With two weeks to go until the SparkFun AVC competition, the good news it that I now have basic autonomous navigation working. Here's a short video demonstration.
The next challenge is to make the robot avoid obstacles. This is important since there will be several large barrels on the course. After many hours trying to get obstacle avoidance working with maxbotix ultrasonic sensors, I have switched to a Parallax Ping sensor. This is working much more reliably. Here's a photo with the new sensor mounted.