Applying Principles from the Locomotion of Small Animals to the Design and Operation of Robots

Transcription

1 bdml.stanford.edu Applying Principles from the Locomotion of Small Animals to the Design and Operation of Robots Mark Cutkosky Center for Design Research Stanford University Stanford, CA 1

2 Origins of bio-inspired design Renaissance discovery: Understanding the body as a marvelous machine Understanding machine elements as examples of limbs, skeletons, muscles and tendons Da Vinci notebooks Da Vinci s programmable spring-powered cart 2

3 Why the recent proliferation of biomimetic designs? 3

4 Biology: better tools for understanding biological systems in detail 1cm Cushions Lamella 1mm Setal shaft 100!m Spatular shaft 2!m Spatula 200nm 4

5 Engineering: better analysis tools, fabrication methods and materials Embedded Component Part Support Deposit (part) 380µm Shape Deposit (support) Embed Shape Synthetic dry adhesive: polymer molds from dual, angled-exposure lithography + micromachining SDM multi-material fabrication 5

6 Behaviors now: discrete, isolated

7 Biomimetics Natural Selection is not Engineering Copy Nature R.J. Full Dept. of Integrative Biology, UC Berkeley Evolution - just good enough 7

8 Lessons from biology for R.J. Full bio-inspired design: 1. Reduce Complexity - Collapse Dimensions 2. Manage Energy 3. Use Multifunctional Materials - Tuned, Integrated & Robust 4. Exploit Interaction with Environment

9 Curse of Dimensionality R.J. Full Designs appear hopelessly complex No detailed history of design plans 72 DOF 230 Muscles? Neurons Full and Ahn, 1995

10 Reducing dimensionality: the sagittal leg spring R.J. Full SIX- Legged EIGHT- Legged Cockroach Crab Full and Tu, 1990 Blickhan and Full, 1987 TWO- Legged FOUR- Legged Human vertical force fore-aft force time B o d y W e i g h t Cavagna et al., 1977 Dog

11 Lessons from Biology 1. Reduce Complexity - Collapse Dimensions 2. Manage Energy 3. Use Multifunctional Materials - Tuned, Integrated & Robust 4. Effective Interaction with Environment 11

12 Shape Deposition Manufacturing (SU/CMU) Embedded Component Part Support Deposit (part) Shape Shape Deposit (support) Embed 12

13 Robot leg with embedded actuator, valves, sensor and circuitry Piston Leaf-spring spacer Valves Sensor and circuit Embedded components 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 Sequence of geometries for fabrication Finished parts [Cham et al. 1999] 13

14 SDM: part number reduction, increased robustness, controlled compliance, damping Left: Kinematic prototype of linkage with 31 parts Center: SDM linkage with thick flexures, 1 part Right: SDM linkage with fabric-reinforced flexures 14

15 Biological Inspiration Control heirarchy Passive component Active component Neural System (CPG) Sensory Feedback (Reflexes) Mechanical System (muscles, limbs) Feedforward Motor Pattern Mechanical Feedback (Preflexes) Environment Locomotion Passive Dynamic Self-Stabilization Full and Koditschek,

16 Solution Approach: Analyze and Optimize Dynamic Model in ADAMS 3D model with geometric similarity to robot - Rigid body with six legs - Linear pneumatic actuators (with valve delays) - Spring-damper rotational joints in sagittal plane - Friction and ground contact models 16

17 Example: mapping from passive mechanical properties of insects to biomimetic robot structures Study biological materials, components, and their roles in locomotion. Servo Motor Study Shape Deposition Manufacturing (SDM) materials and components. viscoelastic material! Displacement Input Force Output Roach leg stiff material! Models of material behavior and design rules for creating! SDM structures with desired properties! 17

18 Example: 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. 6 4 Servo Motor Data Model Hysteresis Force (mn) Roach leg Displacement Input Force Output position (mm) Models of material behavior and design rules for creating! SDM structures with desired properties! 18

19 2. Bioinspiration for smooth climbing F N F T Bioinspiration how do they do it? Biology examine literature, work with biologists Hypotheses regarding the principles at work refinement Analysis test and analyze results Robotics implementations of principles SDM technology 19

20 Principles for climbing with dry adhesion 1. Hierarchical compliance 2. Directional adhesives 3. Distributed force control 20

21 Compliant peeling toe Tendon (steel cable) Hard polyurethane Teflon tube Soft polyurethane Directional Polymeric Stalks Living hinge Fiber mesh embedded 21

22 Anisotropic gecko adhesion Gecko setae dragging with curvature Dragging against curvature Colored: Normal force Gray: Shear force Force (mn) mn of Adhesion Time (s) Force (mn) No Adhesion Time (s) 22

23 Gecko Force-Space Results Autumn et al. JEB 2006 loaded against stalk angle: Coulomb friction Load, then pull off at various angles, and measure force! limit curve ) k l a t s / NFn m ( e c r o F l a m r o N µ m 600 µ m 700 µ m safe region compression Ft adhesion Tangential Force (mn/stalk) loaded with stalk angle: adhesion ~ tangential stress 23

24 Force Control optimal strategy for inverted surface Johnson-Kendall-Roberts Frictional Adhesion F N F N F N F N F T F T F T F T Rear Foot Flipped Generalization: Formulate as linear programming problem to control foot orientation & internal forces for arbitrary loading conditions [Santos, JAST09]. 24

25 Control foot orientation + internal forces 25

26 Directional adhesion facilitates control of forces for smooth, efficient locomotion Contact force limits Normal Force Desired attach/detach state Safe force region Desired loaded state Tangential force 26

27 Current work: compliant hierarchical structures 380µm The gecko s hierarchical adhesive system spans length scales from 1 cm to 100 nm. 20 µm wedges atop 380 µm directional stalks (SEM photo) Synthetic adhesives require hierarchical, directional compliance to conform to rough surfaces and distribute loads over large areas.

28 Stanford hierarchical, directional adhesive!"#$%&'()*+,'*-.$#+/0)*12+3!,/4+!,/+ 5"%#'6$78$2+ 9"$#)#%:"%)*+/-20$.+ ;<+28

29 Bio-Inspired? 29

30 How to get nearly uniform loading over the entire toe, with tolerance to a range of loading angles? Phalanges Fluid-filled sac Lateral digital tendon Lateral digital tendon Lamellae (Russell J. Morphology 1982) Lamella

31 Loading angles: alignment compensation loads 4 leg version of RiSE platform 4 kg gross 31

32 Scaling to larger areas and loads: tiled arrays compliant support adhesive structure pulley Approx. 80cm 2 rigid tile pressure plate pressurized sac tile tendon main tendon 40 kg

33 Scaling to larger areas and loads: results 33

34 Acknowledgements Robots in Scansorial Environments (RiSE) This work has been supported by the RiSE program (DARPA BioDynotics N C-8045) with additional support from NSF NIRT (ID ) and COINS (UCB)