Positioning System for Mobile Robot using LED Marks

Abstract

A sensor system to measure position and the orientation of a mobile robot has been developed. The system measures the robot's position and orientation every 40 msec with an accuracy of 10 mm, in range of 1.5m radius. In this system two or more infra-red LED marks are placed on the ceiling, and a 2D PSD sensor on the mobile robot faces toward them. The PSD senses relative position of a spot light from the mark, and the position and orientation of the PSD are calculated from the relative po-sition of the marks. Since pitching or rolling of the camera affects the 2D measurement, 3D measurement is incorporated. 3D position and orientation are calculated geometrically, using 3 marks. The emission of LED mark is controlled from the robot by sending infra-red light to the marks. Furthermore, lock-in amplifier is used to improve accuracy.