Abstract
The main purpose of this research is to study and develop a robust sonar system for mobile robots. In order to realize the robust system, the sonar which calculates the cross-correlation is used. This sonar transmits wave coded by the pattern that consist of some narrow pulses, then calculates the cross-correlation between the transmitted signal and the received one. But if the sonar can measure multi-obstacles, it may cause erroneous measurement by the wave reflected from each one. The measurement result will keep to include this error, unless the positional relationship of the obstacles changes. It is difficult to navigate a robot safely. In this paper, the necessary conditions for a transmitting signal of the sonar which always obtain an exact result are proposed. Especially we define the proper form of the transmitting signal for the situation, when the cycle of one is varied.
