An investigation of acoustic beam patterns for the sonar localization problem using a beam based method

Abstract

Target localization can be accomplished through an ultrasonic sonar system equipped with an emitter and two receivers. Time of flight of the sonar echoes allows the calculation of the distance of the target. The orientation can be estimated from knowledge of the beam pattern of the receivers and the ratio, in the frequency domain, between the emitted and the received signals after compensation for distance effects and air absorption. The localization method is described and, as its performance strongly depends on the beam pattern, the search of the most appropriate sonar receiver in order to ensure the highest accuracy of target orientation estimations is developed in this paper. The structure designs considered are inspired by the ear shapes of some bat species. Parameters like flare rate, truncation angle, and tragus are considered in the design of the receiver structures. Simulations of the localization method allow us to state which combination of those parameters could provide the best real world implementation. Simulation results show the estimates of target orientations are, in the worst case, 2° with SNR = 50 dB using the receiver structure chosen for a potential practical implementation of a sonar system.

Features in geometric receiver shapes modelling bat-like directivity patterns

“…Distance and orientation of the target with respect to the sonar system allow us to estimate the location of the target. Inspiration from bat acoustics is therefore the most useful suggestion in this case on what is the best receiver to perform target localization, and indeed further research was performed to this purpose [28].…”

Measured beam patterns of biomimetic receivers improve localisation performance of an ultrasonic sonar: Biomimetic receivers improve ultrasonic sonar localisation

“…The Beam Based Method [3,4] was developed by the author as a biomimetic sonar making use of bat inspired receivers to estimate target orientation. The sonar system where to implement the BBM is equipped with one omnidirectional emitter and two directional receivers whose mutual displacement resembles that on a bat head of mouth and ears, see Fig.…”

“…It is important to note that the BBM is strongly dependent on the beam pattern shape across frequencies and how directional and asymmetric it is [4]. These features indeed make it possible to perform a more efficient discrimination between orientations the echo could come from.…”

“…A novel localization method, called Beam Based Method (BBM), for a sonar system equipped with one emitter and two receivers was designed [3,4]. In this method, target orientation is estimated from knowledge of the received signal and of the beam pattern associated with the receivers.…”

Measured beam patterns of biomimetic receivers improve localisation performance of an ultrasonic sonar

“…1 with one emitter and two receivers implements the localization method described in [3,4]. The system as well as the BBM are modelled in MatLab in order to test in simulations the accuracy of the BBM when some receivers are used.…”