Three-Dimensional Dynamic Running with a Point-Foot Biped based on Differentially Flat SLIP

This paper presents a novel framework for point- foot biped running in three-dimensional space. The proposed approach generates center of mass (CoM) reference trajectories based on a differentially flat spring-loaded inverted pendulum (SLIP) model. A foothold planner is used to select touch down location that renders optimal CoM trajectory for upcoming step in real time. Dynamically feasible trajectories of CoM and orientation are subsequently generated by a simplified single rigid body (SRB) model based model predictive control (MPC). A task-space controller is then applied online to compute whole- body joint torques which embeds these target dynamics into the robot. The proposed approach is evaluated on physical simulation of a 12 degree-of-freedom (DoF), 7.95 kg point-foot bipedal robot. The robot achieves stable running at at varying speeds with maximum value of 1.1 m/s. The proposed scheme is shown to be able to reject vertical disturbances of 8 N. s and lateral disturbance of 6.5 N. s applied at the robot base.