No description available.

Parallel and distributed computing systems become more and more powerful and hence place increasingly higher demands on the networks that interconnect their processors or processing nodes. Many of the applications running on such systems, especially embedded systems applications, have real-time requirements and, with increasing application demands, high-performance networks are the hearts of these systems. Fiber-optic networks are good candidates for use in such systems in the future. This thesis contributes to the relatively unexplored area of fiber-optic networks for parallel and distributed real-time computer systems and  suggests and evaluates several fiber-optic networks and protocols. Two different technologies are used in the networks, WDM (Wavelength Division Multiplexing) and fiber-ribbon point-to-point links. WDM offers multiple channels, each with a capacity of several Gbit/s. A WDM star network in which protocols and services are efficiently integrated to support different kinds of real-time demands, especially hard ones, has been developed. The star-of-stars topology can be chosen to offer better network scalability. The WDM star architecture is attractive but its future success depends on components becoming more commercially mature. Fiber-ribbon links, offering instead an aggregated bandwidth of several Gbit/s, have already reached the market with a promising price/performance ratio. This has motivated the development and investigation of two new ring networks based on fiber-ribbon links. The networks take advantage of spatial bandwidth reuse, which can greatly enhance performance in applications with a significant amount of nearest downstream neighbor communication. One of the ring networks is control channel based and not only has support for real-time services like the WDM star network but also low level support for, e.g., group communication. The approach has been to develop network protocols with support for dynamic real-time services, out of time-deterministic static TDMA systems. The focus has been on functionality more than pure performance figures, mostly on real-time features but also on other types of functionality for parallel and distributed systems. Worst-case analyses, some simulations, and case studies are reported for the networks. The focus has been on embedded supercomputer applications, where each node itself can be a parallel computer, and it is shown that the networks are well suited for use in the radar signal processing systems studied. Other application examples in which these kinds of networks are valuable are distributed multimedia systems, satellite imaging and other image processing applications. / Technical report / School of Electrical and Computer Engineering, Chalmers University of Technology, Göteborg, Sweden, 0282-5406 ; 379

This master thesis’s subject is to model an ABB contactor’s dynamics and to develop a hardware-in-the-loop simulation environment. The hardware-in-the-loop method utilizes computer models that are simulated in a real-time simulator. The real-time simulator is connected to hardware components. A contactor is an electrically controlled mechanical switching device and it is used in circuits where large currents can occur. In this thesis, the contactor is divided into three separate subsystems and models are developed for each of them. The three subsystems correspond to the contactor’s mechanics, electromagnetics and electronic components. Computer models are implemented in MATLAB and Simulink to realize the subsystems. The hardware part, of the hardware-in-the-loop simulations, consists of electronic parts that are not modeled. To connect the hardware part to a real-time simulator, from dSPACE, a hardware interface was constructed. This report focuses on the modeling of the mechanics and the electromagnetics as well as the software implementations. The thesis work was carried out in collaboration with another student. The focuses of his report are the modeling of the electronics and the construction of the hardware interface. Validation of the hardware-in-the-loop simulations is done by using measurements collected from a real contactor. The conclusion is that the simulations of the contactor’s behavior correspond well with a real contactor.

Real-time Embedded Systems (RTESs) have an increasing role in controlling society infrastructures that we use on a day-to-day basis. RTES behaviour is not based solely on the interactions it might have with its surrounding environment, but also on the timing requirements it induces. As a result, ensuring that an RTES behaves correctly is non-trivial, especially after adding time as a new dimension to the complexity of the testing process. This research addresses the problem of testing RTESs from Timed Automata (TA) specification by the following. First, a new Priority-based Approach (PA) for testing RTES modelled formally as UPPAAL timed automata (TA variant) is introduced. Test cases generated according to a proposed timed adequacy criterion (clock region coverage) are divided into three sets of priorities, namely boundary, out-boundary and in-boundary. The selection of which set is most appropriate for a System Under Test (SUT) can be decided by the tester according to the system type, time specified for the testing process and its budget. Second, PA is validated in comparison with four well-known timed testing approaches based on TA using Specification Mutation Analysis (SMA). To enable the validation, a set of timed and functional mutation operators based on TA is introduced. Three case studies are used to run SMA. The effectiveness of timed testing approaches are determined and contrasted according to the mutation score which shows that our PA achieves high mutation adequacy score compared with others. Third, to enhance the applicability of PA, a new testing tool (GeTeX) that deploys PA is introduced. In its current version, GeTeX supports Control Area Network (CAN) applications. GeTeX is validated by developing a prototype for that purpose. Using GeTeX, PA is also empirically validated in comparison with some TA testing approaches using a complete industrial-strength test bed. The assessment is based on fault coverage, structural coverage, the length of generated test cases and a proposed assessment factor. The assessment is based on fault coverage, structural coverage, the length of generated test cases and a proposed assessment factor. The assessment results confirmed the superiority of PA over the other test approaches. The overall assessment factor showed that structural and fault coverage scores of PA with respect to the length of its tests were better than the others proving the applicability of PA. Finally, an Analytical Hierarchy Process (AHP) decision-making framework for our PA is developed. The framework can provide testers with a systematic approach by which they can prioritise the available PA test sets that best fulfils their testing requirements. The AHP framework developed is based on the data collected heuristically from the test bed and data collected by interviewing testing experts. The framework is then validated using two testing scenarios. The decision outcomes of the AHP framework were significantly correlated to those of testing experts which demonstrated the soundness and validity of the framework.

This thesis describes the use of a Real-Time Evolutionary Algorithm (RTEA) to optimise an Artificial Neural Network (ANN) on-line (in this context “on-line” means while it is in use). Traditionally, Evolutionary Algorithms (Genetic Algorithms, Evolutionary Strategies and Evolutionary Programming) have been used to train networks before use - that is “off-line,” as have other learning systems like Back-Propagation and Simulated Annealing. However, this means that the network cannot react to new situations (which were not in its original training set). The system outlined here uses a Simulated Legged Robot as a test-bed and allows it to adapt to a changing Fitness function. An example of this in reality would be a robot walking from a solid surface onto an unknown surface (which might be, for example, rock or sand) while optimising its controlling network in real-time, to adjust its locomotive gait, accordingly. The project initially developed a Central Pattern Generator (CPG) for a Bipedal Robot and used this to explore the basic characteristics of RTEA. The system was then developed to operate on a Quadruped Robot and a test regime set up which provided thousands of real-environment like situations to test the RTEA’s ability to control the robot. The programming for the system was done using Borland C++ Builder and no commercial simulation software was used. Through this means, the Evolutionary Operators of the RTEA were examined and their real-time performance evaluated. The results demonstrate that a RTEA can be used successfully to optimise an ANN in real-time. They also show the importance of Neural Functionality and Network Topology in such systems and new models of both neurons and networks were developed as part of the project. Finally, recommendations for a working system are given and other applications reviewed.

International Telemetering Conference Proceedings / October 17-20, 1994 / Town & Country Hotel and Conference Center, San Diego, California / A comprehensive examination of the market demands for cost reduced satellite telemetry & control stations will be presented. These systems are implemented using flexible, open architecture-based high performance real-time systems. The trend for combining telemetry monitoring of satellite data with closed-loop satellite command and control functions will be presented. This combined functionality opens up the possibilities for completely integrated, reduced cost satellite control systems. The market forces driving the demand for this integrated functionality include the broadening of non-military satellite applications, the widening international deployment of commercial satellites and the accompanying drive toward decentralized satellite control. The major requirements for the telemetry processing and command & control functionality of the integrated, reduced cost satellite control system will be presented. These requirements include: full real-time performance for processing telemetry data; flexible architecture for the incorporation of a wide range of I/O devices; capability of performing real-time, closed-loop control based on conditions in the telemetry data; user friendly development environments for application-specific customization of the system; and low system costs with the capability of indigenous support. The divergent requirements of performance, flexibility and price of these integrated, reduced cost satellite control systems is made possible via the use of open architecture building blocks that include standard VME boards combined with specialized real-time software drivers and user oriented, flexible Graphical User Interface (GUI) software.

International Telemetering Conference Proceedings / October 17-20, 1994 / Town & Country Hotel and Conference Center, San Diego, California / The advance from alphanumeric terminals to displays using new graphics technologies like the X Window System and Microsoft Windows has in many cases failed to tap the full potential of these technologies. Many common telemetry tasks continue to use similar user interfaces based on tabular real-time data displays and menus. This paper will demonstrate the application of new techniques which, when used with emerging graphics technologies, will maximize the effectiveness of telemetry ground station consoles. Advances in visualization and animation have greatly enhanced the information content of current displays and significantly improved their ease of use.

International Telemetering Conference Proceedings / October 17-20, 1994 / Town & Country Hotel and Conference Center, San Diego, California / Discover how it is now possible to memory-link all man-in-the-loop and machine-in-the-loop elements, as global resources that share information at memory-access speeds, to provide a unified system paradigm that avows: "the data is there, on time, every time." Regardless of configuration, if your past, present, or future system consists of more than one computer, and it interactively mixes information sources and destinations (e.g. Telemetry data streams, I/O interfaces, information processors, etc.) to achieve a highly integrated system, then the critical path to real-time success mandates a high performance, reliable, and deterministic communications methodology. This softwareless, future technology is already successfully sharing information in other real-time markets and applications, and is ready for more challenging applications.

International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, Nevada / NASA's ground telemetry data systems developed by the Microelectronics Systems Branch at the Goddard Space Flight Center, use a generic but expandable architecture known as the "Functional Components Approach." This approach is based on the industry standard VMEbus and makes use of multiple commercial and custom VLSI hardware based cards to provide standard off-the-shelf telemetry processing functions (e.g., frame synchronization, packet processing, etc.) for many telemetry data handling applications. To maintain maximum flexibility and performance of these systems, a special real-time system environment has been developed, the Modular Environment for Data Systems (MEDS). Currently, MEDS comprises over 300,000 lines of tested and operational code based on a non-UNIX real-time commercial operating system. To provide for increased functionality and adherence to industry standards, this software is being transformed to run under a UNIX-compatible real-time environment. This effort must allow for existing systems and interfaces and provide exact duplicates of the system functions now used in the current real-time environment. Various techniques will be used to provide a relatively quick transition to this new real-time operating system environment. Additionally, all standard MEDS card to card and system to system interfaces will be preserved, providing for a smooth transition and allowing for telemetry processing cards that have not yet been converted to reside side-by-side with cards that have been converted. This paper describes this conversion effort.

International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, Nevada / An artificial neural network (ANN) for use in real time data reduction and analysis will be presented. The use and advantage of hardware and software implementations of neural networks will be considered. The ability of neural networks to learn and store associations between different sets of data can be used to create custom algorithms for some of the data analysis done during missions. Once trained, the ANN can distill the signals from several sensors into a single output, such as safe/unsafe. Used on a neural chip, the trained ANN can eliminate the need for A/D conversions and multiplexing for processing of combined parameters and the massively parallel nature of the network allows the processing time to remain independent of the number of parameters. As a software routine, the advantages of using an ANN over conventional algorithms include the ease of use for engineers, and the ability to handle nonlinear, noisy and imperfect data. This paper will apply the ANN to performance data from a T-38 aircraft.