Cooperative Control of Hybrid FES-Exoskeleton: Dynamic Allocation

Hybrid assistive systems that integrate functional electrical stimulation (FES) and robotic exoskeletons offer a promising approach for neurorehabilitation. However, control of these systems remains challenging due to actuator redundancy and heterogeneous assistive device constraints. This paper introduces a novel cooperative control architecture based on dynamic allocation to address actuator redundancy in a hybrid FES-exoskeleton system. The proposed approach employs a modular control allocator that redistributes required control torques between FES and exoskeleton actuators in real time, accounting for device-specific limitations and user preferences (e.g., prioritizing one assistive device over another). Within this framework, the high-level controller determines the total assistance level, while the allocator dynamically distributes control effort based on these assistive device-specific considerations. Simulation results and experimental validation demonstrate the method's effectiveness in resolving actuator redundancy in the FES-exoskeleton system while reflecting actuator constraints, indicating its potential for deployment in clinical studies to assess patient acceptance and clinical efficacy.