Walking on Partial Footholds Including Line Contacts with the Humanoid Robot Atlas

TL;DR

This paper introduces a novel method enabling the Atlas humanoid robot to walk on partial footholds like small stones and line contacts by exploring contact surfaces and using momentum control.

Contribution

The method allows humanoid robots to walk on partial and uncertain footholds without prior knowledge, combining exploration and momentum control for improved stability.

Findings

Successful walking on small footholds demonstrated experimentally.

Enhanced balance using upper body angular momentum during partial contact stepping.

Performance limitations identified and discussed.

Abstract

We present a method for humanoid robot walking on partial footholds such as small stepping stones and rocks with sharp surfaces. Our algorithm does not rely on prior knowledge of the foothold, but information about an expected foothold can be used to improve the stepping performance. After a step is taken, the robot explores the new contact surface by attempting to shift the center of pressure around the foot. The available foothold is inferred by the way in which the foot rotates about contact edges and/or by the achieved center of pressure locations on the foot during exploration. This estimated contact area is then used by a whole body momentum-based control algorithm. To walk and balance on partial footholds, we combine fast, dynamic stepping with the use of upper body angular momentum to regain balance. We applied this method to the Atlas humanoid designed by Boston Dynamics to walk over small contact surfaces, such as line and point contacts. We present experimental results and discuss performance limitations.