Finding a Pose's Distance to a Boundary

In the particle localization algorithm, it is crucial for each particle to know its distance to the closest boundary. That distance is compared to the distance measured by the ultrasonic sensor on the robot. If the difference in distances is small, the particle is given a high weight. The particle is seen as a potentially good approximation of the robot's true pose.

On the other hand, if the difference between the particle's computed distance and the distance recorded by the sensor is great, the particle is given a low weight. The particle is seen as being a poor approximation of the robot's true pose.

In this document, I give the details of how the algorithm in the MCL.java class computes the particle distances.