Ultrasonic Sensing For A Mobile Robot To Recognize An Environment - Measuring The Normal Direction Of Walls -

Abstract

With a conventional ultrasonic sensor system for a mobile robot, the distance to an ob- ject can be obtained with a time-of-flight (TOF) method, in which a reflected point is regarded to be located directly on the transducer line-of- sight. However, in an indoor environment, flat walls have specular characteristics. So, the real reflected point is not located on the transducer's lime-of-sight, because an echo from the normal in- cidence only returns to the transducer, since ul- trasonic directivity is not so sharp in air. So, to accurately recognize the position of an object, it is important to detect the direction of the re- flected point. One method to obtain the direction is to calculate it from the time difference between two parallel receivers. In this paper, an ultrasonic sensing method with a wide angle and high res- olution in specular environment is proposed, and accurate environment recognition can be realized.