A Meniscus-Like Structure in Anthropomorphic Joints to Attenuate Impacts

During robotic locomotion, shock forces from ground impact propagate through the leg and may cause fatigue or damage to joints and sensitive hardware. To attenuate impacts in diverse aspects and directions, multiple approaches, including active control strategies and passive compliant joints, are essential for providing a comprehensive solution. Here, inspired by human knees, a meniscus-like structure was developed for a compliant anthropomorphic joint to provide a complementary way of shock absorption, especially along the axial direction. The proposed meniscus-like structure comprises a pair of curved arms wrapped with preloaded elastic bands whose elongations produce restoring forces against the axial load. This structure simultaneously realized impact attenuation in three aspects: Decreasing contact stress by designing consistently conformal contact interfaces under axial movement; reducing peak impact forces by tuning load-displacement curves to obtain a high-static-low-dynamic nonlinear stiffness; and dissipating energy by hysteresis due to sliding frictions. The effectiveness in attenuating impacts on robotic legs was further verified by both analytical analyses and impact experiments that it outperforms regular elastic buffers at multiple leg configurations. Inserting meniscus-like structures into anthropomorphic joints efficiently utilized the joint space to attenuate axial impacts, complementing the system of interaction safety for the robot community.