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/

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
2. Legged robotics in the field: status update Vision-60 (30kg, 12dof) Research Scientific Commercial Minitaur (6kg, 8dof direct drive) Jerboa (3kg, 4dof)
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)]
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)]
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
6. Gait control synthesis using compositions of templates
7. Applications [Shamsah, De, Kod (IROS 2018)] [De, Kod in IJRR (2018)] Minitaur bounding, trotting, pacing, pronking Jerboa tailed hopping [De, Kod (ICRA 2014)]
8. Control as reduction (anchoring) + composition Classical (analytical) view Templates are themselves compositions [Full and Koditschek (1999)] “Templates and anchors…”
9. Reduction (anchoring) exposes templates: reactive walking
10. Reduction (anchoring) exposes templates: hopping, running
11. Designing robots for compositional control
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)]
13. Hierarchical synthesis strategy [Shamsah et al (IROS 2018)] [Libby et al (TRO 2016)] [Libby et. al (Nature 2012)]
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
15. Why does it work?
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)]
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)]
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
19. Thanks for your time