Swift Running Robot Leg: Mechanism Design and Motion-Guided Optimization

Toward swift running on biped robots, this article provides a complete design approach for a robot leg featuring reduced rotational inertia and introduces a novel mechanic optimization scheme to meet severe mechanical requirements. We adopt a ballscrew driving setup to design the inertia-reduced driving for the leg. When designing the actuator's transmission to satisfy the joints' speed and torque demands, it is challenging to specify the mechanism parameters because their effects are nonlinear and highly coupled. To address this problem, we invite a novel idea that uses target motion trajectories to guide the optimization process and make the mechanism fit the motion best. For that purpose, the joint space position is divided into a high-speed and high-torque region by analyzing the target joint trajectories. Then, the optimization scheme is formulated according to this division to obtain the optimized joint position-transmission ratio curve. The proposed technique can dramatically reduce the torque demands, making a good tradeoff in reconciling the dilemma between the joint speed and torque demands. Finally, the proposed scheme is validated with a 7 km/h running motion on the biped robot BHR-T, enhancing the robot with the desired athletic capacities.