Distributed state space minimization

We present a new algorithm, and its distributed implementation, for reducing labeled transition systems modulo strong bisimulation. The base of this algorithm is the Kanellakis–Smolka “naive method”, which has a high theoretical complexity but is successful in practice and well suited to parallelization. This basic approach is combined with optimizations inspired by the Kanellakis–Smolka algorithm for the case of bounded fanout, which has the best known time complexity. The distributed implementation is improved with respect to previous attempts by a better overlap between communication and computation, which results in an efficient usage of both memory and processing power. We also discuss the time complexity of this algorithm and show experimental results with sequential and distributed prototype tools.     

Distributed multivariable control system design for coal-fired boilers

This paper describes the multivariable characteristics of industrial coal-fired boilers and associated mathematical models, such as combustion model, a water drum level model and a superheated steam model. The purpose of the paper is to design multivariable control systems using multivariable system frequency domain design theory and the Smith-predictor technique. A specific application shows how to design a model-based distributed multivariable control system for coal-fired boilers in a small-scale power station.     

A verification framework with application to a propulsion system

This paper introduces a novel verification framework for Prognostics and Health Management (PHM) systems. Critical aircraft, spacecraft and industrial systems are required to perform robustly, reliably and safely. They must integrate hardware and software tools intended to detect and identify incipient failures and predict the remaining useful life (RUL) of failing components. Furthermore, it is desirable that non-catastrophic faults be accommodated, that is fault tolerant or contingency management algorithms be developed that will safeguard the operational integrity of such assets for the duration of the emergency. It is imperative, therefore, that models and algorithms designed to achieve these objectives be verified before they are validated and implemented on-board an aircraft. This paper develops a verification approach that builds upon concepts from system analysis, specification definition, system modeling, and Monte Carlo simulations. The approach is implemented in a hierarchical structure at various levels from component to system safety. Salient features of the proposed methodology are illustrated through its application to a spacecraft propulsion system.     

Distributed model predictive control of an experimental four-tank system

A distributed model predictive control (DMPC) framework is proposed. The physical plant structure and the plant mathematical model are used to partition the system into self-sufficient estimation and control nodes. Local measurements at the nodes are used to estimate the relevant plant states. This information is then used in the model predictive control calculations. Communication among relevant nodes during estimation and control calculations provides improvement over the performance of completely decentralized controllers. The DMPC framework is demonstrated for the level control of an experimental four-tank system. The performance of the DMPC system for disturbance rejection is compared with other control configurations. The results indicate that the proposed framework provides significant improvement over completely decentralized MPC controllers, and approaches the performance of a fully centralized design.     

一种新的分布式数据模型的规范说明

在大规模的分布环境下,尤其是当部分网络处于偶联的状态下,数据的分布和访问引发了相当的理论和实践问题.本文从全国人口信息系统的范例出发,提出并定义了数据的典型树状结构的分布,并对该分布模型作出了详细的规范说明.     

Distributed identification and control of spatially interconnected systems with application to an actuated beam

This paper presents a case study on modelling and control of spatially interconnected systems. Considered is a vibration control problem, with experimental results on a flexible beam that is equipped with an array of piezo sensors and actuators. The sensor–actuator array induces a spatial discretization of the beam into an array of interconnected subsystems. Models are experimentally identified that have the structure of spatially interconnected systems. Based on the identified models, distributed control schemes are designed by solving a linear matrix inequality (LMI) problem that has the size of a single subsystem. Modelling and control is considered for both spatially invariant and spatially varying systems; in the latter case the system is represented as linear parameter-varying (LPV) system that is scheduled not over time but over space. Simulation and experimental closed-loop results demonstrate the practicality and efficiency of the underlying framework.     

A Semantics for Distributed Execution of Statemate

We present a semantics for the statechart variant implemented in the Statemate product of i-Logix. Our semantics enables distributed code generation for Statemate models in the context of rapid prototyping for embedded control applications. We argue that it seems impossible to efficiently generate distributed code using the original Statemate semantics. The new, distributed semantics has the advantages that, first, it enables the generation of efficient distributed code, second, it preserves many aspects of the original semantics for those parts of a model that are not distributed, and third, the changes made regarding the interaction of distributed model parts are similar to the interaction between the model and its environment in the original semantics, thus giving designers a familiar execution model. The semantics has been implemented in Grace, a framework for rapid prototyping code generation for embedded control applications.     

一种分布式宽带多媒体通信系统模型

多媒体通信业务在教育和培训领域的影响及多媒体通信系统和学习过程作了简要介绍和分析,提出了玫个适用教育和培训的分布式宽带多媒体通信业务应用模型,并对其主要原理进行了详细讨论。     

Distributed synthesis for well-connected architectures

We study the synthesis problem for external linear or branching specifications and distributed, synchronous architectures with arbitrary delays on processes. External means that the specification only relates input and output variables. We introduce the subclass of uniformly well-connected (UWC) architectures for which there exists a routing allowing each output process to get the values of all inputs it is connected to, as soon as possible. We prove that the distributed synthesis problem is decidable on UWC architectures if and only if the output variables are totally ordered by their knowledge of input variables. We also show that if we extend this class by letting the routing depend on the output process, then the previous decidability result fails. Finally, we provide a natural restriction on specifications under which the whole class of UWC architectures is decidable.     

Taming distributed system complexity through formal patterns

Many distributed systems are real-time, safety-critical systems with strong qualitative and quantitative formal requirements. They often need to be reflective and adaptive, and may be probabilistic in their algorithms and/or their operating environments. All this makes these systems quite complex and therefore hard to design, build and verify. To tame such system complexity, this paper proposes formal patterns, that is, formally specified solutions to frequently occurring distributed system problems that are generic, executable, and come with strong formal guarantees. The semantics of such patterns as theory transformations in rewriting logic is explained; and a representative collection of useful patterns is presented to ground all the key concepts and show their effectiveness.     

分布式系统可靠性模型

文章首先给出分布式系统的一般描述;然后采用建立在图论、概率论及布尔代数基础上的网络分析法建立了分布式系统的可靠性模型,用以综合考虑系统拓朴结构、任务集、通讯路径集和处理单元集等对系统可靠性的影响;最后,针对二维TORUS网,给出了建模实例以及模型的有关应用。     

运行时验证技术的研究进展

运行时验证是一种轻量级的验证方法,通过实时地监测系统的行为,验证系统的正确性,及时发现冲突,并发出警告或作出反应。运行时验证技术已经得到了越来越多的应用,以确保软件系统的正确性。总结了近年来运行时验证技术的研究进展,首先介绍了运行时验证的概念、原理和分类,接着深入分析了现有的几种解决方案,并对该领域中的研究热点进行了深入探讨,最后分析了运行时验证技术面临的主要挑战,并对未来该领域的研究方向进行了展望。     

Promoting social network awareness: A social network monitoring system

To increase communication and collaboration opportunities, members of a community must be aware of the social networks that exist within that community. This paper describes a social network monitoring system – the KIWI system – that enables users to register their interactions and visualize their social networks. The system was implemented in a distributed research community and the results have shown that KIWI facilitates collecting information about social interactions. Furthermore, the visualization of the social networks, given as feedback, appeared to have a positive impact on the group, augmenting their social network awareness.     

Distributed parameter system optimum control design via finite element discretization

The problem of designing an optimum distributed parameter system is considered. Fundamental concepts pertaining to the solution of optimum controls for distributed parameter systems by finite element methods are devised. It is demonstrated that methods can readily be applied to solve problems involving nonlinear Neumann boundary conditions.     

Safety assurance via on-line monitoring

This paper proposes a new approach and new techniques for on-line monitoring of concurrent programs to ensure that some of their safety properties are not violated. The techniques modify erroneous systems, which violate a certain safety property, into new systems which satisfy the safety property. It does so by adding a new layer that controls the scheduling of steps in the system. We formally characterize the relationship between the erroneous and the new system. Safety monitors for mutual-exclusion, -exclusion, and the producer-consumer tasks are presented. Proofs for the mutual-exclusion task and the -exclusion task are presented to demonstrate the applicability of our approach.Received: May 2001, Accepted: December 2002, An extended abstract of this work appears in the Proceedings of the fifth International Symposium on Autonomous Decentralized Systems (ISADS) 2001. Part of this work was done while the first author visited Wayne State University.     

分布式多媒体系统中的多点播送与组通信机制

描述多点播送和组通信机制的基本概念，讨论了通信子网中的多点播送通信机制机和端系统中的且通信机制，最后介绍应用实例。     

Distributed self-tuning consensus and synchronization

The problem of self-tuning of coupling parameters in multi-agent systems is considered. Agent dynamics are described by a discrete-time double integrator with unknown input gain. Each agent locally tunes the strength of interaction with neighboring agents by using a normalized gradient algorithm (NGA). The tuning algorithm minimizes the square of the error between an individual agent’s state (velocity) and the one step delayed average of its own state and the states of its neighbors. Assuming that the network graph is strongly connected, it is proved that the sequence of coupling parameters is convergent and all velocities converge toward the same constant value.     

Anarchic manufacturing: Distributed control for product transition

Manufacturers are poorly equipped to manage product transition scenarios, when moving from one product to another. Most tools consider a mature system, yet during transition and ramp up disturbances and inefficiency are common. The traditional methods, using centralised planning and control structures are too rigid and often resort to simple dispatch heuristics in this highly dynamic environment. Distributed systems have been proposed to leverage their self-organising and flexible traits to manage highly volatile and complex scenarios.Anarchic manufacturing, a free market based distributed planning and control system, delegates decision-making authority and autonomy to system elements at the lowest level; this system has previously been shown to manage job and flowshop style problems. The system has been adapted to use a dynamic batching mechanism, where jobs cooperate to benefit from economies of scale. The batch enables a direct economic viability assessment within the free market architecture, whether an individual machine should changeover production to another product type. This profitability assessment considers the overall system state and an agent’s individual circumstance, which in turn reduces system myopia. Four experiments, including a real-world automotive case study, evaluate the anarchic manufacturing system against two centralised systems, using three different ramp-up curves. Although not always best performing against centralised systems, the anarchic manufacturing system is shown to manage transition scenarios effectively, displaying self-organising and flexible characteristics. The hierarchical system was shown to be impeded by its simplifying structure, as a result of structural rigidity.