Abstract
An ultrasonic range finger that an autonomous robot is equipped with is required to find landmarks at a long distance for navigation, and to detect objects at a short distance for obstacle avoidance. Especially, it is very important to detect an obstacle at a very short distance that has the high danger of a collision. But it is difficult to detect the obstacle at a very short distance using conventional long-range ultrasonic range finders. Because the conventional finders receive a directly transmitted wave and a reflected wave by the obstacle at same time. This paper shows the theoretical and experimental results about wide-range ultrasonic range finders that are able to measure both short range and long range.
