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An ultrasonic transducer array for velocity measurement in underwater vehicles

Record type: Article

A correlation velocity log (CVL) is an ultrasonic navigation aid for marine applications, in which velocity is estimated using an acoustic transmitter and a receiver array. CVLs offer advantages over Doppler velocity logs (DVLs) in many autonomous underwater vehicle (AUV) applications, since they can achieve high accuracy at low velocities even during hover manoeuvres. DVLs require narrow beam widths, whilst ideal CVL transmitters have wide beam widths. This gives CVLs the potential to use lower frequencies thus permitting operation in deeper water, reducing power requirements for the same depth, or allowing the use of smaller transducers.
Moving patterns in the wavefronts across a 2D receiver array are detected by calculating correlation coefficients between bottom reflections from consecutive transmitted pulses, across all combinations of receiver pairings. The position of the peak correlation value, on a surface representing receiver-pairing separations, is proportional to the vessel's displacement between pulses.
A CVL aimed primarily for AUVs has been developed. Its acoustical and signal processing design has been optimised through sea trials and computer modelling of the sound field. This computer model is also used to predict how the distribution of the correlation coefficients varies with distance from the peak position.
Current work seeks to increase the resolution of the peak estimate using surface fitting methods. Numerical simulations suggest that peak estimation methods significantly improve system precision when compared with simply identifying the position of the maximum correlation coefficient in the dataset. The peak position may be estimated by fitting a quadratic model to the measured data using least squares or maximum likelihood estimation. Alternatively, radial basis functions and Gaussian processes successfully predict the peak position despite variation between individual correlation datasets.
This paper summarises the CVL's main acoustical features and signal processing techniques and includes results of sea trials using the device.

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Citation

Boltryk, P., Hill, M., Keary, A., Phillips, B., Robinson, H. and White, P. (2004) An ultrasonic transducer array for velocity measurement in underwater vehicles Ultrasonics, 42, (1-9), pp. 473-478. (doi:10.1016/j.ultras.2003.12.036).

More information

Published date: 2004
Additional Information: Proceedings of Ultrasonics International 2003, Granada, Spain, 1-3 Jul 2003, edited by P.A.Lewin and W. Sachsehttp://www.eaa-fenestra.org/Events/2003/UltrasonicsInternational2003
Keywords: correlation velocity log, doppler velocity log, navigation, peak finding

Identifiers

Local EPrints ID: 10995
URI: http://eprints.soton.ac.uk/id/eprint/10995
ISSN: 0041-624X
PURE UUID: c7d796ee-817a-466e-87d7-3ba958ef60de
ORCID for M. Hill: ORCID iD orcid.org/0000-0001-6448-9448
ORCID for P. White: ORCID iD orcid.org/0000-0002-4787-8713

Catalogue record

Date deposited: 19 Jan 2005
Last modified: 17 Jul 2017 17:05

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Contributors

Author: P. Boltryk
Author: M. Hill ORCID iD
Author: A. Keary
Author: B. Phillips
Author: H. Robinson
Author: P. White ORCID iD

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