Simple Quasi-Static Control of Functional Electrical Stimulation-Driven Reaching Motions

Functional electrical stimulation is a promising technology for restoring functional reaching motions to individuals with upper limb paralysis. We present a control architecture that combines static models of a paralyzed arm and its response to stimulation with a PID controller. The controller is used to drive the wrist of an individual with tetraplegia to a desired wrist position. We compare the performance of our controller with a feedforward component and with no feedforward component. The combined feedforward-feedback controller produced an average accuracy (defined as the distance away from the target wrist position) of 4.9 cm, and the feedback controller produced an accuracy of 4.3 cm. The combined feedforward-feedback controller produced initially larger errors than the feedback controller, but the end performance was similar. The control architecture presented has the potential to be used for arbitrary reaching motions