Yan Pailhas
Heriot-Watt University
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Publication
Featured researches published by Yan Pailhas.
IEEE Transactions on Robotics | 2007
Clement Petres; Yan Pailhas; Pedro Patron; Yvan Petillot; Jonathan Evans; David M. Lane
Efficient path-planning algorithms are a crucial issue for modern autonomous underwater vehicles. Classical path-planning algorithms in artificial intelligence are not designed to deal with wide continuous environments prone to currents. We present a novel Fast Marching (FM)-based approach to address the following issues. First, we develop an algorithm we call FM* to efficiently extract a 2-D continuous path from a discrete representation of the environment. Second, we take underwater currents into account thanks to an anisotropic extension of the original FM algorithm. Third, the vehicle turning radius is introduced as a constraint on the optimal path curvature for both isotropic and anisotropic media. Finally, a multiresolution method is introduced to speed up the overall path-planning process
Journal of the Acoustical Society of America | 2007
Chris Capus; Yan Pailhas; Keith Edgar Brown; David M. Lane; Patrick W. Moore; Dorian S. Houser
This paper uses advanced time-frequency signal analysis techniques to generate new models for bio-inspired sonar signals. The inspiration comes from the analysis of bottlenose dolphin clicks. These pulses are very short duration, between 50 and 80 micros, but for certain examples we can delineate a double down-chirp structure using fractional Fourier methods. The majority of clicks have energy distributed between two main frequency bands with the higher frequencies delayed in time by 5-20 micros. Signal syntheses using a multiple chirp model based on these observations are able to reproduce much of the spectral variation seen in earlier studies on natural dolphin echolocation pulses. Six synthetic signals are generated and used to drive the dolphin based sonar (DBS) developed through the Biosonar Program office at the SPAWAR Systems Center, San Diego, CA. Analyses of the detailed echo structure for these pulses ensonifying two solid copper spherical targets indicate differences in discriminatory potential between the signals. It is suggested that target discrimination could be improved through the transmission of a signal packet in which the chirp structure is varied between pulses. Evidence that dolphins may use such a strategy themselves comes from observations of variations in the transmissions of dolphins carrying out target detection and identification tasks.
Journal of the Acoustical Society of America | 2010
Yan Pailhas; Chris Capus; Keith Edgar Brown; Patrick W. Moore
To date most sonars use narrow band pulses and often only the echo envelope is used for object detection and classification. This paper considers the advantages afforded by bio-inspired sonar for object identification and classification through the analysis and the understanding of the broadband echo structure. Using the biomimetic dolphin based sonar system in conjunction with bio-inspired pulses developed from observations of bottlenose dolphins performing object identification tasks, results are presented from experiments carried out in a wave tank and harbor. In these experiments responses of various targets to two different bio-inspired signals are measured and analyzed. The differences in response demonstrate the strong dependency between signal design and echo interpretation. In the simulations and empirical data, the resonance phenomena of these targets cause strong notches and peaks in the echo spectra. With precision in the localization of these peaks and dips of around 1 kHz, the locations are very stable for broadside insonification of the targets and they can be used as features for classification. This leads to the proposal of a broadband classifier which operates by extracting the notch positions in the target echo spectra.
EURASIP Journal on Advances in Signal Processing | 2010
Yan Pailhas; Yvan Petillot; Chris Capus
Target recognition in sonar imagery has long been an active research area in the maritime domain, especially in the mine-counter measure context. Recently it has received even more attention as new sensors with increased resolution have been developed; new threats to critical maritime assets and a new paradigm for target recognition based on autonomous platforms have emerged. With the recent introduction of Synthetic Aperture Sonar systems and high-frequency sonars, sonar resolution has dramatically increased and noise levels decreased. Sonar images are distance images but at high resolution they tend to appear visually as optical images. Traditionally algorithms have been developed specifically for imaging sonars because of their limited resolution and high noise levels. With high-resolution sonars, algorithms developed in the image processing field for natural images become applicable. However, the lack of large datasets has hampered the development of such algorithms. Here we present a fast and realistic sonar simulator enabling development and evaluation of such algorithms.We develop a classifier and then analyse its performances using our simulated synthetic sonar images. Finally, we discuss sensor resolution requirements to achieve effective classification of various targets and demonstrate that with high resolution sonars target highlight analysis is the key for target recognition.
oceans conference | 2009
Yan Pailhas; Yvan Petillot; Chris Capus; Keith Edgar Brown
New generations of sonars appeared in the last decade. The major interest in SAS systems and high frequency sonars is in the improvement of the sonar resolution and the reduction of noise level. Sonar images are distance-images but at high resolution they tends to appear visually as optical images. Usually the algorithms developed for sidescan were specific for sonar images due to the poor resolution essentially. With high resolution sonars, algorithms developed in the image processing field for natural images became applicable. In this paper we present a real-time and realistic sidescan simulator, and test image-based classification algorithms (such as PCA and eigenface algorithms) with synthetic images in order to characterize the precision necessary for these image-based algorithm to work.
EURASIP Journal on Advances in Signal Processing | 2011
Keith Edgar Brown; Chris Capus; Yan Pailhas; Yvan Petillot; David M. Lane
Marine mammals have developed highly effective sonar systems for detecting, identifying, and following underwater objects. In this paper we demonstrate that bio-inspired wideband sonar offers great capability for tracking cables on the seafloor. The analysis of biological signals, including dolphin clicks, suggests two approaches. The first is to use a wideband signal, integrating the response of an object over many frequencies. For simple forms, this is known to give access to shape and material information. The second idea is to use intelligent signals designed to elicit information from specific target types. In this paper results are presented from sets of experiments using bio-inspired wideband sonar. The aim of these experiments is to determine the feasibility of tracking small diameter marine communications cables using the wideband responses. Echoes from four different cable types are analysed using a variety of signals. Experiments using bio-inspired pulses illustrate the benefits of using this type of wideband signal for detection and recognition. A strong correspondence between theoretical and experimental echoes is shown.
OCEANS'10 IEEE SYDNEY | 2010
Chris Capus; Yan Pailhas; Keith Edgar Brown; David M. Lane
The Ocean Systems Laboratory is developing bio-inspired wideband acoustic sensing methods for underwater target detection and tracking. The wideband sensors themselves are based on bottlenose dolphin sonar, covering a frequency band from around 30kHz to 150kHz and having a frequency dependent beamwidth considerably larger than conventional imaging sonars. The entire system is relatively compact and is suitable for mounting on a variety of platforms including small scale autonomous underwater vehicles (AUVs). In this paper we overview recent efforts applying the sonar to the detection and tracking of various underwater cables, and to the detection and classification of these cables in shallow burial, based on their midwater responses.
2014 Sensor Signal Processing for Defence (SSPD) | 2014
Yan Pailhas; Yvan Petillot
Multiple Input Multiple Output sonar systems offer new perspectives for target detection and underwater surveillance. In this paper we present an unified formulation for sonar MIMO systems and study their properties in terms of target recognition and imaging. Here we are interested in large MIMO systems. The multiplication of the number of transmitters and receivers non only provides a greater variety in term of target view angles but provides also in a single shot meaningful statistics on the target itself. We demonstrate that using large MIMO sonar systems and with a single shot it is possible to perform automatic target recognition and also to achieve super-resolution imaging. Assuming the view independence between the MIMO pairs the speckle can be solved and individual scatterers within one resolution cell decorelate. A realistic 3D MIMO sonar simulator is also presented. The output of this simulator will demonstrate the theoretical results.
IEEE Journal of Oceanic Engineering | 2017
Yan Pailhas; Yvan Petillot; Keith Edgar Brown; Bernard Mulgrew
Multiple-input–multiple-output (MIMO) sonar systems offer new perspectives for target detection and area surveillance. This paper introduces a unified formulation for sonar MIMO systems and focuses on the target detection and recognition capability of these systems. The multiplication of the number of transmitters and receivers not only provides a greater variety in terms of target view angles but also provides meaningful statistics on the target itself. Assuming that views are independent and the MIMO system is large enough, we demonstrate that target recognition is possible with only one MIMO snapshot. By studying the detection performance of MIMO sonars we also demonstrate that such systems solve the speckle noise and decorrelate individual scatterers inside one cell resolution, leading to super-resolution imaging. We also show that, if carefully designed, MIMO systems can surpass the resolution of a synthetic aperture sonar (SAS) system using the same bandwidth. All the discussed properties are derived from the independent view assumption. Fulfilling this assumption drives the design and efficiency of such systems.
ECUA 2012 11th European Conference on Underwater Acoustics | 2013
Yan Pailhas; Yvan Petillot; Chris Capus; Bernard Mulgrew
MIMO systems have raised a lot of interests in the recent years especially in the radar community. For MIMO systems with widely spaced antennas for example it has been shown that channel matrices are decorrelated from one another. The view diversity of an illuminated target is then increased. And as a consequence the detection probability of statistical MIMO systems increases thanks to this gain diversity. In this paper we present the finite scattering point model introduced by Haimovich and demonstrate the equivalence between the MIMO scattering problem using the finite scattering point model and the random walk problem. Studying the convergence of the central limit theorem applied to this problem, we demonstrate that it is possible to estimate the scattering points density for a low number of scatterers in the resolution cell. Finally we show that statistical MIMO system suppresses the interferences between scatterers and maximises the target response.