Lego Mindstorms Robots

Basic Model

Before beginning to use the robots as a swarm a base model had to be created. After some time we came up with a simple but effective design, this model is shown in the following picture:

As can be seen it uses track tyres and two seperate motors to make sure the robot can move forward, backward and turn. This system was chosen as our design was focussed on simplicity and this model negates the need of a steering system or a swivelling wheel.

After building these basic units we needed to find out what extensions were possible, after some digging in the several boxes of lego bits we found the following actuators/sensors:

• Motor (actuator)
• Infrared distance (sensor)
• Axial Pulse Counter (sensor)
• Pressure sensor (sensor)
• light sensor (sensor)

Ofcourse in the swarm idea communication is a must, this will be further discussed in communication.

Programming

Programming of the RCX 2.0 brick used on the robots can be done in several ways. However the communication of a pc with the brick has to be done using a provided InfraRed Lego Tower. As drivers for this tower are only available for 32 bit-windows versions first a windows emulator needed to be found. After this communication with the brick was possible. Using the software and firmware provided on http://www.robotc.net/download/rcx/ called RobotC and after some fiddling with the drivers and the RCX 2.0 Controller the first program was created.

Communication

The NXT Brick, which is a newer version than the RCX 2.0, is able to communicate using cable or bluetooth. Since we use the RCX 2.0 Bricks, bluetooth communication is not possible.

An infrared interface is built-in in the RCX 2.0, which means that the robots can communicate using infrared. Problems with using infrared is that the communication only works over short distance, the robots should be somewhat pointed at each other and while a robot is sending infrared signals, it can not receive infrared signals and vice versa.

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