Out of pure frustration with the fact that my LEGO MINDSTORMS NXT based robot, that was supposed to participate in DTU robocup, turned out to be crap, I thought that I'd try to at least get a decent line follower ready for robocup. This robot is based on my R/C car - an HBX Bonzer Monster Truck XTI - and it will only be able to follow a black line and hopefully also be able to handle line branches.
To start with I was going to build a line sensor based on 8 infrared detectors for 36 KHz modulated infrared light. There were some problems with that so I decided to go for 4 regular infrared photodiodes instead. It is my plan that I will estimate robot position relative to the line by interpolating values between the 4 sensors to get a smooth steering - maybe I will use PD-regulation for this if I have the time.
For controlling the car I'm interfacing the LM-406FB speed controller that came with the car. It is controlled by sending standard servo signals to it, but it does some fancy interpretation of the sequence of signals so one has to be cautious or the car maybe not work the way one intended. For steering the car I'm just using the standard servo that is in the car.
I think maybe I need to get a gear reduction unit for the car, since it goes really fast and I think the robot will be impossible to control at high speed - it tends to skid around when going fast. I'm looking at a 4:1 gear reduction unit which can be bought through eBay.
Friday 28th of March, 2008
I have made the base for the line sensor by cutting a perforated board to a shape that will fit nicely onto the car and can be held in place by a couple af screws that already hold the front bumper in place (I think I might some longer screws though since they just barely hold the board):
Now I just to populate the board with some fancy components that will make the bloody thing work!