Legged robots are advancing towards being fully autonomous as can be seen by the recent developments in academia and industry. To accomplish breakthroughs in dynamic whole-body locomotion, and to be robust while traversing unexplored complex environments, legged robots have to be terrain aware. Terrain-Aware Locomotion (TAL) implies that the robot can perceive the terrain with its sensors, and can take decisions based on this information. The decisions can either be in planning, control, or in state estimation, and the terrain may vary in geometry or in its physical properties. TAL can be categorized into Proprioceptive Terrain-Aware Locomotion (PTAL), which relies on the internal robot measurements to negotiate the terrain, and Exteroceptive Terrain-Aware Locomotion (ETAL) that relies on the robot’s vision to perceive the terrain. This thesis presents TAL strategies both from a proprioceptive and an exteroceptive perspective. The strategies are implemented at the level of locomotion planning, control, and state estimation, and are using optimization and learning techniques. The first part of this thesis focuses on PTAL strategies that help the robot adapt to the terrain geometry and properties. At the Whole-Body Control (WBC) level, achieving dynamic TAL requires reasoning about the robot dynamics, actuation and kinematic limits as well as the terrain interaction. For that, we introduce a Passive Whole-Body Control (pWBC) framework that allows the robot to stabilize and walk over challenging terrain while taking into account the terrain geometry (inclination) and friction properties. The pWBC relies on rigid contact assumptions which makes it suitable only for stiff terrain. As a consequence, we introduce Soft Terrain Adaptation aNd Compliance Estimation (STANCE) which is a soft terrain adaptation algorithm that generalizes beyond rigid terrain. STANCE consists of a Compliant Contact Consistent Whole-Body Control (c3WBC) that adapts the locomotion strategies based on the terrain impedance, and an online Terrain ...
On Terrain-Aware Locomotion for Legged Robots
21.04.2021
doi:10.15167/fahmi-ahmed-mohamed-shamel-bahaaeldeen_phd2021-04-21
Hochschulschrift
Elektronische Ressource
Englisch
DDC: | 629 |
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