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Agency: European Commission | Branch: FP7 | Program: CP-FP | Phase: ENV.2007. | Award Amount: 4.07M | Year: 2008

ACOBAR will develop an observing system for the interior of the Arctic Ocean based on underwater acoustic methods including tomography, data transmission and communication to/from underwater platforms, and navigation of gliders. ACOBAR offers complementary methods to the ARGO system, which has limited capability in ice-covered seas. Data collection and transmission from the water column, the seafloor and the subseafloor will be possible in ice-covered seas based on research conducted in ACOBAR. The research will contribute to filling gaps in the global ocean observing system and thereby support the development of GEOSS. ACOBAR will implement field experiments with acoustic sources and receivers as well as gliders in the Fram Strait. Acoustic travel time data will be used to obtain integrated 3-D fields of temperature, transports and heat fluxes. Long-range acoustic navigation commands will be tested to operate gliders. Data transmission from fixed moorings via acoustic modems to the surface for downloading from ships or for satellite transmission will be implemented. The existing array of acoustic sources from ice-tethered platforms in the Arctic Ocean will be tested for tomographic measurements of water mass properties. Data from tomography arrays and other underwater platforms will be disseminated to users with near real-time capability, including assimilation in ocean models. ACOBAR will extend and improve methods for underwater data collection that was first tested in DAMOCLES IP. The acoustic technologies in ACOBAR aim to be used for transmission of multidisciplinary data from underwater observatories developed in ESONET NoE. Transfer of technology and know-how from USA to Europe and between industry and research institutes will take place, with exchange of scientists, workshops and meetings between scientists, engineers and students. The consortium consists of 9 partners, of which three are SMEs and six are research and educational institutions.

Bonnel J.,ENSTA Bretagne | Chapman N.R.,University of Victoria
Journal of the Acoustical Society of America | Year: 2011

This paper presents a single receiver geoacoustic inversion method adapted for low-frequency impulsive sources. It is applied to light bulb data collected during the Shallow Water 2006 experiment. The inversion is carried out by extracting dispersion curves from the received signal, and comparing them to simulated replicas. To achieve dispersion curve estimation in the time-frequency domain, modal separability is improved using a signal processing method called warping. The inversion scheme allows for a reliable estimation of the New Jersey Shelf sediment properties (compressional sound speed and density). It also provides an accurate estimation of the source/receiver range. © 2011 Acoustical Society of America.

A method of calibration of a navigation and pointing system (10) including a navigation unit (11) integrally connected to a pointing device (12), the navigation unit being configured to measure the orientation of a navigation reference system (21), the pointing device (12) being configured to measure a signal in a pointing reference system (22). The calibration method includes the following steps:

Jaulin L.,ENSTA Bretagne
IEEE Transactions on Robotics | Year: 2011

This paper proposes a new set-membership approach to solve range-only simultaneous localization and mapping (SLAM) problems in the case where the map is described by an arbitrary occupancy set (i.e., we do not assume that the map is composed of segments, punctual marks, etc.). The principle is to transform the SLAM problem into a hybrid constraint satisfaction problem (CSP), where the variables can either be real numbers, vectors, trajectories, or subsets of BBRn. An extension of existing constraint propagation methods is then proposed to solve hybrid CSPs involving set-valued variables. A simulated test case is then proposed to show the feasibility of the approach. © 2011 IEEE.

Jaulin L.,ENSTA Bretagne
Robotics and Autonomous Systems | Year: 2011

Interval methods have been shown to be efficient, robust and reliable to solve difficult set-membership localization problems. However, they are unsuitable in a probabilistic context, where the approximation of an unbounded probability density function by a set cannot be accepted. This paper proposes a new probabilistic approach which makes possible to use classical set-membership localization methods which are robust with respect to outliers. The approach is illustrated on two simulated examples. © 2011 Elsevier B.V. All rights reserved.

Martin E.,CNRS Laboratory for Thermostructural Composites | Leguillon D.,CNRS Jean Le Rond d'Alembert Institute | Carrere N.,ENSTA Bretagne
International Journal of Solids and Structures | Year: 2012

The strength of an open holed composite plate subjected to tensile loading is analysed with the help of a coupled strength and energy criterion. Analytical and numerical models are used to determine the stress distribution and the energy released by crack nucleation in the vicinity of the hole. It is shown that the hole size effect can be described and that the crack length at nucleation both depends on the local geometry and the fracture characteristics of the specimen. These characteristic values can be identified with the help of traction tests performed on unnotched and holed samples. © 2012 Elsevier Ltd. All rights reserved.

Pastor D.,Telecom Bretagne | Socheleau F.-X.,ENSTA Bretagne
IEEE Transactions on Signal Processing | Year: 2012

In many applications, d-dimensional observations result from the random presence or absence of random signals in independent and additive white Gaussian noise. An estimate of the noise standard deviation can then be very useful to detect or to estimate these signals, especially when standard likelihood theory cannot be applied because of too little prior knowledge about the signal probability distributions. The present paper introduces a new scale estimator of the noise standard deviation when the noisy signals have unknown probability distributions and unknown probabilities of presence less than or equal to one half. The latter assumption can be regarded as to a weak assumption of sparsity. Applied to the detection of noncooperative radio-communications, this new estimator outperforms the standard MAD and its alternatives as well as the trimmed and winsorized robust scale estimators. The Matlab code corresponding to the proposed estimator is available at © 2012 IEEE.

Dambreville F.,ENSTA Bretagne
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2014

While there is a variety of approaches and algorithms for optimizing the mission of a sensor, there are much less works which deal with the implementation of several sensors within a human organization. In this case, the management of the sensors is done through at least one human decision layer, and the sensors management as a whole arises as a bi-level optimization process. The following hypotheses are considered as realistic: Sensor handlers of first level plans their sensors by means of elaborated algorithmic tools based on accurate modelling of the environment; Higher level plans the handled sensors according to a global observation mission and on the basis of an approximated model of the environment and submit its plan to a costly assessment by the first level. This problem is related to the domain of experiment design. A generalization of the Efficient Global Optimization method (Jones, Schonlau and Welch) is proposed, based on a rare event simulation approach. © 2014 Springer International Publishing Switzerland.

Bonnel J.,ENSTA Bretagne
Proceedings of Meetings on Acoustics | Year: 2013

In certain shallow water environments the acoustic propagation of low-frequency marine mammal calls can be well-modeled as a discrete set of normal modes. Each mode propagates with a different group velocity, and thus in principle the range of the call can be inferred by comparing relative arrival times of the modal arrivals. Traditionally, several time-synchronized hydrophones are required to spatially filter out individual modes in order to measure relative arrival times. In this presentation a nonlinear signal processing method classed "warping" is used to identify individual mode arrival times on a single receiver, even when the mode arrivals are overlapping in time. Warping processing is limited to frequency-modulated sources with monotonic increases or decreases of frequency with time. It is thus applicable to whale calls that consist of simple frequency-modulated upsweeps or downsweeps. Once the modes are separated, the source range can be estimated using conventional modal dispersion techniques. This method is applied on several bowhead whale vocalizations recorded near Kaktovik (Alaska) in 2012. Bowhead whale calls are ranged up to 35 km under median ambient noise conditions. These single-receiver range estimates are consistent with estimated ranges previously obtained via other methods. © 2013 Acoustical Society of America.

Jaulin L.,ENSTA Bretagne | Le Bars F.,ENSTA Bretagne
IEEE Transactions on Robotics | Year: 2013

This paper proposes an interval-based method for the validation of reliable and robust navigation rules for mobile robots. The main idea is to show that for all feasible perturbations, there exists a safe subset of the state space such that the system cannot escape. The methodology is illustrated on the line-following problem of a sailboat and then validated on an actual experiment where an actual sailboat robot, which is named Vaimos, sails autonomously from Brest to Douarnenez (i.e., more than 100 km). © 2004-2012 IEEE.

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