<title>Steps toward triaural perception</title>

Abstract

By virtue of their low cost and simplicity, ultrasonic sensors are widely used in rangefinding applications. However, when a more detailed map of the environment is needed, as is the case in mobile robotics, the simple-minded use of a single ultrasonic sensor is often insufficient. In this paper we propose a measurement system composed of three ultrasonic sensors, one transmitting and three receiving, to overcome these problems. By combining the information from the three sensors we can accurately determine the position, both in distance and bearing, of all objects in the field of view taking one single snapshot of the scene. Within the limits derived in this paper, it is even possible to discriminate between different types of reflectors. To get these results we have to find the reflections belonging to the same object in the signals received by the three sensors, a problem analogous to the correspondence problem in stereo- vision. We present a maximum likelihood approach as a solution to this problem. A realistic scene will be used to compare our sensor with the traditional ultrasonic ranging sensor.