An Adaptive Multifunction Myoelectric Control System

Myoelectric systems have received widespread use as controls of prosthetic devices for individuals with amputations or congenitally deficient upper limbs, (Parker and Scott, 1988). Many systems are now available commercially to control a single device (hand, elbow, wrist). These systems extract a control signal based on an estimate of the amplitude, (Dorcas and Scott, 1966), or on the rate of change, (Childress, 1969), of the myoelectric signal (MES). This control signal is either derived from a single myoelectric channel, in which case the amplitude of the signal is used to select 1 of 3 states of device operation, or it is derived from 2 channels of myoelectric signal, in which case the channel with the largest amplitude determines the device state,. Once the state is selected its speed may be constant, or it may be controlled in a manner proportional to the level of myoelectric acdvity Although the success of fitting these systems for single device control is apparent, the extension to the control of more than one device (either simultaneously or sequentially) has been difficult. For this reason fittings of high level amputees often have been unsuccessful, (Scott and Parker, 1988). However, it is these individuals who would benefit most from the functional replacement of their lost limbs. The lack of success can be attributed primarily to the inadequacy of present multifunction conuol strategies