TAMOLS: Terrain-Aware Motion Optimization for Legged Systems

Terrain geometry is, in general, nonsmooth, nonlinear, nonconvex, and, if perceived through a robot-centric visual unit, appears partially occluded and noisy. This article presents the complete control pipeline capable of handling the aforementioned problems in real-time. We formulate a trajectory o...

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Bibliographic Details
Published in:IEEE transactions on robotics Vol. 38; no. 6; pp. 3395 - 3413
Main Authors: Jenelten, Fabian, Grandia, Ruben, Farshidian, Farbod, Hutter, Marco
Format: Journal Article
Language:English
Published: New York IEEE 01.12.2022
The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subjects:
Computational modeling
Contact force
Dynamics
Friction
Legged locomotion
Legged robots
Motion control
Numerical stability
optimization and optimal control
perceptive locomotion
Robot control
Stability criteria
Terrain
Trajectory optimization
ISSN:1552-3098, 1941-0468
Online Access:Get full text
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Summary:Terrain geometry is, in general, nonsmooth, nonlinear, nonconvex, and, if perceived through a robot-centric visual unit, appears partially occluded and noisy. This article presents the complete control pipeline capable of handling the aforementioned problems in real-time. We formulate a trajectory optimization problem that jointly optimizes over the base pose and footholds, subject to a height map. To avoid converging into undesirable local optima, we deploy a graduated optimization technique. We embed a compact, contact-force free stability criterion that is compatible with the nonflat ground formulation. Direct collocation is used as transcription method, resulting in a nonlinear optimization problem that can be solved online in less than ten milliseconds. To increase robustness in the presence of external disturbances, we close the tracking loop with a momentum observer. Our experiments demonstrate stair climbing, walking on stepping stones, and over gaps, utilizing various dynamic gaits.
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ISSN:1552-3098
1941-0468
DOI:10.1109/TRO.2022.3186804