Experimental and Theoretical Investigations on the Control of Limbs by the Functional Electrical Stimulation of Muscles

Abstract

Problems occuring during the development of control systems within orthoses for paralyzed patients are analysed. Experimental results obtained from a simple closed-loop position control system showed that more sophisticated control stratenies are necessary to remove the deficiencies of actual control systems.With regard to the implication of appropriate control strategies a model for the “electrically stimulated musc1es-limb-load” system is derived. An adaptive control strategy for the Functional Electrical Stimulation is then described and, in view of the implementation on a digital computer, a feasible performance of this strategy is presented. The effects of different modulation techniques on the feasibility of control systems were also investigated. Pulse frequency modulation systems are found more robust than pulse amplitude modulation systems.