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computing time-DELAY AND ITS EFFECTS ON REAL-time CONTROL-SYSTEMS

IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY 1995年第2期3卷 218-224页

作者： SHIN, KG CUI, XZ Real-Time Computing Laboratory Division of Comuuter Science and Engineering. Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

The reliability of a real-time digital control computer depends not only on the reliability of the hardware and software used, but also on the time delay in computing the control output, because of the negative effects of computing time delay on control system performance. For a given fixed sampling interval, the effects of computing time delay are classified into the delay and loss problems, The delay problem, occurs when the computing time delay is nonzero but smaller than the sampling interval, while the loss problem occurs when the computing time delay is greater than, or equal to, the sampling interval, i,e., loss of the control output, These two problems are analyzed as a means of evaluating real-time control systems, First, a generic analysis of the effects of computing time delay is presented along with necessary conditions for system stability, Then, we present both qualitative and quantitative analyses of the computing time delay effects on a robot control system, deriving upper bounds of the computing time delay with respect to system stability and system performance.

关键词： Delay effects Real time systems Control systems Sampling methods System performance Stability analysis Digital control Hardware Software performance Performance analysis

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Deterministic fault injection of distributed systems

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International Workshop on Theory and Practice in Distributed Systems

作者： Dawson, S Jahanian, F Real-Time Computing Laboratory Electrical Engineering and Computer Science Department University of Michigan Ann Arbor 48109-2122 MI United States

ISBN: (纸本)3540600426

Ensuring that a system meets its prescribed specification is a growing challenge that confronts software developers and system engineers. Meeting this challenge is particularly important for distributed systems with strict dependability and timeliness constraints. This paper presents a technique, called script-driven probing and fault injection, for the evaluation and validation of dependable protocols. The proposed approach can be used to demonstrate three aspects of a target protocol: i) detection of design or implementation errors, ii) identification of violations of protocol specifications, and iii) insight into design decisions made by the implementers. To demonstrate the capabilities of this technique, the paper briefly describes a probing and fault injection tool called the PFI tool, and several experiments on two protocols: the Transmission Control Protocol (TCP) [4, 24] and the Group Membership Protocol (GMP) [19]. The tool can be used to delay, drop, reorder, duplicate, and modify messages. It can also introduce new messages into the system to probe participants. In the case of TCP, we used the PFI tool to duplicate the experiments reported in [7] on several TCP implementations without access to the vendors' TCP source code in a very short time. We also ran several new experiments that are difficult to perform using past approaches based on packet monitoring and filtering. In the case of GMP, we used the tool to test the fault-tolerance capabilities of an implementation under various failure models including daemon/link crash, send/receive omissions, and timing failures. Furthermore, by selective reordering of messages and spontaneous transmission of new messages, we were able to guide a distributed computation into hard to reach global states without instrumenting the protocol implementation.

关键词： Transmission control protocol

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PP-MESS-SIM: A simulator for evaluating multicomputer interconnection networks 28

PP-MESS-SIM: A simulator for evaluating multicomputer interc...

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28th Annual Simulation Symposium, ANSS 1995

作者： Rexford, Jennifer Dolter, James Feng, Wu-chang Shin, Kang G. Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann ArborMI48109-2122 United States

ISBN: (纸本)0818670916

This paper presents pp-mess-sim, an object-oriented discrete-event simulation environment for evaluating multicomputer networks. The simulator provides a toolboz of various network topologies, communication workloads, routing-switching algorithms, and router models. These router models can vary from high-level architectures to low-level specification of actual devices. By decoupling individual parts of the code, pp-mess-sim enables independent code development and creates a flexible and extensible environment for evaluating different aspects of network design. Sample simulation experiments capitalize on this flezibility to compare routing-switching schemes under various application workloads. © 1995 IEEE

关键词： Discrete event simulation

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QoS-Sensitive protocol processing in shared-memory multiprocessor multimedia servers 3

QoS-Sensitive protocol processing in shared-memory multiproc...

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3rd IEEE Workshop on the Architecture and Implementation of High Performance Communication Subsystems, HPCS 1995

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

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Non-preemptive scheduling of messages on controller area network for real-time control applications

Non-preemptive scheduling of messages on controller area net...

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1995 Real-time Technology and Applications Symposium, RTAS 1995

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

Scheduling messages on the controller area network (CAN) corresponds to assigning identifiers (IDs) to messages according to their priorities. If fixed priority scheduling such as deadline monotonic (DM) is used to calculate these priorities, then in general, it will result in low schedulability. Dynamic scheduling schemes such as earliest deadline (ED) can give greater schedulability, but they are not practical for CAN because if the ID is to reflect message deadlines then a long ID must be used. This increases the length of each message to the point that ED is no better than DM. Our solution to this problem is the mixed traffic scheduler (MTS), which is a cross between ED and DM, and provides high schedulability without needing long IDs. Through simulations, we compare the performance of MTS with that of DM and ED* (an imaginary scheduler which works like ED, except it needs only short IDs). We use a realistic workload in our simulations based on messages typically found in computer integrated manufacturing. Our simulations show that MTS performs much better than DM and at the same level as ED, except under high loads and tight deadlines, when ED* is superior. © 1995 IEEE.

关键词： Real time control

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Mapping concurrently-communicating modules onto mesh multicomputers equipped with virtual channels

Mapping concurrently-communicating modules onto mesh multico...

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International Conference on Distributed computing Systems

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

It is difficult to define and evaluate a meaningful performance metric when many packets are generated and exchanged concurrently in mesh-connected multicomputers equipped with wormhole switching and virtual channels. Thus, an approximate metric/cost function must be chosen so that when, task modules are mapped by optimizing this function, the actual performance of the mapping is also optimized. Several low-complexity cost functions are evaluated using the simulated annealing optimization process. The mappings found by optimizing these cost functions are then fed into a flit-level simulator to evaluate their actual performance. One particular cost function is found to be very effective.

关键词： Cost function Measurement Packet switching Simulated annealing

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A distributed table-driven route selection scheme for establishing real-time video channels

A distributed table-driven route selection scheme for establ...

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International Conference on Distributed computing Systems

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

To guarantee the delivery of real-time messages before their deadline, a real-time connection or channel must be established before the transmission of any real-time messages. During this channel-establishment phase, one must first select a route between the source and destination of this channel and then reserve sufficient resources along this route so that the worst-case end-to-end delay over the selected route may not exceed the user-specified delay bound. We propose a table-driven distributed route-selection scheme that is guaranteed to find a "qualified" route, if any, that meets the performance requirement of the requested channel without compromising any of the existing guarantees. The proposed scheme uses the Bellman-Ford shortest path algorithm to build real-time delay tables, and hence, can solve the route-selection problem by a simple table look-up. Several examples are presented to demonstrate the effectiveness of the proposed distributed route-selection scheme.

关键词： Delay

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Localized multicast routing

Localized multicast routing

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IEEE Conference and Exhibition on Global Telecommunications (GLOBECOM)

作者： A. Shaikh S. Lu K. Shin Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

Multicast is a fundamental issue in distributed computing and networking, especially for applications such as audio and video transmission. The minimal cost route selection problem for multicasting is an NP-complete problem even for regular network topologies such as meshes and hypercubes. We therefore present a simple heuristic algorithm for multicast route selection in arbitrarily-connected point-to-point communication networks. Several other heuristics have been presented for finding the minimal multicast route, but most of them are global in the sense that the source uses global cost information to construct a multicast tree. Our algorithm does not require the use of global cost information; it uses cost information only from neighboring nodes as it proceeds which makes it more practical from an implementation paint of view. The performance of the algorithm is analyzed through empirical comparisons and is shown to perform as well against algorithms which use global information.

关键词： Routing Costs Multicast algorithms Distributed computing NP-complete problem Network topology Hypercubes Heuristic algorithms Communication networks Paints

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Real-time communication in FieldBus multiaccess networks

Real-time communication in FieldBus multiaccess networks

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Real-time Technology and Applications Symposium

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

There has been an increasing need of timely and predictable communication services for embedded real-time systems in automated factories and industrial process controls. Work has been done on real-time communication with deadline guarantees in point-to-point, token bus/token ring/FDDI, and DQDB (Distributed Queue Dual Bus) networks. However, due to the random access nature of the CSMA/CD type multiaccess networks, they are not suitable for applications with stringent timing constraints. We consider real-time communication services with absolute deadline guarantees in multiaccess local area networks equipped with a centralized scheduler, such as the SP-50 FieldBus, an industrial standard protocol for process control and manufacturing applications. Similar to most token-passing networks, in a centralized scheduling multiaccess network, the access to the bus is controlled by a token. Only the station currently holding the token has the exclusive right to use the multiaccess bus. Unlike the token bus, token ring, or FDDI network, the multiaccess network uses a centralized token scheduling scheme and the token need not be allocated to the stations in a cyclic fashion. We show that the pinwheel and the distance-constrained scheduling techniques can be adapted to schedule the token in centralized-scheduling multiaccess networks to guarantee message deadlines.

关键词： Field buses Job shop scheduling Communication industry Industrial control Process control Token networks FDDI Real time systems Production facilities electrical equipment industry

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PP-MESS-SIM: a simulator for evaluating multicomputer interconnection networks

PP-MESS-SIM: a simulator for evaluating multicomputer interc...

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Annual Symposium on Simulation

作者： J. Rexford J. Dolter Wu-Chang Feng K.G. Shin Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

Presents PP-MESS-SIM, an object-oriented discrete-event simulation environment for evaluating multicomputer networks. The simulator provides a toolbox of various network topologies, communication workloads, routing-switching algorithms, and router models. These router models can vary from high-level architectures to low-level specification of actual devices. By decoupling individual parts of the code, PP-MESS-SIM enables independent code development and creates a flexible and extensible environment for evaluating different aspects of network design. Sample simulation experiments capitalize on this flexibility to compare routing-switching schemes under various application workloads.< >

关键词： Multiprocessor interconnection networks Object oriented modeling Computational modeling Network topology Routing Communication switching computer networks Telecommunication traffic Discrete event simulation Parallel processing

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