GOAT: A legged robot with 3D agility and virtual compliance

Abstract

Today's cutting-edge in dynamic legged robots use leg topologies which enable agile behaviors such as running and jumping but most of these dynamic behaviors occur primarily in the robot's sagittal plane. Navigating complex environments, however, requires the use of omni-directional dynamic maneuvers for traversing obstacles in confined spaces. This paper introduces GOAT, the Gearless Omnidirectional Acceleration-vectoring Topology - a novel 3-DoF, 3-RSR leg topology combined with a direct-drive or quasi-direct-drive (QDD) actuation scheme to enable high fidelity proprioceptive force control and multi-modal mobility via high-energy, omni-directional jumping, running, and walking. GOAT's kinematics, mechanical design, actuation, drive electronics, and control algorithms are presented. Experimental results successfully demonstrate a mechanically robust GOAT leg performing a) explosive vertical jumping up to 82 cm b) landing using high fidelity virtual compliance and c) high-speed omnidirectional running/jumping trajectories while mounted on a test rig.