For the purpose of guiding a movable robot on a wide and flat floor like that of a gymnasium, for example, we propose a specially designed guiding sign. It consists of a cylinder with four slits, and a fluorescent light placed right on the axis of the cylinder. Two of the slits are parallel to each other, and the other two are angled. A robot takes an image of the sign with a TV camera. After the thresholding operation, we have four bright sets of pixels which correspond to the four slits of the cylinder. By measuring the relative distances between these four points, we can compute the distance and the angle to the direction of the sign of the robot using simple geometrical computations. We have built a movable robot and a sign. Using a personal computer with image processing capability, we have evaluated the accuracy of the proposed position and angle measurement and have compared the experimental results with theoretical error analysis. The data show good agreement between the analysis and the experiments. Finally, we have carried out several trajectory-following control experiments.
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