each joint axis, although it will be limited to physiological standards. The motions replicate elbow flexion/extension, wrist flexion/extension, and forearm supination/pronation. We will implement real-time, myoelectric control using electromyographic (EMG) signals recorded from the biceps brachii for the elbow joint, brachioradialis for the forearm, and the flexor carpi radialis and extensor digitorum communis for the wrist. The control system will correlate the EMG signals with output force of the arm and produce corresponding movements that mimic those produced by humans during voluntary contractions. Ultimately, our arm will serve as a prototype for future designs that utilize the unique characteristics of CMGs to enable upper-limb amputees to return to normal function.