Nach oben pdf GNSS performance modelling for high interrity aircraft applications

GNSS performance modelling for high interrity aircraft applications

GNSS performance modelling for high interrity aircraft applications

The user receiver needs to correct the GPS satellite clock errors. The user receiver must have an accurate representation of GPS system time at the time of transmission for GPS signal it receiving from satellite i. the satellite clock correction ∆t ୱ୴ is obtained using coefficients broadcast from the satellite after being uploaded by the GPS control segment. The control segment actually uploads several different sets of coefficient to the satellite, of which each set is valid over a given time period. The data sets are then transmitted in the downlink DataStream to the users in the appropriate time intervals. These corrections represent a second order polynomial in time. [2, 3]
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Miniaturized Dielectric Resonator Antenna Array for GNSS Applications

Miniaturized Dielectric Resonator Antenna Array for GNSS Applications

In order to fully exploit the offered possibilities and at the same time counteract possible threats, high-performance systems, able to steer the antenna pattern and hence place nulls against interferences and maxima at the direction of arrival (DOA) of signals, are being developed all over the world (see e.g. [3]). These new systems might be particularly useful in mobile applications, such as aircraft or vehicles, where precise localization can play an important role. However, the canonical dimensions of the antennas, as well as of receivers, do not fit with the requirements of low profile and low weight, typical of mobile applications: in the aeronautic sector, for in- stance, the tolerable size is regulamented by ARINC standard dimensions[4]. There is hence a need for miniaturization both of the single radiator and of the overall antenna array, to enable real-life implementation of the developed systems.
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Novel hybrid structural core sandwich materials for aircraft applications

Novel hybrid structural core sandwich materials for aircraft applications

The paper will present an overview of a new EU project CELPACT [2] whose main objective is the development and design of new cellular materials and twin skinned sandwich structures made from hybrid composites and metals. CELPACT is developing fabrication technology for cellular metals based on selective laser melting of periodic cellular cores and new fabrication concepts for hybrid composite sandwich structures with folded structural composite cores. To support the materials developments, computational methods are being developed based on micromechanics cell models with multiscale modelling techniques for understanding progressive damage and collapse mechanisms for use in structural analysis. Impact performance is critical for sandwich aircraft structures and the simulation tools are being used to design efficient impact resistant aircraft structures. Structural integrity of these advanced cellular structures are being assessed by dynamic materials tests and gas gun impact tests on cellular beam and panel structures under high velocity impact conditions relevant to aircraft structures.
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Performance of new GNSS satellite clocks

Performance of new GNSS satellite clocks

Chapter 6 - Performance of Geodetic time transfer This chapter analyses the precision and accuracy of GNSS time transfer by reviewing the quality of the clock estimations performed in th[r]

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Emissions modelling for engine cycle and aircraft trajectory optimisation

Emissions modelling for engine cycle and aircraft trajectory optimisation

In general, flows in actual combustors show high level of turbulence, time dependency and mass transport and energy transfer in three dimensions. Obtaining the solution on such a complex problem where partial differential equations need to be solved for mass, energy and momentum conservation can be very computationally intensive. As such, different approaches are used to approximate the combustion process in order to reduce complexity and computing time. One type of approximation is to focus on the finite rate chemistry and to assume that the mixing takes place at an infinite rate or in a defined way. When mixing is assumed infinite the reactor is called a Perfectly Stirred Reactor (PSR). If one the other hand the mixing is defined by probability distribution functions, the reactor is called a Partially Stirred Reactor (PaSR) or a Well Stirred Reactor (WSR). In both cases, this approximation leads to the reactor theory as discussed in more detailed in section 4.1. As opposed to the finite rate chemistry, another type of approximation is to consider the chemical reaction to happen instantaneously and to focus on the mixing processes. This approach leads to Computational Fluid Dynamics (CFD) applied to combustion processes.
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High-Performance High-Lift Design for Laminar Wings

High-Performance High-Lift Design for Laminar Wings

Within the mentioned projects, we succeeded to design vented folding bull-nose Krueger devices for laminar wing application for both natural laminar flow and hybrid laminar flow control wings. The designed Krueger devices feature guaranteed shielding properties (to prevent insect contamination) and a high aerodynamic performance nearly comparable to classical slat devices. For both types of wings, a feasible kinematics and mechanical integration has been found that fits the Krueger device also in the very restricted space at HLFC leading edges. The design methodology has proven to be suitable for designing directly for real flight conditions. During verification wind tunnel tests the performance targets were met. Based on this data a 5- 7% fuel burn benefit has been assessed on aircraft level for the NLF wing, heavily related to the avoidance of wing size increase due to a satisfactory high-lift performance.
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On High Performance Computing in Geodesy – Applications in Global Gravity Field Determination

On High Performance Computing in Geodesy – Applications in Global Gravity Field Determination

Antarctic Geoid Project Arctic Gravity Project Auto Regressive Moving Average filter Automatically Tuned Linear Algebra Software Byte Basic Linear Algebra Communication Subprograms Basic[r]

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Multi-Frequency GNSS Sensor Fusion With Quality Assessment for Automotive Applications

Multi-Frequency GNSS Sensor Fusion With Quality Assessment for Automotive Applications

This thesis aims to make additional GNSS constellations and frequencies beyond GPS L1 us- able for automotive applications by including them in an integrated GNSS/INS localization algorithm. While the main advantages are increased satellite availability and the elimination of the ionospheric error, modern GNSS signals offer additional benefits like reduced suscepti- bility to multipath errors, higher signal transmission power and faster signal acquisition via pilot components free of navigation data. In order to achieve a high degree of flexibility w. r. t. the available pseudoranges, the GNSS preprocessing is able to work with different types of IF combinations and single-frequency pseudoranges simultaneously. This capability is especially important for GPS processing because the currently broadcast signals vary from satellite to satellite due to the ongoing stepwise modernization of the GPS constellation. Since each signal is affected by different biases, their simultaneous processing requires the consideration of DCBs. While satellite-specific DCBs are obtained from external sources, receiver-specific DCBs are calibrated a-priori for the employed receiver. To account for the signal biases aris- ing from the multi-constellation approach, an additional receiver clock bias entry is included in the integration filter’s state vector. Satellite orbit and clock data are obtained from the predicted half of ultra-rapid precise products published by GFZ instead of the navigation messages, which serve as backup. This preserves the algorithm’s real time capability while reducing the satellite position and clock bias error, which is the largest remaining error after the ionospheric delay has been eliminated through multi-frequency observations. A very im- portant part of the developed GNSS preprocessing module is the measurement noise model. Due to the inherently different error characteristics of IF combinations on the one hand and single-frequency pseudoranges on the other hand, a sophisticated measurement noise model is necessary to enable optimal weighting of all types of input data in the integration filter.
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Wake Vortices of Landing Aircraft, in High Performance Computing in Science and Engineering

Wake Vortices of Landing Aircraft, in High Performance Computing in Science and Engineering

With this novel method we simulated the complete land- ing phase including fi nal approach, fl are, touchdown, and vortex decay. Figure 2(a) shows the roll-up process of the aircraft wake. The tracer is initialized at certain vorticity levels, depicting the vortex structure behind the aircraft. Wing-tip and fl ap-tip vortices as well as a vortex from the engine pylon and from the wing fuselage junc- tion remain at the tail wing position, as strong coherent structures. Wing-tip and fl ap-tip vortices merge in the mid-fi eld constituting the so-called wake vortices.
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Reynolds Stress Modelling for Turbomachinery Flow Applications

Reynolds Stress Modelling for Turbomachinery Flow Applications

The final measurement plane analysed in this section is placed behind stator 2 and shown in Figure 6.30. Two stator 2 pitches are equivalent to one pitch of the upstream stator 1. The secondary flow structures in stator 2 are dominated by the upstream blade rows. The Menter SST k-ω model, in contrast to the DRSMs, shows strong posi- tive streamwise vorticity very close to the shroud corresponding to a corner separation. As Figure 6.29 (top) shows, the strong secondary flow structures associated with the ro- tor tip gap and passage flow have dissipated more than in the DRSM solutions when they enter the stator passage. A possible explanation could be that the stator’s corner separation is suppressed by these features in the DRSM solution, which is in line with the experiment. Remnants of the trailing edge vortex of rotor 1 at 80% relative channel height can be seen in every other blade passage. As the tip vortex, the DRSMs con- vect this vortex downstream much stronger than the LEVM, which corresponds to the measured values. In the hub region, the picture is, again, rather noisy because struc- tures from both upstream rows appear here. The wakes predicted by the simulation are deeper than in the experiment. Furthermore, there is a strong minimum in Mach number in the region of the hub corner separation in every other stator 2 passage. In contrast, the experiments show less variation from one stator 2 passage to the other. To summarise the discussions above, a quantitative comparison is presented in Fig- ure 6.31. It shows radial traverses of circumferentially mass averaged streamwise vor- ticity ω sw (top) and Mach number M (bottom) computed from the averaged unsteady simulations with the Menter SST k-ω, SSG/LRR-ω and JH-ω h models compared with experiments. For the Mach number, the measurement uncertainty is equivalent to roughly the size of the symbols. As seen above in the discussion of the 2D plots, the differences between the models are more pronounced in the streamwise vorticity than in the Mach number. For the latter, especially in stator 1 there are only marginal differ- ences between the models; a similar conclusion can be drawn for stator 2. The general trends of the experimental data are followed rather well by all models. The only major differences can be seen in the rotor tip region. There, the passage vortex is predicted closer to shroud wall by the DRSMs, which does not agree as well with the measured data as the result obtained with the Menter SST k-ω model. The tip gap vortex, how- ever, dissipates too quickly in the LEVM simulation. Both DRSMs capture the peak in streamwise vorticity which corresponds to this vortex both in position and amplitude. In the upstream row, the peak vorticity of the shroud passage vortex is predicted better than with the LEVM. As argued above, the numerical data in stator 2 show numerous peaks and only qualitatively agree with the measurements.
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The Namuru Receiver as Development Platform for Spaceborne GNSS Applications

The Namuru Receiver as Development Platform for Spaceborne GNSS Applications

The use of reflected GPS signals bounced off Earth’s surface has been suggested as a new source for remote sensing technique [9] especially in the field of ocean altimetry and sea roughness surface state [10]. Its main advantages are the abundant availability of GPS signals which allows the sensing of a wider area compared with traditional active monostatic radars and the use of signals by the GPS system in the L band which is robust to weather conditions [8]. The reflectome- try/scatterometry GNSS receiver is a passive instrument that has reduced size and cost, making it suitable to be deployed in several satellites as payload forming an efficient constellation for Earth remote sensing. Its main disadvantage is that the GPS signals weren’t designed for this kind of applications which requires a higher bandwidth to be able to resolve with higher precision the parameters of the ocean surface.
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High-Lift Research for Future Transport Aircraft

High-Lift Research for Future Transport Aircraft

extended to represent the aero-elastic degrees of freedom by integrating the reduced order model described above. The flight dynamical database allowed a range of in-depth analyses. In aircraft performance, steep climb and land- ing trajectories and low approach speeds are possible, but climb rates with OEI are critical, due to the large induced drag [6]. Furthermore, the circulation control system pro- vides the exceptional possibility to uncouple pitch ampli- tude, angle of attack and lift, opening the opportunity to integrate an advanced flight-path control system. Coupling of the flight mechanical modes and aero-elastic modes is generally weak, even though rapid control input can excite structural modes [6]. A major focus of current research are flight-mechanical consequences of the nonlinear in- teraction of propeller slipstream with the aft fuselage, which become an important factor of directional stability. The database reveals a strong dependence of the lateral motion on angle of attack and thrust setting, with varying instability intervals for small yawing angles [68]. There exist flow conditions where the vertical tail even loses its stabilising effect [62]. The interaction of slipstream and fuselage has a strong impact on pitching moment, thereby coupling lateral and longitudinal motions. Further anal- yses screens aircraft eigenmodes with frequency and damping used as criteria for handling quality over air- speed and yaw angle [68]. Six-degrees-of-freedom simu- lations quantify aircraft response to sudden crosswind. Further simulations went into crosswind landings and investigated the use of differential blowing along the span. In conclusion, the aircraft shows an eccentric directional stability, with its equilibrium at sideslip angles of β±10° [68]. It is believed that such aircraft can be stabilized by an adequate control system.
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A Method for IMU/GNSS/Doppler Velocity Log Integration in Maritime Applications

A Method for IMU/GNSS/Doppler Velocity Log Integration in Maritime Applications

data. As the quality of the estimation is often affected by both the nonlinearity and the mismatched models, the pre- sented approach allows us to address both these issues and provides results which are far more representative for real- world applications. Although it is not easy to decouple the influence of both these effects, the modeling and sensor errors seem to play far larger role in limiting the performance of the presented system as so-called Iterated UKF (IUKF) [21] did not show any improvement in HPE figures. What is even more interesting, the IUKF was sometimes performing even worse compared to non-iterative scheme. This could be, probably, explained both by the fact that IMU/GNSS/DVL fusion does not posses any severe nonlinearities and by presence of the modeling errors in the measurement (e.g. DVL’s Z-axis pseu- domeasurement and GNSS compass geometry errors). Further improvement is expected if special maneuvers are applied in order to improve the observability of some instrument errors. Although the preliminary results are promising, the system performance is strongly dependent on observability of some sensor errors and is conditioned by the dynamics of the vessel exactly before and during the GNSS outage. Here the richness of the associated dynamics could have an extreme influence on the final performance of this multi-sensor system. The presented approach is consistent with the development of the e-Navigation strategy and results in an affordable setup due to lower costs with a promising potential for both performance and robustness improvement due to constantly increasing qual- ity of inertial MEMS sensors.
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Modelling geared turbofan and open rotor engine performance for year-2050 long-range and short-range aircraft

Modelling geared turbofan and open rotor engine performance for year-2050 long-range and short-range aircraft

Table 2: Summary data for TF2050 When comparing data for the final TF2050 engine with the baseline from Appendix A, several differences stand out. First, the net thrust rating has been reduced by 37.9% at cruise and by 31.5% at TOC, due to a more-aerodynamic and lighter aircraft and more fuel-efficient engines. This is despite an assumed 8.3% increase in the number of seats and a 44% increase in design range. TOC thrusts also reduce because of a ‘cascading effect’. Lower SFC leads to reduced block fuel weight, which enables the resizing of structures, such as wings and landing gear, giving more weight savings resulting in lower thrusts etc.
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High Integrated Electric Machine for Aircraft Autonomous Taxiing

High Integrated Electric Machine for Aircraft Autonomous Taxiing

question of whether it is possible to tax a passenger aircraft without emissions and self-sufficient on the taxiing field. A positive side effect is the reduction of the ground-based transport vehicles traffic, especially the tractors, and thus a reduction in the risk of accidents. The German Centre for Aerospace has dealt with the question and the Institute of Vehicle Concepts has designed and built a prototype of an electric nose wheel drive for a commercial aircraft Airbus A320. The project was part of the overall research project for the integration of fuel cells in aircraft. The paper describes the boundary conditions, the requirements, the design of the electrical machine, the gear and the test result.
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NeQuick-G Performance Assessment for Space Applications

NeQuick-G Performance Assessment for Space Applications

computing the effective ionization level Az of the NeQuick- G model, are transmitted as part of the Galileo navigation message (EU 2016 ) and are generally included in the header of RINEX (Receiver INdependent EXchange format; IGS/ RTCM 2019 ) navigation files collected by the IGS. Given the limited data coverage in early years of the IGS multi- GNSS network (Hoque et al. 2019 ), we made additional use of raw navigation data from the COperative Network for GNSS Observations (CONGO, Montenbruck et al. 2011 ) to retrieve the respective parameters for the year 2014. It may be noted that ionospheric correction parameters may be updated more often than once per day in the Galileo navi- gation message, but only one randomly chosen set of daily values is typically made available in archived RINEX navi- gation data files. Accordingly, all tests reported in this work have been performed with just a single set per test day. No systematic quality assessment of sub-daily parameter sets has been done, but the impact of more frequent updates can be expected to be well within the overall uncertainty bounds of the NeQuick-G model and the scatter of iono- spheric parameter estimates by the Galileo ground segment. GPS measurements in the RINEX observation format are independently used within the present study to compute pseudorange-based single-point positioning (SPP) solutions of Swarm-C on the days of interest with different types of ionospheric corrections. Precise GPS orbit and clock solu- tions for this purpose are provided by the CODE Analysis
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High-energy proton imaging for biomedical applications

High-energy proton imaging for biomedical applications

Recent research on medical proton imaging is mostly motivated by the need for particle range determination in hadron therapy. Typically an X-ray CT scan is performed prior to a particle therapy treatment. This scan is used for outlining structures, but also provides a map of stopping power used to derive the beam energies necessary to focus the dose on the target region. The conversion of X-ray absorption, encoded in the grey values of the CT (Hounsfield units) to stopping power provides an appreciable source of error. This source of a systematic error could be avoided by proton computed tomography (proton CT), which relies on proton interaction instead of X-ray absorption. For a long time, the practical applicability of proton imaging remained limited, mostly because of insufficient spatial resolution (a few mm) due to multiple Coulomb scattering (MCS) inside an imaged object: When a proton beam traverses matter, the protons are not only slowed down in interactions with atomic elec- trons, but they are also deflected from their initial direction in electromagnetic interactions with atomic nuclei. The angular spread of a proton beam leaving an object is the result of many such deflections. If the scattered protons fall on a screen behind the object, their spatial distribution is very nearly Gaussian 1 . This makes proton images blurry unless a more sophisticated approach is chosen. Single particle tracking is one way to compensate blurring induced by MCS and current research has become focused on this method. We present an alternative method relying on magnetic optics to compensate for the image blur induced by MCS. This method even employs MCS for enhancing the image contrast. Both, single particle approaches and our method produce 2-dimensional images of an object. These can be combined to derive tomographic reconstructions of an object.
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Novel Low-Twist Bast Fibre Yarns from Flax Tow for High-Performance Composite Applications

Novel Low-Twist Bast Fibre Yarns from Flax Tow for High-Performance Composite Applications

Materials 2021, 14, 105 Materials 2021, 14, x FOR PEER REVIEW 6 of 27 6 of 27 Figure 2. Schematic representation of the resin injection process in the autoclave (autoclave injection). Furthermore, a vacuum infusion process was used with an epoxy matrix to form the quasi-UD fabrics into composites. Before processing, the flax fabric was dried for 16 h at 80 °C and was subsequently placed on a glass plate coated with a release agent. Peel ply and a flow aid were placed on top of this assembly. A spiral hose was used for filling with the epoxy resin and as a suction. A vacuum foil was applied, and the tightness of the vacuum was tested with a Greisinger GDH 200 measuring device (Regenstauf, Germany). The vacuum was generated with a vacuum pump type 20/2 from Vacmobiles (Auckland, New Zealand). The filling of the plates took 3–4 min each. Curing took place under ambi- ent conditions. The composite plates from the vacuum infusion and autoclave injection process resulted in a thickness of approx. 2 mm and were cut by water jet cutting to the appropriate dimensions for further tests to determine the tensile, bending, impact and interlaminar shear strength (ILSS) properties. The characterisation of the specimens with regard to their mechanical properties took place at least three weeks after production.
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A Dual-Band Conformal Antenna for GNSS Applications in Small Cylindrical Structures

A Dual-Band Conformal Antenna for GNSS Applications in Small Cylindrical Structures

the performance of antennas used in global navigation satellite systems (GNSS) are evaluated. Both performance metrics measure the ability of the antenna to efficiently receive the very weak satellite signals as they arrive at the receiver and the antenna’s ability to suppress multipath signals which distort the computed pseudoranges of the receiver from the satellites. In order to improve the availability of the navigation system and to reduce the geometric dilution of precision, it is important that the performance of the antenna does not degrade considerably at low elevations. Good antenna performance at low elevation angles allows a GNSS receiver to reduce its elevation mask as signals are received with acceptable signal-to-noise ratio from more satellites. This requirement has motivated research and development of antennas with wide angular coverage in terms of gain and axial ratio [1]–[3].
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A GNSS Prototyping Platform with Digital Beamforming Capabilities for SoL Applications

A GNSS Prototyping Platform with Digital Beamforming Capabilities for SoL Applications

Future navigation services provided by upcoming global navigation satellite systems like Galileo will require corresponding improvements on the navigation receiving systems. Therefore, the Institute of Communciations and Navigation of the German Aerospace Center originated the development of a GNSS prototyping platform for development and research on navigation receivers with improved capabilities for interference and multipath mitigation by utilization of array antenna processing techniques. Interference and multipath signals can cause serious performance degradations, which cannot be tolerated for Sol applications. New digital beam-forming and signal-processing algorithms will contribute to overcome this problem by suppressing interference and multipath signals and improving the reception of useful line-of-sight satellite signals and thus enable a more accurate and reliable navigation solution. The aim is to develop a complete Safety-of-Life (SoL) receiver demonstration system which includes the whole chain including array antenna, RF front-end, digital signal processing, navigation solution and integrity assessment.
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