Concerted control framework for human-exoskeleton co-adaptation using ground reaction forces.

Effective coordination between the human neuromuscular system and wearable assistive devices remains a key challenge in enhancing gait performance. We propose a concerted control strategy synchronizing biological and artificial actuators using shared feedback. Positioned between centralized (e.g., CPG) and distributed (e.g., reflex-based) control, this approach avoids a central controller by relying on a coordinating signal. Ground reaction force (GRF) emerged as a strong candidate for this role. To implement this concept, we use Force Modulated Compliance (FMC) - a control mechanism that adjusts joint stiffness based on real-time GRF input. FMC has been validated in simulations and robotic platforms, confirming its ability to synchronize joint actuation. We applied this strategy in an active soft biarticular thigh exosuit (BATEX) and tested it in human walking experiments. The GRF-informed controller increased preferred walking speed, advanced the walk-to-run transition, and reduced metabolic cost. These results highlight the effectiveness of GRF-based control in enhancing human-exosuit coordination and aligning assistance with natural gait dynamics. This bioinspired approach offers a scalable framework for real-world locomotion support by harmonizing human and robotic contributions.