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Morrison K.,Defence Academy of the UK | Andre D.,Defence Academy of the UK | Blacknell D.,UK Defence Science and Technology Laboratory | Muff D.,UK Defence Science and Technology Laboratory | Nottingham M.,UK Defence Science and Technology Laboratory
IEEE National Radar Conference - Proceedings | Year: 2015

We report on an investigation into the detection of power and telephone cables in SAR imagery by the presence of diffraction patterning. Laboratory SAR imaging measurements on metal pipes suspended above a gravel surface produced downrange fringe patterns in both backscatter and interferometric phase. Modelling was carried out using an incremental diffraction algorithm, and the positioning and modulation characteristics of the fringes could be understood by the relative positioning of the targets above the gravel and the imaging geometries. Whereas previous studies have relied upon the direct return from the cables, this study has shown their presence might still be inferred from the persistent presence of ground fringes even when a direct return is absent. The effect could find an application in collision avoidance of power and telephone cables by low-flying aircraft, as well as in surveillance and monitoring. © 2015 IEEE. Source


Morrison K.,Defence Academy of the UK | Andre D.,Defence Academy of the UK | Blacknell D.,UK Defence Science and Technology Laboratory | Muff D.,UK Defence Science and Technology Laboratory | And 3 more authors.
2016 IEEE Radar Conference, RadarConf 2016 | Year: 2016

A laboratory-based study was carried out to assess the performance and unique intelligence capabilities of an extreme wideband 10-50GHz SAR. Very high resolution range-profile measurements were obtained of samples used in building construction. Periodic features in reflectivity with frequency were interpreted as a resonance between the front and back face reflections of a sample. The feature's characteristics were in good agreement with the idea of a sample as a resonant microwave cavity. The resonance behaviour was preserved in SAR imaging of the samples, examined by sub-band analysis. Selecting a composite Perspex-MDF target, there was good agreement between simulation and measurement. © 2016 IEEE. Source


Shin H.-S.,Defence Academy of the UK | Lee J.-I.,Agency for Defense Development | Tsourdos A.,Defence Academy of the UK | Tahk M.-J.,KAIST
AIAA Guidance, Navigation, and Control Conference 2012 | Year: 2012

In this paper, a new homing guidance is developed to reduce sensitivity to initial heading error at the beginning of the terminal guidance phase. In order to reshape the control input alleviating the sensitivity, a new per- formance index is proposed by introducing distribution functions to the input weighting. The distribution functions are expressed in terms of sec- ond order polynomials of time-to-go, so that it is possible to distribute the input weighting over the ight. Then, a homing guidance law is derived by applying the LQ optimal control theory to the guidance problem with the new performance index. Whilst the navigation gain is constant in the general PN guidance, the proposed guidance laws have time varying gains to ease the sensitivity to the initial heading error. The performance of the proposed guidance algorithms are verified by the mathematical analysis and various numerical examples. © 2012 by Hyo-Sang Shin. Source


Morrison K.,Defence Academy of the UK | Andre D.,Defence Academy of the UK | Blacknell D.,UK Defence Science and Technology Laboratory | Muff D.,UK Defence Science and Technology Laboratory | Nottingham M.,UK Defence Science and Technology Laboratory
2014 International Radar Conference, Radar 2014 | Year: 2014

We report on an investigation into the secondary detection of objects in SAR imagery by the presence of diffraction patterning. Laboratory SAR imaging measurements were carried on metal pipes suspended above a gravel surface. Clear fringe patterns were seen across the imaged gravel in both backscatter and interferometric phase. Modelling was carried out using an incremental diffraction algorithm. The positioning and modulation characteristics of the fringes could be understood by the relative positioning of the targets above the gravel and the imaging geometries. Even if the pipes or wires are not visible in the imagery from the direct return, their presence might be inferred from the persistent presence of ground fringes. © 2014 IEEE. Source


Shanmugavel M.,Defence Academy of the UK | Tsourdos A.,Defence Academy of the UK | White B.,Defence Academy of the UK | Zbikowski R.,Defence Academy of the UK
Control Engineering Practice | Year: 2010

This paper describes co-operative path planning of a group of unmanned aerial vehicles (UAVs). The problem undertaken for this study is that of simultaneous arrival on target of a group of UAVs. The problem of path planning is formulated in order to produce feasible (flyable and safe) paths and the solution is divided into three phases. The first phase is that of producing flyable paths, the second is to add extra constraints to produce safe paths that do not collide with other UAV members or with known obstacles in the environment, and the third is to produce paths for simultaneous arrival. In the first phase, Dubins paths with clothoid arcs are used to produce paths for each UAV. These paths are produced using the principles of differential geometry. The second phase manipulate these paths to make them safer by meeting safety constraints: (i) to maintain minimum separation distance, (ii) to produce non-intersection of paths at equal lengths, and (iii) to fly-through intermediate way-points/poses. Finally, in the third phase, the simultaneous arrival is achieved by making all the paths equal in lengths. Some simulation results are given to illustrate the technique. © 2009 Elsevier Ltd. Source

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