Scanned monocular sonar and the doorway problem

A sonar system is presented that relies on scanning a single ultrasonic transducer and measuring echo amplitude and arrival times. Bearing angles to targets are estimated far more accurately than the transducer beamwidth as obtained with conventional sonar rings based on the Polaroid ranging module. A Gaussian beam characteristic is fitted using least squares to the amplitudes of corresponding echoes in the scan to obtain an estimate of the bearing to specular targets. As an illustration of the information gain over conventional sonar rings, the sensor approach is used on a mobile robot to find, traverse and map doorways reliably and with minimal algorithmic effort. This is compared with other work that claims the problem is difficult to solve using a conventional sonar ring of 24 Polaroid ranging modules [4].