1. System Architecture Event-Based Modular Hierarchical
Modules “subscribe” to the information they need and receive it as soon as it is obtained
Modular
Took under one hour to reconfigure the system to use the Applanix Position/Orientation System
Hierarchical
e.g. speed control algorithm does not need to deal with brake motor power output; only with desired tension
if (desiredSpeed < 0.5) // Stop the vehicle { AcceleratorPedal.Position = 0; Brakes.DesiredTension = 65; }
Nov. 17, 2005

2. Applanix Position/Orientation System
GPS Antennas
Up to 200 Hz output of current vehicle position
Uses inertial measurements and rear wheel odometry data during GPS outages
Distance Measurement
Inertial Measurement
Nov. 17, 2005

3. Applanix System Calibration
The system uses multiple Kalman filters to optimally combine the many sensor inputs:
GPS position data – Wheel rotation measurement
Inertial data – GPS heading data
GPS heading provides accuracy of degrees when perfectly aligned
Our antennas were rotated by about 1.5 degrees from their calibration point, creating a GPS offset
After recalibrating the system, we had a perfect run
Nov. 17, 2005

4. Why we stopped after nine miles
We store a list all obstacles we are currently concerned about
Each time a new obstacle is received, we add it to this list
Each obstacle needs to have its relative position updated each time we get new vehicle position information
It gets these updates by subscribing to the RelativeFrameUpdated event
When we have passed an obstacle by more than twenty feet, we remove it from the list
However, we were not unsubscribing the obstacle from the RelativeFrameUpdated event
Thus, nine miles down the road, our computer was still processing a bush it saw near the beginning of the course!
 C# is a powerful language, but it has to be used carefully
Nov. 17, 2005