Foot Arch Stiffness-Based Dynamic Plantar Support Control of Human Walking Gait with Active Pneumatic Insoles

The human foot arch plays a significant role in bearing weight, keeping balance, and walking efficiently. In this study, we present a pneumatic arch support insole (PASI) and a foot arch stiffness-based dynamic plantar support control to reduce the metabolic cost of walking. We first obtain the foot arch quasi-stiffness estimation over the gait phase by conducting multiple subject experiments. The design and modeling of the PASI and foot-insole interactions are then discussed. A model predictive control scheme is presented to dynamically regulate the foot arch stiffness over the gait phase by using the active PASI. We validate the system experimentally and conduct multi-subject walking tests. The results show that dynamic plantar support control of the foot arch stiffness reduces the metabolic cost by 7.99% compared to regular walking. In contrast, passive support without dynamic regulation increases the metabolic cost by 6.60%. The new pneumatic insoles and dynamic support method demonstrate promising potential for everyday and medical applications.