How does it work with having two ultrasonic sensors (one on each side) what are they used for? To find the distance from the walls? How can they be effectively used?
Thanks,
Putting ultrasonics on the sides can be used for a variety of things. You could use them to help derive the position of your robot if you are using a field mapped into memory or something similar. You can use them see if a robot is next to you. You can use them to stay perpendicular or parallel to certain walls. You can use them to see when the robot is next to a field object. Pretty much anything to do with sensing the distance of an object. They can be especially useful for a holonomic robot (though what is the side on a holonomic robot anyway?)
Team 3018 TECHNA PWN ROBOTICS used those sensors last year. They did good.
We are planning on using sensors this year. We didn’t last year 
I’m flattered :-), however we didn’t end up using ultrasonic sensors in our code at competition (we were using easyC and had timeout issues).
I believe we will consider using them this year though! (Now that we have ROBOTC 
)