Adaptive Biarticular Exosuit Assistance for Faster and More Efficient Walking

This study presents an adaptive biarticular thigh exosuit (BATEX) that enhances walking efficiency and speed through bioinspired actuation and a self-tuned, ground reaction force (GRF)-driven controller. The BATEX employs Force-Modulated Compliance (FMC) to coordinate hip and knee assistance via artificial biarticular muscles, with users tuning a single control gain to personalize assistance. Twelve healthy adults participated in experiments evaluating preferred walking speed (PWS), preferred transition speed (PTS), metabolic cost, and muscle activation under no-exosuit (NE), zero-torque (ZT), and assisted (EXO) conditions. Compared with NE, BATEX increased PWS by 14.3% and PTS by 9.0% ( ${p} \lt {0}.{01}$ ). Furthermore, BATEX assistance can also reduce net metabolic cost at PWS of unassisted walking by 9.5% relative to NE and 17.9% relative to ZT ( ${p} \lt {0}.{01}$ ). Electromyography revealed significant reductions in lower-limb muscle activation, particularly in the biceps femoris, gluteus maximus, and gastrocnemius. Moreover, positive exosuit mechanical power was correlated with changes in metabolic cost, indicating that mechanical assistance effectively offset biological energy expenditure. These results demonstrate that GRF-driven, user-tuned biarticular assistance effectively improves walking economy and gait speed in healthy adults, providing a framework that could be adapted in future studies to enhance mobility in broader populations.