Walking on Partial Footholds Including Line Contacts with the Humanoid Robot Atlas
This addresses the challenge of robust locomotion on uneven terrain for humanoid robots, representing an incremental advance in dynamic walking algorithms.
The paper tackles the problem of enabling humanoid robots to walk on partial footholds like small stepping stones and line contacts, presenting a method that dynamically explores and estimates contact surfaces to achieve stable walking without prior knowledge of the terrain.
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.