Sensory control of a multifunction hand prosthesis

The current generation of prostheses that are fitted to limb deficient individuals have only a single degree of freedom which limits their functional range. Furthermore, electrically powered prostheses have a limited user input. Electrical signals generated by the contraction of muscles in the user's stump open and close the hand in an 'on and off' fashion. Since the only feedback is visual, the prostheses tend to be used less dexterously than body powered devices. A different approach has been adopted by the Control Engineering Group at Southampton University. They have retained a single electromyographic input channel, but added sensory feedback to an electronic controller, which decides on the grip posture and tension. Satisfactory operation of the hand depends on the sensors employed. A review of transducers used on previous prostheses at Southampton is followed by a description of recent sensor developments. Finally the intentions for a new generation of prostheses are outlined. These include combining sensory input with an integrated circuit microcontroller to provide a more reliable system.