基于Petri网的动态Web服务组合建模

基于广义随机Petri网,提出了一种动态Web服务组合建模的方法.利用广义随机Petri网(GSPN)以及OWL-S组合过程对Web服务组合过程构建动态组合模型,实现Web服务的动态组合.并通过一个实例证明该方法的可行性.与现有的方法相比,该方法可以更有效地描述动态Web服务组合.     

Delay‐dependent stability criterion and H∞ analysis for Markovian jump systems with time‐varying delays

This paper deals with the problems of stochastic stability and H_∞ analysis for Markovian jump linear systems with time‐varying delays. In terms of linear matrix inequalities, a less conservative delay‐dependent stability criterion for Markovian jump systems is proposed by constructing a different Lyapunov‐Krasovskii functional and introducing improved integral‐equalities approach, and a sufficient condition is derived from the H_∞ performance. Numerical examples are provided to demonstrate the efficiency and reduced conservatism of the results in this paper. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Petri nets based FPGA controller of PDP sustainer with half‐voltage energy recovery circuit

This paper proposes a FPGA controller design of a driver circuit based Petri nets for the Plasma Display Panel (PDP). In such a driver circuit, complicated control logic is required in the PDP sustainer circuit to implement the sustaining voltage waveform. The control logic has the zero‐switching behaviour for the driver circuit to provide better efficiency for the driving circuit. Conventionally, the VHDL programmer does not have a systematic way to program the control logic. Time delay problem of logic components in logic controller may occur under high frequency operation. With the help of the proposed Petri nets approach, the VHDL programming for the PDP driver circuit can be easier in a systematic way. Also, this paper illustrates three types of sustainers with Petri nets based FPGA controller. The basic full‐bridge and full‐voltage sustainers are used to compare the performance with the proposed half‐voltage sustainer. Details of the circuit operation are described. From the experimental results, the performance such as efficiency, luminance, and gamma curve are assessed to show the effectiveness of the proposed half‐voltage sustainer. It is believed that the proposed Petri nets based control circuit is very powerful for the practical application of the PDP sustainer circuit. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Performance analysis of stochastic timed Petri nets using linearprogramming approach

Stochastic timed Petri nets are a useful tool in the performance analysis of concurrent systems such as parallel computers, communication networks and flexible manufacturing systems. In general, performance measures of stochastic timed Petri nets are difficult to obtain for practical problems due to their sizes. In this paper, we provide a method to efficiently compute upper and lower bounds for the throughputs and mean token numbers for a large class of stochastic timed Petri nets. Our approach is based on uniformization technique and linear programming     

基于广义随机Petri网的CIMS多任务可靠性研究

CIMS生产的复杂性要求其可靠性模型可以精确地反映生产过程,由于传统的可靠性建模方法无法兼顾CIMS的时间动态特性,所以针对一个复杂的有多个加工任务的CIMS制造单元,由于其机器加工工件的时间均为指数分布,则采用广义随机Petri网进行多任务可靠性建模,在此基础上基于Petri网行为表达式,将矩母函数思想引入其中,不必生成可达标识图就可通过计算模型的传递函数,进而得到整个系统的多任务可靠度,该可靠性指标可以更直观地反映具有多种加工任务的整个CIMS的运行性能。     

H∞ fuzzy control design of discrete‐time nonlinear active fault‐tolerant control systems

This paper is concerned with the problem of H_∞ fuzzy controller synthesis for a class of discrete‐time nonlinear active fault‐tolerant control systems (AFTCSs) in a stochastic setting. The Takagi and Sugeno (T–S) fuzzy model is employed to exactly represent a nonlinear AFTCS. For this AFTCS, two random processes with Markovian transition characteristics are introduced to model the failure process of system components and the fault detection and isolation (FDI) decision process used to reconfigure the control law, respectively. The random behavior of the FDI process is conditioned on the state of the failure process. A non‐parallel distributed compensation (non‐PDC) scheme is adopted for the design of the fault‐tolerant control laws. The resulting closed‐loop fuzzy system is the one with two Markovian jump parameters. Based on a stochastic fuzzy Lyapunov function (FLF), sufficient conditions for the stochastic stability and H_∞ disturbance attenuation of the closed‐loop fuzzy system are first derived. A linear matrix inequality (LMI) approach to the fuzzy control design is then developed. Moreover, a suboptimal fault‐tolerant H_∞ fuzzy controller is given in the sense of minimizing the level of disturbance attenuation. Finally, a simulation example is presented to illustrate the effectiveness of the proposed design method. Copyright © 2008 John Wiley & Sons, Ltd.     

Stochastic stability and extended dissipativity analysis for uncertain neutral systems with semi‐Markovian jumping parameters via novel free matrix–based integral inequality

This paper investigates the issues of stochastic stability and extended dissipativity analysis for uncertain neutral systems with semi‐Markovian jumping parameters. A new criterion about the stochastic stability and extended dissipativity of uncertain neutral systems with semi‐Markovian jumping parameters is obtained based on the new Lyapunov‐Krasovskii functionals together with the introduced novel free matrix–based integral inequality. The major contribution of this study is that the stochastic stability and extended dissipativity concept for uncertain neutral systems with semi‐Markovian jumping parameters can be developed to simultaneously analyze the solutions of the L₂ ? L_∞ performance, H_∞ action, passivity behavior, and dissipativity by selecting different weighting matrices. Finally, several interesting numerical examples are provided to show the effectiveness and less conservatism of the proposed method.     

Stochastic stability of semi‐Markovian jump systems with mode‐dependent delays

Semi‐Markovian jump systems, due to the relaxed conditions on the stochastic process, and its transition rates are time varying, can be used to describe a larger class of dynamical systems than conventional full Markovian jump systems. In this paper, the problem of stochastic stability for a class of semi‐Markovian systems with mode‐dependent time‐variant delays is investigated. By Lyapunov function approach, together with a piecewise analysis method, a sufficient condition is proposed to guarantee the stochastic stability of the underlying systems. As more time‐delay information is used, our results are much less conservative than some existing ones in literature. Finally, two examples are given to show the effectiveness and advantages of the proposed techniques. Copyright © 2013 John Wiley & Sons, Ltd.     

Product form solution for a class of PEPA models

The advantages of the compositional structure within the Markovian process algebra PEPA for model construction and simplification have already been demonstrated. In this paper we show that for some PEPA models this structure may also be used to advantage during the solution of the model. Several papers offering product form solutions of stochastic Petri nets have been published during the last 10 years. In [R. Boucherie, A characterisation of independence for competing Markov chains with applications to stochastic Petri nets, IEEE Trans. Software Engrg. 20 (7) (1994) 536–544], Boucherie showed that these solutions were a special case of a simple exclusion mechanism for the product process of a collection of Markov chains. The results presented in this paper take advantage of his observation. In particular we show that PEPA models that generate such processes may be readily identified and show how the product form solution may be obtained. Although developed here in the context of PEPA the results presented can be easily generalised to any of the other Markovian process algebra languages.     

Markovian timed Petri nets for performance analysis ofsemiconductor manufacturing systems

A subclass of generalized stochastic Petri nets (GSPNs) with priorities, called Markovian timed Petri nets, are proposed to model semiconductor manufacturing systems that consider process priorities, routing priorities, resource re-entrance, and nonpreemptive operations. Uniformization technique is used to establish both lower and upper bounds of the performance of interest. These bounds are computable using linear programming. Numerical experiments have been conducted to evaluate the accuracy of the bounds using models adapted from real-world systems. The experiments show that the upper bounds are very close to the simulation results. Thus, performance measures can be accurately estimated using these bounds.     

A moment generating function based approach for evaluating extendedstochastic Petri Nets

A moment-generating-function (MGF)-based approach for performance analysis of extended stochastic Petri nets (ESPNs) is presented. The method integrates Petri nets, MGF and stochastic network concepts, and Mason's rule into a tool for evaluating various discrete-event dynamic systems. The ESPNs are modeled, given the specification of a system. Then, the state machine PN is derived, the transfer functions based on the MGFs of the related transitions are found, the network is reduced to a single transition with its transfer function for each performance measure, and system performance is calculated. Firing delays of transitions in ESPNs can be either deterministic or stochastic with an extended distribution. Three fundamental structures that can be reduced into a single transition are discussed. The machine-repairman model with a buffer is given as an example to illustrate the method for evaluating performance parameters     

Event‐triggered finite‐time reliable control for nonhomogeneous Markovian jump systems

This article investigates the event‐triggered finite‐time reliable control problem for a class of Markovian jump systems with time‐varying transition probabilities, time‐varying actuator faults, and time‐varying delays. First, a Luenberger observer is constructed to estimate the unmeasured system state. Second, by applying an event‐triggered strategy from observer to controller, the frequency of transmission is reduced. Third, based on linear matrix inequality technique and stochastic finite‐time analysis, event‐triggered observer‐based controllers are designed and sufficient conditions are given, which ensure the finite‐time boundedness of the closed‐loop system in an H_∞ sense. Finally, an example is utilized to show the effectiveness of the proposed controller design approach.     

基于行为表达式的任意随机Petri网的品质分析

提出一种基于行为表达式的品质分析方法,可以做任意分布的有界或无界随机 Petri网的品质分析.该方法不仅拓广了分析范围,解决了文献[4]中没有解决的问题,而且 不必画出Petri网的可达标识图,使分析过程更为简洁.     

基于随机Petri网模型的网络协议性能测试

分析了协议性能测试需要解决的主要问题,并以随机Petri网为形式化工具,描述了网络协议的服务质量.提出从随机Petri网模型到TTCN(tree and tabular combined notation)测试集的转换规则,并根据随机Petri网模型生成了协议性能测试例.     

Event‐driven model predictive control of timed hybrid Petri nets

Hybrid Petri nets represent a powerful modeling formalism that offers the possibility of integrating, in a natural way, continuous and discrete dynamics in a single net model. Usual control approaches for hybrid nets can be divided into discrete‐time and continuous‐time approaches. Continuous‐time approaches are usually more precise, but can be computationally prohibitive. Discrete‐time approaches are less complex, but can entail mode‐mismatch errors due to fixed time discretization. This work proposes an optimization‐based event‐driven control approach that applies on continuous time models and where the control actions change when discrete events occur. Such an approach is computationally feasible for systems of interest in practice and avoids mode‐mismatch errors. In order to handle modelling errors and exogenous disturbances, the proposed approach is implemented in a closed‐loop strategy based on event‐driven model predictive control. Copyright © 2013 John Wiley & Sons, Ltd.     

Performance analysis of distributed real-time databases

In a distributed process control system, information about the behavior of physical processes is usually collected and stored in a real-time database which can be remotely accessed by human operators. In this paper we propose an analytic approach to compute the response-time distribution of operator consoles in a distributed process control environment. The technique we develop is based on Markov regenerative processes (MRGPs) and described with the assistance of deterministic and stochastic Petri nets (DSPNs). We construct exact models for performance analysis of centralized and decentralized database architectures. However, due to limitations on the exact solution, we also propose an approximate solution which is then used to study response-time distributions of large systems.