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Conference on Local comput.r Networks (LCN)

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

A strategy for handling real-time communications under the FieldBus protocol, which provides end-to-end delivery delay guarantees for time-critical messages, is proposed. This strategy provides a fast local mechanism for establishing intraworkcell real-time connections, while supporting global interworkcell real-time connections. The proposed strategy is fully compatible with the current draft proposal of the FieldBus protocol and also provides flexibility for the choice of scheduling algorithms and adaptability for different traffic loads. Numerical examples are given based on a typical manufacturing network.< >

关键词： real time systems Field buses Manufacturing systems Protocols Delay Manufacturing processes Process control time factors Job shop scheduling comput.r network management

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Communication-oriented assignment of task modules in hypercubic multicomput.rs

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

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International Conference on Distributed computing Systems

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

The problem of mapping a task that is composed of interacting modules onto a hypercube multicomput.r 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.< >

关键词： Hypercubes Costs Timing Performance evaluation Laboratories comput.r science Parallel processing Fault tolerance comput.tional efficiency time measurement

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SCHEDULING JOB OPERATIONS IN AN AUTOMATIC ASSEMBLY LINE

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IEEE TRANSACTIONS ON ROBOTICS AND AUTOMATION 1991年第3期7卷 333-341页

作者： SHIN, KG ZHENG, Q Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

This paper addresses the problem of scheduling job operations in an automatic assembly line used for manufacturing a small to medium volume of mixed workparts. The assembly line model used here differs from the classical flow shop model in the following three aspects: 1) there are no buffers at machine stations, 2) constraints associated with the material transport system are included, and 3) for each batch of production, workparts are distinguished in groups, rather than individually. An "optimal" algorithm that requires very little comput.tion is derived first by minimizing the total finish time for two machine assembly lines. This result is then generalized to the problem of scheduling an assembly line with m > 2 machines processing single-operation jobs. In order to reduce the comput.tional complexity of the latter problem, heuristic algorithms are also proposed and shown to work quite well for all the cases considered. Finally, a heuristic solution to the problem of scheduling an assembly line with m > 2 machines processing multioperation jobs is discussed.

关键词： Job shop scheduling Processor scheduling Heuristic algorithms Flexible manufacturing systems Optimal scheduling Assembly systems Manufacturing automation Pulp manufacturing Scheduling algorithm Mass production

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real-time COMMUNICATIONS IN A comput.R-CONTROLLED WORKCELL

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IEEE TRANSACTIONS ON ROBOTICS AND AUTOMATION 1991年第1期7卷 105-113页

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

A comput.r-integrated manufacturing (CIM) system is composed of several workcells, each of which contains robots, NC machines, sensors, and a transport mechanism. Each CIM workcell is controlled by multiple processors interconnected by an intracell bus, but the individual cells are interconnected by an arbitrary network. This paper considers a communication subsystem that is designed to support real-time control and coordination of devices in each CIM cell. The concept of a poll number is proposed to control the access to the intracell bus. The bus access mechanism with the poll number is intended to minimize the probability of real-time messages missing their deadlines. When a CIM task generates a time-constrained message, a poll number is comput.d for this message according to the message's deadline and the task's prority. When the intracell bus is free, the various tasks at a workcell that desire to use the bus write the poll number onto the bus and read it back, one bit at a time, starting from the most significant bit. If at any time the bit read back is different from the bit written, then the corresponding task drops out of the contention for the bus. Use of a poll number provides not only for decentralized control of the intracell bus, but also a high degree of flexibility in scheduling messages. The performance of the bus access mechanism with a poll number is analyzed and compared with that of a token bus, which is widely used in CIM systems such as MAP networks. The probability of a real-time message missing its deadline in a token bus is found to be much higher than that of the proposed mechanism.

关键词： comput.r integrated manufacturing Communication system control Robot sensing systems Robot kinematics Sensor systems Distributed control Job shop scheduling Performance analysis Manufacturing automation Access protocols

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INTELLIGENT COORDINATION OF MULTIPLE SYSTEMS WITH NEURAL NETWORKS

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IEEE TRANSACTIONS ON SYSTEMS MAN AND CYBERNETICS 1991年第6期21卷 1488-1497页

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

Many control applications require cooperation of two or more independently designed, separately located, but mutually affecting, subsystems. In addition to the good behavior of each subsystem, effective coordination of these subsystems is very important to achieve the desired overall system performance. However, such coordination is very difficult to accomplish due mainly to the lack of precise system models and/or dynamic parameters as well as the lack of efficient tools for system analysis, design, and real-time comput.tion of optimal solutions. A new multiple-system coordinator that combines the techniques of intelligent control and neural networks, and forms the high-level coordinator in a hierarchical structure, is proposed. The basic idea is to estimate the effects of the control commands to subsystems using a predictor and modify these commands using a knowledge-based coordinator so as to achieve the desired performance. The predictor is designed for multiple-input, multiple-output systems using neural networks. The knowledge-based coordinator is responsible for a goal-oriented search in its knowledge base and the overall system stability. Because the internal structure and parameters of the low level are not affected by using the proposed method, some commercially designed servo controllers for single systems can be coordinated to perform more sophisticated tasks for multiple systems than originally intended.

关键词： Intelligent networks Neural networks Control systems System performance Intelligent control real time systems Humans Intelligent structures Stability Design methodology

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DESIGN OF A KNOWLEDGE-BASED CONTROLLER FOR INTELLIGENT CONTROL-SYSTEMS

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IEEE TRANSACTIONS ON SYSTEMS MAN AND CYBERNETICS 1991年第2期21卷 368-375页

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

A hierarchical knowledge-based controller is proposed to improve the performance of complex control systems, such as robots. Unlike parameter- and performance- adaptive controllers, this controller is designed only to modify the reference input of a lower-level servo controller. Because the internal parameters and structure of the lower-level controller are not affected, commercial servo controllers can be made to perform more sophisticated tasks than originally intended. The principle of the knowledge-based controller, modification of the reference input, knowledge representation, existence of the solution, and analyses of the controller's stability and tracking error are described in detail. A self-tuning multiple-step predictor is designed as part of the controller to eliminate the undesirable effects of system time delay. Both linear and nonlinear example control systems are tested via extensive simulations and have all shown promising performances.

关键词： servo controller control systems reference input intelligent control system internal parameter Controllers undesirable effects

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Optimal load sharing in distributed real-time systems 6

Optimal load sharing in distributed real-time systems

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6th Distributed Memory computing Conference, DMCC 1991

作者： Chang, Yi-Chieh 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)0818622903

In hard real-time systems, the problem of scheduling periodic tasks to meet their deadlines has been studied extensively, but scheduling aperiodic tasks has been addressed far less, due mainly to their uncertain arrivals. The main intent of this paper is to derive an approximate, closed-form solution for the decentralized, dynamic load sharing (LS) problem treated in our early paper [1], Based on the derived solutions, we show that the probability of missing task deadlines can be kept below any required level while minimizing the communication overhead resulting from task transfers and state-information collection. Specifically, "optimal" threshold patterns and buddy set sizes are derived for different system loads by minimizing the communication overhead subject to a constraint of keeping the probability of missing task deadlines below any given level. (One can also derive optimal solutions by minimizing the probability of missing deadlines while keeping the communication overhead below a specified level.). © 1991 IEEE.

关键词： Probability

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Load sharing in hypercube multicomput.rs in the presence of node failures

Load sharing in hypercube multicomputers in the presence of ...

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International Symposium on Fault-Tolerant computing (FTCS)

作者： Y.-C. Chang K.G. Shin Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan USA

Two important issues associated with load sharing (LS) in hypercube multicomput.rs are discussed and analysed: (i) ordering fault-free nodes as preferred receivers of overflow tasks and (ii) developing an LS mechanism to handle node failures. The authors previously (1989) proposed to order the nodes in each node's proximity into its preferred list of receivers for the purpose of LS in distributed real-time systems. However, the occurrence of node failures will destroy the original structure of a preferred list if the failed nodes are simply dropped from the list. Three algorithms are proposed to modify the preferred list to retain its original features. Based on the modified preferred lists, node failures can be tolerated by equipping each node with a backup queue which stores and updates the arriving/completing tasks at its most preferred node. Simulation results show that this approach, despite its simplicity, can greatly reduce the number of task losses compared to approaches that do not use backup queues.< >

关键词： Hypercubes real time systems Broadcasting Fault tolerance Laboratories Failure analysis Algorithm design and analysis Delay time factors

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Generating Synthetic Workloads for real-time Systems

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IFAC Proceedings Volumes 1991年第2期24卷 103-105页

作者： D.L. Kiskis K.G. Shin Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science The University of Michigan Ann Arbor MI 48109-2122 USA

In this paper, we describe a software system which generates synthetic workloads for use in the performance evaluation of distributed real-time comput.r systems. The software system consists of a high-level description language and its compiler. The language provides a flexible, easy-to-use description of the structure and behavior of the real-time workload. The compiler, called a synthetic workload generator (SWG), uses this description to produce an executable synthetic workload (SW). The SW may then be used to drive the system under evaluation while measurements are being made.

关键词： comput.r selection and evaluation real-time comput.r systems software tools specification languages

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Design of an Industrial Process Controller using Neural Networks

Design of an Industrial Process Controller using Neural Netw...

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American Control Conference (ACC)

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

There are many problems in industrial process control systems due to a long system response delay, dead-zone and/or saturation of the actuator mechanisms, uncertainties in the system model and/or parameters, and process noise. To overcome these problems, an adaptive controller is designed using neural networks and tested extensively via simulations. One of the key problems in designing such a controller is to develop an efficient training algorithm. Neural networks are usually trained using the output errors of the network, instead of using the output errors of the controlled plant. However, when a neural network is used to control a plant directly, the output errors of the network are unknown, since the desired control actions are unknown. In this paper, we propose a simple training algorithm for a class of nonlinear systems, which enables the neural network to be trained by the output errors of the controlled plant. The only a priori knowledge of the controlled plant is the direction of its output response. A detailed analysis of the algorithm is presented and the corresponding theorems are proved. Due to its simple structure and algorithm, and good performance, the proposed controller has high potential for handling difficult problems in industrial process control systems.

关键词： Industrial control Process control Neural networks Error correction electrical equipment industry Algorithm design and analysis Control systems Delay systems Actuators Uncertainty

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