Ultrasonic relative positioning for multi-robot systems

Coordination of a group of mobile robots is facilitated when they are able to determine their positions relative to each other. Instead of using an absolute positioning approach with fixed beacons in the operating environment, we have developed a ultrasonic relative positioning system that allows each robot to perceive the distance and the angle of other nearby robots in relation to its own position. The system is based on time-of-flight evaluation of ultrasonic pulses and a RF communication link. The system has a precision of 8 mm and of 3deg over a 6.7 m range. This paper describes the system, its performance and its use on four Pioneer 2 robots moving in formation.