Gait and Trajectory Optimization for Legged Systems Through Phase-Based End-Effector Parameterization

By Alexander W. Winkler, C. D. Bellicoso, Marco Hutter, Jonas Buchli. IEEE Robotics and Automation Letters, 2018

484 citations recorded by the source corpus.

We present a single trajectory optimization formulation for legged locomotion that automatically determines the gait sequence, step timings, footholds, swing-leg motions, and six-dimensional body motion over nonflat terrain, without any additional modules. Our phase-based parameterization of feet motion and forces allows to optimize over the discrete gait sequence using only continuous decision variables. The system is represented using a simplified centroidal dynamics model that is influenced by the feet's location and forces. We explicitly enforce friction cone constraints, depending on the shape of the terrain. The nonlinear programming problem solver generates highly dynamic motion plans with full flight phases for a variety of legged systems with arbitrary morphologies in an efficient manner. We validate the feasibility of the generated plans in simulation and on the real quadruped robot ANYmal. Additionally, the entire solver software TOWR, which used to generate these motions is made freely available.

Subfields: Biomedical Engineering, Civil and Structural Engineering, Control and Systems Engineering

View Paper: https://www.semanticscholar.org/paper/07e2a6eee7a333e57a08aef3e8628e61527007b4

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Citations in the corpus

Dynamic Locomotion in the MIT Cheetah 3 Through Convex Model-Predictive Control (2018, methodology): “Another common approach is to use both a high-level planner, such as in [10], [11] and a lower level controller to track the plan.”
Crocoddyl: An Efficient and Versatile Framework for Multi-Contact Optimal Control (2019, background): “It has several advantages compared with state-of-the-art approaches in which a whole-body controller compliantly tracks an optimized centroidal trajectory [1], [2], [3], [4], [5], [6].”
Heuristic Planning for Rough Terrain Locomotion in Presence of External Disturbances and Variable Perception Quality (2018, background): “Despite the considerable efforts and recent advances in this ﬁeld [3], [4], [7], [8], optimal planning that takes into account terrain conditions is still far from being executed online on a real platform, due to the computational complexity involved in the optimization.”