Functional assessment of control systems for cybernetic elbow prostheses. II. Application of the technique

For pt.I see ibid., vol.37, no.11, p.1025-36 (1990). An application of the technique described in pt.I for the functional assessment of two myoelectric elbow-prosthesis controllers is presented: the controller implemented in the Boston Elbow, a state-of-the-art elbow prosthesis, and a proposed control scheme that, to a crude degree, mimics control of the intact elbow. Assessment of the controllers was achieved by evaluating an amputee subject´s functional capability as he performed a constrained motion task with a prosthesis that implemented each control scheme. Evaluation of the amputee´s capability was accomplished offline using sampled values of myoelectric activity, limb kinematics, and the interface forces at the constraint. Superior performance was observed with the proposed scheme. Namely, the subject exhibited better synergy among elbow and shoulder muscles. Furthermore, when using the proposed controller, some natural patterns of muscle coordination were exhibited.