A Position Measurement Method for a Miniature Mobile Robot Using Three Moving Landmarks

Abstract

We studied a position measurement system for a small autonomous mobile robot. The system uses three line laser projectors above the robot, and the line laser projectors move on three linear stages. Three position sensitive detectors (PSDs) arranged in a triangle are carried on the robot. The line laser beams are irradiated on the active surface of the PSDs, and the robot’s position is obtained by the lasers’ positions and PSDs’ outputs. In our previous method, the position of the robot is measured by the positions of movable lasers and PSD outputs. Since the system required that the laser beams be irradiated on the center the PSDs, a real-time measurement is difficult. In this paper, the lasers’ positions are obtained by the elapsed time of the position measurement. By measuring the time when the PSD output becomes zero, the position of the robot is calculated with the PSDs’ outputs and the timer output. The preliminary experimental results are discussed. In our experimental conditions, the measurement accuracy is smaller than 0.01 mm.