The paper discusses modeling and analysis of real-time systems subject to random time delays in the communication network. A new method for analysis of existing schemes is presented. The method is used to evaluate dif...
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The paper discusses modeling and analysis of real-time systems subject to random time delays in the communication network. A new method for analysis of existing schemes is presented. The method is used to evaluate different suggested schemes from the literature. A new scheme for handling the random time delays is then developed and successfully compared with previous schemes. The new scheme is based on stochastic control theory and a separation property is shown to hold for the optimal controller.
The term ''open system'' is used in a variety of ways, in many different situations. In particular, almost all vendors of distributedcontrolsystems (DCSs) for process automation claim to provide an o...
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The term ''open system'' is used in a variety of ways, in many different situations. In particular, almost all vendors of distributedcontrolsystems (DCSs) for process automation claim to provide an open system, in information sheets, etc. This paper presents a state-of-the-practice study on open systems, where a large number of commercial DCSs have been examined. The main focus is on achieving interaction between components from different vendors in a distributed DCS environment. Here, the study has clearly shown that the DCSs of today are not very open. The fields in which openness can actually be achieved today have been distinguished and are dealt with in some detail.
Prediction of future Supervisory control and Data Acquisition (SCADA) system configuration is difficult because it is closely related with varyings of strategies of system's control/operation and computer architec...
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Prediction of future Supervisory control and Data Acquisition (SCADA) system configuration is difficult because it is closely related with varyings of strategies of system's control/operation and computer architecture. This paper proposes a new approach to realize a reliable and flexible SCADA system under which application programs can hardly be affected by the varyings. SCOPE is a new infrastructure supporting to build the SCADA system. It consists of “Execution dependence part” and “Operation dependence part” in order to realize a reliable and flexible SCADA system under distributed environments. This paper introduces a new design concept, a reliable technique and the evaluation result on SCOPE prototype system.
Petri nets (PN's), in general, are a formal model well suited for representing distributed, parallel and real-time systems. Major problems for the analysis of complex models of large scale systems are the identifi...
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Petri nets (PN's), in general, are a formal model well suited for representing distributed, parallel and real-time systems. Major problems for the analysis of complex models of large scale systems are the identification of the underlying stochastic process and the computational complexity. This paper outlines the identification of a Petri net model underlying stochastic process and the computation of the equilibrium solutions. This is practically shown for a defined FDDI MAC Petri net for the analysis of FDDI-based communication systems for integral plant automation. From the steadystate distributions it is possible to obtain performance indices related to the behaviour of the Petri net model and thus of the states of the discrete event dynamic system (DEDS). This paper deeply bridges and applies untimed Petri net theory , used for the functional analysis of a Petri net model, and stochastic Petri net theory , used for the performance analysis of a Petri net model; leading to a performance prediction and setting up a foundation for a supervisory control of a DEDS.
With the advent of standards in distributed object technology, it is now feasible to reuse control objects in a deterministic manner across controlsystems. The CERN-based CICERO project aims to use object-oriented me...
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With the advent of standards in distributed object technology, it is now feasible to reuse control objects in a deterministic manner across controlsystems. The CERN-based CICERO project aims to use object-oriented methods to design the main building blocks of a generic control information system to be based on the distributed object standard CORBA (CORBA 1992). CICERO is producing an integrating environment (Cortex, Barillere 1994a) into which distributed user control objects will ultimately be ‘plugged and played’ and a supporting information system for the configuration and management of that environment Cortex has been designed to be sufficiently generic in nature to allow its use both in scientific and industrial applications.
The great majority of tasks in a real-time system are periodic. Moreover, a complex task can be modelized by precedence and communication graph. This paper compare two static heuristic algorithms which try to pre-run-...
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The great majority of tasks in a real-time system are periodic. Moreover, a complex task can be modelized by precedence and communication graph. This paper compare two static heuristic algorithms which try to pre-run-time schedule periodic complex real-time tasks on sites in a distributed system fully interconnected by a bus. These algorithms have to deal with the periodicity constraints, and communication and precedence requirements while imposing no migration to the subtasks (the elementary software instances) between the different periods. They determine the mapping of the subtasks, their schedule on the processors and the schedule of the communications along the bus.
作者：
Martin TörngrenDAMEK-Mechatronics
Dept. of Machine Design The Royal Institute of Technology S-100 44 Stockholm Sweden. Fax: +46-8-20 22 87
For the successful design and implementation of distributed real-time control applications, models that adequately state real-time behavioural requirements and provide information needed to assess different decentrali...
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For the successful design and implementation of distributed real-time control applications, models that adequately state real-time behavioural requirements and provide information needed to assess different decentralization approaches are essential. Real-time behavioural models for control applications based on precisely time-triggered actions, synchronous execution and the specification of multirate interactions are introduced. Contemporary computer science models are subsequently evaluated. The use of the modelling approach in design of distributedcontrolsystems is discussed.
The purpose of this paper is to present some extensions to the IDERS environment, in order to deal with the development of distributed real-time systems. The IDERS method and tools are intended to support the user in ...
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The purpose of this paper is to present some extensions to the IDERS environment, in order to deal with the development of distributed real-time systems. The IDERS method and tools are intended to support the user in the development of embedded monoprocessor real-time systems. This environment is based on a risk oriented process model. The development of the systems relies on a set of heterogeneous and incremental prototypes that can be animated in order to assess the system behaviour. In this paper, an extension of this toolset for supporting the development of distributed real-time systems is proposed. This extension includes the modeling of the communication media, in order to have information on the whole system behaviour. Special emphasis will be made for including mechanisms for assessing the system timing requirements.
Petri Nets have been proved to be an effecient tool to represent complicated systems. Nevertheless, in general it is not easy to implement a technical system given as a Petri Net on a multiprocessor system. This contr...
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Petri Nets have been proved to be an effecient tool to represent complicated systems. Nevertheless, in general it is not easy to implement a technical system given as a Petri Net on a multiprocessor system. This contribution presents a new approach for this procedure. The main difference compared to other methods is the effective use of message passing communication during the implementation.
The efficient matrix algorithms for digital simulation of a general random process (multidimensional or multivariate) using cross-spectral density matrix computed from the spectral density function of the multidimensi...
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The efficient matrix algorithms for digital simulation of a general random process (multidimensional or multivariate) using cross-spectral density matrix computed from the spectral density function of the multidimensional excitation process, dimensional spectral analysis and control for multispace vibroacoustic test and also multilevel hierarchical system with decomposition of purposes and tasks are presented in this paper. The main concept of the designing is that all system parts - hardware, software and functional - have a certain autonomy, and can independently increase or reduce. The digital system is intended to automate bench tests of new products for space-manydimensional random vibration.
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