fischertechnik COMPUTING ROBO MOBILE SET 8 Mode D'emploi page 44

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The Tracker
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• The main program finally looks like
this:
• You will find the finished program
under Lightseeker.rpp.
• Use a flashlight as light source. Take
care that the beam of light is not
focused too narrowly so that both
photosensors are illuminated by the
light source. Please note that in a
very bright space another source of
light such as sunlight through a big
window might outshine
flashlight. This might cause the
robot to drive right past your lamp
toward the brighter light.
■ Search and pursuit are fundamental characteristics
inherent to intelligent beings. With the Lightseeker you
built and programmed a robot that is able to react to direct
signals from its target.
With the Tracker we apply another search principle. Instead of
a targeted approach to the source of light we mark a black line
that the robot is supposed to follow. This assignment can be solved relatively
easily by using the phototransistors. They measure the light reflected by the marking and the motors are
corrected accordingly. To make sure this functions accurately the line is illuminated with the lamp. Take
care to avoid an unfavorable configuration that causes stray light from the lamp to throw off the photo
sensors. The light focusing properties of the incandescent bulb's optical lens is especially helpful in this
regard.
Now follow the construction manual to put together the Tracker Model.
A s s i g n m e n t 1
● First write the subprogram used to find the track. In order to do this the robot should
turn around once.
● If it is unable to find a track it should drive straight for a short while and then start
searching again. The phototransistors are queried for track recognition.
● If the robot has detected a track it should follow it.
● If the track has run out or the robot lost it, due to a sharp directional change for
example, it should start a new search.
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