Evaluating an open-loop functional electrical stimulation controller for holding the shoulder and elbow configuration of a paralyzed arm

Functional electrical stimulation (FES) is a promising solution for restoring functional motion to individuals with paralysis, but the potential for achieving full-arm reaching motions with FES for various desired tasks has not been realized. We present an open-loop controller capable of calculating and applying the necessary muscle stimulations to hold the wrist of an individual with high tetraplegia at any desired position. We used the controller to hold the wrist at a series of static positions. The controller was capable of discriminating between different wrist positions. The average distance to the target wrist position, or accuracy, was 7.7 cm. The average radius of the 95% confidence ellipsoid for a set of trials with the same muscle stimulations, or precision, was 6.7 cm. Adding feedback or online model updates will likely improve the accuracy for tasks requiring finer control. The controller is a good first step to controlling full-arm motions with FES.