Lower-Limb Exoskeleton Reflecting Asymmetric Movements of Femoral Condyle

The human knee has an asymmetric biomechanical structure, with the medial condyle being larger than the lateral condyle to support loads and facilitate diverse movements, thus leading to complex joint movements. These complex biomechanical properties often lead to kinematic misalignment between the knee joint and conventional wearable robots, resulting in restricted movement, unexpected forces, and frame disengagement. To address these limitations, we propose an asymmetric lower-limb exoskeleton with distinct features for the medial and lateral sides of the knee joint to suitably adapt to the knee characteristics. The exoskeleton aims to evenly distribute the load applied to the joint and naturally track its complex movements. The exoskeleton reflects the load-bearing properties of the medial side and the flexibility of the lateral side. Moreover, its frame structure supports both the medial and lateral sides to minimize the load on the knee. Fewer degrees of freedom (DOFs) are applied to the medial side to distribute the load on the joint, while additional DOFs are introduced in the lateral side for flexible movement tracking. Tendon-driven actuation assists knee motion, minimizes the joint volume and weight, and separates the joint from the actuator. Experimental results demonstrate that the proposed exoskeleton improves misalignment issues and complements the wearer's muscle strength during walking, indicating its potential for assistance and enhanced functionality.