Experiments with CHRELMS patient-driven stimulator controllers for the restoration of function to paralysed legs

This paper examines the control of electrical stimulators for restoring the standing function to paraplegics. Patient-driven controllers are based on the knowledge that standing, using support handles, is guided by the neurol ogically intact natural motor control system, acting through the arms. One category of patient-driven controller is CHRELMS (Control by Handle Reactio ns of Leg Muscle Stimulation). The first experiments with patient-driven co ntrollers are reported. Experiments in the CHRELMS control of one volunteer are described. Proportional control did not allow the subject to stand up because of the strategy he used, but integral control was successful. With it, he could stand up and sit down slowly, entirely guided by himself, as w ell as making other manoeuvres. Without changing controller mode, and by le aning forwards and backwards, he could 'posture switch' his support muscles . These are significant achievements and justify a larger study of patient- driven controllers. The subject's control strategies are discussed.