Comparing the Locomotion Dynamics of a Cockroach and a Shape Deposition Manufactured Biomimetic Robot

Sean A. Bailey, Jorge G. Cham, Mark R. CutkoskyBiomimetic Robotics Lab

Stanford University

December 12, 2000

Robert J. FullPolyPedal Laboratory

University of California at Berkeley

Intro SDM Design Dynamics Conclusions

Overview• Introduction

• Shape Deposition Manufacturing

• Robot Design

• Locomotion Dynamics

• Conclusions

Intro SDM Design Dynamics Conclusions

Introduction

• Motivation– Small– Fast– Robust

• Integrated approach– Biomimetic structures– Biologically-inspired control

De-mining in an unstructured environment

Intro SDM Design Dynamics Conclusions

Prototype Limb with Embedded Pneumatic Actuator, Sensor, Leaf Spring and Valves

Leaf-spring

Piston

Pressure Sensor

Fitting

Inlet Valve

Exhaust Valve

Shape Deposition Manufacturing (SDM)

Manufacturing

Intro SDM Design Dynamics Conclusions

• Arbitrary geometries

• Embedded components

• No fasteners

• Multi-materials

• Tailored compliance

Shape Deposition Manufacturing (SDM)

Graded, multi-material 5-bar

Multi-material partw/ embedded components

Biological Example• Death-head cockroach Blaberus discoidalis

• Fast– Speeds of up to 10 body/s

• Rough terrain– Can easily traverse fractal terrain of

obstacles 3X hip height

Intro SDM Design Dynamics Conclusions

Blaberus discoidalis running over fractal terrain

Intro SDM Design Dynamics Conclusions

Biological Inspiration• Control heirarchy

– Passive component

– Active component

Full and Koditschek, 1999

MechanicalSystem

(muscles, limbs)

Environment

MechanicalFeedback(Preflexes)

SensoryFeedback(Reflexes)

Neural System(CPG)

FeedforwardMotor Pattern

Passive DynamicSelf-Stabilization

Locomotion

Intro SDM Design Dynamics Conclusions

Cockroach Geometry

•Passive Compliant Hip Joint•Effective Thrusting Force

Functional Biomimesis

•Damped, Compliant Hip Flexure•Embedded Air Piston

Robot Implementation

Robot Design

•Rotary Joint•Prismatic Joint

Cham et al., 2000, Clark et al., 2001

Intro SDM Design Dynamics Conclusions

Sprawlita• Mass - .27 kg

• Dimensions - 16x10x9 cm

• Leg length - 4.5 cm

• Max. Speed - 55 cm/s 3+ body/sec

• Hip height obstacle traversal

Legs with CompliantFlexures

Actuators andwiring embeddedinside structure

2.5 cm

Intro SDM Design Dynamics Conclusions

Movie

• Superficially insect-like

• Stable running

• Obstacle traversal

Whole Body Dynamics• Force plate

• High speed video

Intro SDM Design Dynamics Conclusions

High-speed Footage with Markers

Force Plate Data

450 550 650 750-5

0

5

10

15

Time (ms)

For

ce (

N)

filtered vertical force unfiltered horizontal force

LocomotionDirection

Force plate

Highspeed videomarkers

Highspeed videomarkers

Animal Running - the SLIP model

Intro SDM Design Dynamics Conclusions

Human

TWO-Legged

Cockroach Crab

LeggedEIGHT-

Dog

LeggedFOUR-VerticalForce

BodyWeight

ForceTime

Fore-aft

Blickhan 1989

SIX-Legged

Spring-LoadedInverted Pendulum

SLIP

Cavagna et al., 1975

Time

Intro SDM Design Dynamics Conclusions

Whole Body Ground Reaction Forces

0.015

0.02

0.025

-.004

0

.004

20 40 60 80

2

4

6

-2

0

2

0 50 100

Spring-LoadedInverted Pendulum

(SLIP)

Vertical Force

Fore-aft Force

Blaberusdiscoidalis

Sprawlita

Time (ms) Time (ms)

Decelerate Accelerate Decelerate Accelerate DecelerateAccelerate

Dragging

Individual leg forces• Sprawlita drags middle and rear foot

• Individual legs have functions dissimilar from cockroach legs

• More questions– Relative contact time

Intro SDM Design Dynamics Conclusions

ms

mN

0-6

140

0

12

0 60 140-6

0

10

0-6

140

0

10

0 50-2

0

4

0 50-2

0

4

0 20 50-2

0

4

ms

N

Front Leg Middle Leg Hind Leg

filtered vertical force filtered horizontal force

Dragging

Intro SDM Design Dynamics Conclusions

• Sprawlita– Physically robust

– Operationally robust

– Open loop

• Comparing locomotion dynamics suggests design improvements– Foot drag - longer stroke

• If more SLIP-like...• faster?

• more efficient?

• more robust?

Summary and Conclusions

Intro SDM Design Dynamics Conclusions

Future Work• Sprawley Davidson

• Leg extensions

• The Sprawlettes

• High level, not real-time sensor-based control

MechanicalSystem

(muscles, limbs)

Environment

MechanicalFeedback(Preflexes)

SensoryFeedback(Reflexes)

Neural System(CPG)

FeedforwardMotor Pattern

Passive DynamicSelf-Stabilization

LocomotionDouble piston extension SDM linkage extension

Prototype with close proximity valve and cylinder

Valve

Cylinder

Intro SDM Design Dynamics Conclusions

Acknowledgements• Stanford

– Center for Design Research

– Dexterous Manipulation Lab

– Rapid Prototyping Lab

• Berkeley– PolyPedal Lab

• Sponsors– Office of Naval Research

– National Science Foundation