Mechatronic Design and Control of a Rigid-Soft Hybrid Knee Exoskeleton for Gait Intervention

Knee exoskeletons have gained increasing attention for gait training and intervention. The effectiveness of conventional rigid exoskeletons is degraded by bulkiness, high inertia, and joint misalignment. The soft configurations relax the constraints on the knee joint, thus circumvent the misalignment issue, and reduce the system size and weight. However, the soft exoskeletons sacrifice the load sharing capability from rigid support, and also the mechanical stop for constraining joint working range to avoid unsafe knee hyperextension. This article presents a novel rigid-soft hybrid exoskeleton to provide bidirectional interventions safely for knee joint motion. The design is lightweight (1.2 kg to wear), avoids the rigid rotation center that induces knee joint misalignment, has minimal impact on normal walking kinematics, and is able to provide support to the human body. A gait intervention strategy is designed under the hybrid model of human and exoskeleton. Comprehensive experiments are conducted to demonstrate the capability of the presented exoskeleton on gait intervention.