# A Platform for Local Interactions between Robots in Large Formations

AI and Robotics

Nov 2, 2013 (4 years and 8 months ago)

136 views

A Platform for Local
Interactions between Robots
in Large Formations

Jerry B. Weinberg

Jeffrey R. Croxell

A Platform for Local Interactions between

Robots in Large Formations

Problem

swarm

formation

A Platform for Local Interactions between

Robots in Large Formations

Background

Fredslund & Mataric 2002

Balch & Arkin 1998

Reynolds 1987

Farritor & Goddard 2004

A Platform for Local Interactions between

Robots in Large Formations

Formation Control

Utilize
reactive

robot control strategies

closely couple sensor input to actions

Treat the formation as a
cellular automaton

lattice of computational units (
cells
)

each cell is in one of a given set of states

governed by a set of rules

A Platform for Local Interactions between

Robots in Large Formations

A desired formation,
F
, is defined as a
geometric description…

i.e., mathematical function

F

← y = ax
2
, where
a

is some constant

Formation Control

F

← y = ax
2

A Platform for Local Interactions between

Robots in Large Formations

A robot is chosen as the
seed
, or starting
point, of the formation.

Formation Control

F

← y = ax
2

seed

A Platform for Local Interactions between

Robots in Large Formations

Formation Control

The desired location on the formation is determined by
calculating a relationship vector from
c,

where
c

is the formation
-
relative position (
x
i
,
y
i
) of the robot,

… and the intersection of the function
F

and a circle
centered at
c

r
, where
r

is the distance to
maintain between neighbors in the formation.

c

← (
x
i
,
y
i
)

r
2

← (x
-
c
x
)
2

+ (y
-
c
y
)
2

F

← y = ax
2

r

r

seed

A Platform for Local Interactions between

Robots in Large Formations

Relationships and states are communicated locally to
robots in the seed’s neighborhood, which propagates
changes in each robot’s neighborhood in succession.

Using sensor readings, robots attempt to acquire and
maintain the calculated relationship with their neighbors.

Formation Control

c

← (
x
i
,
y
i
)

r
2

← (x
-
c
x
)
2

+ (y
-
c
y
)
2

F

← y = ax
2

r

r

seed

A Platform for Local Interactions between

Robots in Large Formations

c

← (
x
i
,
y
i
)

r
2

← (x
-
c
x
)
2

+ (y
-
c
y
)
2

Despite only local communication, the calculated
relationships between neighbors results in the
overall organization of the desired global
structure.

Formation Control

F

← y = ax
2

seed

A Platform for Local Interactions between

Robots in Large Formations

Thus, it follows that a movement command sent
to a single robot would cause a chain reaction in
neighboring robots, which then change states
accordingly, resulting in a global transformation.

Formation Control

seed

A Platform for Local Interactions between

Robots in Large Formations

Formation Control

A Platform for Local Interactions between

Robots in Large Formations

Formation Control

Likewise, to change a formation, a seed
robot is simply given the new geometric
description, and the process is repeated.

F

← y = 0

seed

A Platform for Local Interactions between

Robots in Large Formations

Robot Platform

Each robot features:

a
Scooterbot II

base

differential steering system

an
XBC v2

microcontroller

executes formation control algorithm

a color
-
coding system and color camera

visual identification and tracking of neighbors

an
XBee

sharing information within a robot’s neighborhood

A Platform for Local Interactions between

Robots in Large Formations

Robot Platform

Scooterbot II

base

precision cut double
-
decker base

rigid expanded PVC

strong, but very light

2" risers for additional decks

differential steering system

http://www.budgetrobotics.com/

A Platform for Local Interactions between

Robots in Large Formations

Robot Platform

XBC v2

microcontroller

executes formation algorithm

back
-
EMF PID motor control

fast charging

~1 hour to fully charge

http://www.botball.org/

A Platform for Local Interactions between

Robots in Large Formations

Robot Platform

Color
-
coding system

visual identification and
tracking of neighbors

Color camera

multi
-
color, multi
-
blob
simultaneous color tracking

Start
y

Stop
y

ID
y

Start
y

-

ID
y

ID
y

-

Stop
y

Start
y

Stop
y

Start
y

-

Stop
y

Robot
ID

= ID
max

* (Start
y

-

ID
y
) / (Start
y

-

Stop
y
)

A Platform for Local Interactions between

Robots in Large Formations

Robot Platform

XBee

sharing state information within a robot’s neighborhood

ZigBee/IEEE 802.15.4

specification

up to 65,535 nodes on a network

support for multiple network topologies

low duty cycle

long battery life

collision avoidance

retries and acknowledgements

128
-
bit AES encryption

http://www.maxstream.net/

A Platform for Local Interactions between

Robots in Large Formations

References

Balch, T. & Arkin R. 1998. “Behavior
-
based Formation Control for Multi
-
robot Teams” IEEE Transactions on
Robotics and Automation, 14(6), pp.
926
-
939.

Bekey G., Bekey, I., Criswell D.,
Friedman G., Greenwood D., Miller D.,
& Will P. 2000. “Final Report of the
NSF
-
NASA Workshop on Autonomous
Construction and Manufacturing for
Space Electrical Power Systems”, 4
-
7
April, Arlington, Virginia.

Farritor, S.M., & Goddard, S. 2004.
“Intelligent Highway Safety Markers”,
IEEE Intelligent Systems, 19(6), pp. 8
-
11.

Fredslund J., & Mataric, M.J. 2002.
“Robots in Formation Using Local
Information”, The 7th International
Conference on Intelligent Autonomous
Systems, Marina del Rey, California.

Reynolds, C.W. 1987. “Flocks, Herds,
and Schools: A Distributed Behavioral
Model, in Computer Graphics”, 21(4)
SIGGRAPH ’87 Conference
Proceedings, pages 25
-
34.

Tejada S., Cristina A., Goodwyne P.,
Normand E., O’Hara R., & Tarapore,
S. 2003. “Virtual Synergy: A Human
-
Robot Interface for Urban Search and
Rescue”. In the Proceedings of the
AAAI 2003 Robot Competition,
Acapulco, Mexico.

Questions?