Hybrid Half-Gaussian Selectively Adaptive Fuzzy Control of an Actuated Ankle–Foot Orthosis

To control an actuated ankle–foot orthosis (AAFO) during walking, a selectively adaptive hybrid fuzzy control employing particle-swarm optimization was used in conjunction with a Lyapunov-theory-based adaptive fuzzy-logic control. Adaptation (a computationally expensive process) was performed only when the tracking error exceeded a certain half-Gaussian function. The stability of the overall closed-loop system was proved using Lyapunov theory. The proposed control strategy was verified both by simulations and by experiments with five healthy subjects. The proposed control strategy significantly reduced both tracking error and required control torque when compared to other competing control schemes.