Gait generation and walking stabilization

Due to the complexity of the full dynamics of a humanoid robot, it is common to use simplified models – so called template models – which represent only parts of the robot’s dynamics (typically the Center of Mass (CoM) dynamics). These template models include Inverted Pendulum (IP => Compass Gait Walking), Spring Loaded Inverted Pendulum (SLIP, typically used for running and bio-inspired walking) and Linear Inverted Pendulum (LIP; used in most state-of-the-art walking robots; assumes a constant CoM height). Our work was traditionally based on the LIP. To handle the robots CoM dynamics, we used the concept of 'Capture Point' (introduced by Jerry Pratt [1] in 2006). Recently (see thumbnail of paper below), we extended the concept of 'Capture Point' to 3D, such that the CoM height is no longer constrained to be constant and walking over three-dimensional ground surfaces is facilitated (see figure).

The embedding of the concept of Capture Point into a more general multi-body control framework is part of our current efforts. This multi-body framework will make use of torque-control techniques, allowing for a robust and compliant interaction with the robot’s environment. The control framework will make use of multi-level hierarchies. Thereby, the robot will be able to do “multi-tasking” while in challenging situations all resources are available for the most critical tasks, such as balance.

Englsberger, Ott, and Albu-Schäffer: Three-dimensional bipedal walking control using Divergent Component of Motion. In: IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2013, Tokyo, Japan.

Experiments with TORO