GRASP SYNTHESIS FOR UPPER-EXTREMITY FNS .1. AUTOMATED-METHOD FOR SYNTHESIZING THE STIMULUS MAP

Functional neuromuscular stimulation (FNS) has been used in open-loop upper-extremity neuroprostheses to provide grasp and release for quadr iplegic individuals. A principal issue in implementation of the open-l oop neuroprosthesis is the synthesis of the grasp stimulus map, which is the relationship between the input control signal and the output st imulus applied to each electrode. The goal of this project was to deve lop a method of stimulus map synthesis which compensates for the influ ence of the electrode-position-dependent recruitment properties on the grasp output, and which can be performed using automated procedures. A method called the external moment grasp synthesis procedure (GSP) ha s been developed which meets these criteria. The GSP uses an external moment of model of the hand which describes the interaction between th e active moments produced by electrical stimulation, the passive joint moments and the total joint moment and angle. The GSP was used to dev elop the stimulus map for three paralysed subjects, and in all cases t he GSP-generated grasp patterns had lower errors than grasp patterns d eveloped using the previously implemented rule-based method of stimulu s map synthesis. The GSP was successfully implemented by computer and was able to compensate for the effects of the electrode recruitment pr operties on the grasp pinch force.