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Biomimetic Robots for Robust Operation in Unstructured Environments

Biomimetic Robots for Robust Operation in Unstructured Environments. M. Cutkosky and T. Kenny Stanford University R. Full and H. Kazerooni U.C. Berkeley R. Howe Harvard University R. Shadmehr Johns Hopkins University. Site visit -- Stanford University, Aug. 9, 2000.

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Biomimetic Robots for Robust Operation in Unstructured Environments

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  1. Biomimetic Robots for Robust Operation in Unstructured Environments M. Cutkosky and T. KennyStanford University R. Full and H. KazerooniU.C. Berkeley R. HoweHarvard University R. Shadmehr Johns Hopkins University Site visit -- Stanford University, Aug. 9, 2000 Supported by the Office of Naval Research under grant N00014-98-1-0669 http://cdr.stanford.edu/biomimetics August 1, 2000

  2. High-Level Control Project approach: Low-Level Control Biomimetic Robots MURI Study mechanical properties and “preflexes” in insects. Study locomotion in insects, adaptation in humans. Create structures with tailored materials properties and embedded components. Shape DepositionManufacturing 2

  3. High-Level Control MURI Guiding questions What passive properties are found in Nature? Preflexes: Muscle and Exoskeleton Impedance Measurements (Berkeley Bio.) Low-Level Control What properties in mechanical design? Biological implications for Robotics Basic Compliant Mechanisms for Locomotion (Stanford) Effects of compliance in joints (Harvard, Stanford) Fast runner with biomimetic trajectory (Berkeley ME) Fabrication How should properties be varied for changing tasks, conditions ? Matching impedance for unstructured dynamic tasks (Harvard, Johns Hopkins)

  4. Low level:mapping from passive mechanical properties of insects to biomimetic robot structures Study biological materials, components, and their roles in locomotion. Study Shape Deposition Manufacturing (SDM) materials and components. viscoelasticmaterial Hysteresis loop @10Hz stiff material Models of material behavior and design rules for creating SDM structures with desired properties

  5. Guiding questions How is Compliance used in Locomotion? MURI Low-Level Control High-Level Control Berkeley & Stanford: Measurements of Cockroach Locomotion What Compliance Strategies in Human-level Tasks? Fabrication Harvard & Johns Hopkins: Learning and Compliance Strategies for Unstructured Environments

  6. Long-latency feedback adapts to force field, through adaptation of the forward model. Primitive motions can be combined for complex behavior. The tool used, a parametric approximator, can also be used in model-based control of robots. Next step: test the approach on a robot -- vary walking parameters. High level:results of experiments on human motion adaptation

  7. MURI Guiding questions Low-Level Control High-Level Control How do we build robust biomimetic structures and systems? Shape deposition manufacturing of integrated parts, with embedded actuators and sensors (Stanford) Fabrication How do we build-in tailored compliance and damping? Structures with functionally graded material properties (Stanford) Effects of Compliance in simple running machine (Stanford, Berkeley ME)

  8. Piston Leaf-spring spacer Valves Embedded components Sensor and circuit Detail of part just after inserting embedded components 7. Top support 6. Part material 5. Embedded parts 4. Part material 3. Embedded sensor 2. Part material 1. Support material Finished parts Sequence of geometries for fabrication Fabrication process example:creating a robot leg

  9. SprawlitaRobust, Dynamic Locomotion with a Hand-Sized Robot • Cockroach inspired design • 0.27Kg mass, 15 cm long • Robust, dynamic locomotion • Speed over 2.5 body/sec • Hip height (3 cm) obstacle traversal • Shape Deposition Manufactured [First SDM hexapod completed 1.25.2000] Body in mold, half way through fabrication process Legs with flexures, half waythrough fabrication process

  10. 9:15 - 10:30 Low level biological mechanisms • New results on measurements of muscles, exoskeleton, compliance, damping. Comparison with artificial muscles (Full et al. ~40min) • Gecko foot adhesion (Liang, Kenny ~15 min) • Discussion of low level mechanisms 10:30 – 12:15 High level biological control and adaptation • Cockroach locomotion results and implications (Full et al. ~ 30 min.) • New measurement techniques (Bartsch ~ 10 min.) • Adaptation and impedance matching strategies (Howe, Shadmehr ~50 min)

  11. 12:45 - 1:15 Low level robotic mechanisms • Introduction to fabrication issues (Cutkosky ~ 5 min) • SDM robot fabrication – overview and results (Clark ~20 min) 1:15 - 2:00 Lab tours and live demonstrations

  12. Robot leg fabrication for low-level biomimetic stabilization Cockroach Geometry Functional Biomimesis Shape Deposition Manufactured Robot flexure • Passive Compliant Hip Joint • Effective Thrusting Force • Damped, Compliant Hip Flexure • Embedded Air Piston

  13. <1998 Sept 99 Nov 99 Jan-June 99 Looking ahead eSprawl ? Roach Sprawlita(Jan 25) Sprawl Franken sprawl Sprawlettes Robots 3D linkages SDM Pneumatic leg with components Sensors Sprawl Family History last year’s site visit today MiniSprawl (power, compliance) Flexures (bend @hip only)

  14. uphill downhill Hill climbing: adaptation is needed for best results Velocity versus slope for different stride frequencies 60 24 deg. Frequency = 5 Hz Sprawlita on 24 deg. slope 40 Frequency = 11 Hz 20 0 -10 0 10 20

  15. 2:00 - 3:30 High level robotic control • Introduction to control issues (Cutkosky ~ 2 min). • Alternative robot locomotion results and implications (Motohide, Kazerooni ~30 min) • Robot locomotion modeling and implications for design, control, adaptation (Bailey, Cham ~30 min) • SDM robot locomotion experiments and ongoing work (Cham, Froehlich ~20 min.)

  16. another Guiding Question: Are we “doomed to succeed?”* In other words, Is a springy, damped, hexapod bound to locomote? • In one sense, yes: locomotion will almost certainly occur. • And stable locomotion is not difficult to achieve, in practice or in simulation. • But fast, efficient locomotion is another matter. It is quite sensitive to minor changes in environmental parameters (e.g. slope, terrain) and robot parameters (e.g. leg angles, stride frequency, compliance). *per Dan Koditschek’s IJRR paper on the theory behind the one legged hopper

  17. Wrap up • Status • Programmatic issues • Plans • Feedback

  18. Status (last site visit 9.2.99) • Detailed characterization of passive (fixed) and active components (adjustable) of preflexes in cockroach. • Gecko foot adhesion characterized using new micromachined sensors. New sensor for cockroach leg forces being designed. • SDM* environment used to create small robot limbs with embedded sensing and actuation and functionally graded material properties. • SDM robot limbs and compliant non-SDM robot undergoing testing and comparison with results from insect legs. • Compliant whole-arm-manipulator test-bed and minimum impedance control strategies demonstrated. Human impedance testing in progress. • Model of human motor control learning tested and validated. • Fast walker with biomimetic foot trajectory designed and tested; SDM compliant limb retrofit underway. *Shape Deposition Manufacturing

  19. Status (today 8.9.2000) • Detailed characterization of passive (fixed) components in cockroach and correlations with SDM* structures • Detailed characterization of cockroach muscles under working conditions and correlations with artificial muscle • Gecko foot adhesion characterized using new micromachined sensors. MEMS sensors for insect leg forces being tested. • First small hexapedal robots created using SDM* -- ahead of schedule • run at over 2.5 body lengths/second (0.4 m/second) • climb belly-height obstacles (3 cm) • climb slopes to 24 degrees • exhibit robust, stable locomotion without complex feedback • Models of human motor adaptation and impedance regulation tested and validated. Testing on robot nearly ready. *Shape Deposition Manufacturing

  20. Gecko adhesion in the news... The article in Nature evidently caught the public eye: • Scientific American • ABC today • In local papers • and many more...

  21. Sprawl robots in the news... MiniSprawl, from Robosapiens (MIT Press)

  22. Plans for next year • Focus on sensing and adaptation to variations in slope, terrain. • Continue work on insect measurement with new sensors • Continue development of alternative platforms, including un-tethered designs (eSprawl). • Funds permitting: design and fabricate a batch of Sprawlettes for distribution to members of this MURI and to others (e.g., Koditschek) for analysis, testing, comparison with animals, and validation of control & adaptation algorithms.

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