Efficient and predictable high-speed storage access for real-time embedded systems

As the speed, size, reliability and power efficiency of non-volatile storage media increases, and the data demands of many application domains grow, operating systems are being put under escalating pressure to provide high-speed access to storage. Traditional models of storage access assume devices to be slow, expecting plenty of slack time in which to process data between requests being serviced, and that all significant variations in timing will be down to the storage device itself. Modern high-speed storage devices break this assumption, causing storage applications to become processor-bound, rather than I/O-bound, in an increasing number of situations. This is especially an issue in real-time embedded systems, where limited processing resources and strict timing and predictability requirements amplify any issues caused by the complexity of the software storage stack. This thesis explores the issues related to accessing high-speed storage from real-time embedded systems, providing a thorough analysis of storage operations based on metrics relevant to the area. From this analysis, a number of alternative storage architectures are proposed and explored, showing that a simpler, more direct path from applications to storage can have a positive impact on efficiency and predictability in such systems

Third International Conference on Inverse Design Concepts and Optimization in Engineering Sciences (ICIDES-3)

Papers from the Third International Conference on Inverse Design Concepts and Optimization in Engineering Sciences (ICIDES) are presented. The papers discuss current research in the general field of inverse, semi-inverse, and direct design and optimization in engineering sciences. The rapid growth of this relatively new field is due to the availability of faster and larger computing machines

Robust real-time control of an adaptive optics system

This research contributes to the understanding of the limitations when designing a robust control real-time system for Adaptive Optics (AO). One part of the research is a new method regarding the evaluation of a Shack-Hartmann wavefront sensor (SHWFS) to enhance the overall performance. The method is presented based on the application of a Field Programmable Gate Array (FPGA) using Connected Component Labeling (CCL) for blob detection. The FPGA has been utilized since the resulting delay is crucial for the general AO performance. In this regard, the FPGA may accelerate the evaluation largely by its parallelism. The developed algorithm does not rely on a fixed assignment of the camera sensor area to the lenslet array to maximize the dynamic range. In extension to the SHWFS evaluation, a new rapid control prototyping (RCP) system based on hard real-time RTAI-patched Linux kernel has been developed. This system includes the required hardware e.g.~the analog output cards and FPGA based frame-grabber. Based upon a Simulink model, accelerated C/C++ code is automatically generated which uses the available parallel features of the processor. A continuative contribution is the application of a robust control scheme using H-infinity methods for designing a controller while considering uncertainty of the identified model. For synthesizing the controller, a special optimization technique called non-smooth mu-synthesis is utilized which minimizes the H-infinity norm while coping with pre-specified controller schemes. Depending on the pre-specified controller scheme, the resulting controller can be computationally costly but the RCP approach is designed to cope with the problem. Based on simulations and according to experiments, the validity of the identified models of the AO setup is assured. At the same time, the enhanced performance of the new RCP setup is demonstrated.Die wissenschaftliche Arbeit trägt maßgeblich zum Verständnis der gängigen Limitierungen bei robusten echtzeit-fähigen Regelungssystemen für Adaptiv Optische (AO) Systeme bei. Ein wesentlicher Teil der Arbeit befasst sich mit einer neuartigen Methode der Auswertung eines Shack-Hartmann Wellenfrontsensors (SHWFS). Die Methode basiert auf der Anwendung eines Field Programmable Gate Arrays (FPGA) zur Auswertung des SHWFS. Die zu Grunde liegende Methode ist ein Resultat der Graphentheorie zur Erkennung zusammenhängender Bildbereiche. Der Einsatz eines FPGA ermöglicht hierbei, dass die resultierende Verzögerung durch die Auswertung des SHWFS auf ein Minimum reduziert wird. Hinzu kommt, dass die neuartige Auswertungsmethode den dynamischen Bereich des Wellenfrontsensors gegenüber dem üblichen Verfahren erweitert, da für die Methode keine feste Zuordnung der Spots zu dem Linsenarray notwendig ist. Zusätzlich zu dem neuartigen Verfahren für die Auswertung wurde ein Rapid Control Prototyping (RCP) System entworfen, welches auf einem echtzeitfähigen Linux Kernel basiert. Die Echtzeitfähigkeit wird durch die Verwendung des Real-Time Application Interface for Linux (RTAI) erreicht. Der Entwurf des RCP Systems umfasst die Entwicklung spezieller Hardware wie beispielsweise eine analoge Ausgangskarte und der PCIe FPGA Framegrabber. Aus einem Simulink Modell wird automatisch C/C++ Quellcode generiert. Dieser generierte Code nutzt die vorhandenen parallelen Erweiterungen des Prozessors zur Beschleunigung der vorkommenden Berechnungen. Basierend auf diesem System wurde ein robustes Regelungsverfahren angewendet, welches auf der H_infty Entwurfsmethodik basiert. Das Entwurfverfahren des Reglers (non-smooth mu Synthese) berücksichtigt die vorhandene Unsicherheit der identifizierten Modelle bereits während der Synthese. Das Verfahren ermöglicht die H_infty Norm des geschlossenen Regelkreises zu minimieren, wobei die Regler-Struktur vorgegeben werden kann. Basierend auf verschiedenen Simulationen und experimentellen Versuchen wurde die Gültigkeit der identifizierten Modelle des AO Systems nachgewiesen. Zudem wird gezeigt, dass das entworfene RCP System deutlich leistungsfähiger als vergleichbare Systeme ist und somit eine deutlich verbesserte Performance aufweist

Aeronautical Engineering: A special bibliography with indexes, supplement 75, October 1976

This bibliography lists 300 reports, articles, and other documents introduced into the NASA scientific and technical information system in September 1976

Bibliography of Lewis Research Center technical contributions announced in 1976

Abstracts of Lewis authored publications and publications resulting from Lewis managed contracts which were announced in the 1976 issues of STAR (Scientific and Technical Aerospace Reports) and IAA (International Aerospace Abstracts) are presented. Research reports, journal articles, conference presentations, patents and patent applications, and these are included. The arrangement is by NASA subject category. Citations indicate report literature (identified by their N-numbers) and the journal and conference presentations (identified by their A-numbers). A grouping of indexes helps locate specific publications by author (including contractor authors), contractor organization, contract number, and report number

Rotordynamic Instability Problems in High-Performance Turbomachinery, 1988

The continuing trend toward a unified view is supported with several developments in the design and manufacture of turbomachines with enhanced stability characteristics along with data and associated numerical/theoretical results. The intent is to provide a continuing impetus for an understanding and resolution of these problems. Topics addressed include: field experience, dampers, seals, impeller forces, bearings, and compressor and rotor modeling

Ninth European Powder Diffraction Conference – Prague, September 2-5, 2004

Zeitschrift für Kristallographie. Supplement Volume 23 presents the complete Proceedings of all contributions to the IX European Powder Diffraction Conference in Prague 2004: Method Development and Application, Instrumental, Software Development, Materials Supplement Series of Zeitschrift für Kristallographie publishes Proceedings and Abstracts of international conferences on the interdisciplinary field of crystallography

The Design of a High-Integrity Disk Management Subsystem

This dissertation describes and experimentally evaluates the design of the Logical Disk, a disk management subsystem that guarantees the integrity of data stored on disk even after system failures, while still providing performance competitive to other storage systems. Current storage systems that use the hard disk as storage medium, such as file systems, often do not provide sufficient protection against loss of data after a system failure. The designers of such systems are afraid that the amount of effort necessary for data protection would also result in too much loss of performance. The Logical Disk uses many different techniques to guarantee data integrity, including the support to execute multiple commands as one atomic action and avoiding `in-place updates' at all times. The techniques used to provide competitive performance include the technique of combining many, small write commands into one large, sequential, and thus efficient, write to disk, and clustering the data on disk continuously and automatically.Tanenbaum, A.S. [Promotor]Jonge, W. de [Copromotor