Development and Testing of a Dual Accelerometer Vector Sensor for AUV Acoustic Surveys

Abstract

This paper presents the design, manufacturing and testing of a Dual Accelerometer Vector Sensor (DAVS). The device was built within the activities of the WiMust project, a EU project, supported under the Horizon 2020 Framework Programme, which aims to improve the efficiency of the methodologies used to perform geophysical acoustic surveys at sea by the use of Autonomous Underwater Vehicles (AUVs). The DAVS contributes to this aim in various ways, for example, owing to its spatial filtering capability, it can measure reflections at the desired direction therefore reducing the amount of post processing related to deghosting and multipath removal. Also its compact size allows easier integration with AUVs and hence facilitates the vehicle manoeuvrability compared to the classical towed arrays. The DAVS device consists of two tri-axial accelerometers and one hydrophone moulded in one unit. The device's directional estimation capabilities were evaluated on an AUV, which was sailing around a deployed sound source. Results of this experiment are presented in this paper.

Dual accelerometer vector sensor mounted on an autonomous underwater vehicle (AUV) - Experimental results

“…The DAVS system overview, the characteristics of the sensors, the electronic part, the connections, the acquisition system and the power supply are described in detail in Ref. 17 .…”

“…The procedure used to perform the calibration test, as well as the resulting measured hydrophone and accelerometers' sensitivities, are described in Ref. 17 . Figure 5 presents the normalized radiation diagrams in dB scale for the hydrophone and particle velocity components at two different frequencies, 1 kHz (left) and 2 kHz (right), and when the source and receiver range was 2 m. The results for the hydrophone (green dots) and x particle velocity component (blue dots for accelerometer #49 and red dots for #50) are presented in Fig.…”

“…In the framework of the WiMUST project, a Dual Accelerometer Vector Sensor (DAVS) was developed in order to complement the streamers' data, allowing for the reduction of their size and facilitating the operation of the WiMUST distributed configuration 17 . The use of a dual accelerometer configuration with a single hydrophone, known as the DAVS system, was based on a previous study 15 , which showed that a combination of the particle velocity with pressure or with the particle velocity gradient has the ability to cancel or significantly attenuate the direct and the surface-reflected paths, improving bottom-reflected paths useful for seismic imaging.…”