2005 Keeper
   
The omni directional keeper is controlled by two RCX's and programmed in NQC. Two RCX's are used to accommodate the 4 motors and 6 sensor ports needed to run the keeper. One RCX controls the motors and sensors on the front and back, and the second RCX controls motors and sensors on the sides of the RCX. If information needs to be passed between the master and slave, a message is sent.
 
The four-wheeled omni directional configuration is used because it does not require the computations that are necessary for three-wheel systems and also proves getting to the ball to be smoother, quicker and on the whole more efficient. The omni directional wheels that are on the keeper are different to the striker's omni wheels. The omni wheels on the keeper come stock with Lego shafts already cast in them. They are thinner and have a larger diameter compared to the striker's wheels. They do not provide as much surface area contact between wheel and ground as the striker's wheels but this is not an issue due to the small ground it covers and the relative simplicity of its path.
 
The keeper has a range of sensors for tracking the ball, reading the grey scale and defining direction. To track the ball the keeper uses a 'FlyEye' and a total of 6 light sensors (2 in parallel on each side except the front). The grey scale is read by another 2 light sensors connected in parallel facing down, underneath the robot. A Wiltronics compass is used for direction.
 
The compass is used for a small search rotation that results in the keeper always remaining facing down the field. If the robot is somehow turned around to face the wrong way it will automatically spin back to the right direction. This proves effective for constant monitoring of the ball. If the ball is beside or in front of the robot, it will manoeuvre around the ball and chase it down the field until it loses sight, then attempt to return to its previous position.
 
The FlyEye was given to us at RoboCup Junior Queensland and has 7 mounted photodiodes facing around 180 degrees. The FlyEye supplies the RCX with two different values. These two values indicate either direction or intensity of the ball. The two values switch about ten times a second when the light source is steady. It is currently available from 'IME' in Brisbane and as far as we know, will appear at Educational Experience soon.

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