Path-Following Autonomous Convoy with Multiple Asynchronous Nodes

Kyle Lemons, Heather Macfie,Tri Pho, G. M. Ewout van Bekkum

PACMAN

Georgia Institute of TechnologySchool of Electrical and Computer Engineering

Final Project PresentationECE 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

 

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 systemo Photo-Reflector circuit including analog to discrete

conversion for odometryo  Bidirectional 3.3v to 5v level shiftingo  IR Camera array with 35 degrees between cameras

IR Camera Array• Mounted three infrared cameras taken from Nintendo's Wii

Remoteo 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 LEDso 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

VHDL System Block Diagram

VHDL System Block Diagram

VHDL System Block Diagram

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 Waypointso Current ACV positiono Total sum of all waypoints

• Relative coordinateso Waypoints relative to previouso Current relative to last passed

• Absolute coordinateso Reads from odometryo Calculates and uses deltaso Ignores overflow

Adding Future Waypoints• Given:

o Sum of waypointso Current positiono 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 angleo Constantly updated

• Steers using linear approximationo Deadband in centero Configurably aggressive turns

• Throttle gets "kickstart" and returnso Overcome momentum requiremento Sustain slower speed

Waypoint Queue Maintenance• Approaching next waypoint

o Linear distance approximationo Drops waypoint earlyo Avoids unstable turning angles

• Minimum waypoint sum for followingo Linear distance approximationo Disables output to ESCo Avoids collisions

Acceptance Testing Overview• Path-following

o Max deviation from path Using a fixed set of waypoints, test runs show ACVs

pass over waypointso 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-followingo Follow distance: <200 cmo Max deviation from path: <10 cm

• Autonomous operationo Speed: >40 cm/so Turning radius: <200 cm

• Passive operation

• Modular ACVs

Objectives and Achievements

• Path-followingo Follow distance: <200 cm  ~98 cmo Max deviation from path: <10 cm  ~9 cm

• Autonomous operationo Speed: >40 cm/s  ~60 cm/so Turning radius: <200 cm  ~133 cm

• Passive operation

• Modular ACVs

Objectives and Achievements

• Path-followingo Follow distance: <200 cm  ~98 cmo Max deviation from path: <10 cm  ~9 cm

• Autonomous operationo Speed: >40 cm/s  ~60 cm/so 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 conversiono More accurate and flexible

odometry, such as optical flow

o More capable vision systemo More robust processing unit,

including a floating point unit and a trigonometry unit

Questions?