Comparing the Locomotion Dynamics of a
Cockroach and a Shape Deposition
Manufactured Biomimetic Robot
Sean A. Bailey, Jorge G. Cham, Mark R. Cutkosky
Biomimetic Robotics Lab
Stanford University
Robert J. Full
PolyPedal Laboratory
University of California at Berkeley
December 12, 2000
Overview
• Introduction
• Shape Deposition Manufacturing
• Robot Design
• Locomotion Dynamics
• Conclusions
Intro
SDM
Design
Dynamics
Conclusions
Introduction
• Motivation
– Small
– Fast
– Robust
De-mining in an unstructured environment
• Integrated approach
– Biomimetic structures
– Biologically-inspired control
Intro
SDM
Design
Dynamics
Conclusions
Shape Deposition Manufacturing (SDM)
Piston
Fitting
Inlet Valve
Pressure Sensor
Exhaust Valve
Leaf-spring
Manufacturing
Prototype Limb with Embedded Pneumatic Actuator, Sensor,
Leaf Spring and Valves
Intro
SDM
Design
Dynamics
Conclusions
Shape Deposition Manufacturing (SDM)
•
•
•
•
•
Arbitrary geometries
Embedded components
No fasteners
Multi-materials
Tailored compliance
Graded, multi-material 5-bar
Multi-material part
w/ embedded components
Intro
SDM
Design
Dynamics
Conclusions
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
Blaberus discoidalis running over fractal terrain
Intro
SDM
Design
Dynamics
Conclusions
Biological Inspiration
• Control heirarchy
– Passive component
– Active component
Neural System
(CPG)
Sensory
Feedback
(Reflexes)
Feedforward
Motor Pattern
Mechanical
System
(muscles, limbs)
Mechanical
Feedback
(Preflexes)
Environment
Passive Dynamic
Self-Stabilization
Locomotion
Intro
Full and Koditschek, 1999
SDM
Design
Dynamics
Conclusions
Robot Design
Cockroach Geometry
Functional Biomimesis
•Passive Compliant Hip Joint
•Effective Thrusting Force
•Rotary Joint
•Prismatic Joint
Robot Implementation
•Damped, Compliant Hip Flexure
•Embedded Air Piston
Cham et al., 2000, Clark et al., 2001
Intro
SDM
Design
Dynamics
Conclusions
Sprawlita
•
•
•
•
Actuators and
wiring embedded
inside structure
Mass - .27 kg
Dimensions - 16x10x9 cm
Leg length - 4.5 cm
Max. Speed - 55 cm/s
3+ body/sec
• Hip height obstacle traversal
Intro
SDM
Legs with
Compliant
Flexures
Design
2.5 cm
Dynamics
Conclusions
Movie
• Superficially insect-like
• Stable running
• Obstacle traversal
Intro
SDM
Design
Dynamics
Conclusions
Whole Body Dynamics
15
filtered vertical force
unfiltered horizontal force
Force (N)
10
• Force plate
• High speed video
5
0
High
speed
video
markers
-5
450
550
650
750
Time (ms)
Force Plate Data
Force
plate
Locomotion
Direction
High-speed Footage with Markers
Intro
SDM
Design
Dynamics
Conclusions
Animal Running - the SLIP model
SIX-Legged
EIGHT- Legged
Cockroach
TWO-Legged
Crab
Body
Weight
Vertical
Force
FOUR- Legged
Fore-aft
Force
Time
Spring-Loaded
Blickhan
1989
Inverted Pendulum
SLIP
Human
Dog
Cavagna et al., 1975
Intro
SDM
Design
Dynamics
Conclusions
Whole Body Ground Reaction Forces
Spring-Loaded
Inverted Pendulum
(SLIP)
Blaberus
discoidalis
Sprawlita
6
0.025
4
Vertical Force
0.02
2
0.015
Fore-aft Force
.004
2
0
0
-.004
-2
20
Time
Decelerate
Intro
40
60
80
0
Time (ms)
Accelerate
SDM
Decelerate
100
Time (ms)
Accelerate
Design
50
Decelerate
Dynamics
Dragging
Accelerate
Conclusions
Individual leg forces
• Sprawlita drags middle and rear foot
• Individual legs have
functions dissimilar
from cockroach legs
Front Leg
mN
ms
• More questions
– Relative contact time
N
ms
Middle Leg
Hind Leg
12
10
10
0
0
0
-6
0
-6
140 0
60
-6
140 0
4
4
4
0
0
0
-2
0
50
-2
0
50
-2
0
140
20
50
filtered vertical force
filtered horizontal force
Dragging
Intro
SDM
Design
Dynamics
Conclusions
Summary and 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?
Intro
SDM
Design
Dynamics
Conclusions
Future Work
• Sprawley Davidson
• Leg extensions
Valve
• The Sprawlettes
• High level, not real-time
sensor-based control
Cylinder
Prototype with close proximity valve and cylinder
Neural System
(CPG)
Sensory
Feedback
(Reflexes)
Feedforward
Motor Pattern
Mechanical
System
(muscles, limbs)
Mechanical
Feedback
(Preflexes)
Environment
Passive Dynamic
Self-Stabilization
Locomotion
Intro
Double piston extension
SDM
Design
Dynamics
SDM linkage extension
Conclusions
Acknowledgements
• Stanford
– Center for Design Research
– Dexterous Manipulation Lab
– Rapid Prototyping Lab
• Berkeley
– PolyPedal Lab
• Sponsors
– Office of Naval Research
– National Science Foundation
Intro
SDM
Design
Dynamics
Conclusions