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Gabriel F.,Royal Military Academy RMA | De Belief F.,Ghent University | Druyts P.,Royal Military Academy RMA | Neyt X.,Royal Military Academy RMA | Lataire P.,Vrije Universiteit Brussel
8th International Conference on Power Electronics - ECCE Asia: "Green World with Power Electronics", ICPE 2011-ECCE Asia | Year: 2011

Last decades, important progress have been made in sensorless control methods based on the tracking of magnetic anisotropies linked to the rotor. These methods allow to estimate the rotor position at low speed down to standstill. The magnetic anisotropy is generally approached by a sinusoidal shaped function. However, the theory must be adapted in case of additional harmonic content in the anisotropy function. This paper specifically addresses the problem for the surface-mounted permanent-magnet brush-less DC machines with diametric windings. They present a peculiar magnetic anisotropy that suggests a simple method to detect the inversion of the magnetic field as a replacement to the dedicated sensors which are often used. © 2011 IEEE.

Santafe Iribarren B.,Royal Military Academy RMA | Santafe Iribarren B.,Roosevelt University | Berke P.,Roosevelt University | Bouillard P.,Roosevelt University | And 2 more authors.
Engineering Structures | Year: 2011

This contribution deals with the modelling of reinforced concrete (RC) structures in the context of progressive collapse simulations. One-dimensional nonlinear constitutive laws are used to model the material response of concrete and steel. These constitutive equations are introduced in a layered beam approach, in order to derive physically motivated relationships between generalised stresses and strains at the sectional level. This formulation is used in dynamic progressive collapse simulations to study the structural response of a multi-storey planar frame subjected to a sudden column loss (in the impulsive loading range). Thanks to the versatility of the proposed methodology, various analyses are conducted for varying structural design options and material parameters, as well as progressive collapse modelling options. In particular, the effect of the reinforcement ratio on the structural behaviour is investigated. Regarding the material modelling aspects, the influence of distinct behavioural parameters can be evaluated, such as the ultimate strain in steel and concrete or the potential material strain rate effects on the structural response. Finally, the influence of the column removal time in the sudden column loss approach can also be assessed. Significant differences are observed in terms of progressive failure patterns for the considered parametric variations. © 2011 Elsevier Ltd.

Spranghers K.,Vrije Universiteit Brussel | Vasilakos I.,Vrije Universiteit Brussel | Lecompte D.,Royal Military Academy RMA | Sol H.,Vrije Universiteit Brussel | Vantomme J.,Royal Military Academy RMA
International Journal of Impact Engineering | Year: 2013

Protection of buildings against explosions due to terrorism actions or accidents is a growing concern in civil engineering. Full-field measuring techniques as well as finite element simulations are two valuable tools in the hands of engineers to understand the structural mechanisms during blast load events. The research leading to this article is motivated by the fact that only limited knowledge about finite element simulations and experimental validation of structures under free air explosions seems to be available. This article investigates the benefits and accuracy of a finite element simulation of a blast loaded thin aluminum plate by validating the results with small-scale blast loading experiments. Experimental data obtained from 3D high-speed digital image correlation, during the first 7 ms with a frame rate of 25,000 frames per second, is compared with results obtained from the finite element analysis. The influence of different parameters (amongst others: the element type, element size and integration method) with respect to the accuracy of the finite element results is investigated. It is shown that for the modeling of the deformation of the investigated thin plate, the use of shell elements is allowed as the transverse shear strains appear to be sufficiently small. Furthermore, it is concluded that the use of an explicit integration scheme instead of an implicit scheme dramatically reduces the computational effort without significant loss of accuracy. © 2012 Elsevier Ltd. All rights reserved.

Le Nir V.,Royal Military Academy RMA | Scheers B.,Royal Military Academy RMA
2012 Military Communications and Information Systems Conference, MCC 2012 | Year: 2012

Cognitive radio is envisioned to solve the problem of spectrum scarcity in military networks and to autonomously adapt to rapidly changing radio environment conditions and user needs. Dynamic spectrum management techniques are needed for the coexistence of multiple cognitive tactical radio networks. Previous work has investigated the iterative waterfilling algorithm (IWFA) as a possible candidate to improve the coexistence of such networks. It has been shown that adding a constraint on the number of transmitter's sub-channels improves the convergence of IWFA. In this paper, we propose an adaptive orthogonal frequency division multiple access (OFDMA) physical (PHY) and medium access control (MAC) for the coexistence of multiple cognitive tactical radio networks. The proposed scheme is implemented on universal software radio peripheral (USRP) platforms using Qt4/IT++ and the USRP hardware driver (UHD) application programming interface (API). © 2012 Military Univ of Tech.

Scheers B.,Royal Military Academy RMA | Mahoney A.,Saab | Akermark H.,Saab
2012 Military Communications and Information Systems Conference, MCC 2012 | Year: 2012

Cognitive radio (CR) technology has to date not been adopted by the military even though more than a decade has passed since its inception. This paper describes how cognitive radio and associated dynamic spectrum management (DSM) procedures can be introduced in military tactical radio communication. CR and DSM address key challenges that face future military tactical radio communication and their successful introduction can reduce or even overcome current spectrum scarcity and deployment difficulty. A DSM roadmap is introduced where military users develop trust in, and experience with, these novel technologies in manageable steps. The first step in this DSM roadmap involves the introduction of a military band dedicated for CRs and subsequent steps gradually increase the spectrum that may be utilized for military cognitive operation. A high-level vision of how existing military spectrum management procedures will change in the future with the introduction of DSM is also presented resulting in a significant reduction in the workload of spectrum management personnel. © 2012 Military Univ of Tech.

Spranghers K.,Vrije Universiteit Brussel | Vasilakos I.,Vrije Universiteit Brussel | Lecompte D.,Royal Military Academy RMA | Sol H.,Vrije Universiteit Brussel | Vantomme J.,Royal Military Academy RMA
Experimental Mechanics | Year: 2012

Assessment of the structural dynamic response caused by an explosion is complex due to the high velocity impact, the transient nature of the deformation and the interactions between the structure and the pressure wave. This paper deals with full-field measurements of aluminum plates under free air blast loading conditions. Forty grams of explosive material C4 is detonated at a stand-off-distance of 250 mm and two synchronized high-speed cameras in a stereoscopic setup are used to capture the plate response with an inter frame rate of 6,000 fps. The transient deformation fields are calculated using a three-dimensional digital image correlation technique. The observations appeared to be interesting and somewhat counter intuitively. Results show that a free air blast load induces a highly localized, rapid material response which can be essentially divided in two different stadia. First, when the shock impulse occurs, all particles are forced to move out-of-plane and provided with initial velocities. Secondly, when the pressure wave has vanished, the deformation is further driven by this imparted momentum. This paper shows that a 3D high-speed DIC system is a powerful tool for the assessment of the dynamic response of a structure subjected to extreme loading conditions such as explosions and that this system is capable of accurately measuring surface displacement and deformation data at high rates. Moreover, a free air blast load makes it possible to load a plate specimen at different strain rates in different zones. This makes the test suitable for future material identification using inverse methods, which profit from heterogeneous displacement and strain fields. © 2012 Society for Experimental Mechanics.

Spranghers K.,Vrije Universiteit Brussel | Vasilakos I.,Vrije Universiteit Brussel | Lecompte D.,Royal Military Academy RMA | Sol H.,Vrije Universiteit Brussel | Vantomme J.,Royal Military Academy RMA
International Journal of Solids and Structures | Year: 2014

This article describes an inverse method for the identification of the plastic behavior of aluminum plates subjected to sudden blast loads. The method uses full-field optical measurements taken during the first milliseconds of a free air explosion and the finite element method for the numerical prediction of the blast response. The identification is based on a damped least-squares solution according to the Levenberg-Marquardt formulation. Three different rate-dependent plasticity models are examined. First, a combined model based on linear strain hardening and the strain rate term of the Cowper-Symonds model, secondly, the Johnson-Cook model and finally, a combined model based on a bi-exponential relation for the strain hardening term and the strain rate term of the Cowper-Symonds model. A validation of the method and its sensitivity to measurement uncertainties is first provided according to virtual measurements generated with the finite element method. Next, the plastic behavior of aluminum is identified using measurements from real free air explosions obtained from a controlled detonation of C4. The results show that inverse methods can be successfully applied for the identification of the plastic behavior of metals subjected to blast waves. In addition, the material parameters identified with inverse methods enable the numerical prediction of the material's response with increased accuracy. © 2013 Elsevier Ltd. All rights reserved.

Nir V.L.,Royal Military Academy RMA | Scheers B.,Royal Military Academy RMA
Electronics Letters | Year: 2015

A robust blind carrier frequency synchronisation technique applicable to direct sequence spread spectrum (DSSS) systems is presented. The proposed method extends a blind timing synchronisation technique based on an autocorrelation matrix by applying open-loop single-frequency estimation algorithms to the eigenvector of the time synchronised autocorrelation matrix of the largest eigenvalue. A comparison of different single-frequency estimation algorithms is given. Simulation results show that some algorithms attain the Cramer-Rao bound (CRB) even at low signal-to-noise ratios (SNRs). © The Institution of Engineering and Technology 2015.

Scheers B.,Royal Military Academy RMA
Proceedings - IEEE Military Communications Conference MILCOM | Year: 2013

To facilitate the introduction of Dynamic Spectrum Access (DSA) technology and associated dynamic spectrum management (DSM) procedures in military tactical radio communication, a roadmap was presented to NATO CaP3 military session in Oct 2012. The main objective of the roadmap was to create a dedicated band for cognitive radio, in the hope that this would take away uncertainties about spectrum regulations and be a sufficient incentive for military communication industry to start investing and developing products. This paper describes the proposed roadmap and formulates the critics of the NATO spectrum managers (CaP3) on this proposition. Taking into account the remarks of CaP3, a possible way ahead is described. The most promising idea is to create a Military dual-priority band that would take into account the existing saturation of the VHF/UHF band, and meanwhile create a clear spectrum access model for future DSA systems. © 2013 IEEE.

Milisavljevic N.,Royal Military Academy RMA | Closson D.,Royal Military Academy RMA | Bloch I.,Telecom ParisTech
2010 2nd International Conference on Image Processing Theory, Tools and Applications, IPTA 2010 | Year: 2010

This paper describes detection and interpretation of temporal changes in an area of interest using coherent change detection in repeat-pass Synthetic Aperture Radar imagery, with the main goal of detecting subtle scene changes such as potential human activities. Possibilities of introducing knowledge sources in order to improve the final result are also presented. ©2010 IEEE.

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