Trajectory Optimization for Wheeled-Legged Quadrupedal Robots Driving in Challenging Terrain
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Date
2020-07
Publication Type
Journal Article
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yes
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Abstract
Wheeled-legged robots are an attractive solution for versatile locomotion in challenging terrain. They combine the speed and efficiency of wheels with the ability of legs to traverse challenging terrain. In this letter, we present a trajectory optimization formulation for wheeled-legged robots that optimizes over the base and wheels' positions and forces and takes into account the terrain information while computing the plans. This enables us to find optimal driving motions over challenging terrain. The robot is modeled as a single rigid-body, which allows us to plan complex motions and still keep a low computational complexity to solve the optimization quickly. The terrain map, together with the use of a stability constraint, allows the optimizer to generate feasible motions that cannot be discovered without taking the terrain information into account. The optimization is formulated as a Nonlinear Programming (NLP) problem and the reference motions are tracked by a hierarchical whole-body controller that computes the torque actuation commands for the robot. The trajectories have been experimentally verified on quadrupedal robot ANYmal equipped with non-steerable torque-controlled wheels. Our trajectory optimization framework enables wheeled quadrupedal robots to drive over challenging terrain, e.g., steps, slopes, stairs, while negotiating these obstacles with dynamic motions.
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Publication status
published
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Journal / series
Volume
5 (3)
Pages / Article No.
4172 - 4179
Publisher
IEEE
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Methods
Software
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Date collected
Date created
Subject
RSL; NCCR; Legged robots; Wheeled robots; Motion planning; Optimization and optimal control
Organisational unit
03737 - Siegwart, Roland Y. / Siegwart, Roland Y.
09570 - Hutter, Marco / Hutter, Marco
02284 - NFS Digitale Fabrikation / NCCR Digital Fabrication