title: Finite state control of a variable impedance hybrid neuroprosthesis for locomotion after paralysis.
abstract: We have previously reported on a novel variable impedance knee mechanism (VIKM). The VIKM was designed as a component of a hybrid neuroprosthesis to regulate knee flexion. The hybrid neuroprosthesis is a device that uses a controllable brace to support the body against collapse while stimulation provides power for movement. The hybrid neuroprosthesis requires a control system to coordinate the actions of the VIKM with the stimulation system; the development and evaluation of such a controller is presented. Brace mounted sensors and a baseline open loop stimulation pattern are utilized as control signals to activate the VIKM during stance phase while simultaneously modulating muscle stimulation in an on-off fashion. The objective is twofold: reduce the amount of stimulation necessary for walking while simultaneously restoring more biologically correct knee motion during stance using the VIKM. Custom designed hardware and software components were developed for controller implementation. The VIKM hybrid neuroprosthesis (VIKM-HNP) was evaluated during walking in one participant with thoracic level spinal cord injury. In comparison to walking with functional neuromuscular stimulation alone, the VIKM-HNP restored near normal stance phase knee flexion during loading response and pre-swing phases while decreasing knee extensor stimulation by up to 40%.
authors.affiliation: Functional and Applied Biomechanics Section, National Institutes of Health, Bethesda, MD 20892, USA. thomas.bulea@nih.gov
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Bulea
authors.forename: Rudi
authors.initials: R
authors.lastname: Kobetic
authors.forename: Musa L
authors.initials: ML
authors.lastname: Audu
authors.forename: John R
authors.initials: JR
authors.lastname: Schnellenberger
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Triolo
mesh_terms: D001676:Biofeedback, Psychology / Q000295:instrumentation*; D017097:Electric Impedance; D004599:Electric Stimulation Therapy / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005246:Feedback; D020233:Gait Disorders, Neurologic / Q000503:physiopathology* / Q000534:rehabilitation*; D006801:Humans; D007595:Joint Prosthesis; D007866:Leg / Q000503:physiopathology*; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000503:physiopathology*; D012371:Robotics / Q000295:instrumentation; D013813:Therapy, Computer-Assisted / Q000295:instrumentation