Path-Following Autonomous Convoy with Multiple Asynchronous Nodes Kyle Lemons, Heather Macfie, Tri Pho, G. M. Ewout van Bekkum PACMAN Georgia Institute of Technology School of Electrical and Computer Engineering Final Project Presentation ECE 4007, L01 DK2 April 26, 2010

Project Overview Proof of Concept Prototype Autonomous Convoy Vehicles (ACVs) Path-follow Algorithm Modularity Passive Operation Cost: $450 Military convoy applications Reduction of human requirements Supplement to existing navigation systems Alternative to complex inter- vehicle communications

Final Design Motor Steering Servomechanism Photo- Reflectors Battery Bay

Final Design

Altera DE2 FPGA Development Board

Final Design Electronic Speed Control

Final Design I/O Daughter Board

Final Design Steering Servomechanism Electronic Speed Control Left Photo-Reflector Right Photo-Reflector

Final Design GPIO to Altera DE2 FPGA Development Board

Final Design Nintendo Wii Sensor Bar

Final Design IR Band-pass filter

Final Design

I/O Daughter Board Interface between the FPGA and the rest of the system o Photo-Reflector circuit including analog to discrete conversion for odometry o Bidirectional 3.3v to 5v level shifting o IR Camera array with 35 degrees between cameras

IR Camera Array Mounted three infrared cameras taken from Nintendo's Wii Remote o Slightly overlapping field of view between cameras results in an overall system horizontal FOV of 105 degrees

IR Emitter Bar Purchased after-market Sensor Bars o Poor angular response resulted in unreliable tracking when not straight to the camera o Ambiguity arose since the sensor bar could be interpreted as two or four blobs Custom machined sensor bars with extra angled LEDs o Distance between IR LEDs was not sufficient to be reliably tracked at far distances Borrowed the more expensive official Nintendo branded sensor bars from peers

VHDL System Block Diagram

Odometry and Coordinate System Decided to maintain an absolute non-moving coordinate system in the odometry module. o Origin is fixed at midpoint of the rear axle of the car's initial position Rollover is not a concern as millimeter precision still allows for an operating range of more than 4000 kilometers in either axis

Waypointed Path-following Waypoints to the preceding vehicle are generated by calculating their relative displacement in the absolute coordinate system Compensation for the disparity between rear wheel axle and camera position uses orientation information from the odometry module

Waypointed Path-following Waypoints to the preceding vehicle are generated by calculating their relative displacement in the absolute coordinate system Compensation for the disparity between rear wheel axle and camera position uses orientation information from the odometry module

Waypointed Path-following Waypoints to the preceding vehicle are generated by calculating their relative displacement in the absolute coordinate system Compensation for the disparity between rear wheel axle and camera position uses orientation information from the odometry module

Waypointed Path-following Waypoints to the preceding vehicle are generated by calculating their relative displacement in the absolute coordinate system Compensation for the disparity between rear wheel axle and camera position uses orientation information from the odometry module

Waypoint Queue Queue maintains: o Waypoints o Current ACV position o Total sum of all waypoints Relative coordinates o Waypoints relative to previous o Current relative to last passed Absolute coordinates o Reads from odometry o Calculates and uses deltas o Ignores overflow

Adding Future Waypoints Given: o Sum of waypoints o Current position o Position of LED bar Calculate: o Vision - QueueSum + Current Add to end of queue

Waypoint Steering and Throttle Control Compare current and first waypoint output from queue o Gives distance and angle o Constantly updated Steers using linear approximation o Deadband in center o Configurably aggressive turns Throttle gets "kickstart" and returns o Overcome momentum requirement o Sustain slower speed

Waypoint Queue Maintenance Approaching next waypoint o Linear distance approximation o Drops waypoint early o Avoids unstable turning angles Minimum waypoint sum for following o Linear distance approximation o Disables output to ESC o Avoids collisions

Acceptance Testing Overview Path-following o Max deviation from path  Using a fixed set of waypoints, test runs show ACVs pass over waypoints o Follow distance  Images captured from test runs using known distances to verify actual following distance o Turning radius  Driving the lead vechicle around a turn and observing the ACV following performance Modular ACVs o Placing multiple ACVs in a line and driving the lead vehicle while observing following behavior

Path-following Characteristic

In-motion Specifications

The PACMAN

Objectives Path-following o Follow distance: <200 cm o Max deviation from path: <10 cm Autonomous operation o Speed: >40 cm/s o Turning radius: <200 cm Passive operation Modular ACVs

Objectives and Achievements Path-following o Follow distance: <200 cm ~98 cm o Max deviation from path: <10 cm ~9 cm Autonomous operation o Speed: >40 cm/s ~60 cm/s o Turning radius: <200 cm ~133 cm Passive operation Modular ACVs

Objectives and Achievements Path-following o Follow distance: <200 cm ~98 cm o Max deviation from path: <10 cm ~9 cm Autonomous operation o Speed: >40 cm/s ~60 cm/s o Turning radius: <200 cm ~133 cm Passive operation Modular ACVs Demonstrate the feasibility of an autonomous path- following system

Future Work Integration of system into a full-scale convoy Improvements to hardware during full-scale conversion o More accurate and flexible odometry, such as optical flow o More capable vision system o More robust processing unit, including a floating point unit and a trigonometry unit

Questions?