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17TH CONF ON LOCAL computer NETWORKS

作者： SHIN, KG CHOU, CC Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor 48109-2122 MI United States

ISBN: (纸本)0818630957

It is well-known that the ability to support predictable inter-process communication is of great significance to manufacturing and process control systems. In this paper, we propose a strategy for a soon-to-be industrial standard, the SP-50 Field Bus, to support both intra-cell and inter-cell real-time communications. We first describe our strategy in detail and show that it is compatible with the current FieldBus draft proposal. Under our strategy, the capacity of each link is divided into two parts. The first part is managed by the local Link Active Scheduler (LAS) for intra-cell (intra-link) communication. The second part is managed by the global network manager for inter-cell (inter-link) communication. By dividing the link capacity in this way, our strategy can allow for fast local intra-cell connection establishment, while supporting global inter- cell connections. Numerical examples are also given for a typical manufacturing network. © 1992 IEEE.

关键词： computer COMMUNICATION NETWORKS MANUFACTURING SYSTEMS FIELDBUS real-time COMMUNICATION real-time CHANNEL

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Communication-oriented assignment of task modules in hypercubic multicomputers 12

Communication-oriented assignment of task modules in hypercu...

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12th International Conference on Distributed computing Systems, ICDCS 1992

作者： Tsai, Bing-Rung Shin, Kang G. Real-Time Computing Laboratory Computer Science and Engineering Division Department of Electrical Engineering and Computer Science University of Michigan Ann ArborMI48109-2122 United States

ISBN: (纸本)0818628650

The problem of mapping a task that is composed of interacting modules onto a hypercube multicomputer is formulated and solved by minimizing an objective function called the communication traffic. The objective function allows module assignments to be found with the usual straightforward combinatorial optimization techniques. The problem of finding an assignment that minimizes the communication traffic is proved to be NP-hard, so a standard state-space search algorithm as well as other heuristic algorithms are used to find optimal/suboptimal solutions. The relative performances of various algorithms are evaluated using simulations. The assignments obtained from these algorithms are evaluated using an event-driven simulator to learn how they perform in real-world execution environments. © 1992 IEEE.

关键词： Heuristic algorithms

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Allocation of periodic task modules with precedence and deadline constraints in distributed real-time systems

Allocation of periodic task modules with precedence and dead...

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1992 real-time Systems Symposium, RTSS 1992

作者： Hou, Chao-Ju Shin, Kang G. Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI 48109-2122 United States

ISBN: (纸本)0818631953

This papei addresses the problem of allocating (assigning and scheduling) periodic task modules to processing nodes (PNs) in distributed real-time systems subject to task precedence and timing constraints. Using the branch-and-bound technique, a module allocation algorithm (MAA) is proposed to find an "optimal" allocation that maximizes the probability of meeting task deadlines. The task system within a planning cycle is first modeled with a task flow graph (TG) which describes computation and communication modules as well as the precedence constraints among them. To incorporate both timing and logical correctness into module allocation, the probability of meeting task deadlines is used as the objective function. The MAA is then applied to find an optimal allocation of task modules in a distributed system. The timing aspects embedded in the objective function drive the MAA not only to assign task modules to PNs, but also to use a module scheduling algorithm (MSA) (with polynomial time complexity) for scheduling all modules assigned to each PN so that all tasks may be completed in time. Several numerical examples are presented to demonstrate the effectiveness and practicality of the proposed algorithms. © 1992 IEEE.

关键词： Scheduling algorithms

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Modeling resource contention among distributed periodic processes 4

Modeling resource contention among distributed periodic proc...

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4th IEEE Symposium on Parallel and Distributed Processing, SPDP 1992

作者： Welch, Lonnie R. Stoyenko, Alexander D. Marlowe, Thomas J. Real-Time Computing Laboratory Department of Computer and Information Science New Jersey Institute of Technology NewarkNJ07102 United States

ISBN: (纸本)0818632003

Modern real-time systems consist of distributed periodic processes that have critical timing constraints and share replicated resources. A mathematical model of the resource requirements of periodic processes that are specified using RT-Chari [9] is described. We provide novel techniques for computing "rates of progress" for clients of resources and show how to use the rates to predict the execution times of processes. © 1992 IEEE.

关键词： real time systems

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Hard Deadlines in real-time Control Systems

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IFAC Proceedings Volumes 1992年第20期25卷 9-14页

作者： Kang G. Shin Hagbae Kim Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science The University of Michigan Ann Arbor MI 48109-2122

In a real-time control system where the control input is computed by a controller computer, the transient computer failures caused by an electromagnetic interference may seriously affect system stability. The faulty controller computer causes either a long delay in the feedback loop thus failing to update the control input for one or more sampling intervals, or control input disturbances by updating the control inputincorrectly until the fault is handled properly. If the period of this abnormal behavior exceeds a certain limit called a hard deadline, either the necessary conditions for system stability will be violated or the system willleave the allowed state space. In such a case a dynamic failure is said to occur in the system. We present a method for deriving hard deadlines for linear time-invariant control systems by examining the stability of the state difference equations resulting from the modification of the original state equations with an assumed maximum delay and several random sequences that represent the effects of stationary occurrences of the disturbances to, as well as the random delays of, the control input. Moreover, a one-shot event model, in which a single long-lasting fault causes a dynamic failure, is presented based on the state trajectory and the allowed state space.

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Allocation of periodic task modules with precedence and deadline constraints in distributed real-time systems

Allocation of periodic task modules with precedence and dead...

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real-time Systems Symposium (RTSS)

作者： C.-J. Hou K.G. Shin Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

The authors address the problem of allocating (assigning and scheduling) periodic task modules to processing nodes (PNs) in distributed real-time systems subject to task precedence and timing constraints. Using the branch-and-bound technique, a module allocation algorithm (MAA) is proposed to find an optimal allocation that maximizes the probability of meeting task deadlines. To incorporate both timing and logical correctness into module allocation, the probability of meeting task deadlines is used as the objective function. The MAA is then applied to find an optimal allocation of task modules in a distributed system. The timing aspects embedded in the objective function drive the MAA not only to assign task modules to PNs, but also to use a module scheduling algorithm for scheduling all modules assigned to each PN so that all tasks may be completed in time. Several numerical examples are presented to demonstrate the effectiveness and practicality of the proposed algorithms.< >

关键词： real time systems Timing Distributed computing Processor scheduling Laboratories Flow graphs Scheduling algorithm Polynomials Load management Hazards

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TEMPLATE MATCHING ANALYSIS OF UNIPOLAR AND BIPOLAR ELECTROGRAMS IN THE DIFFERENTIATION OF VENTRICULAR-TACHYCARDIA AND FIBRILLATION FROM SINUS RHYTHM

TEMPLATE MATCHING ANALYSIS OF UNIPOLAR AND BIPOLAR ELECTROGR...

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CONF ON computerS IN CARDIOLOGY

作者： SILKA, MJ RANVILLE, S JENKINS, JM YAN, MC DICARLO, LA Department of Electrical Engineering and Computer Science University of Michigan Medical Computing Laboratory Ann Arbor 48109-2122 MI United States

ISBN: (纸本)0818635509

The failure of automated morphologic detection of ventricular tachycardia (VT) or fibrillation (VF) is a limitation of implantable cardioverter-defibrillators. As an adjunct to rate-based criteria, this study evaluated the use of waveform analysis of intracardiac electrograms with correlation waveform analysis (CWA). Using digital signal processing, unipolar and bipolar electrograms were evaluated in sinus rhythm (SR), VT, and VF at 1-500 Hz and 10-80 Hz in 15 patients. There was complete differentiation of SR from VF in 13/15 patients and VT in 14/15 with unipolar and 14/15 patients with bipolar electrograms at 1-500 Hz;at 10-80 Hz SR was differentiated from VF in 12/15 patients and VT in 13/15 with unipolar and from VF in 14/15 patients and VT in 13/15 with bipolar electrograms. It is concluded that differentiation of intracardiac waveforms by CWA is independent of electrode configuration and is not significantly altered by moderate signal filtering. © 1992 IEEE.

关键词： Template matching

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Derivation of Hard Deadlines for real-time Control Systems

Derivation of Hard Deadlines for Real-Time Control Systems

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American Control Conference (ACC)

作者： Kang G. Shin Hagbae Kim Department of Electrical Engineering and Computer Science Real-Time Computing Laboratory University of Michigan Ann Arbor MI USA

The computation-time delay in the feedback controller of a real-time control system may cause failure to update the control input during one or more sampling periods. A dynamic failure is said to occur if this delay exceeds a certain limit called a hard deadline. We present a method for calculating the hard deadlines in linear time-invariant control systems. To derive necessary conditions for (asymptotic) system stability, the state difference equation is modified based on an assumed maximum delay and the probability distribution of delays whose magnitudes are less than, or equal to, the assumed maximum delay. Moreover, the allowed state-space - which is derived from given input and state constraints - is used to calculate the hard deadline as a function of time and the system state. We also consider a one-shot delay model in which a single event causes a dynamic failure.

关键词： real time systems Control systems Delay effects Electric variables control Electromagnetic interference computer aided instruction Linear feedback control systems Sampling methods Difference equations Probability distribution

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Fault-tolerant real-time communication in distributed computing systems

Fault-tolerant real-time communication in distributed comput...

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International Symposium on Fault-Tolerant computing (FTCS)

作者： Q. Zheng K.G. Shin Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

An increasing number of applications require packets to be delivered reliably within prespecified delay bounds. It is shown how this can be achieved by using real-time channels that make soft reservation of network resources to ensure the timely delivery of real-time packets. Algorithms are presented for the establishment of real-time channels, and it is shown how the basic real-time channels can be enhanced to be fault tolerant using the multiple paths between a pair of communicating nodes. The contribution of the former is a tighter schedulability condition that makes more efficient use of network resources than other existing approaches, and the contribution of the latter is a significant improvement in fault tolerance over the basic real-time channel, which is inherently susceptible to component failures.< >

关键词： Fault tolerant systems real time systems Distributed computing Circuits Bandwidth Delay Fault tolerance Asynchronous transfer mode Intelligent networks computer networks

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real-time communication in local area ring networks

Real-time communication in local area ring networks

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Conference on Local computer Networks (LCN)

作者： Q. Zheng K.G. Shin Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

The feasibility of using buffered transmission, which has the advantages of eliminating the token passing overhead and relieving the network interface from the complex token handling operations, is considered. The concept of a real-time channel (RTC) and the RTC establishment procedures are reviewed. Its performance is then compared with the FDDI timed token protocol. Simulation results show that the buffered transmission in local area ring networks equipped with real-time channels enhances both the networks' throughput and the ability to support heterogeneous real-time traffic. The implementation of the network interface is also examined with an example design showing the feasibility of real-time channels in high-speed local area networks.< >

关键词： Intelligent networks FDDI Throughput Access protocols Local area networks Network topology Token networks Delay effects Media Access Protocol Network interfaces

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