BSAC ©2003 Fall IAB. Confidential Information. Not to be made public without permission from UC Regents.

Localization for Off-the-Shelf Distributed Robots (CotsBots)

Sarah BergbreiterKris Pister

September 9, 2003

BSAC ©2003 Fall IAB. Confidential Information. Not to be made public without permission from UC Regents.

History of CotsBots – Building More of Less

Solar Cell Array

CCRs

XLCMOS

IC

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Similar Robot Platforms

• Khepera II– > $2500 each

• Robomote (USC)– custom hardware

• Millibots (CMU)– custom hardware

• CotsBots (UCB)– standard hardware and

software platform– ~$200

BSAC ©2003 Fall IAB. Confidential Information. Not to be made public without permission from UC Regents.

CotsBots: Hardware

• Atmel ATMEGA103 – 4 Mhz 8-bit CPU– 4KB RAM– 128KB Program Memory

• RFM TR1000 radio– 50 kb/s – ASK– Focused hardware acceleration

• Network programming

• Atmel ATmega8L– 1-8MHz CPU– 8KB Program Memory– 1KB RAM

• 2 Discrete H-Bridge Circuits– Speed and Direction Control

of Motors– up to 4A, 30V load

• Same 51-pin bus

Mica Mote MotorBoard

Kyosho Mini-Z RC Car Platform

Additional sensor boards available including ADXL202e, magnetometer, light, temp, sound, etc.

BSAC ©2003 Fall IAB. Confidential Information. Not to be made public without permission from UC Regents.

CotsBots: Software• Use Open-Source NesC

language and code provided by TinyOS group (available on SourceForge)

• Abstract as much as possible from the application writer (developer should focus on algorithms)

• Remain flexible by keeping component-based design

RobotApplication

Clock Robot

MotorPacket

Motor Software

MotorPacket

MZ, Tank, ...

Motor1 MZServo

ADC

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CotsBots Sample Application: Robot Diffusion

T--------z - 1

K

T--------z - 1

K

30

. . .

ROBOT MOTOR

+

_

+_

+

DISTANCE/LOCATION SENSOR

_

FEEDBACK AND CONTROL LOOP

Conceptual Vision of Robot Diffusion – could be used for mapping or maximal sensor network coverage

Controller designed for diffusion along 1DOF – only tested in simulation thus far

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Fisheye LensHigh Power

LED

PhotoBeacon IC

Localization: PhotoBeacon Concept• Triangulation v. Trilateration• Use light/lens/detector system on each

robot to determine relative angles• Design an IC with ~1o resolution and 5-

10m ranges with conventional off-the-shelf LEDs

• IC should be computationally simple• Additional benefits of optical

communication and obstacle detection

d

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PhotoBeacon: System Architecture

256x1Analog

Mux

.....

..Programmable Gain Amplifier (KSJP20)

Photodiodes in circular array

3-wire bus

Differential Analog Output

190o field-of-view lens

5o

Lens

LED

Low divergence, high power LEDs

PhotoBeacon IC (detector)

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PhotoBeacon IC: Final LayoutPhotoDiodes

3-wire bus block

1Mbps Optical Receiver

~4mm

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PhotoBeacon IC: Preliminary Results

• Tested ¼ ring PhotoBeacon IC• All blocks are functional,

including optical receiver, multiplexer, and 3-wire bus

• 3-D manipulator used to position fisheye lens over IC

• Difficulty in focusing results in an intensity graph instead of binary output

LaserLens+IC

LabView

DAQ Box

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Conclusions and Future Work

• Continue testing PhotoBeacon localization system• Apply lessons learned to new PhotoBeacon IC utilizing

latest optical receiver from Brian Liebowitz and the SALT project in KSJP20

• Investigate algorithms for PhotoBeacon system based on Lance Doherty’s work in Convex Position Estimation in Wireless Sensor Networks. Infocom 2001

• Integrate PhotoBeacon system with CotsBots’ hardware and software