A novel wideangle ultrasonic sensor utilizing a curved radiator developed for use in an AUV obstacle avoidance system

This paper presents work on the development and testing of a wideangle ultrasonic transducer developed for use as a low cost short range obstacle avoidance system (OAS) on an autonomous underwater vehicle (AUV). The transducer design is novel in that it utilizes a commercial focusing-bowl piezo element as a convex curved radiator in order to achieve a wide-angled beam profile. The operating frequency of the piezo sensor has been selected to have a short wavelength in water yielding good range resolution. The dimensions of the experimental transducer are small and power consumption is low. It is proposed to use several sensors together with overlapping detection cones to build a sensing system that can provide useful information about objects in an AUV's environment. The principle advantages of such a sensing approach are that it would provide fast detection and location of close range targets and could be implemented with less hardware complexity and signal processing than a typical phased-array sonar approach thus reducing the overall system cost. The sound-pressure distribution, ultrasonic sensitivity, and pulse-echo acoustic performance of the transducer prototype are discussed. Water tank testing carried out to evaluate the acoustic response of the prototype in detecting various dimensioned reflectors in the laboratory is reported.