Localization and classification of target surfaces using two pairs of ultrasonic sensors

Ultrasonic sensors have been widely used in recognizing the working environment for a mobile robot. However, their intrinsic problems, such as the specular reflection, the wide beam angle, and the slow propagation velocity, require an excessive number of sensors to be integrated to achieve the various sensing goals. This paper proposes a new measurement scheme which uses only two sets of ultrasonic sensors to determine the location and the type of target surface. By measuring the time difference between the returned signals from the target surface, which are generated by two transmitters with 1 ms difference, it classifies the type and determines the pose of the target surface. Since the proposed sensor system uses only the two sets of ultrasonic sensors to recognize and localize the target surface, it significantly simplifies the sensing system and reduces the signal processing time so that the working environment can be recognized in real time. (C) 2000 Elsevier Science B.V. All rights reserved.