Upgrade to Pro — share decks privately, control downloads, hide ads and more …

Template Composition for Synthesis of New Behaviors from Simpler Constituents

Avik De
October 31, 2018
3

Template Composition for Synthesis of New Behaviors from Simpler Constituents

This talk was given at the IROS 2018 templates workshop https://iros18wsdll.netlify.app/talks/

Avik De

October 31, 2018
Tweet

Transcript

  1. Template Composition for Synthesis of
    New Behaviors from Simpler Constituents
    Avik De
    Post-doctoral scholar; Ph.D. with Daniel Koditschek (2017), University of Pennsylvania
    Cofounder & CTO, Ghost Robotics (Philadelphia)
    ARL/GDRS RCTA W911NF-1020016
    AFRL grant FA865015D1845 (subcontract 669737-1)
    ONR/OSD Vanevar Bush Fellowship N00014-16-1-2817

    View Slide

  2. Legged robotics in the field: status update
    Vision-60 (30kg, 12dof)
    Research Scientific Commercial
    Minitaur (6kg, 8dof direct drive)
    Jerboa (3kg, 4dof)

    View Slide

  3. What do we want from our control algorithms? (long-term view)
    [Raibert (1980’s)]
    [DRC (2017)]
    Robust against
    • State perturbations
    • Feedback control, MPC, …
    • Parameter perturbations
    • Modeling errors
    • “robust” control, model reduction
    Verifiable
    • Repeatability, accountability
    • Convergence
    • Local/global stability
    Generalizable solns
    • Across tasks
    • Across platforms
    • “online” solution, …
    …Modularity
    [Seyfarth (2015) [Schaal (2006)]

    View Slide

  4. Inspiration from Biology
    [Ting et. al. (2016)]
    Biology Robotics
    Motor abundance Multiple solutions
    Preferred patterns of
    coordination are
    modulated across
    movements
    Reuse modules across
    behaviors
    Facilitate multifunctionality
    (same muscle, different
    function)
    Manage complexity of
    high-dimensional robots
    [Ting (2007)]

    View Slide

  5. • Gait control synthesis using compositions of templates
    • Jerboa [ICRA 2015] [ISRR 2015] [IROS 2016] [IROS 2018]
    • Minitaur [IJRR 2018]
    • Role of design in enabling compositional control
    • Direct-drive machines [RAL 2016]
    • Multifunctional design [in prep]
    • Analysis for understanding when it works, and providing guarantees
    • Hybrid averaging [IJRR 2018]
    • Symmetry paper [in prep]
    Outline = Research Agenda

    View Slide

  6. Gait control synthesis using
    compositions of templates

    View Slide

  7. Applications
    [Shamsah, De, Kod (IROS 2018)]
    [De, Kod in IJRR (2018)]
    Minitaur bounding, trotting, pacing, pronking Jerboa tailed hopping
    [De, Kod (ICRA 2014)]

    View Slide

  8. Control as reduction (anchoring) + composition
    Classical (analytical) view
    Templates are themselves compositions
    [Full and Koditschek (1999)] “Templates and anchors…”

    View Slide

  9. Reduction (anchoring) exposes templates: reactive walking

    View Slide

  10. Reduction (anchoring) exposes templates: hopping, running

    View Slide

  11. Designing robots for
    compositional control

    View Slide

  12. Role of design in enabling simpler control strategies
    Design for composition?
    [Shamsah, De, Koditschek (IROS 2018)]
    Tuesday,
    October 2,
    2018
    18:00-
    18:50
    Session
    TuETS4
    Chair Yoshida,
    Eiichi
    (National Inst.
    of AIST), Co-
    chair Ramirez-
    Amaro,
    Karinne (Inst.
    for Cognitive
    Systems.
    Tech. Univ.
    München)
    Legged
    Robots II −
    TuETS4
    Room 2.L2
    Analytically-guided tailed hopper design—IROS 2018
    [Raibert (1980s)]

    View Slide

  13. Hierarchical synthesis strategy
    [Shamsah et al (IROS 2018)] [Libby et al (TRO 2016)]
    [Libby et. al (Nature 2012)]

    View Slide

  14. Preliminary observations about parameter regions
    Orthogonal parameter gradients
    • “Decoupled parameters”
    • Cross-product instantiation
    Feasible parameter regions
    • Composition must lie in intersection
    • Affects possible template behaviors
    [De, Kod (in prep)]
    Parameter space
    Contours of
    performance metric

    View Slide

  15. Why does it work?

    View Slide

  16. (Hybrid) dynamical averaging as a verification tool
    Hybrid averaging
    [De, Burden, Kod in IJRR (2018)]
    [Raibert (1986)]
    Q: When can you do this?
    [De (2017)]

    View Slide

  17. • Not merely symmetry of
    trajectories; property of dynamics
    [Altendorfer et. al. (2004)]
    • “Reversible systems” ≈
    “Hamiltonian systems” [Lamb &
    Roberts (1998)]
    • Analytical benefit: find the
    “neutral” limit cycles
    Time-reversal symmetry
    [Raibert (1986)]
    or, why averaging is particularly suited to analysis of locomotion
    Neutral orbit
    Non-neutral
    [Raibert (1986)]

    View Slide

  18. Putting together coupled systems as if they were decoupled
    Only terms with even* symmetry remain:
    Shank energy →
    Leg angle energy →
    Using all the prior ideas [De & Koditschek (in prep)]
    — Full dynamics
    — Averaged

    View Slide

  19. Thanks for your time

    View Slide