Expert system decision support for low-cost launch vehicle operations

Progress in assessing the feasibility, benefits, and risks associated with AI expert systems applied to low cost expendable launch vehicle systems is described. Part one identified potential application areas in vehicle operations and on-board functions, assessed measures of cost benefit, and identified key technologies to aid in the implementation of decision support systems in this environment. Part two of the program began the development of prototypes to demonstrate real-time vehicle checkout with controller and diagnostic/analysis intelligent systems and to gather true measures of cost savings vs. conventional software, verification and validation requirements, and maintainability improvement. The main objective of the expert advanced development projects was to provide a robust intelligent system for control/analysis that must be performed within a specified real-time window in order to meet the demands of the given application. The efforts to develop the two prototypes are described. Prime emphasis was on a controller expert system to show real-time performance in a cryogenic propellant loading application and safety validation implementation of this system experimentally, using commercial-off-the-shelf software tools and object oriented programming techniques. This smart ground support equipment prototype is based in C with imbedded expert system rules written in the CLIPS protocol. The relational database, ORACLE, provides non-real-time data support. The second demonstration develops the vehicle/ground intelligent automation concept, from phase one, to show cooperation between multiple expert systems. This automated test conductor (ATC) prototype utilizes a knowledge-bus approach for intelligent information processing by use of virtual sensors and blackboards to solve complex problems. It incorporates distributed processing of real-time data and object-oriented techniques for command, configuration control, and auto-code generation

BB-RTE: a Budget-Based RunTime Engine for Mixed and Safety Critical Systems

International audienceThe safety critical industry is considering a shift from single-core COTS to multi-core COTS processor for safety and time critical computers in order to maximize performance while reducing costs.In a domain where time predictability is a major concern due to the regulation standards, multi-core processors are introducing new sources of time variations due to the electronic competition when the software is accessing shared hardware resources, and characterized by timing interference.The solutions proposed in the literature to deal with timing interference are all proposing a trade-off between performance efficiency, time predictability and intrusiveness in the software. Especially, none of them is able to fully exploit the multi-core efficiency while allowing untouched, already-certified legacy software to run.In this paper, we introduce and evaluate BB-RTE, a Budget-Based RunTime Engine for Mixed and Safety Critical Systems, that especially focuses on mixed critical systems. BB-RTE guarantees the deadline of high-critical tasks 1) by computing for each shared hardware resource a budget in terms of extra accesses that the critical tasks can support before their runtime is significantly impacted; 2) by temporarily suspending low-critical tasks at runtime once this budget as been consumed

Ethernet - a survey on its fields of application

During the last decades, Ethernet progressively became the most widely used local area networking (LAN) technology. Apart from LAN installations, Ethernet became also attractive for many other fields of application, ranging from industry to avionics, telecommunication, and multimedia. The expanded application of this technology is mainly due to its significant assets like reduced cost, backward-compatibility, flexibility, and expandability. However, this new trend raises some problems concerning the services of the protocol and the requirements for each application. Therefore, specific adaptations prove essential to integrate this communication technology in each field of application. Our primary objective is to show how Ethernet has been enhanced to comply with the specific requirements of several application fields, particularly in transport, embedded and multimedia contexts. The paper first describes the common Ethernet LAN technology and highlights its main features. It reviews the most important specific Ethernet versions with respect to each application field’s requirements. Finally, we compare these different fields of application and we particularly focus on the fundamental concepts and the quality of service capabilities of each proposal

System level airborne avionics prognostics for maintenance, repair and overhaul

The aim of this study is to propose an alternative approach in prognostics for airborne avionics system in order to enhance maintenance process and aircraft availability. The objectives are to analyse the dependency of avionic systems for fault propagation behaviour degradation, research and develop methods to predict the remaining useful life of avionics Line Replaceable Units (LRU), research and develop methods to evaluate and predict the degradation performances of avionic systems, and lastly to develop software simulation systems to evaluate methods developed. One of the many stakeholders in the aircraft lifecycle includes the Maintenance, Repair and Overhaul (MRO) industry. The predictable logistics process to some degree as an outcome of IVHM gives benefit to the MRO industry. In this thesis, a new integrated numerical methodology called ‘System Level Airborne Avionic Prognostics’ or SLAAP is developed; looking at a top level solution in prognostics. Overall, this research consists of two main elements. One is to thoroughly understand and analyse data that could be utilised. Secondly, is to apply the developed methodology using the enhanced prognostic methodology. Readily available fault tree data is used to analyse the dependencies of each component within the LRUs, and performance were simulated using the linear Markov Model to estimate the time to failure. A hybrid approach prognostics model is then integrated with the prognostics measures that include environmental factors that contribute to the failure of a system, such as temperature. This research attempts to use data that is closest to the data available in the maintenance repair and overhaul industry. Based on a case study on Enhanced Ground Proximity Warning System (EGPWS), the prognostics methodology developed showed a sufficiently close approximation to the Mean Time Before Failure (MTBF) data supplied by the Original Equipment Manufacturer (OEM). This validation gives confidence that the proposed methodology will achieve its objectives and it should be further developed for use in the systems design process

System level airborne avionics prognostics for maintenance, repair and overhaul

The aim of this study is to propose an alternative approach in prognostics for airborne avionics system in order to enhance maintenance process and aircraft availability. The objectives are to analyse the dependency of avionic systems for fault propagation behaviour degradation, research and develop methods to predict the remaining useful life of avionics Line Replaceable Units (LRU), research and develop methods to evaluate and predict the degradation performances of avionic systems, and lastly to develop software simulation systems to evaluate methods developed. One of the many stakeholders in the aircraft lifecycle includes the Maintenance, Repair and Overhaul (MRO) industry. The predictable logistics process to some degree as an outcome of IVHM gives benefit to the MRO industry. In this thesis, a new integrated numerical methodology called ‘System Level Airborne Avionic Prognostics’ or SLAAP is developed; looking at a top level solution in prognostics. Overall, this research consists of two main elements. One is to thoroughly understand and analyse data that could be utilised. Secondly, is to apply the developed methodology using the enhanced prognostic methodology. Readily available fault tree data is used to analyse the dependencies of each component within the LRUs, and performance were simulated using the linear Markov Model to estimate the time to failure. A hybrid approach prognostics model is then integrated with the prognostics measures that include environmental factors that contribute to the failure of a system, such as temperature. This research attempts to use data that is closest to the data available in the maintenance repair and overhaul industry. Based on a case study on Enhanced Ground Proximity Warning System (EGPWS), the prognostics methodology developed showed a sufficiently close approximation to the Mean Time Before Failure (MTBF) data supplied by the Original Equipment Manufacturer (OEM). This validation gives confidence that the proposed methodology will achieve its objectives and it should be further developed for use in the systems design process

Use of high performance networks and supercomputers for real-time flight simulation

In order to meet the stringent time-critical requirements for real-time man-in-the-loop flight simulation, computer processing operations must be consistent in processing time and be completed in as short a time as possible. These operations include simulation mathematical model computation and data input/output to the simulators. In 1986, in response to increased demands for flight simulation performance, NASA's Langley Research Center (LaRC), working with the contractor, developed extensions to the Computer Automated Measurement and Control (CAMAC) technology which resulted in a factor of ten increase in the effective bandwidth and reduced latency of modules necessary for simulator communication. This technology extension is being used by more than 80 leading technological developers in the United States, Canada, and Europe. Included among the commercial applications are nuclear process control, power grid analysis, process monitoring, real-time simulation, and radar data acquisition. Personnel at LaRC are completing the development of the use of supercomputers for mathematical model computation to support real-time flight simulation. This includes the development of a real-time operating system and development of specialized software and hardware for the simulator network. This paper describes the data acquisition technology and the development of supercomputing for flight simulation

Virtual Timing Isolation Safety-Net for Multicore Processors

Multicore processors promise to offer the performance as well as the reduced space, weight and power needed by future aircrafts. However, commercial off-the-shelf multicore processors suffer from timing interferences between cores which complicates applying them in hard real-time systems like avionic applications. In this thesis, a safety-net system is proposed which enables a virtual timing isolation of applications running on one core from all other cores. The technique is based on hardware external to the multicore processor and completely transparent to the applications, i.e. no modification of the observed software is necessary. The basic idea is to apply a single-core execution based worst-case execution time analysis and to accept a predefined slowdown during multicore execution. If the slowdown exceeds the acceptable bounds, interferences will be reduced by controlling the behavior of low-critical cores to keep the main application’s progress inside the given bounds. Measuring the progress of the applications running on the main core is performed by tracking the application’s fingerprint. A fingerprint is created by extraction of the performance counters of the critical core in very small timesteps which results in a characteristic curve for every execution of a periodic program. In standalone mode, without any running applications on the other cores, a model of an application is created by clustering and combining the extracted curves. During runtime, the extracted performance counter values are compared to the model to determine the progress of the critical application. In case the progress of an application is unacceptably delayed, the cores creating the interferences are throttled. The interference creating cores are determined by the accesses of the respective cores to the shared resources. A controller that takes the progress of a critical application as well as the time until the final deadline into account throttles the low priority cores. Throttling is either performed by frequency scaling of the interfering cores or by halt and continue with a pulse width modulation scheme. The complete safety-net system was evaluated on a TACLeBench benchmark running on an NXP P4080 multicore processor observed by a Xilinx FPGA implementing a MicroBlaze soft-core microcontroller. The results show that the progress can be measured by the fingerprinting with a final deviation of less than 1% for a TACLeBench execution with running opponent cores and indicate the non-intrusiveness of the approach. Several experiments are conducted to demonstrate the effectiveness of the different throttling mechanisms. Evaluations using a real-world avionic application show that the approach can be applied to integrated modular avionic applications. The safety-net does not ensure robust partitioning in the conventional meaning. The applications on the different cores can influence each other in the timing domain, but the external safety-net ensures that the interference on the high critical application is low enough to keep the timing. This allows for an efficient utilization of the multicore processor. Every critical application is treated individually, and by relying on individual models recorded in standalone mode, the critical as well as the non-critical applications running on the other cores can be exchanged without recreating a fingerprint model. This eases the porting of legacy applications to the multicore processor and allows the exchange of applications without recertification.Der Einsatz von Multicore Prozessoren in Avioniksystemen verspricht sowohl die Performancesteigerung als auch den reduzierten Platz-, Gewichts- und Energieverbrauch, der zur Realisierung von zukünftigen Flugzeugen benötigt wird. Die Verwendung von seriengefertigten (COTS) Multicore Prozessoren in sicherheitskritischen Echtzeitsystemen ist jedoch sehr komplex, da eine gegenseitige zeitliche Beeinflussung der Anwendungen auf den unterschiedlichen Kernen nicht ausgeschlossen werden kann. In dieser Arbeit wird ein Konzept vorgestellt, das eine virtuelle zeitliche Trennung der Anwendungen, die auf einem Prozessorkern ausgeführt werden, von denen der übrigen Kerne ermöglicht. Die Grundidee besteht darin, eine auf einer Single-Core-Ausführung basierende Laufzeitanalyse (WCET) durchzuführen und eine vordefinierte Verlangsamung während der Multicore-Ausführung zu akzeptieren. Wenn die Verlangsamung die zulässige Grenze überschreitet, wird das Verhalten niedrigkritischer Kerne so gesteuert, dass der Fortschritt der Hauptanwendung innerhalb der Deadlines bleibt. Die Bestimmung des Fortschritts der kritischen Anwendungen erfolgt durch das Verfolgen eines sogenannten Fingerprints. Ein Fingerprint wird durch Auslesen der Performance Counter des kritischen Kerns in sehr kleinen Zeitschritten erzeugt, was zu einer charakteristischen Kurve für jede Ausführung eines periodischen Programms führt. Ein Modell einer Anwendung wird erstellt, indem die extrahierten Kurven gruppiert und kombiniert werden. Während der Laufzeit werden die ausgelesenen Werte mit dem Modell verglichen, um den Fortschritt zu bestimmen. Falls die zeitliche Ausführung einer ktitischen Anwendung zu stark verzögert wird, werden die Kerne gedrosselt, welche die Störungen verursachen. Das Konzept wurde mit einem TACLeBench-Benchmark evaluiert, der auf einem NXP P4080 Multicore Prozessor ausgefüht, und von einem Xilinx-FPGA beobachtet wurde. Es konnte gezeigt werden, dass der Fortschritt durch den Fingerprint mit einer endgültigen Abweichung von weniger als 1% für eine TACLeBench-Ausführung mit laufenden konkurrierenden Kernen gemessen werden kann. Die Evaluation mit einer realen Avionik-Anwendung zeigte, dass das Konzept für integrierte modulare Avionik-Anwendungen (IMA) genutzt werden kann. Der Ansatz gewährleistet keine robuste Partitionierung im herkömmlichen Sinne. Die Anwendungen auf den verschiedenen Kernen können sich zeitlich gegenseitig beeinflussen, aber ein externes Sicherheitsnetz stellt sicher, dass die Verlangsamung der hochkritischen Anwendung niedrig genug ist, um die Deadlines zu halten. Dies ermöglicht eine effiziente Auslastung des Multicore Prozessors. Außerdem wird jede kritische Anwendung einzeln behandelt und verfügt über ein individuelles Modell. Somit können die kritischen und nicht kritischen Anwendungen, die auf den anderen Kernen ausgeführt werden, ausgetauscht werden, ohne ein Modell neu zu erstellen. Dies vereinfacht die Portierung von bestehenden Anwendungen auf Multicore Prozessoren und ermöglicht den Austausch von Anwendungen ohne eine erneute Zertifizierung

Application of technology developed for flight simulation at NASA. Langley Research Center

In order to meet the stringent time-critical requirements for real-time man-in-the-loop flight simulation, computer processing operations including mathematical model computation and data input/output to the simulators must be deterministic and be completed in as short a time as possible. Personnel at NASA's Langley Research Center are currently developing the use of supercomputers for simulation mathematical model computation for real-time simulation. This, coupled with the use of an open systems software architecture, will advance the state-of-the-art in real-time flight simulation

Space Station Freedom data management system growth and evolution report

The Information Sciences Division at the NASA Ames Research Center has completed a 6-month study of portions of the Space Station Freedom Data Management System (DMS). This study looked at the present capabilities and future growth potential of the DMS, and the results are documented in this report. Issues have been raised that were discussed with the appropriate Johnson Space Center (JSC) management and Work Package-2 contractor organizations. Areas requiring additional study have been identified and suggestions for long-term upgrades have been proposed. This activity has allowed the Ames personnel to develop a rapport with the JSC civil service and contractor teams that does permit an independent check and balance technique for the DMS