A neural network model for fault detection in conjunction with a programmable logic controller

This paper discusses the feasibility of using neural networks as a tool in the fault detection process. A neural network is integrated with a state language programmable logic controller, an important device in an automatic control system. Time series data related to time spent in a state is gathered and used as input into a neural network, for the purpose of identifying when a fault has occurred. A feedforward neural network is used to identify which (if any) of three types of faults may have occurred. Experimental results related to sensitivity and accuracy measures are presented. A brief review of related applications and research is also presented.     

Implementation of a RISC microprocessor for programmable logic controllers

A special purpose RISC (reduced instruction set computer) microprocessor for programmable logic controllers (PLC), named PLCRISC, is proposed. To develop an optimal PLCRISC, we analysed existing PLC programs currently used in factories, with special attention to the instruction execution characteristics and features required for a high performance PLC processor. Based on this analysis, an optimal RISC-style instruction set and an architecture suitable for the required features are suggested. In particular, the instruction format, the instruction pipeline, and the detailed internal architecture are the significant characteristics of the proposed PLCRISC. The performance enhancement achieved with a PLCRISC is seen from a straightforward evaluation. ASIC implementation with VHDL is also discussed. The PLCRISC is under fabrication in a 0.8 μm CMOS technology.     

Petri net based process scheduling: A model of the control system of flexible manufacturing systems

In this paper, we propose a class of algorithms for the sub-optimal solution of a particular class of problems of process scheduling, particularly focusing on a case study in the area of flexible manufacturing systems (FMSs). The general class of problems we face in our approach is characterized as follows: there is a set of concurrent processes, each formed by a number of temporally related tasks (segments). Tasks are executable by alternate resource sets, different both in performance and costs. Processes and tasks are characterized by release times, due dates, and deadlines. Time constraints are also present in the availability of each resource in resource sets. It has been proven that such a problem does not admit an algorithm for an optimal solution in polynomial time. Our proposed algorithm finds a sub-optimal schedule according to a set of optimization criteria, based on task and process times (earliness, tardiness), and/or time independent costs of resources. Our approach to process scheduling is based on Timed Coloured Petri Nets. We describe the structure of the coordination and scheduling algorithms, concentrating on (i) the general-purpose component, and (ii) the application-dependent component. In particular, the paper focuses on the following issues: (i) theautomatic synthesis of Petri net models of the coordination subsystem, starting from the problem knowledge base; (ii) the dynamic behavior of the coordination subsystem, whose kernel is a High Level Petri net executor, a coordination process based on an original, general purpose algorithm; (iii) the structure of the real-time scheduling subsystem, based on particular heuristic sub-optimal multi-criteria algorithms. Furthermore, the paper defines the interaction mechanisms between the coordination and scheduling subsystems. Our approach clearly distinguishes the mechanism of the net execution from the decision support system. Two conceptually distinct levels, which correspond to two different, interacting implementation modules in the prototype CASE tool, have been defined: theexecutor and thescheduler levels. One of the outstanding differences between these levels is that the executor is conceived as a fast, efficient coordination process, without special-purpose problem-solving capabilities in case of conflicts. The scheduler, on the other hand, is the adaptive, distributed component, whose behavior may heavily depend on the problem class. If the scheduler fails, the executor is, in any case, able to proceed with a general-purpose conflict resolution strategy. Experimental results on the real-time performance of the kernel of the implemented system are finally shown in the paper. The approach described in this paper is at the basis of a joint project with industrial partners for the development of a CASE tool for the simulation of blast furnaces.     

基于可编程控制器和工业以太网的电加热温控系统设计

研究了一种基于可编程控制器(programmable logic controller,PLC)和工业以太网的电加热温控系统,该系统采用先进的可编程控制器作为基本控制器实现了对大滞后、强非线性电加热系统温度的自动控制。并采用先进的工业以太网通讯方式,实现了西门子S7-200 PLC和STEP7 Micro/WIN编程软件以及S7-200和组态王监控软件之间的通讯。实验结果表明,采用可编程控制器作为主控制器对电加热温控系统进行PID控制可以达到化工实验过程中对温度控制的要求。同时,采用工业以太网进行通讯具有很好的可靠性和安全性。     

A rule-based procedure for generating programmable logic controller code from graphical input in the form of ladder diagrams

This paper is concerned with a procedure for the automatic generation of code for programmable logic controllers. Input to the procedure is data from a graphical model of the discrete event dynamic system which is to be implemented. The model is constructed in the form of a ladder diagram at a graphics workstation. The data are held as Prolog tuples, and Prolog is used in the procedure to implement a rule base through which the data are mapped into the programmable logic controller code. Underlying the rule base are two methodologies. The first is a top-down decomposition of the ladder diagram to a level of three basic structures. The second is a bottom-up integration of code based on these structures into code for the whole system. An example is used throughout and the approach is shown to be effective.     

Automatic generation of ladder diagram with control Petri Net

This paper presents a design method to generate a ladder diagram (LD) automatically with the control Petri Net (CPN) for control of discrete event system. This method describes the specification of a practical system with the CPN that associates operations with places and conditions with transitions. Based on the firing regulation of transition, the relationship of places, conditions, and events are formulated with Boolean functions. These functions can be easily converted into LD and implemented on a programmable logic controller (PLC). An application example in a liquid mixture system shows that the proposed method is effective and has the advantages of ease of understanding, modification, and maintenance.     

A component framework for system modeling based on high-level replacement systems

The aim of this paper is to present a generic component framework for system modeling that satisfies main requirements for component-based development in software engineering. In this sense, we have defined a framework that can be used, by providing an adequate instantiation, in connection with a large class of semi-formal and formal modeling techniques. Moreover, the framework is also flexible with respect to the connection of components, providing a compositional semantics of components. This means more precisely that the semantics of a system can be inferred from the semantics of its components. In contrast to other component concepts for data type specification techniques, our component framework is based on a generic notion of transformations. In particular, refinements and transformations are used to express intradependencies, between the export interface and the body of a component, and interdependencies, between the import and the export interfaces of different components. The generic component framework generalizes module concepts for different kinds of Petri nets and graph transformation systems proposed in the literature, and seems to be also suitable for visual modeling techniques, including parts of the UML, if these techniques provide a suitable refinement or transformation concept. In this paper the generic approach is instantiated in two steps. First to high-level replacement systems generalizing the transformation concept of graph transformations. In a second step it is further instantiated to low-level and high-level Petri nets. To show applicability we present sample components from a case study in the domain of production automation as proposed in a priority program of the German Research Council (DFG).     

逻辑控制器设计与离散事件系统监控理论

物联网等通信技术将越来越多的控制元件集成起来,导致系统规模快速增长,逻辑控制规范也日益复杂,任何逻辑错误都可能造成重大事故和人身灾难,再加上"维数灾"问题,安全可靠的逻辑控制程序的设计和调试面临巨大的计算复杂性难题.而离散事件系统监控理论旨在研究复杂控制规范的设计和实现问题,将连锁、互斥、字符串语言等复杂控制逻辑描述为自动机或Petri网,然后转换为可编程逻辑控制器或现场可编程门阵列上执行的程序代码.本文综述了现有的逻辑控制器的形式化设计方法,主要涉及如何利用监控理论(自动机或Petri网)来缩短程序开发周期、提高程序可重用性和确保程序可靠性和安全性等问题.     

基于PLC和变频器的液位控制系统设计与实现

采用PLC为主控制器、变频器为执行器,MCGS监控软件为人机交互界面,设计了一套液位控制系统,并利用西门子S7-200PLC的PID参数自整定功能实现了控制参数的在线自调整。MCGS监控软件构成了控制系统的操作站,可以实现实时数据采集、控制参数输入、控制模式转换等多项功能。在液位控制实验中,MCGS监控软件记录了在设定液位下的PID参数整定过程和设定液位控制效果,S7-200PLC整定出的PID参数较好地实现了设定液位的稳定跟踪。整套系统具有控制灵活、精确度高、故障率低的特点,能满足一般化工生产过程中对液位的控制要求。     

脉冲发电机组计算机控制系统的研究

介绍了一种脉冲发电机组的计算机控制系统, 介绍了该系统的励磁控制系统、模式识别系统和工业控制网络, 介绍了该系统的软、硬件设计以及控制系统特点。     

Neurovision-based logic control of an experimental manufacturing plant using neural net le-net5 and automation Petri nets

In this paper, Petri nets and neural networks are used together in the development of an intelligent logic controller for an experimental manufacturing plant to provide the flexibility and intelligence required from this type of dynamic systems. In the experimental setup, among deformed and good parts to be processed, there are four different part types to be recognised and selected. To distinguish the correct part types, a convolutional neural net le-net5 based on-line image recognition system is established. Then, the necessary information to be used within the logic control system is produced by this on-line image recognition system. Using the information about the correct part types and Automation Petri nets, a logic control system is designed. To convert the resulting Automation Petri net model of the controller into the related ladder logic diagram (LLD), the token passing logic (TPL) method is used. Finally, the implementation of the control logic as an LDD for the real time control of the manufacturing system is accomplished by using a commercial programmable logic controller (PLC).     

基于Profibus和Ethernet的加速器高频控制系统设计

根据加速器高频控制的网络化和自动化的要求,设计了一种基于Profibus-DP和Ethernet的并适用于加速器高频系统的强磁场运行环境的控制系统。采用PLC为核心控制设备,并结合分布式I/O模式构建控制网络。采用STEP7和Wincc分别进行PLC程序设计和上位机人机界面设计。重点介绍了系统的硬件配置、网络结构、频率微调、软件设计和系统功能。该系统设计简化了网络结构,提高了系统的可靠性和稳定性。     

数字锁相环在电力系统谐波检测中的应用

分析了非同步采样对谐波测量精度的影响,提出采用数字锁相环来同步被测信号的方法。数字锁相环电路采用VHDL语言和可编程逻辑器件设计实现,并用MAX+plusⅡ软件进行仿真。仿真和测试结果表明,所设计的数字锁相环可以很好地跟踪被测信号,如果模值K设为1,当跟踪至180ms时,频率误差仅为0.01Hz。     

A hybrid PC/PLC architecture for manufacturing-system control—theory and implementation

This paper presents a novel and generic PC/PLC-based software/hardware architecture for the control of flexible manufacturing workcells. The proposed implementation methodology is based on the utilization of any one of the available formal discrete-event-system control theories in conjunction with state-of-the-art industrial programmable-logic controllers (PLCs). The methodology has been illustrated to be a viable technique through its actual implementation in our laboratory using a robotic-workcell testbed. The specific control theory used is a combination of Extended Moore Automata and Ramadge-Wonham Automata that has been developed by our research group. The modular control software architecture has been developed for MS-Windows environments (running on one PC interfaced to the PLCs) and allows the use of different formal control theories as well as different commercial PLC hardware. The effective graphical user interface provides a transparent programming environment, where users are not expected to have a full knowledge of the formal control theory used.     

基于混合逻辑动态模型的混杂系统预测控制

针对过程工业控制对象的混杂特性，采用基于混合逻辑动态模型的预测控制策略。给出混杂系统的建模方法，并对其稳定性进行分析。仿真结果表明基于混合逻辑动态模型的预测控制能使混杂系统跟踪设定值并满足操作约束，为研究新一代复杂工业控制系统提供了新的思路。     

A program logic for resources

We introduce a reasoning infrastructure for proving statements about resource consumption in a fragment of the Java Virtual Machine Language (JVML). The infrastructure is based on a small hierarchy of program logics, with increasing levels of abstraction: at the top there is a type system for a high-level language that encodes resource consumption. The infrastructure is designed to be used in a proof-carrying code (PCC) scenario, where mobile programs can be equipped with formal evidence that they have predictable resource behaviour.