HyperLeg: Biomechanics-Inspired High-DOF Leg and Toe Mechanism for Highly Dynamic Motions

A human foot with high degrees of freedom (DOF) that has multi-DOF toe joints and a two-DOF ankle provides multiple benefits, such as increased stride length and walking speed, impact mitigation, and enhanced balancing. However, creating such mechanisms for legged robots has been challenging due to increased complexity, heavy weight, and vulnerability to impact. In this paper, a novel leg and toe mechanism inspired by human biomechanics, featuring a one-DOF knee joint, two-DOF ankle joint, and one-DOF toe joint, is developed. All actuators are located at the proximal part of the thigh frame to minimize the distal mass. High payload timing belts and unique linkage mechanisms are utilized in the transmission to achieve high backdrivability and high joint stiffness. Actuation torques are intentionally coupled inspired by human anatomy, enduring the high propulsive force to the ground for dynamic movements, such as jumping. The implemented leg and toe mechanisms weigh 8.16 kg, and the height from the ground to the hip center is 786 mm. The proposed mechanism has been proven to be effective through force test and distance jump experiments.