Preliminary developments towards closed-loop FES-assistance of posture and gait

This article presents a general approach and some on-going developments to restore coordination between unaffected and paretic limbs in the context of functional electrical stimulation (FES) assisted posture and gait. The principle is to ensure posture global control through local muscle control when considering functional assistance. This supposes that both natural and artificial controllers are provided with sufficient information concerning the global state of the system. In other words, voluntary movements of unaffected limbs should cooperate with artificially controlled deficient limbs in order to guarantee an optimal behaviour and posture. The approach is described from a theoretical and technical aspect and some experimental results are presented. The system is based on a Body Area Network (BAN) embedding both sensor and actuator (electrical stimulators) nodes. In the present paper only surface FES is discussed through two main applications: gait assistance in post-stroke hemiplegia and sit-to-stand transfer in complete paraplegia. The approach is transposable to other applications as well as to implanted neuroprosthetics from a conceptual point of view.