Scale Model Automated Road Vehicle

Advanced Transit Association Annual Technical Meeting

January 10, 2010

College Park, Maryland

Robert Johnson

R. E. Johnson ConsultingRockville, Maryland

www.REJConsult.com

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Examples ofSmall Automated Road Vehicles

CyberCab: proposed by 2getthere which developed the first public automated road vehicle (ParkShuttle)

ULTra: scheduled to begin service in 2010 at Heathrow airport, London

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Alternative Interior Layouts and Service Concepts

Typical PRT– Two fixed seats– Two fold-down seats

– Could have pure PRT or some sharing

“Automated Microbus”– Four fixed seats– Two fold-down seats– More suitable for

shared operation

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Choice of Scale

• Want smallest possible vehicle to allow small infrastructure

• Want vehicle big enough to hold useful electronics

• Popular Mini-ITX computer board is 6.7 x 6.7 in. (17 x17 cm)

• Full-sized vehicle will be higher than it’s wide, so height is critical dimension

Choice of Scale (cont.)

• An 8 in. (20 cm) high model would hold Mini-ITX board with 1.3 in (3 cm) allowance for ground clearance and vehicle structure

• Assuming full-sized vehicle is 72 in (183 cm) high, this gives a scale of 8/72 = 1/9

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Why Not Modify Radio Controlled Car?

• R/C car over ten times as fast as needed

• Front track to wheelbase ratio – R/C cars are typically wide for stability

• Custom built model can provide flexible interior space

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Aspects of Vehicle that are Realistically Modeled

• Length, width, height

• Wheelbase, front track

• Ackermann steering – inside front wheel angled more sharply in turns

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Aspects Not Realistically Modeled

• One central rear wheel instead of two wheels and differential

• No suspension – only operates on smooth, level surface

• Motor braking only (will add brake if necessary)

• No power doors or other passenger-related systems

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Initial Hardware Choices

• Mainboard – Intel D945GSEJT with 1 GB ram and 2 GB solid state hard disk

• Low-level microcontroller – Atmel AVR 8-bit microprocessor packaged on small board with motor driver chip by www.pololu.com (Item 1220)

• Steering – standard “radio controlled” servo

• Drive motor – standard DC gearmotor

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For more information about (full size) Automated Road Vehicles, please see:

www.AutoRoadVehicles.com