Knee-Inspired Hinge Absorbs Longitudinal Impacts to Enhance Robot-Environment Interaction Safety

Abstract

As robots integrate into human society, safe robot-environment interaction has emerged as a growing priority. A promising solution is introducing compliance to existing robots, akin to musculoskeletal systems, to absorb impacts. However, mimicking longitudinal compliance in biological joints remains a challenge due to its complex architecture. Here, adapting the elastic longitudinal movement structure of knee, we incorporate mechanical hinges with a compact buffer structure to enable both simple rotation and effective longitudinal impact absorption. Under longitudinal loading, the buffer structure transmits the limited compression to amplified deformations of elastic elements, and thus produces resistance. The load-displacement curve is tailored for a high-static-low-dynamic stiffness to improve energy absorption efficiency. Drop tests and walking robot demonstrations confirm that our knee-inspired hinge not only mitigates acceleration transmitted to robot body but also reduces ground reaction forces, thus improving robot-environment interaction safety. This work highlights the design paradigm of adapting natural solutions, and holds potential for direct integration into robots.