76 research outputs found

    ADVANCED BRAKING SYSTEM CONTROL PROTOTYPING USING NETWORKED HARDWARE-IN-THE-LOOP TECHNIQUE

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    Control functions for the base-braking and emergency braking situations are important element of the vehicle active safety and have high requirements to robustness. The corresponding control algorithms should be reliable, provide sufficient level of system adaptiveness and be able to reject external disturbances. This demands not only the well-organized controller from the theoretical point of view, but also its systematic experimental validation. Moreover, effects and factors, which can potentially produce deterioration of braking system control functions, should be properly taken into account in the simulation and during the experiments. Another important factor is that brake control systems have a closed-loop operation with the tyre-road interaction, and its operation is accompanied by such complex effects like (i) variation of disc/pad friction coefficient and (ii) brake hysteresis. This produces strong demand on extension of the conventional testing facilities for the braking system control evaluation. Therefore, besides the part of the control system design, this paper represents possible advancement of hardware-in-the-loop testing procedure for development and validation of braking system control functions

    Distributed local X-in-the-loop environment - a tool for electric vehicle systems design

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    The paper describes methodology and corresponding environment for development, validation and testing of complex electric vehicle (EV) systems. The proposed approach is based on distribution of relevant design tasks between remotely working testing equipment with real-time (RT) data sharing and data exchange. The approach is demonstrated by the example of X-in-the-loop (XIL) environment uniting electric motor test setup, hardware-in-the-loop (HIL) platform with brake-by-wire system, and the brake dynamometer. The study introduces how this configuration of experimental tools can be used by designing the brake blending and control of an EV

    Survey on modelling and techniques for friction estimation in automotive brakes

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    The increased use of disc brakes in passenger cars has led the research world to focus on the prediction of brake performance and wear under different working conditions. A proper model of the brake linings’ coefficient of friction (BLCF) is important to monitor the brake operation and increase the performance of control systems such as ABS, TC and ESP by supplying an accurate estimate of the brake torque. The literature of the last decades is replete with semi-empirical and analytical friction models whose derivation comes from significant research that has been conducted into the direction of friction modelling of pin-disc couplings. On the contrary, just a few models have been developed and used for the prediction of the automotive BLCF without obtaining satisfactory results. The present work aims at collecting the current state of art of the estimation techniques for the BLCF, with special attention to the models for automotive brakes. Moreover, the work proposes a classification of the several existing approaches and discusses the relative pro and cons. Finally, based on evidence of the limitations of the model-based approach and the potentialities of the neural networks, the authors propose a new state observer for BLCF estimation as a promising solution among the supporting tools of the control engineering

    Connected and shared X-in-the-loop technologies for electric vehicle design

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    The presented paper introduces a new methodology of experimental testing procedures required by the complex systems of electric vehicles (EV). This methodology is based on real-time connection of test setups and platforms, which may be situated in different geographical locations, belong to various cyber-physical domains, and are united in a global X-in-the-loop (XIL) experimental environment. The proposed concept, called XILforEV, allows exploring interdependencies between various physical processes that can be identified or investigated in the process of EV development. The paper discusses the following relevant topics: global XILforEV architecture; realization of required high-confidence models using dynamic data driven application systems (DDDAS) and multi fidelity models (MFM) approaches; and formulation of case studies to illustrate XILforEV application

    Bond-disordered Anderson model on a two dimensional square lattice - chiral symmetry and restoration of one-parameter scaling

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    Bond-disordered Anderson model in two dimensions on a square lattice is studied numerically near the band center by calculating density of states (DoS), multifractal properties of eigenstates and the localization length. DoS divergence at the band center is studied and compared with Gade's result [Nucl. Phys. B 398, 499 (1993)] and the powerlaw. Although Gade's form describes accurately DoS of finite size systems near the band-center, it fails to describe the calculated part of DoS of the infinite system, and a new expression is proposed. Study of the level spacing distributions reveals that the state closest to the band center and the next one have different level spacing distribution than the pairs of states away from the band center. Multifractal properties of finite systems furthermore show that scaling of eigenstates changes discontinuously near the band center. This unusual behavior suggests the existence of a new divergent length scale, whose existence is explained as the finite size manifestation of the band center critical point of the infinite system, and the critical exponent of the correlation length is calculated by a finite size scaling. Furthermore, study of scaling of Lyapunov exponents of transfer matrices of long stripes indicates that for a long stripe of any width there is an energy region around band center within which the Lyapunov exponents cannot be described by one-parameter scaling. This region, however, vanishes in the limit of the infinite square lattice when one-parameter scaling is restored, and the scaling exponent calculated, in agreement with the result of the finite size scaling analysis.Comment: 23 pages, 11 figures. RevTe

    Surgery for complications of trans-catheter closure of atrial septal defects: a multi-institutional study from the European Congenital Heart Surgeons Association

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    Objective: This study aims to analyse the collective experience of participating European Congenital Heart Surgeons Association centres in the surgical management of complications resulting from trans-catheter closure of atrial septal defects (ASDs). Methods: The records of all (n=56) patients, aged 3-70 years (median 18 years), who underwent surgery for complications of trans-catheter ASD closure in 19 participating institutions over a 10-year period (1997-2007) were retrospectively reviewed. Risk factors for surgical complications were sought. Surgical outcomes were compared with those reported for primary surgical ASD closure in the European Association of Cardio-thoracic Surgery Congenital Database. Results: A wide range of ASD sizes (5-34mm) and devices of various types and sizes (range 12-60mm) were involved, including 13 devices less than 20mm. Complications leading to surgery included embolisation (n=29), thrombosis/thrombo-embolism/cerebral ischaemia or stroke (n=12), significant residual shunt (n=12), aortic or atrial perforation or erosion (n=9), haemopericardium with tamponade (n=5), aortic or mitral valve injury (n=2) and endocarditis (n=1). Surgery (39 early emergent and 17 late operations) involved device removal, repair of damaged structures and ASD closure. Late operations were needed 12 days to 8 years (median 3 years) after device implantation. There were three hospital deaths (mortality 5.4%). During the same time period, mortality for all 4453 surgical ASD closures reported in the European Association of Cardio-Thoracic Surgery Congenital Database was 0.36% (p=0.001). Conclusions: Trans-catheter device closure of ASDs, even in cases when small devices are used, can lead to significant complications requiring surgical intervention. Once a complication leading to surgery occurs, mortality is significantly greater than that of primary surgical ASD closure. Major complications can occur late after device placement. Therefore, lifelong follow-up of patients in whom ASDs have been closed by devices is mandator

    The Seventh Data Release of the Sloan Digital Sky Survey

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    This paper describes the Seventh Data Release of the Sloan Digital Sky Survey (SDSS), marking the completion of the original goals of the SDSS and the end of the phase known as SDSS-II. It includes 11663 deg^2 of imaging data, with most of the roughly 2000 deg^2 increment over the previous data release lying in regions of low Galactic latitude. The catalog contains five-band photometry for 357 million distinct objects. The survey also includes repeat photometry over 250 deg^2 along the Celestial Equator in the Southern Galactic Cap. A coaddition of these data goes roughly two magnitudes fainter than the main survey. The spectroscopy is now complete over a contiguous area of 7500 deg^2 in the Northern Galactic Cap, closing the gap that was present in previous data releases. There are over 1.6 million spectra in total, including 930,000 galaxies, 120,000 quasars, and 460,000 stars. The data release includes improved stellar photometry at low Galactic latitude. The astrometry has all been recalibrated with the second version of the USNO CCD Astrograph Catalog (UCAC-2), reducing the rms statistical errors at the bright end to 45 milli-arcseconds per coordinate. A systematic error in bright galaxy photometr is less severe than previously reported for the majority of galaxies. Finally, we describe a series of improvements to the spectroscopic reductions, including better flat-fielding and improved wavelength calibration at the blue end, better processing of objects with extremely strong narrow emission lines, and an improved determination of stellar metallicities. (Abridged)Comment: 20 pages, 10 embedded figures. Accepted to ApJS after minor correction

    Chromosome-scale genome assembly provides insights into rye biology, evolution and agronomic potential

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    Rye (Secale cereale L.) is an exceptionally climate-resilient cereal crop, used extensively to produce improved wheat varieties via introgressive hybridization and possessing the entire repertoire of genes necessary to enable hybrid breeding. Rye is allogamous and only recently domesticated, thus giving cultivated ryes access to a diverse and exploitable wild gene pool. To further enhance the agronomic potential of rye, we produced a chromosome-scale annotated assembly of the 7.9-gigabase rye genome and extensively validated its quality by using a suite of molecular genetic resources. We demonstrate applications of this resource with a broad range of investigations. We present findings on cultivated rye's incomplete genetic isolation from wild relatives, mechanisms of genome structural evolution, pathogen resistance, low-temperature tolerance, fertility control systems for hybrid breeding and the yield benefits of rye-wheat introgressions.Peer reviewe

    Ein modellbasierter Ansatz zur integralen Systementwicklung im Gesamtfahrzeug

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    Moderne Fahrzeuge werden komfortabler, sicherer und effizienter wie nie zuvor. Um dies zu erreichen, unterliegen sie aufgrund zunehmender Bedeutung von Elektromobilität und Automatisierung einem Systemwandel. Infolgedessen nehmen ihre Komplexität und die damit verbundenen Anforderungen stark zu, was den Entwicklungsaufwand erheblich erhöht. Darüber hinaus wird die Forderung nach kürzer werdenden Durchlaufzeiten immer größer. Daher bedarf es neuartiger Entwicklungsumgebungen, die die Entwicklung solcher Systeme effizienter gestalten. Zwar existieren bereits eine Reihe an Werkzeugen zur Spezifikation des Systementwurfs, jedoch gibt es kein einheitliches Verständnis, keine standardisierten Taxonomien und kein methodisches Vorgehen bei der Systemsynthese. Die wissenschaftliche Arbeit greift dies auf und liefert einen modularen Lösungsansatz zur modellbasierten Entwicklung von Fahrzeugsystemen. Insbesondere spielt die Funktionsabsicherung mit dem sogenannten X-in-the-Loop-Ansatz eine große Rolle, mit dem eine schlanke, robuste und durchgängige Entwicklung möglich werden soll. Hierbei liefert die Arbeit eine einheitliche Schnittstellen-Architektur, mit der das monolithische Vorgehen in der Entwicklung aufgelöst wird. Dabei dienen Simulationswerkzeuge als wichtige Integratoren, mit denen heterogene Prüfumgebungen unabhängig von Werkzeugen, Domänen und Organisationen flexibel miteinander gekoppelt werden können. Die entwickelte Methodologie dient als Rahmen und verringert den Konfigurationsaufwand der Werkzeuge zur Umsetzung von X-in-the-Loop. Damit können die Prozesse zum Systementwurf, zur Systemsynthese und zur Validierung schon frühzeitig in der Entwicklung realisiert werden. Ein weiterer Beitrag der Dissertation ist die Umsetzung einer lokal und global verteilten X-in-the-Loop-Umgebung, die auf ihre Echtzeitfähigkeit, Robustheit und Allgemeingültigkeit überprüft wurde. Dazu wurde eine Beobachter-Distributor-Struktur genutzt, um die verteilten Simulationswerkzeuge und Prüfstände in Echtzeit zu synchronisieren. Als Fallstudie wurde ein elektrohydraulisches Bremssystem betrachtet, da seine Systemarchitektur aufgrund steigender Automatisierung und Elektrifizierung von Fahrzeugsystemen einem systemischen 'Wandel ausgesetzt ist. Zur Demonstration der Methode werden die domänenspezifischen Verfahren wie Model-in-the-Loop, Test-Rig-in-the-Loop, Hardware-in-the-Loop und ein gesamtheitliches X-in-the-Loop-Verfahren, das alle Domänen integriert, entwickelt und anhand des elektrohydraulischen Bremssystem miteinander verglichen.Driven by the increasing needs for automation and e-mobility, the design of cars has had to change in order that they become more comfortable, safer, and more efficient. As a result, the complexity and requirements have increased significantly, which leads to a large increase in the required development effort. As well, the demand for shorter lead times is increasing. Therefore, new development environments are needed to make the implementation of such systems more efficient. Although, a number of tools for the specification of system design already exist, there is no common understanding, no standardised taxonomies, or approaches for system integration. Thus, this thesis contributes a modular solution for the model-based development of vehilce systems. In particular, functional validation using the X-in-the-loop approach plays a major role to allow lean, robust, integrated development. In this context, the thesis provides a generic interface architecture to resolve the monolithic approaches in development. Simulation tools serve as important integrators, with which heterogeneous testing environments can be flexibly coupled regardless of tools, domains, and organisations. The proposed methodology provides a framework that reduces the required configuration effort of tools for X-in-the-loop implementation. Thus, the processes for system design, system integration, and validation can be realised at an early development stage. A further contribution of the thesis is that a locally and globally distributed X-in-the-loop environment was implemented and verified for its real-time capability, robustness, and validity. An observer-distributor structure was used to synchronise the distributed simulation tools and test benches in real time. An electrohydraulic braking system was considered as the case study. Its system architecture is exposed to systemic change due to the increasing automation of vehicle systems and the electrification of the propulsion unit. To demonstrate the method, domain-specific approaches, such as model-in-the-loop, test-rig-in-the-loop, hardware-in-the-loop and a holistic X-in-the-loop approach integrating all domains, were implemented and compared
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