Author/Editor		Mihelj, M; Munih, M
Title		Minimum effort optimal control of ankle joints for unsupported standing in paraplegia
Type		članek
Source		In: Karčnik T, Veltink P, Jaeger R, editors. IFESS 2002. Proceedings of the 7th annaual conference of the International functional electrical stimulation society; 2002 Jun 25-29; Ljubljana. Ljubljana: Faculty of electrical engineering,
Publication year		2002
Volume		str. 295-7
Language		eng
Abstract		Limited unsupported standing has been restored in a patient with thoracic spinal cord injury through functional electrical stimulation of paralyzed ankle joint muscles and voluntary activity of intact upper trunk musculature. The paraplegic subject was considered an underactuated double inverted pendulum structure with an active degree of freedom in upper trunk and paralyzed ankle joints. An optimal control system for paralyzed ankle muscles was designed that enables the subject to stand without support in sagittal plane. The control system design was based on minimization of a cost function that estimates the effort of ankle joint muscles through observation of the ground reaction force position relative to the ankle joint axis. The designed control system integrates voluntary upper trunk activity and artificial control of ankle joint muscles resulting in a robust standing posture, while minimizing stimulated muscles effort. The benefits of the proposed control are the prolonged standing sessions and the fact that the subject maintains voluntary control over the upper body orientation in space resulting in a simple functional standing.
Descriptors		SPINAL CORD INJURIES PARAPLEGIA ANKLE JOINT GAIT ORTHOTIC DEVICES ELECTRIC STIMULATION THERAPY