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This is a sketch in which the location of the robot is calculated continuously in an absolute manner by using the ultrasonic sensor, which measures the distance from the walls. The errors of the sensor are too large to be able to reconstruct the two rows of squares.

In this sketch the robot uses a mixture of the imagined position and calculating the absolute distance with the ultrasonic sensor. The distance is calculated only when the robot passes through the angles 0 or 270 that mark the positions of the nearest walls.

Here, the robot is using only its imagination, It only calculates its position to move to the first point. From then on, it only imagines how much he has moved by taking in account the number of turns that its wheel performed and the angle used in those movements. We can observe that the angle measurements with the magnetic sensors, also have a high level of error, which produces that the drawing steers to the left as it goes downwards.

Drawing the error. We can observe in the image how the final result is produced. Left, the drawing created by the robot. Right, the blue lines connect the points that should have been drawn together.

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Carlos Molinero. Architect + PhD. in computer science. Contact: mail@carlosmolinero.com