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1、1、PLC design criteria A systematic approach to designing PLC software can overcome deficiencies in the traditional way of programming manufacturing control systems, and can have wide ramifications in several industrial applications. Automation control systems are modeled by formal languages or, equi

2、valently, by state machines. Formal representations provide a high-level description of the behavior of the system to be controlled. State machines can be analytically evaluated as to whether or not they meet the desired goals. Secondly, a state machine description provides a structured representati

3、on to convey the logical requirements and constraints such as detailed safety rules. Thirdly, well-defined control systems design outcomes are conducive to automatic code generation- An ability to produce control software executable on commercial distinct logic controllers can reduce programming lea

4、d-time and labor cost. In particular, the thesis is relevant with respect to the following aspects. In modern manufacturing, systems are characterized by product and process innovation, become customer-driven and thus have to respond quickly to changing system requirements. A major challenge is ther

5、efore to provide enabling technologies that can economically reconfigure automation control systems in response to changing needs and new opportunities. Design and operational knowledge can be reused in real-time, therefore, giving a significant competitive edge in industrial practice. Studies have

6、shown that programming methodologies in automation systems have not been able to match rapid increase in use of computing resources. For instance, the programming of PLCs still relies on a conventional programming style with ladder logic diagrams. As a result, the delays and resources in programming

7、 are a major stumbling stone for the progress of manufacturing industry. Testing and debugging may consume over 50% of the manpower allocated for the PLC program design. Standards IEC 60848, 1999; IEC-61131-3, 1993; IEC 61499, 1998; ISO 15745-1, 1999 have been formed to fix and disseminate state-of-

8、the-art design methods, but they normally cannot participate in advancing the knowledge of efficient program and system design. A systematic approach will increase the level of design automation through reusing existing software components, and will provide methods to make large-scale system design

9、manageable. Likewise, it will improve software quality and reliability and will be relevant to systems high security standards, especially those having hazardous impact on the environment such as airport control, and public railroads. The software industry is regarded as a performance destructor and

10、 complexity generator. Steadily shrinking hardware prices spoils the need for software performance in terms of code optimization and efficiency. The result is that massive and less efficient software code on one hand outpaces the gains in hardware performance on the other hand. Secondly, software pr

11、oliferates into complexity of unmanageable dimensions; software redesign and maintenance-essential in modern automation systems-becomes nearly impossible. Particularly, PLC programs have evolved from a couple lines of code 25 years ago to thousands of lines of code with a similar number of 1/O point

12、s. Increased safety, for instance new policies on fire protection, and the flexibility of modern automation systems add complexity to the program design process. Consequently, the life-cycle cost of software is a permanently growing fraction of the total cost. 80-90% of these costs are going into so

13、ftware maintenance, debugging, adaptation and expansion to meet changing needs. Today, the primary focus of most design research is based on mechanical or electrical products. One of the by-products of this proposed research is to enhance our fundamental understanding of design theory and methodolog

14、y by extending it to the field of engineering systems design. A system design theory for large-scale and complex system is not yet fully developed. Particularly, the question of how to simplify a complicated or complex design task has not been tackled in a scientific way. Furthermore, building a bri

15、dge between design theory and the latest epistemological outcomes of formal representations in computer sciences and operations research, such as discrete event system modeling, can advance future development in engineering design. From a logical perspective, PLC software design is similar to the ha

16、rdware design of integrated circuits. Modern VLSI designs are extremely complex with several million parts and a product development time of 3 years Whitney, 1996. The design process is normally separated into a component design and a system design stage. At component design stage, single functions

17、are designed and verified. At system design stage, components are aggregated and the whole system behavior and functionality is tested through simulation. In general, a complete verification is impossible. Hence, a systematic approach as exemplified for the PLC program design may impact the logical

18、hardware design. 2、SIEMENS PLC SIMATIC S7-300 series PLC applied to all walks of life and various occasions in the detection, monitoring and control of automation, its power to both the independent operation of, or connected to a network able to achieve complex control. The photoelectric products wi

19、th isolation, high electromagnetic compatibility; have high industrial applicability, allowing the ambient temperature of 60 ; has strong anti-jamming and anti-vibration and impact resistance, so in a harsh working environment has been widely Applications. I also mean freedom of communication S7-300

20、 type PLC s a very unique feature, which allows S7-300-PLC can deal openly with any other communications equipment, communications controller, or PLC S7-300 type can be defined by the users own Communications protocol (of the agreement ASCII), the baud rate to 1.5 M bit / s (adjustable). So that can

21、 greatly increase the scope of communications so that the control system configuration more flexible and convenient. Of any kind with a serial interface peripherals, such as: printers or bar code readers, Drives, a modem (Modem), the top PC-connected, and so can be used. Users can program to develop

22、 communication protocols, the exchange of data (for example: ASCII character code), RS232 interfaces with the equipment can also be used PC / PPI cable linking the free communication communications. When the PC offline, under the control of the next crew, the whole system can operate normally. PC th

23、at is by control centre, mainly by the PC and laser printer components, using SIMATIC WINCC software platform, the all-Chinese interface, friendly man-machine dialogue. Managers and operators can be observed through a PC, shown in the various kinds of information to understand the present and past t

24、he ice-storage operation of the automatic control system and all the parameters, and through the mouse to print equipment management and implementation tasks. WINCC software in the field of automation can be used for all the operators control and monitoring tasks. Can be controlled in the process of

25、 the events clearly show, and shows the current status and order records, the recorded data can show all or select summary form, or may be required for editing, printing and output statements and trends . WINCC able to control the critical situation in the early stages of the report, and the signal

26、can be displayed on the screen, can also use sound to be felt. It supported by online help and operational guidelines to eliminate failure. WINCC a workstation can be devoted to the process control to the process so that important information not is shielded. Software-assisted operation strategy ens

27、ures that the process was not illegal to visit and to provide for non-industrial environment in the wrong operation. WINCC is MICRSOFT WINDOWS98 or WINDOWS NT4.0 operating system, running on a PC object-oriented class 32-bit application, OLE through the window and ODBC standard mechanism, as an idea

28、l partner to enter the communications world WINDOWS, it can be easily WINCC To integrate a company-wide data processing system. 3、Communications Communications are vital to an individual automation cell and to the automated factory as a whole. Weve heard a lot about MAP in the last few years, and a

29、lot of companies have jumped on the band wagon. Many, however were disappointed when a fully-defined and completed MAP specification didnt appear immediately. Says Larry Kumara:” Right now, MAP is still a moving target for the manufacturers specification that is not final. Presently, for example, pe

30、ople are introducing products to meet the MAP 2.1standard.Yet 2.1-based products will be obsolete when the new standard for MAP, 3.0is introduced.” Because of this, many PLC vendors are holding off on full MAP implementations. Omron, for example, has an ongoing MAP-compatibility program, but Frank N

31、ewborn, vice president of Omrons Industrial Division, reports that because of the lack of a firm definition, Omrons PLCs dont yet talk to MAP. Since its unlikely that an individual PLC would talk to broadband MAP anyway, makers are concentrating n proprietary networks. According to Sal Provanzano, u

32、sers fear that if they do get on board and vendors withdraw from MAP, they all pulse width modulation control system be the ones left holding a communications structure thats not supported.1、PLC的设计标准 一个系统化的设计 PLC程序的方法可以克服传统程序生产控制系统的缺点，并且在一些工业应用总有很大的不同。自动控制系统是状态模型用公式语言或等价的语言描述的。公式描述对被控制的系统的行为提供一个精确的描

33、述。可以通过分析估计看状态模型是否达到想要的目标。第二，为状态模型的描述提供结构描述，这个结构描述可以说明逻辑要求和如细节安全规则的限制。第三，好的控制系统设计是对自动控制代码生成有益的一种能够产生可执行的控制软件的能力，不同的逻辑控制器可以减少程序扫描时间和执行那个时间。特别的，这个主题与随后的部分的是有关的。 在现代制造业中，系统是用过程和结果的革新来描述的，并且因此不得不改变系统性能以快速做出反应。因此，一个大的挑战是提供技术以限制自动控制系统对变化需要和新机会的反应，所以，设计和操作知识可以实时的被再次利用，在工业实践中提供了一个重要的竞争面。 研究表明，在自动化系统中，程序实现的方法

34、已经与计算机资源应用的急速增长不能匹配。例如，可编程逻辑控制器（）程序仍然依靠一种方便的有逻辑梯形图的程序实现模式。结果，程序上的延迟和资源成了生产工业过程的主要绊脚石。在可编程逻辑控制器程序设计过程中，测试和调试可能会占用超过百分之五十的人力。在发展和传播“”已经形成标准IEC 60848, 1999; IEC-61131-3, 1993; IEC 61499, 1998; ISO 15745-1, 1999，但是，基本上这些标准都不能参与有效的程序和系统设计方面知识的革新。 系统的方法通过使用原有的软件模块，有助于增加设计自动化的水平，同时也将提供一种可管理的大规模系统设计的方法。同样的，

35、它也将改善软件的质量的可靠性，以及关系到系统的较高安全标准，尤其是这些对环境有危害影响的，比如：机场控制、公共铁路运输。 软件工业被认为是系统性能的破坏者和系统复杂性的产生者。逐渐下降的硬件价格，破坏了对通过优化程序获得的软件性能的需要。其结果是，一方面造成了大量而低效率的程序代码，另一方面并没有获得高的硬件性能。其次，软件变得难以掌握其程度的复杂；在现代自动化系统中，软件设计和保持系统本质几乎变得不可能。尤其是，可编程逻辑控制器（）程序设计从二十五年前的两条主线，发展到现在的成千上万条。现在安全性增加了，例如，关于防火的新措施，以及现代自动化系统的柔韧性增加了程序设计过程的复杂性。因此，软件

36、的使用周期花费是总共花费的一个固定不变的增长部分。百分之八十到九十的花费用于软件维护、调试、优化（改进）、和扩展以满足不断变换的需求。 目前，大部分设计研究的主要焦点都集中在机械和电子产品上。这种有目的性的研究产生了一个副产品，就是通过推广这中研究到系统工程设计领域，从而加固了我们对设计理论和技巧的基本理解。针对大规模和复杂系统的系统设计理论并没有成熟。尤其是，对如何简化一个繁冗而复杂的设计任务这一问题，仍然没有被科学的处理。而且，正在设计理论和代表计算机科学及运筹学研究的认识论结果之间构建一条桥梁，这样的具体应该是逻辑硬件电路设计。 从逻辑学的角度来看，可编程逻辑控制器（PLC）的软件设计类

37、似与集成电路的硬件设计。现代超大规模集成电路设计（Very Large Scale Integration-VLSI）是及其复杂的，一个集成电路一般有几百万个晶体管，而且产品开发周期大都三年左右。设计过程一般都分成局部功能块设计和系统设计两个阶段。在局部功能块设计阶段，单个功能将被设计出来，并予以验证。在系统设计阶段，所有功能块都将被整合起来，整个系统行为特性和功能将会通过仿真形式加以测试。一般来说，所有部分都完全的验证是不可能的。因此，统计学可以作为可编程逻辑控制器（PLC）设计的一个例子，并有可能影响逻辑硬件设计。 2、AK 1703 ACP AK 1703 ACP 凭借着一贯创新的精神与

38、稳定的技术，在以稳定为基础的产品平台中，拥有高级的功能性和适应性。 ACP（自动化，控制和保护）系统概念保证了 AK 1703 ACP 功能的实现。稳定的功能性使得自动化控制，远程控制和通信协议三者完美结合。可升级的性能与多种冗余结构，使得 AK1703 ACP 可以完美处理各种功能要求。 AK 1703 ACP 拥有适合现代化自动控制的综合的远程控制技术： * 水电站远程控制与中控设备 * 拥有自治功能的自动控制单元 * 数据节点, 设备控制站, 尖端科技 * 拥有现场或远程外围设备 * 为后面板安装而设计的 19 英寸设备 * 专为多种现场应用和高产品要求设计的中间产品 * 多种通信手段

39、* 简洁的编程 * 唯一的设备插座 * 开放型系统体系结构 * 可升级的冗余 * 智能终端- TM 1703 AK 1703 ACP 基本外部设备原件拥有两个基本系统原件 CP-2010/CPC25（主控原件）和CP-2012/PCCE25（处理和通信原件），一个总线最多可以连接 16个外围设备原件。 CP-2010/CPC25 特征与功能 系统功能： * 核心元件，协调所有系统功能 连接所有基本功能原件的中心站点 * 时间管理 自动控制单元的中控时钟 设定并保持自身时钟的时间，分辨率为 10ms 通过互联网或当地的服务通信进行同步 * 冗余 在处理与通信中为自动控制单元选择并转变冗余单元 通

40、过SCA-RS 外部冗余开关支持选择与转变功能 通过外接系统实现选择与支持,例如控制系统 * 与SAT TOLLBOX|连接 在闪存卡里存储固件和参数 通信： * 通过相应的协议原件与高级或附属自动控制单元进行通信 * 为数据流自动选择路径 * 优先基本数据的传输(优先级控制) * 为每个联检站设立自己的循环缓冲器和处理信息(数据保持) * 为冗余通信提供路径 与对方站的冗余进行通信 * 通过拨号上网方式对特殊应用实施特殊功能 为可进行冗余的站点进行测试 . 具有处理功能的外围设备： * 通过Ax 1703 外围设备串口总线自发地将信息传输到外围设备单元 自动控制功能： * 通过CAEX+按照

41、IEC 61131-3协议创建的可自由定义的拥有开闭环控制功能的用户程序 512KB 的用户程序空间 大约50000 个可变信号源,2000 个常用信号源 10ms 的循环时间 网上测试 可随时下载 * 冗余的开闭环功能控制 通过冗余线路进行同步 通过Ax 1703外围设备串口总线在开闭环控制功能与外围接口单元之间不断传输处理信息。3、SIEMENS可编程序控制器 SIMATIC S7-300 系列PLC适用于各行各业、各种场合中的检测、监测及控制的自动化，其强大功能使其无论在独立运行中，或相连成网络皆能实现复杂控制功能。 该产品具有光电隔离，高电磁兼容；具有很高的工业适用性，允许的环境温度达

42、60；具有很强的抗干扰、抗振动与抗冲击性能，因此在严酷的工作环境中得到了广泛的应用。 自由通讯口方式也是 S7-300 型PLC的一个很有特色的功能，它使 S7-300型PLC可以与任何通讯协议公开的其它设备、控制器进行通讯，即 S7- 300 型PLC可以由用户自己定义通讯协议（例 ASCII 协议），波特率为1。5Mbit/s（可调整）。因此使可通讯的范围大大增加，使控制系统配置更加灵活、方便。任何具有串行接口的外设，例如：打印机或条形码阅读器、变频器、调制解调器（Modem）、上位PC 机等都可连接使用。用户可通过编程来编制通讯协议、交换数据（例如：ASCII码字符），具有RS232接口

43、的设备也可用PC/PPI 电缆连接起来进行自由通讯方式通讯。 当上位机脱机时，在下位机控制下，整个系统能正常运行。 上位机即图文控制中心，主要由 PC机和激光打印机组成，采用 SIMATIC WINCC软件平台，采用全中文操作界面，人机对话友好。管理人员和操作者，可以通过观察PC机所显示的各种信息来了解当前和以往整个冰蓄冷自控系统的运行情况和所有参数，并且通过鼠标进行设备管理和执行打印任务。WINCC软件在自动化领域中可用于所有的操作员控制和监控任务。可将过程控制中发生的事件清楚地显示出来，可显示当前状态并按顺序记录，所记录的数据可以全部显示或选择简要形式显示，可连续或按要求编辑，并可输出打印

44、报表和趋势图。 WINCC 能够在控制过程中危急情况的初发阶段进行报告，发出的信号既可以在屏幕上显示出来，也可以用声音表现出来。它支持用在线帮助和操作指南来消除故障。某一 WINCC 工作站可专门用于过程控制以使那些重要的过程信息不被屏蔽。软件辅助操作策略保证过程不被非法访问，并提供用于工业环境中的无错操作。 WINCC 是MICRSOFT WINDOWS98 或WINDOWS NT4。0 操作系统下，在PC机上运行的面向对象的一流32 位应用软件，通过 OLE 和ODBC 视窗标准机制，作为理想的通讯伙伴进入WINDOWS 世界，因此WINCC 可容易地结合到全公司的数据处理系统中。 4、通

45、信 通信对于个人自动单元是很重要的。在过去的几年里，我们听到许多关于生产自动化协议的事情，并且许多公司已经加入大有成功希望的事业。然而，当一个完整的生产自动化协议说明书没有及时出现时许多公司都很失望。Larry Kotare 说:”现在，生产自动化协议仍然是生产中一个发展的对象，一个说明书并不是最终的结果。例如，虽然当新的生产自动化协议 MAP3.0 版本使用之时以MAP2.1 版本为基础的产品将会被汰，但是现在人们仍然将产品用于 MAP2.1版。” 由于这些原因，许多 PLC厂家紧盯着MAP 的最新结果。如欧姆龙公司正在进行一个有关MAP 兼容性的项目。但是欧姆龙生产部门总经理 Frank Newborn说由于缺少一个固定的标准，欧姆龙的产品并不涉及到 MAP。由于工业PLC无论何时不可能广泛的涉及到 MAP，生产厂家正在考虑专用网络。根据Sal Probanzano 说法，用户担心如果他们广泛的应用生产厂家将会收回MAP，这样将会留下一个不支持通信的交流框架。