Underactuated mechanical hand control by EMG sensors

The control of the human hand uses several neural impulses to control muscles and tendons, which allow an almost limitless range of gestures and movements. If we want to consider only the most common gestures - greet, indicate, open palm, shake hands - use should be made of monitoring and acquisition of at least four pairs of muscle impulses. To acquire this large quantity of pulses in a patient fitted with a prosthesis, it would require a large number of electrodes, placed on different areas of the arm and forearm. However, this is not always possible due to the different degrees of impairment to which the patient may be subject. In addition, the yield of the movement to be faithful to that of a human hand, would require the use of at least 15 motors. The studies carried out at the Department of Industrial Engineering of the University of Naples, allowed the realization of an prosthetic hand prototype equipped with a single pair of electrodes and a single motor. In this paper different types of control developed for the above prototype, are described. By means of such control techniques, making use of a finite state language, the user is able to control the hand with on-off and proportional techniques, that provide a wide range of situations in which the prosthesis is effective and responsive