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

Model of PRT Vehicle that Steers Itself on a Flat Surface Ultra 2getthere Masdar Vehicle

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 1/12 th scale model – 12.5 in (32 cm) long

PRT Scale Model – Right Side

PRT Scale Model Showing Lateral Sensor Ahead of Front Wheel

External Appearance

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.

Lateral Control Demonstration

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

Small, Inexpensive, Low-Power ARM Computers for Vision Processing

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)

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

Vehicle Following

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