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DOC: Differentiable Optimal Control for Retargeting Motions onto Legged Robots

Published: 26 July 2023 Publication History

Abstract

Legged robots are designed to perform highly dynamic motions. However, it remains challenging for users to retarget expressive motions onto these complex systems. In this paper, we present a Differentiable Optimal Control (DOC) framework that facilitates the transfer of rich motions from either animals or animations onto these robots. Interfacing with either motion capture or animation data, we formulate retargeting objectives whose parameters make them agnostic to differences in proportions and numbers of degrees of freedom between input and robot. Optimizing these parameters over the manifold spanned by optimal state and control trajectories, we minimize the retargeting error. We demonstrate the utility and efficacy of our modeling by applying DOC to a Model-Predictive Control (MPC) formulation, showing retargeting results for a family of robots of varying proportions and mass distribution. With a hardware deployment, we further show that the retargeted motions are physically feasible, while MPC ensures that the robots retain their capability to react to unexpected disturbances.

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    cover image ACM Transactions on Graphics
    ACM Transactions on Graphics  Volume 42, Issue 4
    August 2023
    1912 pages
    ISSN:0730-0301
    EISSN:1557-7368
    DOI:10.1145/3609020
    Issue’s Table of Contents
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    Published: 26 July 2023
    Published in TOG Volume 42, Issue 4

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    Author Tags

    1. differentiable optimal control
    2. differential dynamic programming
    3. motion retargeting
    4. model-predictive control

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