Design of high-speed robot leg based on double four-bar mechanism

High-speed ground motion is inevitably related to high acceleration and large loads on the leg. This imposes a challenge in robot leg design. This paper introduces an novel electric-drive robot leg based on double four-bar mechanism which is used to transform continuous rotation of motors to back and forth motion of the leg. This scheme avoids the ever-changing status of frequent acceleration and deceleration of the motors, and thus may reach higher rotation speed. Then the crank trajectory is optimized by inserting a piece of uniform motion, and the rocker trajectory is interpolated to obtain the optimized foot trajectory. These make the peak angular velocity decreased by 18.9% and the motion stability improved. In addition, the multiple lighten treatment using finite element analysis software is adopted to decrease leg’s mass and rotary inertia under the premise of guaranteeing the safety of leg strength. Considering the fact that a tendon–bone co-location architecture not only provides compliance in the leg, but can also reduce bone stresses caused by bending on structures, we attach an elastic tendon to the ankle to reduce the pulse stress on the leg. Finally, the prototypes of robot leg are built to conduct the no-load walking experiment in the self-developed test bench of one-legged movement. The experiment results demonstrate that the highest walking speed can reach 1 m/s, which is 2.2 times leg length per second. Meanwhile, the peak torques of hip, elbow motor are markedly reduced by attaching the elastic tendon. These results verify the correctness and validity of the proposed design in this paper. © 2019, Cefin Publishing House. All rights reserved.