This paper presents a new logic algorithm for real-time control of regulation valves in water distribution networks. This method entails identifying in realtime the appropriate closure setting of regulation valves in...
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This paper presents a new logic algorithm for real-time control of regulation valves in water distribution networks. This method entails identifying in realtime the appropriate closure setting of regulation valves in order to reach and keep the desired piezometric height at the control node(s), by making use of measurements concerning both the piezometric height at the control node(s) and the water discharge in the pipes fitted with regulation valves. In the numerical application herein described this control algorithm is implemented within a hydraulic simulation model and is tested in the case study of a real distribution network, in which there is only one control valve, installed in the pipe linking the serving tank to the network. Results showed excellent performance in terms of pressure regulation (with very small deviations from the desired set-point value) and leakage reduction under various operation conditions.
The Ada task system is critically evaluated from the point of view of real-time applications. Based on such an evaluation an abstract machine, supplying both an operational semantics and an implementation schema for i...
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The Ada task system is critically evaluated from the point of view of real-time applications. Based on such an evaluation an abstract machine, supplying both an operational semantics and an implementation schema for it, is derived. Such a schema, depending on parameters, may supply a standard implementation following the Ada Reference Manual specifications, or may allow the user to implement ad hoc policies required by the time constraints of the specific application.
This paper is a survey of research of my colleagues and myself aimed at developing a comprehensive logical framework for the verification of real-time distributed systems. The framework is based on predicate logics wi...
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This paper is a survey of research of my colleagues and myself aimed at developing a comprehensive logical framework for the verification of real-time distributed systems. The framework is based on predicate logics with explicit time. To choose such a logic we pursue two goals: first, to make formalization of verification problems rather direct, without unjustified simplifications, and second, to have a logic which permits to describe decidable classes of the verifications problem covering the particular problems we are interested in. Notice that our intention is not to introduce new specification languages, but work directly with those of the user. In this paper we describe First Order timed Logic (FOTL) that is sufficient to express the main part of verification of systems without uncertainty. The time is continuous (the formalism work as well for discrete time - in our context this case is less interesting and less efficient from algorithmic viewpoint). We give examples of problems that can be treated, describe how to represent runs of programs in FOTL, introduce decidable classes, discuss aspects of practical efficiency. We conclude with open questions.
The presentation of packet-level communication network performance data to a user in an easy to assimilate, visual form by computer screen is considered. Standard presentation mechanisms such as bar graphs and numeric...
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The presentation of packet-level communication network performance data to a user in an easy to assimilate, visual form by computer screen is considered. Standard presentation mechanisms such as bar graphs and numeric (text) displays require considerable concentration on behalf of the operator if more than a very small number of measurement values are presented. However, for many network operation tasks the initial requirement is for the relative value of the measurements and any trends in these measurements to be readily identifiable. A different approach to measurement presentation has therefore been considered whereby an object's shape is distorted in proportion to the values of a set of measurement data. A casual viewing of the object therefore immediately indicates the relative values of the measurements. This approach has been applied to the presentation of packet delay values for a commercially operational network, and its use in a performance measurement system for the commercial communication network is described.
Traffic engineers and technicians are faced with the challenge of testing traffic controllers to ensure that they comply with different software and hardware requirements prior to deployment. Currently the testing is ...
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Traffic engineers and technicians are faced with the challenge of testing traffic controllers to ensure that they comply with different software and hardware requirements prior to deployment. Currently the testing is done manually using traditional "suitcase testers". These manual tests can be tedious and time-consuming and have many limitations such as the inability to document the test results and the difficulty in replicating field conditions. This paper presents a traffic controller automated testing tool and a new script language (CIDScript) to implement and facilitate automated testing of traffic controller functionality using the controller interface device (CID) technology. The paper also describes three CIDScript test examples to demonstrate: (1) an automated suitcase tester can test conditions that cannot be tested with a standard suitcase tester;(2) an automated suitcase tester can conduct tests faster and more efficiently than a standard tester;(3) the automated suitcase tester can document the results of a number of tests that can be compared and evaluated later, something that the standard suitcase tester cannot do. (c) 2007 Elsevier Ltd. All rights reserved.
EMBEDDED COMPLEX SYSTEMS REQUIRE AN INTEGRATED AND BEST-BALANCED SET OF COMPONENTS. To USE THESE COMPONENTS REQUIRES SOME SORT OF VERIFIABLE COMPOSITIONALITY, A CONCEPT THAT IMPLIES THE PRESERVATION OF PROPERTIES AND ...
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EMBEDDED COMPLEX SYSTEMS REQUIRE AN INTEGRATED AND BEST-BALANCED SET OF COMPONENTS. To USE THESE COMPONENTS REQUIRES SOME SORT OF VERIFIABLE COMPOSITIONALITY, A CONCEPT THAT IMPLIES THE PRESERVATION OF PROPERTIES AND THE ABILITY TO VERIFY THEM.
Peer-to-peer systems that dynamically organize, interact, and share resources are increasingly being deployed in large-scale environments. The location, intermittent connectivity, and organization of the peers have si...
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Peer-to-peer systems that dynamically organize, interact, and share resources are increasingly being deployed in large-scale environments. The location, intermittent connectivity, and organization of the peers have significant impact on meeting the quality of service requirements of distributed applications. This article presents the design, implementation, and empirical evaluation of a middleware architecture for managing distributed objects in peer-to-peer systems. The architecture consists of a self-organizing infrastructure that uses only local knowledge to dynamically form overlays of multiple peers and respond to changing processing and networking conditions;and a management. layer that monitors the behavior of the applications transparently, schedules object invocations over multiple machines, and obtains accurate resource projections. The system works in a two-level feedback loop structure that uses measurements of elapsed time and resource loads to refine the initial estimates and revise the peer connections. Our empirical evaluation shows that the system manipulates the peer connections dynamically in response to changes in resource utilization to meet application end-to-end soft real-time requirements.
Model-based design of embedded control systems using Synchronous Reactive (SR) models is among the best practices for software development in the automotive and aeronautic industry. SR models allow to formally verify ...
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Model-based design of embedded control systems using Synchronous Reactive (SR) models is among the best practices for software development in the automotive and aeronautic industry. SR models allow to formally verify the correctness of the design and automatically generate the implementation code. This feature is a major productivity enhancement and, more importantly, can ensure correct-by-design software provided that the code generator is provably correct. This paper presents an improvement of code generation technology for SR obtained via a novel algorithm for optimizing the multitask implementation of Simulink models on single-processor platforms with limited availability of memory. Existing code generation tools require the addition of zero-order hold (ZOH) blocks, and therefore additional memory, and possibly also additional functional delays whenever there is a rate transition in the computation and communication flow. Our algorithm leverages a novel efficient encoding of the scheduling feasibility region to find the task implementation of function blocks with minimum additional functional delays within timing and memory constraints. The algorithm is applied to an automotive case study with tens of function blocks and very high utilization to test its applicability to complex systems.
With the advent of real-time extensions for communication middleware, new Quality of Service (QoS) aspects have to be considered. These include specification of constraints, timely delivery, validation and exception h...
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With the advent of real-time extensions for communication middleware, new Quality of Service (QoS) aspects have to be considered. These include specification of constraints, timely delivery, validation and exception handling mechanisms. For that to be accomplished modifications of the communication platforms including the transport layer are necessary. In this context we evaluate which tasks should be performed by the middleware or preferably by the transport system for the provision of real-time guarantees. Furthermore, requirements for a real-time transport system as well as an architecture for object communication within ATM networks will be introduced. Based on a developed optimised transport system for local ATM networks that is the foundation for our realtime approach, we will present performance results. Another aspect is that deterministic operations may degrade performance. Since this performance degradation can not be ignored, mechanisms for applying ATM traffic classes will be introduced to support normal operation as well as worst case scenarios. As a result this paper outlines possible gains and limits for real-time distributed object communication within pure ATM networks.
A suboptimal midcourse guidance law is obtained for interception of free-fall targets in the three-dimensional (3D) space. Neural networks are used to approximate the optimal feedback strategy suitable for real-time i...
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A suboptimal midcourse guidance law is obtained for interception of free-fall targets in the three-dimensional (3D) space. Neural networks are used to approximate the optimal feedback strategy suitable for real-time implementation. The fact that the optimal trajectory in the 3D space does not deviate much from a vertical plane justifies the use of the two-dimensional (2D) neural network method previously studied. To regulate the lateral errors in the missile motion produced by the prediction error of the intercept point, the method of feedback linearization is employed. Computer simulations confirm the superiority of the proposed scheme over linear quadratic regulator (LQR) guidance and proportional navigation (PN) guidance as well as its approximating capability of the optimal trajectory in the 3D space.
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