Showing papers by "Saab Automobile AB published in 2019"

Bivariate Gamma Distribution for Wavelength-Resolution SAR Change Detection

Abstract: A gamma probability density function (pdf) is shown to be an alternative to model the distribution of the magnitudes of high-resolution, i.e., wavelength-resolution, synthetic aperture radar (SAR) images. As investigated in this paper, it is more appropriate and more realistic statistical in comparison with, e.g., Rayleigh. A bivariate gamma pdf is considered for developing a statistical hypothesis test for wavelength-resolution incoherent SAR change detection. The practical issues in implementation of statistical hypothesis test, such as assumptions on target magnitudes, estimations for scale and shape parameters, and implementation of modified Bessel function, are addressed. This paper also proposes a simple processing scheme for incoherent change detection to validate the proposed statistical hypothesis test. The proposal was experimented with 24 CARABAS data sets. With an average detection probability of 96%, the false alarm rate is only 0.47 per square kilometer.

Polarimetric Wireless Indoor Channel Modeling Based on Propagation Graph

Abstract: This paper generalizes a propagation graph model to polarized indoor wireless channels. In the original contribution, the channel is modeled as a propagation graph in which vertices represent transmitters, receivers, and scatterers, while edges represent the propagation conditions between vertices. Each edge is characterized by an edge transfer function accounting for the attenuation, delay spread, and the phase shift on the edge. In this contribution, we extend this modeling formalism to polarized channels by incorporating depolarization effects into the edge transfer functions and hence, the channel transfer matrix. We derive closed form expressions for the polarimetric power delay spectrum and cross-polarization ratio of the indoor channel. The expressions are derived considering average signal propagation in a graph and relate these statistics to model parameters, thereby providing a useful approach to investigate the averaged effect of these parameters on the channel statistics. Furthermore, we present a procedure for calibrating the model based on method of moments. Simulations were performed to validate the proposed model and the derived approximate expressions using both synthetic data and channel measurements at 15 GHz and 60 GHz. We observe that the model and approximate expressions provide good fit to the measurement data.

The COST IRACON Geometry-based Stochastic Channel Model for Vehicle-to-Vehicle Communication in Intersections

Abstract: Vehicle-to-vehicle (V2V) wireless communications can improve traffic safety at road intersections and enable congestion avoidance. However, detailed knowledge about the wireless propagation channel is needed for the development and realistic assessment of V2V communication systems. We present a novel geometry-based stochastic MIMO channel model with support for frequencies in the band of 5.2-6.2 GHz. The model is based on extensive high-resolution measurements at different road intersections in the city of Berlin, Germany. We extend existing models, by including the effects of various obstructions, higher order interactions, and by introducing an angular gain function for the scatterers. Scatterer locations have been identified and mapped to measured multi-path trajectories using a measurement-based ray tracing method and a subsequent RANSAC algorithm. The developed model is parameterized, and using the measured propagation paths that have been mapped to scatterer locations, model parameters are estimated. The time variant power fading of individual multi-path components is found to be best modeled by a Gamma process with an exponential autocorrelation. The path coherence distance is estimated to be in the range of 0-2 m. The model is also validated against measurement data, showing that the developed model accurately captures the behavior of the measured channel gain, Doppler spread, and delay spread. This is also the case for intersections that have not been used when estimating model parameters.

SAR Processing Without a Motion Measurement System

Abstract: This paper leads a discussion on how to form a Synthetic Aperture Radar (SAR) image without knowing the relative track. That is, within the scope of factorized geometrical autofocus (FGA). The FGA algorithm is a base-2 fast factorized back-projection (FFBP) formulation with six free geometry parameters (per subaperture pair). These are tuned step by step until a sharp image is obtained. This innovative autofocus concept can compensate completely for an erroneous geometry. The FGA algorithm has been applied successfully on two ultrawideband (UWB) data sets, acquired by the CARABAS II system at very high frequency (VHF)-band. The relative tracks are known (measured accurately). We, however, adopt and modify a basic geometry model. A linear equidistant track at fixed altitude is initially assumed. Apart from deviations due to linearization, a ~2.5-m/s along-track velocity error is also introduced. Resulting FGA images are compared to reference images and verified to be focused. This indicates that it is feasible to form a wavelength-resolution SAR image at VHF-band without support from a motion measurement system. The execution time for the examples in this paper is about five times longer with autofocus than without. Hence, the FGA algorithm is now fit for use on a regular basis.

Shielding Effectiveness and HPM Vulnerability of Energy-Saving Windows and Window Panes

Abstract: In this paper, we report results from shielding effectiveness measurements on energy-saving windows and individual, coated window panes of different generations, as well as results from high-power microwave irradiation on single panes. Shielding effectiveness was measured with two complementary methods: first, with near isotropic irradiation in nested reverberation chambers, and the other with irradiation at normal incidence in a semianechoic chamber. The measurements show that the construction of the energy conserving windows has a clear impact on how well they attenuate radio frequency signals. The more modern the window or pane, the higher is the shielding effectiveness. The high-power irradiation on coated panes showed that depending on the type of coating, hotspots can build up causing the coating to crack and, hence, deteriorate the shielding effectiveness. These results may serve as guidance when reviewing high-altitude electromagnetic pulse (EMP), high-power microwave, or intentional electromagnetic interference protection of critical infrastructures, and provide assistance in the work with reduction of compromising emanations.

Competitive Sorption of Metal Ions on Titanium Phosphate Sorbent (TiP1) in Fixed-Bed Columns: A Closed-Mine Waters Study

Abstract: Sorption fixed-bed column experiments were performed using a titanium phosphate ion-exchanger composed of −H2PO4 units [TiO(OH)(H2PO4)·H2O]. Model mine water containing five divalent metal ions (Cu...

On-Board System Concept for Drones in the European U-space

Abstract: This paper describes the findings of the AIRPASS (Advanced Integrated RPAS Avionics Safety Suite) project. The project aims to develop an on-board system concept to be used for drones that intend to operate in the European U-space. The Single European Sky ATM Research Joint Undertaking (SESAR JU) drafted the U-space blueprint to describe a set of services that shall enable the safe, efficient and secure integration of a large number of drones into non-segregated airspace, especially for Very Low Level (VLL) operations). Services are not limited to drones but are also intended to support manned flights in VLL as well as drones carrying passengers. The U-space concept also supports the EASA classes of operation, covering open, specific and certified.

Determining Direction‐of‐Arrival Accuracy for Installed Antennas by Postprocessing of Far‐Field Data

Abstract: Direction‐of‐arrival (DoA) estimation accuracy can be degraded due to installation effects, such as platform reflections, diffraction from metal edges, and reflections and refraction in the radome. ...

Automatic Gas Turbine Matching Scheme Adaptation for Robust GPA Diagnostics

Abstract: When performing gas turbine diagnostics using Gas Path Analysis (GPA), a convenient way of extracting the degradations is by feeding the measured data from a gas turbine to a well-tuned gas turbine ...

An Ontological Approach to System of Systems Engineering in Product Development

Abstract: This paper presents an approach to system-of-systems engineering for product development with the use of ontology. A proposed method for building as well as using ontology to generate and explore system-of-systems design spaces based on identified system-of-system needs is presented. The method is largely built to cover the first levels of related work, where a process for system of systems in the context of product development is introduced. Within this work, it is shown that scenarios for a system-of-systems can be used to identify needs and subsequently the system-of-systems capabilities that fulfils them. The allocation of capabilities to possible constituent systems is used to show the available design space. The proposed method of this paper therefore addresses these initial challenges and provides a framework for approaching the system-of-systems design space creation using ontology. A case study is used to test the method on a fictitious search and rescue scenario based on available resources and information from the Swedish Maritime Administration. The case study shows that a representation of a system-of-systems scenario can be created in an ontology using the method. The ontology provides a representation of the involved entities from the fictitious scenario and their existing relationships. Defined ontology classes containing conditions are used to represent the identified needs for the system-of-systems. The invocation of a description logic reasoner is subsequently used to classify and create an inferred ontology where the available system-of-systems solutions are represented as sub-classes and individuals of the defined classes representing the needs. Finally, several classes representing different possible system-of-systems needs are used to explore the available design space and to identify the most persistent solutions of the case study.

Garteur AD/AG-52: Surrogate-Based Global Optimization Methods in Preliminary Aerodynamic Design

Abstract: This work presents a summary of the results obtained during the activities developed within the GARTEUR AD/AG-52 group GARTEUR stands for “Group for Aeronautical Research and Technology in Europe” and is a multinational organization that performs high quality, collaborative, precompetitive research in the field of aeronautics to improve technological competence of the European Aerospace Industry The aim of the AG52 group was to make an evaluation and assessment of surrogate-based global optimization methods for aerodynamic shape design of aeronautical configurations The structure of the paper is as follows: Sect “Introduction” will introduce the state-of-the-art in surrogate-based optimization for aerodynamic design and Sect “Definition of Common Test Cases and Methods” will detail the test cases selected in the AG52 group Optimization results will be then showed in Sect “Optimization Results”, and conclusions will be provided in the last section

TLM-Based Asynchronous Co-simulation with the Functional Mockup Interface

Abstract: Numerical stability is a key aspect in co-simulation of physical systems. Decoupling a system into independent sub-models will introduce time delays on interface variables. By utilizing physical time delays for decoupling, affecting the numerical stability can be avoided. This requires interpolation, to allow solvers to request input variables for the time slot where they are needed. The FMI for co-simulation standard does not support fine-grained interpolation using interpolation tables. Here, various modifications to the FMI standard are suggested for improved handling of interpolation. Mechanical and thermodynamic models are used to demonstrate the need for interpolation, as well as to provide an industrial context. It is shown that the suggested improvements are able to stabilize the otherwise unstable connections.

A Detector for Wavelength Resolution SAR Incoherent Change Detection

Abstract: This paper introduces an effective detector for wavelength-resolution SAR incoherent change detection. The detector is derived from Bayes' theorem. The input of the detector is the differences between surveillance and reference magnitude images simply obtained by a subtraction while the output is a summary of the detected changes. The proposed detector is tested with 24 CARABAS images that were obtained from the measurement campaign in northern Sweden in 2002. The testing results show that the detector can provide a high average detection probability, e.g., about 96%, with a very low false alarm rate, e.g., only 0.35 per square kilometer.

Automatically Generating the Technology Compatibility Matrix Using Graph Transformations

Abstract: One of the first stages during technology evaluation and selection is constructing the technology compatibility matrix, which indicates the compatibility of each pair in a technology portfolio. Construction of the technology compatibility matrix usually involves subjective expert judgment, which inhibits assessing each pair consistently and storing the decision rationale. Therefore, this study develops a method based on graph transformations, allowing for a formal theoretical description of technologies. In order to automate this process, two algorithms use these graph transformations to deduce technology compatibility and dependencies between technologies. The first checks whether changes made by a pair of transformations are compatible with each other. The second defines dependencies for each technology and attempts to resolve these using other technologies. The method is put into practice for a technology portfolio within Saab Aeronautics and the automatically generated compatibility matrix is compared to a pre-existing expert-judgment-based matrix for the same portfolio. Roughly 90% of the entries in the algorithm-based TCM are identical to the expert-based TCM. Therefore, the automated method is capable of capturing much of human reasoning in this context. However, in order to fully agree with human expertise, physics and design reasoning should be included to expand the scope of inference.

Factorized Geometrical Autofocus at UHF-band

Abstract: This paper describes an autofocus experiment at UHF-band. That is within the scope of factorized geometrical autofocus (FGA). The FGA algorithm is a base-2 fast factorized back-projection (FFBP) formulation with six free geometry parameters (per sub-aperture pair). These are tuned step-by step until a sharp image is obtained. This innovative autofocus technique can compensate completely for an erroneous geometry. The FGA algorithm has been applied successfully on an UWB data set, acquired by the LORA system (i.e. at UHF band). Before processing, we add errors due to a constant quadratic bias to the measured track. This emulates a drifting inertial measurement unit (IMU) and motivates the use of autofocus. The resulting FGA image is compared to a reference image and verified to be focused (even sharper actually). Hence, the FGA algorithm is fit for use at UHF-band.

Competence Networks in the Era of CPS : Lessons Learnt in the ICES Cross-Disciplinary and Multi-domain Center

Abstract: Cyber-Physical Systems (CPS) are evolving to become more intelligent, autonomous and collaborating, playing an important role in societal infrastructure. The amount of knowledge required in developing and managing future CPS will be unprecedented, leading to stronger needs for collaboration, competence provisioning, continuous learning and renewal of education. This is where “competence” (or learning) “networks” involving academia and industry play an important role. We elaborate and discuss needs, lessons learnt and challenges for such competence networks in the context of CPS. We draw upon our experiences gained from ICES - the KTH-industry cross-disciplinary and multi-domain competence network which in 2019 has been operational for 11 years, growing from 6 to more than 30 participating organizations. The ICES network focuses on activities to support students, industrial engineers and managers, and academic faculty, acting as a network, catalyst and competence provider directed towards these stakeholders. We elaborate challenges faced during the operation of ICES including the lack of prioritization of competence networks and education, the paradox with strong needs for competence networks but perceived lack of time, the challenges of reaching out to stakeholders, and fragmented efforts addressing competence provisioning. We finally discuss ways forward. In conclusion, we believe that the ICES type of network could be relevant in many other areas characterized by complex systems.

Shape disrupter for net support system

Abstract: A shape disrupter for a net support system may have a conical body and an elliptical shape in plan view. The shape disrupter may have low thermal signature and low weight. The shape disrupter may be stackable. The shape disrupter may have a protrusion on the shape disrupter for fixing each of the shape disrupters in place during stacking. The shape disrupter may have cutouts or openings to reduce the weight and thermal signature of the shape disrupter. The shape disrupter of the present disclosure may cooperate with support poles or nets to provide a support system for large nets or screens.

Balancing Antenna Performance vs. Radar Cross Section for a Passive Radar-Detecting Sensor on an Aircraft

Abstract: Balancing Antenna Performance vs. Radar Cross Section for a Passive Radar-Detecting Sensor on an Aircraft

Spares provisioning strategy for periodically replaced units within the fleet retirement period

Abstract: Within aviation enterprises, the process of dismantling an aircraft at the end of its life is referred to as parting-out. Obviously, the asset value of the units and materials parted out from the retired airframes can be considerable. The benchmarked best practice within the aviation industry is to dismantle the retired aircraft and use the parted-out spares to support the remaining fleet or to offer them on the surplus market. Part-out-based spares provisioning (PBSP) has been a major focus of attention for aviation companies. The PBSP approach is a complex task that requires a multidisciplinary and integrated decision-making process. In order to control the stock level and fulfil the decision criteria within PBSP, it is necessary to make decisions on the termination, at specific times, of both the parting-out process and the maintenance and repair actions performed on the units. This paper considers repairable units and introduces a computational model to identify the applicable alternatives for repair termination times that will minimize the number of remaining spares at the end of the retirement period, while fulfilling the availability requirement for spares during the PBSP period, at the lowest possible cost. The feasible alternatives are compared with regard to their respective costs, and the most cost-effective solution is selected. The cost model uses estimates of future maintenance requirements, the turn-around times, and the cost of the various maintenance tasks, the future spares consumption, and the estimated salvage of spares from retired aircraft. The output of the model is a set of applicable alternatives which satisfy the availability requirements for spares for the active fleet. The method is illustrated using a case study performed on the Saab-105 training aircraft.

Plane wave spectrum in radome applications

Abstract: This paper presents an analysis technique that has its focus on radome applications, but serves the purpose of being useful for a wider range of scattering problems. The analysis technique is based on classical integral representations in combination with the concepts of plane wave expansion of the wave fields. The introduction of a plane wave decomposition implies that the assumption on local plane wave incidence can be relaxed in the computation of reflected and transmitted field contributions due to the scatterer e.g., the radome. The method is adapted for taking into account in general bianisotropic slabs, either homogeneous, stratified or with continuously varying material parameters in the direction normal to the surface. The theory is also applicable to frequency selective structures (FSS).

Research on Wideband Phased Array Antennas - Special Session in Memory of Dr. Hans Steyskal

Abstract: A summary of the research on wideband phased array antennas that Dr. Hans Steyskal and Dr. Henrik Holter conducted during the years 1997–2005 is presented. The research resulted in software, based on a new method for FDTD unit cell analysis, used by a number of researchers and at SAAB. This work led to a number of journal and conference papers, an IEEE R. W. P. King Award and laid the foundation to the wideband array antennas for Electronic Warfare at SAAB.