Manipulators and Upper-extremity Prosthetics

Wilson, N R C , for an informal chat on a number of ideas stimulated by the conference some on historical developments and some on older concepts of prosthetics that might be applicable to today's manipulator problems. T h e following notes are an outline of some of those thoughts, which, as Dr. Murphy Propulsion Ofice, U S A E C , "to some extent represent our joint thinking, but the wilder ideas should be regarded strictly as m y own!" W e feel sure that for anyone who knows the ramifications of prosthetics research, Dr. Murphy's notes will sound more fascinhting than wild. And for anyone who might ever have thought that research and development in prosthetics and sensory aids had limited applicability, these notes are a must! T h e Editors In 1946-47, early in the government-sponsored Artificial Limb Program coordinated by the National Academy of Sciences, UCLA conducted extensive experiments on motions and gripping forces required for selected and common activities of everyday living. (These were deliberately selected as representative of independent living even for severely disabled bilateral amputees, though many of them were also difficult for unilateral amputees. Some were mutually exclusive, like holding a knife and holding a fork during cutting of meats, so that even a unilateral must perform either one or the other with a prosthesis. Industrial activities were not specifically studied, on the presumption that vocational guidance could locate suitable jobs among the tremendous variety requiring motions and forces no more severe than those required in everyday living and thus within the capacity of rehabilitated amputees.) The typical gripping or pinching forces for a great many tasks were found to be 3 pounds or less at the finger tips, with only occasional tasks requiring as much as 6 pounds. The maximum pinching force encountered (pulling on shoes under certain conditions) was 14 pounds. Such high forces could be avoided fairly easily by use of a loop on the shoes, by further unlacing, or by wearing elasticized shoes. Independently, it was found that most amputees wearing voluntary-opening hooks closed by