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Book ChapterDOI

Engineering Predictable Real-Time Systems

01 Jan 1994-pp 31-46
TL;DR: The argument is put forward that understandability is the most important common denominator for achieving a variety of other important real-time computing abilities; for example, reliability, testability, verifiability, maintainability, and so on.
Abstract: The demands placed upon real-time systems (or portions thereof) in respect to predictability continue to increase as these systems become integrated into a wide variety of safety critical applications. It is essential to be able to guarantee that all critical processing is accomplished accurately and on time. In this contribution, a point of view is established in respect to achieving predictability in combination with another vital ability, namely understandability. The argument is put forward that these two goals can be jointly attained; further, that understandability is the most important common denominator for achieving a variety of other important real-time computing abilities; for example, reliability, testability, verifiability, maintainability, and so on.
Citations
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Journal ArticleDOI
TL;DR: A real-time behavioral model for control applications illuminates key execution strategies to ensure the required timing behavior and implications on design and implementation and directions for further work are discussed.
Abstract: Automatic control applications are real-time systems which pose stringent requirements on precisely time-triggered synchronized actions and constant end-to-end delays in feedback loops which often constitute multi-rate systems. Motivated by the apparent gap between computer science and automatic control theory, a set of requirements for real-time implementation of control applications is given. A real-time behavioral model for control applications is then presented and exemplified. Important sources and characteristics of time-variations in distributed computer systems are investigated. This illuminates key execution strategies to ensure the required timing behavior. Implications on design and implementation and directions for further work are discussed.

164 citations


Cites background from "Engineering Predictable Real-Time S..."

  • ...With relation to this paper, Lawson (1992) discusses the need for synchronization in multi-rate control systems and advocates the use of global static scheduling....

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  • ...Over recent years it has been understood that scheduling theory, in order to support the design of real-time applications, must be considered in conjunction with policies for triggering, synchronization and communication (see e.g., Kopetz et al. (1989) and Lawson (1992))....

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Journal ArticleDOI
TL;DR: This paper gives an overview of the BASEMENT concept, as well as presenting two system realizations, one based on the commercial real-time kernel Rubus, while the second is an ultra-dependable architecture (DACAPO) with provisions for fault tolerance at various system levels.
Abstract: BASEMENT/sup TM/ is a distributed real-time architecture developed for vehicle internal use in the automotive industry. BASEMENT covers application development, as well as the hardware and software that provide execution and communication support. This paper gives an overview of the BASEMENT concept, as well as presenting two system realizations. The first realization is based on the commercial real-time kernel Rubus, while the second is an ultra-dependable architecture (DACAPO) with provisions for fault tolerance at various system levels. BASEMENT is designed for the automotive systems of the future. These systems will be required to simultaneously handle multiple safety critical functions and a large number of less critical functions. All of these features are to be provided at a production cost substantially lower than that of current systems, and, at the same time, with a reliability allowing vehicles to be built without mechanical backup systems, even for safety critical subsystems such as braking and steering.

42 citations

Book ChapterDOI
01 Jan 1995
TL;DR: The number of artificial intelligence methods applied to actual industrial process control and/or to plant-wide control has been rapidly increasing and expert systems for automated decision making in production control and in supporting the managerial activities have proven their effectiveness.
Abstract: The number of artificial intelligence methods applied to actual industrial process control and/or to plant-wide control has been rapidly increasing. For example, the application of fuzzy controllers in continuous process control and manufacturing, expert systems for automatic and/or automated decision making in production control and in supporting the managerial activities, have proven their effectiveness.

13 citations

Journal ArticleDOI
TL;DR: In this article, the authors present techniques to support the construction of parallel, embedded systems from reusable software components, and describe accurate and efficient performance prediction functions for processes and objects that have been assigned to processing elements (PEs) in parallel systems.

11 citations

Proceedings ArticleDOI
TL;DR: In this article, a mathematical model (the Q-model) which enables analytical study of a wide range of timing properties is suggested and some results obtained are listed, but the main attention of the paper is devoted to justifying the necessity of a new model against the wonderful existing formalisms.
Abstract: A mathematical model (the Q-model) which enables analytical study of a wide range of timing properties is suggested and some results obtained are listed. Main attention of the paper, however, is devoted to justifying the necessity of a new model against the wonderful existing formalisms. Three important features of real-time software, not really supported by the existing formalisms, are pointed out. A classification of basic requirements for timing correctness is given. It is suggested that , many essential timing properties -- analyzable in the Q-model -- can not be thoroughly studied in widely used formalisms since they do not capture the necessary multitude of time concepts.

11 citations

References
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Book
01 Jun 1991
TL;DR: A new architecture for controlling mobile robots is described, building a robust and flexible robot control system that has been used to control a mobile robot wandering around unconstrained laboratory areas and computer machine rooms.
Abstract: A new architecture for controlling mobile robots is described. Layers of control system are built to let the robot operate at increasing levels of competence. Layers are made up of asynchronous modules that communicate over low-bandwidth channels. Each module is an instance of a fairly simple computational machine. Higher-level layers can subsume the roles of lower levels by suppressing their outputs. However, lower levels continue to function as higher levels are added. The result is a robust and flexible robot control system. The system has been used to control a mobile robot wandering around unconstrained laboratory areas and computer machine rooms. Eventually it is intended to control a robot that wanders the office areas of our laboratory, building maps of its surroundings using an onboard arm to perform simple tasks.

7,759 citations

Journal ArticleDOI
TL;DR: The problem of multiprogram scheduling on a single processor is studied from the viewpoint of the characteristics peculiar to the program functions that need guaranteed service and it is shown that an optimum fixed priority scheduler possesses an upper bound to processor utilization.
Abstract: The problem of multiprogram scheduling on a single processor is studied from the viewpoint of the characteristics peculiar to the program functions that need guaranteed service. It is shown that an optimum fixed priority scheduler possesses an upper bound to processor utilization which may be as low as 70 percent for large task sets. It is also shown that full processor utilization can be achieved by dynamically assigning priorities on the basis of their current deadlines. A combination of these two scheduling techniques is also discussed.

7,067 citations

Journal ArticleDOI
TL;DR: The bulk-synchronous parallel (BSP) model is introduced as a candidate for this role, and results quantifying its efficiency both in implementing high-level language features and algorithms, as well as in being implemented in hardware.
Abstract: The success of the von Neumann model of sequential computation is attributable to the fact that it is an efficient bridge between software and hardware: high-level languages can be efficiently compiled on to this model; yet it can be effeciently implemented in hardware. The author argues that an analogous bridge between software and hardware in required for parallel computation if that is to become as widely used. This article introduces the bulk-synchronous parallel (BSP) model as a candidate for this role, and gives results quantifying its efficiency both in implementing high-level language features and algorithms, as well as in being implemented in hardware.

3,885 citations

Journal ArticleDOI
TL;DR: The authors focus on the maintainability of the Mars architecture, the Mars operating system, and the control of a rolling mill that produces metal plates and bars, and discuss timing analysis.
Abstract: The authors describe the Maintainable Real-Time System, a fault-tolerant distributed system for process control, developed under the Mars project started in 1980 at the Technische Universitat Berlin. They explore the characteristics of distributed real-time systems and then present the Mars approach to real-time process control, its architectural design and implementation, and one of its applications. The authors focus on the maintainability of the Mars architecture, describe the Mars operating system, and discuss timing analysis. The control of a rolling mill that produces metal plates and bars is examined. >

633 citations

Journal ArticleDOI
C. Douglass Locke1
TL;DR: It is concluded that the fixed priority approach, when priorities are assigned using rate monotonic priorities, generally dominates the cyclic executive approach for hard real-time systems.
Abstract: We contrast the software architecture of a hard real-time application using a fixed priority task structure against the software architecture of the same system using a cyclic executive structure to satisfy hard real-time deadlines in response to a set of embedded system requirements We identify the perceived and actual advantages and disadvantages of both approaches, consider the types of applications which can take advantage of these approaches, and make recommendations related to the attributes of such applications that might be needed with both approaches We conclude that the fixed priority approach, when priorities are assigned using rate monotonic priorities, generally dominates the cyclic executive approach for hard real-time systems

294 citations