1. 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 http://cdr.stanford.edu/biomimetics August 1, 2000 Supported by the Office of Naval Research under grant N00014-98-1-0669 Site visit -- Stanford University, Aug. 9, 2000

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

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

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

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

6. MURI 6 High level: results of experiments on human motion adaptation 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.

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

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

9. MURI 9 Sprawlita Robust, 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 Body in mold, half way through fabrication process Legs with flexures, half way through fabrication process [First SDM hexapod completed 1.25.2000]

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

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

14. MURI 14 Hill climbing: adaptation is needed for best results uphilldownhill Velocity versus slope for different stride frequencies 24 deg. 0 20 40 60 -1001020 Frequency = 11 Hz Frequency = 5 Hz Sprawlita on 24 deg. slope

15. MURI 15 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.) 2:00 - 3:30 High level robotic control

16. MURI 16 Are we “ doomed to succeed ?”* *per Dan Koditschek’s IJRR paper on the theory behind the one legged hopper 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). In other words, Is a springy, damped, hexapod bound to locomote? Guiding Question another Guiding Question:

17. MURI 17 Wrap up Status Programmatic issues Plans Feedback

18. MURI 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. MURI 19 *Shape Deposition Manufacturing 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.

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

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

22. MURI 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.