Control System for
Scale Model PRT Vehicle
Advanced Transit Association Annual Technical Meeting
January 13, 2013
College Park, Maryland
Robert Johnson
R. E. Johnson Consulting
Rockville, Maryland
www.REJConsult.com
Model of PRT Vehicle that
Steers Itself on a Flat Surface
• Ultra
• 2getthere Masdar
Vehicle
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Why Use Scale Model to Develop
Control Software?
• More realistic than pure simulation
• Avoids assumptions that are not physically
possible
• Can demonstrate system operation
• Suitable for computer vision based control, which
is independent of scale
• Modern electronics are small enough to fit inside
1/12th scale model – 12.5 in (32 cm) long
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PRT Scale Model – Right Side
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PRT Scale Model Showing Lateral
Sensor Ahead of Front Wheel
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External Appearance
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Autonomous Vehicle with Three
Levels of Computer Control
• Central control (like taxi dispatcher, not
safety related)
• On-board computer vision system running
Linux -- provides longitudinal control
• On-board microcontroller (only vital system)
– Monitors vision computer
– Provides lateral control by using sensor to
measure distance to sidewall
– Controls steering, drive motor, brakes, etc.
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Lateral Control Demonstration
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Updates Since Last Year’s Technix
• Finalized vehicle design except vision
system
• Electro/mechanical aspects of vision
system complete (power supply, etc.)
• Achieved basic vehicle following using
netbook as vision computer
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Small, Inexpensive, Low-Power ARM
Computers for Vision Processing
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Small Multi-Core ARM Computers for
Less Than $200 with Linux Support
• Pandaboard
• Texas Instruments
• 4.5”x4.0” (114x102 mm)
• i.MX6 Q Sabre Lite
• Freescale Semiconductor
• 3.3”x3.3” (83x83 mm)
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Current Status of Vision-Based
Longitudinal Control
• OpenCV vision software operational on x86 PC
running Ubuntu Linux
• Webcam support not an issue for x86 Ubuntu
• Basic vehicle following using color tracking of
target on rear of lead vehicle
• As temporary measure, communicate with
microcontroller by changing brightness of portion
of PC display
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Vehicle Following
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Future Work – Requires Mostly
OpenCV and Linux Skills
• Port existing software to small ARM
computer
• Establish suitable communications link
between vision computer and
microcontroller
• Merging
• Station operations
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