判定非确定离散事件系统稳定性的梯度搜索算法

讨论基于非确定自动机/形式语言模型的非确定离散事件系统(NDES)稳定性问题.引入非确定离散事件系统稳定性的定义,并得到了稳定性的判据定理.给出了基于梯度的搜索算法,该算法可有效消除观测器的冗余,从而降低了计算复杂度.     

离散事件系统N步稳定性分析

讨论基于自动机/形式语言模型的离散事件系统(DES)稳定性问题,引入了确定性离散事件系统N步稳定性定义,并得到了稳定性的判据定理,推导了具体的算法实现。该算法具有多项式复杂度。     

非确定型离散事件系统双模拟控制的实现

近年来,双模拟等价关系与离散事件系统监控理论相结合的研究引起了国内外许多学者的广泛关注.本文针对作者在前期工作中提出的非确定型离散事件系统的双模拟控制机制,进一步探讨其实现问题.利用投影映射对系统规范说明语言进行等价类划分,构造了一棵计算树,得到了一个判断规范说明是否具有基于模拟关系可观性的多项式算法,证明了双模拟控制机制是多项式时间算法可实现的.同时,通过对控制器配备具有存储和判断功能的模拟关系识别器,阐述了这种双模拟控制机制是物理可实现的.     

离散事件系统拟同余关系的改进算法

针对离散事件系统, 本文主要研究计算最优拟同余关系时减少时间复杂度的算法. 基于Paige & Tarjan提出且Fernandez修改的、可有效计算最粗粒度划分问题的算法, 本文给出一种时间复杂度为O(mlog n)的计算最优拟同余关系的算法. 该算法适用于离散事件系统比较复杂, 尤其是可观事件很少的情况. 与Ramadge和Wonham提出的时间复杂度为O(mn)的算法相比, 该算法计算过程耗时较短. 本文还讨论了计算拟同余关系的边界情况的改进方法. 仿真结果表明所提出算法的有效性.     

离散切换系统观测器存在性讨论及降维观测器设计

对具有未知输入的离散切换系统讨论了未知输入观测器（Unknown input observer,UIO）设计方法.首先,对一般离散系统的未知输入观测器匹配条件的Lyapunov-type表示,进行了等价性论证;然后,基于不具有未知输入的离散切换系统的稳定性理论,对具有未知输入的离散切换系统提出了一种切换降维观测器设计方法.通过矩阵分块确定出的观测器增益矩阵,使得降维观测器能直接消去未知输入的影响;然后,在此基础上提出了一种未知输入代数重构方法;最后,通过仿真验证了方法的有效性和正确性.     

离散事件系统的可测性

讨论基于自动机/形式语言模型的离散事件系统（DES）的可测性问题。可测性即为根据系统的可观事件和状态输出的信息估计系统的当前状态。定义了四种可测性：强可测性,弱可测性,强周期可测性,弱周期可测性。给出了这些可测性的充要条件,这些充要条件可通过构建观测器进行有效的判定。     

分布式随机离散事件系统的模式故障预测EI北大核心CSCD

本文以随机自动机为模型,研究分布式随机离散事件系统的模式故障预测问题.首先根据分布式随机离散事件系统的分布特性对模式故障协同可预测性概念进行形式化,并通过构造模式故障识别器来识别系统中发生的模式故障.然后,构造一个模式故障协同预测器,提出一种基于协同预测器的具有多项式复杂度的算法,得到关于分布式随机离散事件系统模式故障协同可预测性的充分必要条件,实现对分布式随机离散事件系统的模式故障预测.     

一类离散非线性不确定互联系统的模糊分散控制

利用模糊控制方法研究一类离散非线性互联系统的分散控制问题.首先采用模糊(T-S)模型对离散非线性不确定互联系统进行模糊建模,应用并行分布补偿算法(PDC)给出状态反馈分散模糊控制方案,并基于李亚普诺夫函数方法证明了闭环系统的稳定性.然后当系统的状态不完全可测时,设计模糊分散观测器来估计各子系统的状态,从而给出基于观测器的状态反馈分散模糊控制设计的方法.因为该分散模糊控制设计问题是以线性矩阵不等式的形式给出,所以很容易用凸优化方法求解.仿真结果验证了所提出控制方法的有效性.     

对称离散事件系统事件重标记观测器性质研究

当离散事件系统(discrete-event systems,DES)由多组结构相同的组件构成时,则称离散事件系统具有对称性.为了化简对称离散事件系统的状态空间,本文提出事件重标记映射,将完成相同任务的事件标记为同一事件,将与控制无关的不可控事件设为不可观测事件,并将其标记为空字符擦除.为了确保事件重标记前后系统对应的最大监督控制器具有相同的控制效果,本文引入重标记观测器(relabeling observer property,ROP)的概念并给出判断被控对象对应的语言关于事件重标记映射是否具有重标记观测器性质的算法;然后运用重标记观测器性质证明事件重标记前后监督控制器控制效果的等价性,从而可用简化后的监督控制器实现与事件重标记操作前相同的控制任务.最后通过实例验证所提理论的正确性.     

DoS攻击下网络化控制系统基于观测器的记忆型事件触发预测控制

本文研究了DoS攻击下网络化控制系统记忆型事件触发预测补偿控制问题. 首先, 由于网络带宽资源有限 和系统状态不完全可观测性, 引入了记忆型事件触发函数, 为观测器提供离散事件触发传输方案. 然后, 分析了网络 传输通道上发生的DoS攻击. 结合上述记忆型事件触发方案, 在控制节点设计一类新颖的预测控制算法, 节省网络 带宽资源并主动补偿DoS攻击. 同时, 建立了基于观测器的记忆型事件触发预测控制的闭环系统, 并且分析稳定性. 通过线性矩阵不等式(LMI)和Lyapunov稳定性理论, 建立了控制器、观测器和记忆型事件触发矩阵的联合设计方案, 并验证了该方案的可行性. 仿真结果表明, 该方案结合记忆型事件触发机制可以有效补偿DoS攻击, 节约网络带宽 资源.     

On the stability of qualitative models

This paper considers a discrete-time continuous-variable autonomous system for which only a quantised state measurement [x(k)] is available. The qualitative model of this system is a nondeterministic automaton thay describes, for a given quantised initial state [x(0)], the sequence of quantised states [x(k)]. The paper deals with the question for which stable linear systems is the qualitative model also stable. A necessary and sufficient condition on the qualitative model is proved under which the continuous-variable system is stable. This condition refers to the eventual boundedness of the nondeterministic automation. An example demonstrates that this stability criterion can be used only if a qualitative model of the system is available.     

Robust and nonblocking supervisory control of nondeterministicdiscrete event systems using trajectory models

This note considers the robust supervisory control problems of uncertain nondeterministic discrete-event systems (DESs). The uncertain DES to be controlled is assumed to be modeled as a set of some possible nondeterministic automata. Then, the control objective is to achieve a given language specification and guarantee the nonblockingness of any nondeterministic automata of the set which are controlled by a robust nonblocking supervisor. Based on trajectory models, this note presents the necessary and sufficient conditions for the existence of a robust nonblocking supervisor for a given uncertain nondeterministic DES     

基于不确定观测下离散事件系统可诊断性的研究

在实际应用系统中,由于传感器故障、传感器限制和网络中的数据包丢失等原因,事件的可观测值变得不确定,使得观测系统行为变得尤为复杂。针对离散事件系统中,同个事件串可能有多个观测值以及不同状态下同个事件观测值也可能不同的问题,提出一种不确定观测下故障诊断验证的方法。首先对不确定观测的离散事件系统的可诊断性进行形式化,然后构建出用于上述故障诊断验证的验证器;基于验证器提出了系统基于不确定观测下可诊断的充要条件及验证算法;最后,实例说明不确定观测下故障诊断验证算法的应用。与现有研究相比,提出的方法对故障事件的观测值没有约束,可以为0个或多个观测值,使此方法应用的场景更为广泛。     

Control of nondeterministic discrete-event systems for bisimulation equivalence

Most prior work on supervisory control of discrete event systems is for achieving deterministic specifications, expressed as formal languages. In this paper we study supervisory control for achieving nondeterministic specifications. Such specifications are useful when designing a system at a higher level of abstraction so that lower level details of system and its specification are omitted to obtain higher level models that may be nondeterministic. Nondeterministic specifications are also meaningful when the system to be controlled has a nondeterministic model due to the lack of information (caused for example by partial observation or unmodeled dynamics). Language equivalence is not an adequate notion of behavioral equivalence for nondeterministic systems, and instead we use the finest known notion of equivalence, namely the bisimulation equivalence. Choice of bisimulation equivalence is also supported by the fact that bisimulation equivalence specification is equivalent to a specification in the temporal logic of /spl mu/-calculus that subsumes the complete branching-time logic CTL*. Given nondeterministic models of system and its specification, we study the design of a supervisor (possibly nondeterministic) such that the controlled system is bisimilar to the specification. We obtain a small model theorem showing that a supervisor exists if and only if it exists over a certain finite state space, namely the power set of Cartesian product of system and specification state spaces. Also, the notion of state-controllability is introduced as part of a necessary and sufficient condition for the existence of a supervisor. In the special case of deterministic systems, we provide an existence condition that can be verified polynomially in both system and specification states, when the existence condition holds.     

Backtracking in independent and-parallel implementations of logicprogramming languages

In this paper, we present an implementation model which efficiently supports backtracking in an independent and-parallel nondeterministic system. The problem is tackled in the context of logic programming, although the solution proposed is sufficiently general to be easily extended to different nondeterministic systems, such as constraint programming systems. The complexity of the problem is demonstrated by the fact that most existing and-parallel systems either do not support backtracking over and-parallel calls or simply avoid analyzing the performance of their systems in the presence of nondeterministic benchmarks. The implementation model we present is an extension of the backtracking scheme developed by Hermenegildo and Nasr (1986) and relies on a novel memory organization scheme and on the use of various optimizations to reduce communication and overhead. The solution developed has been implemented in the ACE Parallel Prolog system. The performance of the system is analyzed on a variety of benchmarks. The results obtained are remarkable: speedups achieved during forward execution are not lost in heavy backtracking activities and, frequently, super-linear speedups are obtained thanks to a semi-intelligent backtracking scheme     

Nonblocking supervisory control of nondeterministic systems viaprioritized synchronization

Shayman and Kumar (1995) showed that supervisory control of nondeterministic discrete-event systems, in the presence of driven events, can be achieved using prioritized synchronous composition as a mechanism of control, and trajectory models as a modeling formalism, first introduced by Heymann (1990). The specifications considered in this earlier work were given by prefix-closed languages. In this paper, we extend this work to include markings so that nonclosed specifications and issues such as blocking can be addressed. It is shown that the usual notion of nonblocking, called language model nonblocking, may not be adequate in the setting of nondeterministic systems, and a stronger notion, called trajectory model nonblocking, is introduced. Necessary and sufficient conditions for the existence of language model nonblocking as well as trajectory model nonblocking supervisors are obtained for nondeterministic systems in the presence of driven events in terms of extended controllability and relative-closure conditions and a new condition called the trajectory-closure condition     

Nondeterministic Temporal Relations in Multimedia Data

Synchronization is an important issue in multimedia systems which integrate a variety of temporally related media objects.One part of synchronization is the representation of temporal information.Wish the emerging interactive multimedia,deterministic temporal models are replaced by nondeterministic ones with more expressiveness.This paper classifies temporal models by their expressiveness,and evealuates relevant nondeterministic temporal relations in multimedia data.Additionally,an interval-based nondeterministic model based on a complete temporal operator set is proposed providing high-leval abstractions and a high degree of expressiveness for interactive multimedia systems.     

Polynomial synthesis of supervisor for partially observed discrete-event systems by allowing nondeterminism in control

We study the supervisory control of discrete-event systems (DESs) under partial observation using nondeterministic supervisors. We formally define a nondeterministic control policy and also a control & observation compatible nondeterministic state machine and prove their equivalence. The control action of a nondeterministic supervisor is chosen online, nondeterministically from among a set of choices determined offline. Also, the control action can be changed online nondeterministically (prior to any new observation) in accordance with choices determined offline. The online choices, once made, can be used to affect the set of control action choices in future. We show that when control is exercised using a nondeterministic supervisor, the specification language is required to satisfy a weaker notion of observability, which we define in terms of recognizability and achievability. Achievability serves as necessary and sufficient condition for the existence of a nondeterministic supervisor, and it is weaker than controllability and observability combined. When all events are controllable, achievability reduces to recognizability. We show that both existence, and synthesis of nondeterministic supervisors can be determined polynomially. (For deterministic supervisors, only existence can be determined polynomially.) Both achievability and recognizability are preserved under union, and also under intersection (when restricted over prefix-closed languages). Using the intersection closure property we derive a necessary and sufficient condition for the range control problem for the prefix-closed case. Unlike the deterministic supervisory setting where the complexity of existence is exponential, our existence condition is polynomially verifiable, and also a supervisor can be polynomially synthesized.     

On the supremal controllable sublanguage in the discrete-eventmodel of nondeterministic hybrid control systems

This paper is concerned with the logical control of hybrid control systems (HCS). It is assumed that a discrete-event system (DES) plant model has already been extracted from the continuous-time plant. The problem of hybrid control system design can then be solved by applying logical DES controller synthesis techniques to the extracted DES plant. Traditional DES synthesis methods, however, are not always applicable since the extracted plant DES will often exhibit nondeterministic transitions. This paper presents an extension of certain DES controller synthesis techniques to the nondeterministic control automaton found in HCS. In particular, this paper derives a formula computing the supremal controllable sublanguage of a given specification language under the assumption that the DES plant exhibits nondeterministic transitions