Line Walking and Balancing for Legged Robots with Point Feet

TL;DR

This paper introduces a novel balance controller enabling legged robots to walk along narrow lines by balancing on two feet, demonstrated through simulation and preliminary experiments on a quadruped robot.

Contribution

The paper presents a new low-dimensional virtual model-based controller specifically designed for line walking and balancing on nearly null support regions in legged robots.

Findings

Successfully simulated a quadruped crossing a 6 cm wide bridge.

Demonstrated preliminary experimental balancing on two legs under disturbance.

Showed the controller's effectiveness in highly constrained environments.

Abstract

The ability of legged systems to traverse highly-constrained environments depends by and large on the performance of their motion and balance controllers. This paper presents a controller that excels in a scenario that most state-of-the-art balance controllers have not yet addressed: line walking, or walking on nearly null support regions. Our approach uses a low-dimensional virtual model (2-DoF) to generate balancing actions through a previously derived four-term balance controller and transforms them to the robot through a derived kinematic mapping. The capabilities of this controller are tested in simulation, where we show the 90kg quadruped robot HyQ crossing a bridge of only 6 cm width (compared to its 4 cm diameter spherical foot), by balancing on two feet at any time while moving along a line. Lastly, we present our preliminary experimental results showing HyQ balancing on two legs while being disturbed.