Building the robot

The robot needs three light sensors and one compass, as it is now. It has to be stable. The main idea for the robot are from the manual LEGO Mindstorm Education Base set 9797. As you can see at the pictures below, the lower structure of the robot car is similar to 9797.

Picture of the robot

The NXT only has 4 sensor ports, one of those has to be used for the compass, which leads to three ports for the light sensors. These are placed in the corners of the robot car and as vertical as possible. Below is a drawing of placement. The center of the car is between the front wheels. If there were more sensorports we would use them, because the algorithm gets more precise the more sensors it has.

Drawing of the sensor placement, sensor 1-3 is light sensor. Seen from the top

The light sensors is stabilized so the the vibration of them is minimize and the measurement is more stable. The positions of the light sensors should be as far as possible (without making the construction unstable and to big for the map) from the robot center. This is to make the sensors change more while turning the robot. Otherwise the shouldn't be to far from the robots center because we would easily touch the border of the environment, which is not anymore represented in the map.