Liveness Problem of Petri Nets Supervisory Control Theory for Discrete Event Systems

A quite great progress of the supervisory control theory for discrete event systems (DES)has been made in the past nearly twenty years, and now, automata, formal language and Petri nets become the main research tools. This paper focus on the Petri nets based supervisory control theory of DES. Firstly, we review the research results in this field, and claim that there generally exists a problem in Petri nets based supervisory control theory of DES, that is, the deadlock caused by the controller introduced to enforce the given specification occurs in the closed-loop systems, especially the deadlock occurs in the closed-loop system in which the original plant is live. Finally, a possible research direction is presented for the solution of this problem.

Supervisory Control of Fuzzy Discrete Event Systems Based on Agent

FDES(fuzzy discrete event systems) can effectively represent a kind of complicated systems involving deterministic uncertainties and vagueness as well as human subjective observation and judgement from the view of discrete events, here the information system is divided into some independent intelligent entitative Agents. The concept of information processing state based on Agents was proposed. The processing state of Agent can be judged by some assistant observation parameters about the Agent and its environment around, and the transition among these states can be represented by FDES based on rules. In order to ensure the harmony of the Agents for information processing, its upstream and downstream buffers are considered in the modeling of the Agent system, and the supervisory controller based on FDES is constructed. The processing state of Agent can be adjusted by the supervisory controller to improve the stability of the system and the efficiency of resource utilization during the process according to the control policies. The result of its application was provided to illustrate the validity of the supervisory adjustment.

Discrete Event Net Based Modeling and Control System Design for Real-Time Concurrent Control of Multiple Robot Systems

This paper deals with control system design and implementation problems encountered in multiple robot systems. The methodology developed is depicted by a set of coordination mechanisms using hierarchical net structures and their accompanying rules. With the net models, the hierarchical and distributed control system is designed for an assembly task. Synchronization commands allow coordination of the movements of the robots. The net models make concurrency of the movements of the robots transparent to users. The net based machine controller executes robot motion control through the communication with the external robot controller using the command/response concept. Sensory signals indicating the change of state of robots are used to trigger or initiate tasks. Simultaneous movement of the robots is obtained by creating different background threads running in parallel under Windows OS. The multilevel hierarchical control system can be consistently constructed using net models.

Implementation of Hierarchical and Distributed Control for Discrete Event Robotic Manufacturing Systems

The large scale and complex manufacturing systems have a hierarchical structure where a system is composed several lines with some stations and each station also have several machines and so on. In such a hierarchical structure, the controllers are geographically distributed according to their physical structure. So it is desirable to realize the hierarchical and distributed control. In this paper, a methodology is presented using Petri nets for hierarchical and distributed control. The Petri net representation of discrete event manufacturing processes is decomposed and distributed into the machine controllers, which are coordinated through communication between the coordinator and machine controllers so that the decomposed transitions fire at the same time. Implementation of a hierarchical and distributed control system is described for an example robotic manufacturing system. The demonstrations show that the proposed system can be used as an effective tool for consistent modeling and control of large and complex manufacturing systems.

DECS的产生式规则建模与规则的结构错误检测

文章研究的离散事件控制系统采用基于规则的系统结构,系统的控制逻辑存放于规则库中,推理机完成规则匹配工作。该文以数字矿井中皮带运输系统为例,详细说明了基于规则的系统结构和利用产生式描述系统的原理、方法、步骤;针对规则系统中典型的结构错误,如冗余、不一致、不完备和死循环,进行了检测,保证了系统的一致性和完备性。

Research on cubic polynomial acceleration and deceleration control model for high speed NC machining

To satisfy the need of high speed NC (numerical control) machining, an acceleration and deceleration (acc/dec) control model is proposed, and the speed curve is also constructed by the cubic polynomial. The proposed control model provides continuity of acceleration, which avoids the intense vibration in high speed NC machining. Based on the discrete characteristic of the data sampling interpolation, the acc/dec control discrete mathematical model is also set up and the discrete expression of the theoretical deceleration length is obtained furthermore. Aiming at the question of hardly predetermining the deceleration point in acc/dec control before interpolation, the adaptive acc/dec control algorithm is deduced from the expressions of the theoretical deceleration length. The experimental result proves that the acc/dec control model has the characteristic of easy implementation, stable movement and low impact. The model has been applied in multi-axes high speed micro fabrication machining successfully.

A learning-based synthesis approach to decentralized supervisory control of discrete event systems with unknown plants

In this paper, we consider the problem of automatic synthesis of decentralized supervisor for uncertain discrete event systems. In particular, we study the case when the uncontrolled plant is unknown a priori. To deal with the unknown plants, we first characterize the conormality of prefix-closed regular languages and propose formulas for computing the supremal conormal sublanguages; then sufficient conditions for the existence of decentralized supervisors are given in terms of language controllability and conormality and a learning-based algorithm to synthesize the supervisor automatically is proposed. Moreover, the paper also studies the on-line decentralized supervisory control of concurrent discrete event systems that are composed of multiple interacting unknown modules. We use the concept of modular controllability to characterize the necessary and sufficient conditions for the existence of the local supervisors, which consist of a set of local supervisor modules, one for each plant module and which determines its control actions based on the locally observed behaviors, and an on-line learning-based local synthesis algorithm is also presented. The correctness and convergence of the proposed algorithms are proved, and their implementation are illustrated through examples.

面向飞机装配批架次完工时间的仿真预测方法

针对传统离散事件仿真方法缺乏对产品间差异化分析的局限性,提出一种面向飞机装配批架次作业过程的仿真预测方法。围绕飞机架次标签,研究对批架次装配作业过程中各类基本要素与交互关系的形式化定义,由此完成站位、整线仿真模型的构建;研究支持产品差异化分析的仿真推进框架与执行机制;以仿真结果数据为基础,提出基于区间估计法的架次完工时间预测方法。实验结果表明:该方法能准确地输出各架次预计完工时间的置信区间,为现场提供可靠的评估依据。

基于事件驱动离散时不变系统的无线传感器网络节能输出反馈控制机制

针对无线传感器网络节能输出控制过程中,受到网络系统时滞性的影响,导致节能控制输出与期望输出之间存在较大控制误差的问题,提出利用事件驱动离散时不变系统研究无线传感器网络节能输出反馈控制机制。根据无线传感器系统的组成结构,针对反馈关联大系统进行建模,通过对系统的时滞项进行状态约束,并结合模糊控制调节规则构造网络节能输出反馈控制函数,以此为基础,通过设计驱动条件和时不变系统的状态空间模型,完成网络节能输出反馈控制机制的研究。仿真对比实验结果表明,所提控制机制的控制输出与期望输出之间的控制相对误差更小,节能效果较好。

Control of Non-Deterministic Systems With μ-Calculus Specifications Using Quotienting

The supervisory control problem for discrete event system(DES) under control involves identifying the supervisor, if one exists, which, when synchronously composed with the DES,results in a system that conforms to the control specification. In this context, we consider a non-deterministic DES under complete observation and control specification expressed in action-based propositional μ-calculus. The key to our solution is the process of quotienting the control specification against the plan resulting in a new μ-calculus formula such that a model for the formula is the supervisor. Thus the task of control synthesis is reduced a problem of μ-calculus satisfiability. In contrast to the existing μ-calculus quotienting-based techniques that are developed in deterministic setting, our quotienting rules can handle nondeterminism in the plant models. Another distinguishing feature of our technique is that while existing techniques use a separate μ-calculus formula to describe the controllability constraint(that uncontrollable events of plants are never disabled by a supervisor), we absorb this constraint as part of quotienting which allows us to directly capture more general state-dependent controllability constraints. Finally, we develop a tableau-based technique for verifying satisfiability of quotiented formula and model generation. The runtime for the technique is exponential in terms of the size of the plan and the control specification. A better complexity result that is polynomial to plant size and exponential to specification size is obtained when the controllability property is state-independent. A prototype implementation in a tabled logic programming language as well as some experimental results are presented.

Stabilization of Discrete-Time Dynamical Systems Under Event-Triggered Impulsive Control with and Without Time-Delays

这份报纸由被触发事件的冲动的控制为分离时间的动态系统(DDS ) 调查稳定的问题(非位) 。基于一些相对简单的阀值常数，事件条件的三个层次被设置，因此，非位的计划被设计。三个案例为有或没有时间延期和数据退学学生非位分别地被学习，并且指数的稳定性上的标准为控制 DDS 被导出。在指数的稳定性形式的稳定为 DDS 被完成在下面设计与或没有时间延期非位。并且在非位的数据退学学生，的情况中，指数的稳定的条件为 DDS 和最大的许可的退学学生率被导出为非位被估计。最后，有数字模拟的一个例子为说明被得出。

Integration of Fault Analysis and Interlock Controller Synthesis for Batch Processes

在各种各样的决策之中的集成处理，例如计划，图案，和操作对动态、灵活的批生产必要。完成批生产集成，为各种各样的决策过程使用的普通模型的利用是一条有效途径。从这个观点，一个批系统由一张 Petri 网描述了的普通模型被建议。在这篇文章，为批进程的一种故障诊断技术用差错繁殖和差错分析的集成的可能性的信息被介绍，控制器合成根据 Petri 网络被讨论基于的普通模型。

基于Simevents的机电自动化生产系统控制

针对机电自动化生产系统控制涵盖大量制造信息与复杂决策优化过程的特征,设计有效的软件控制系统对其进行分析与优化。应用Matlab的工具箱Simevents及基于离散事件仿真机制设计与开发机电自动化生产控制系统。首先分析了机电自动化控制系统的运行机制,以及应用Simevents的离散事件仿真机理进行机电自动化控制系统的开发方法。具体研究了零件族工艺规程的软件描述与生产订单生成的方法、根据零件工艺规程进行加工任务分解与决策、生产单元的生产逻辑实现等系统开发关键技术。以固高公司的FMS作为实例系统对所开发系统进行了验证。

基于事件触发机制的离散时变时滞多智能体一致性研究

为降低资源的消耗和浪费,并处理时变时滞对于多智能体的影响,针对离散线性时变时滞多智能体系统,提出一种基于事件触发机制的一致性协议,以减少系统的通信次数。在事件触发机制的框架下,提出一种基于预测控制的分段时滞补偿方法来补偿时变时滞对多智能体系统一致性的影响。在此基础上,通过构造基于延迟划分的Lyapunov-Krasovskii函数分析离散线性多智能系统的稳定性。最后,通过MATLAB仿真验证所提方法的有效性。研究结果表明:事件触发机制可以有效减少系统更新次数,降低消耗,所提出的基于预测控制的分段时滞补偿方法可以弥补时变时滞对于多智能体系统的影响,且基于延迟划分的分段补偿能够降低系统的保守性。

电力电子混杂系统多时间尺度分析控制与应用(二):应用部分

文中在系列论文上篇介绍电力电子混杂系统多时间尺度分析和控制理论的基础上,进一步介绍其应用。首先从大容量和大规模电力电子系统应用需求出发,阐述电力电子技术应用面临的机遇和挑战;分析和介绍基于数值凸透镜原理的离散状态事件驱动建模仿真方法;分析和介绍基于多时间尺度的主动控制和能量平衡综合控制方法;特别综合展示这些方法在兆瓦级多端口多功能电力电子变压器中的实际应用情况;最后对多时间尺度分析控制方法的未来发展进行展望。

基于离散事件的直喷发动机轨压自适应抗扰控制

为了使直喷发动机在工况复杂且多扰动的运行环境中快速精确地响应相应目标轨压,提出了基于离散事件的轨压自适应抗扰控制算法。基于GT⁃Power平台建立被控对象的一维数字模型,通过仿真试验对喷油器和高压泵进行参数辨识,并与试验数据对比以确保模型的准确性。结合泵油、喷油和嵌入式控制器的离散系统,设计扩张状态观测器,利用自适应算法识别总扰动。设计抗扰控制算法,利用得到的总扰动对控制进行补偿。在发动机转速为1500 r/min时,设定5 ms喷油脉宽、8 MPa压力阶跃输入系统,进行仿真试验分析。仿真结果表明:被控对象压力的上升时间为80 ms,即在1个发动机循环内完成;调节时间为100 ms,比单独使用比例−积分(PI)控制降低了50%;稳态误差为±0.2 MPa,比单独使用PI控制降低了60%。

基于GMEC转换算法的Petri网结构控制器综合方法

针对含不可控变迁Petri网系统禁止状态控制器设计问题,提出了一种基于矩阵变换和整数线性规划的结构控制器综合方法。该方法的关键是对代表系统合法状态的广义互斥约束(generalized mutual exclusion constraint,GMEC)进行转换。首先,根据Petri网系统的关联矩阵,将库所集分为无关库所集、不可控库所集和补足库所集。其次,通过对非允许GMEC中补足库所的权值和不可控库所的权值进行处理,并运用整数线性规划将非允许GMEC转换为允许GMEC。在允许GMEC的基础上,根据库所不变量原理设计出Petri网系统的结构控制器。最后,以某零件加工系统为例验证了所提方法的泛用性和高效性,为实际智能制造系统的监督控制器设计提供有效参考方案。

离散事件系统最优监督控制算法

离散事件系统的监控器可以通过禁止可控事件来使系统满足安全性和活性规范。然而,监控器并不对允许发生的可控事件主动进行选择,所以存在同时允许多个可控事件发生的情况。但在实际应用中,如交通调度、机器人路径规划中,要求系统在每个状态下最多只允许一个可控事件的发生。针对上述问题,引入一种最优机制来量化控制成本,并提出一种离散事件系统最优监督控制算法,以确保系统的安全性和活性,并使事件执行累计的成本最小。首先,给定受控系统和行为约束的自动机模型,并基于Ramadge和Wonham的监督控制理论求解出无阻塞和行为最大许可的监控器;其次,通过定义的成本函数为监控器中每个事件的执行赋予相应成本;最后,利用动态规划思想迭代计算求解出最优定向监控器,从而实现每个状态下最多发生一个可控事件和事件执行累计的成本最小的目标。使用单向列车导轨案例和多轨道列车控制案例来验证所提算法的有效性和正确性。对于上述两个案例,所提算法求解的定向监控器到达目标状态所需的事件执行累计的成本分别为26.0和14.0,低于贪心算法的27.5和16.0,以及Q-learning算法的26.5和14.0。

基于事件驱动间歇控制的离散复杂网络有限时间同步

研究了一类基于间歇控制的离散时间异构复杂动态网络有限时间有界同步问题。首先,设计了一个基于事件驱动的间歇控制机制。在该机制下,控制器是否工作取决于Lyapunov函数轨迹和预设的工作区域。与现有的间歇性控制方案相比,该方法中控制器的工作/休息时间是非周期的且不可预测的。其次,提出了有限时间有界性的概念,并利用类整定时间函数来衡量控制性能。通过求解不等式约束的优化问题,进一步得到有限时间有界同步的类整定时间。最后,通过数值仿真实验验证了该结论的准确性和有效性。

HEURISTIC SUPERVISION OF DISCRETE EVENT SYSTEMS

Results on supervisory control of discrete event processes are mainly concernedwith designing a controller such that the closed loop system generates a language L whichcoincides with the target language.In this paper we consider supervisory control problem for aclass of discrete event processes when the design target is that a certain set of language patternscan not occur in the closed loop language.A heuristic supervisor is constructed via the heuristicsearch method developed in AI.This scheme requires only the information about thecontrollability of the event symbol set.It is capable of designing a modular heuristic supervisorwhen there are many such forbidden strings.Effectiveness of such a supervisor is proved forsystems with perfect and partial observation.