PLC英文文献+翻译

1、 安歳理工犬爭 ANHUI CNIVERSITYOI SCIENCH： Second，programming visual, simple; Third, adaptability good; Fourth functional improvements, strong functional interface. TWO ： History of PLC Programmable Logic Controllers (PLC), a computing device invented by Richard E. Morley in 1968, have been widely used in

2、industry including manufacturing systems, transportation systems, chemical process facilities, and many others. At that time, the PLC replaced the hardwired logic with soft-wired logic or so-called relay ladder logic (RLL), a programming language visually resembling the hardwired logic, and reduced

3、thereby the configuration time from 6 months down to 6 days Moody and Morley, 1999. Although PC based control has started to come into place, PLC based control will remain the technique to which the majority of industrial applications will adhere due to its higher performance, lower price, and super

4、ior reliability in harsh environments. Moreover, according to a study on the PLC market of Frost and Sullivan 1995, an increase of the annual sales volume to 15 million PLC per year with the hardware value of more than 8 billion US dollars has been predicted, though the prices of computing hardware

5、is steadily dropping. The inventor of the PLC, Richard E Morley, fairly considers the PLC market as a 5-billion industry at the present time. Though PLCs are widely used in industrial practice, the programming of PLC based control systems is still very much relying on trial-and-error. Alike software

6、 engineering, PLC software design is facing the software dilemma or crisis in a similar way. Morley himself emphasized this aspect most forcefully by indicating If houses were built like software projects, a single woodpecker could destroy civilization. ” Particularly, practical problems in PLC prog

7、ramming are to eliminate software bugs and to reduce the maintenance costs of old ladder logic programs. Though the hardware costs of PLC are dropping continuously, reducing the scan time of the ladder logic is still an issue in industry so that low-cost PLC can be used. In general, the productivity

8、 in generating PLC is far behind compared to other domains, for instance, VLSI design, where efficient computer aided design tools are in practice. Existent software engineering methodologies are not necessarily applicable to the PLC based software design because PLC-programming requires a simultane

9、ous consideration of hardware and software. The software design becomes, thereby, more and more the major cost driver. In many industrial design projects, more than of the manpower allocated for the control system design and installation is scheduled for testing and debugging PLC programs. In additi

10、on, current PLC based control systems are not properly designed to support the growing demand for flexibility and reconfigurability of manufacturing systems. A further problem, impelling the need for a systematic design methodology, is the increasing software complexity in large-scale projects. The

11、objective of this thesis is to develop a systematic software design methodology for PLC operated automation systems. The design methodology involves high-level description based on state transition models that treat automation control systems as discrete event systems, a stepwise design process, and

12、 set of design rules providing guidance and measurements to achieve a successful design. The tangible outcome of this research is to find a way to reduce the uncertainty in managing the control software development process, that is, reducing programming and debugging time and their variation, increa

13、sing flexibility of the automation systems, and enabling software reusability through modularity. The goal is to overcome shortcomings of current programming strategies that are based on the experience of the individual software developer. Three ：now of PLC From the structure is divided into fixed P

14、LC and Module PLC, the two kinds of PLC including CPU board, I/O board, display panel, memory block, power, these elements into a do not remove overall. Module type PLC including CPU module, I/O modules, memory, the power modules, bottom or a frame, these modules can be according to certain rules co

15、mbination configuration. In the user view, a detailed analysis of the CPUs internal unnecessary, but working mechanism of every part of the circuit. The CPU control works, by it reads CPU instruction, interprets the instruction and executes instructions. But the pace of work by shock signal control.

16、 Unit work under the controller command used in a digital or logic operations.In computing and storage register of computation result, it is also among the controller command and work. CPU speed and memory capacity is the important parameters fot PLC . its determines the PLC speed of work, IO PLC nu

17、mber and software capacity, so limits to control size. Central Processing Unit (CPU) is the brain of a PLC controller. CPU itself is usually one of the microcontrollers. Aforetime these were 8-bit microcontrollers such as 8051, and now these are 16-and 32-bit microcontrollers. Unspoken rule is that

18、you ll find mostly Hitachi and Fujicu microcontrollers in PLC controllers by Japanese makers, Siemens in European controllers, and Motorola microcontrollers in American ones. CPU also takes care of communication, interconnectedness among other parts of PLC controllers, program execution, memory oper

19、ation, overseeing input and setting up of an output. System memory (today mostly implemented in FLASH technology) is used by a PLC for a process control system. Aside form. this operating system it also contains a user program translated foram ladder diagram to a binary form. FLASH memory contents c

20、an be changed only in case where user program is being changed. PLC controllers were used earlier instead of PLASH memory and have had EPROM memory instead of FLASH memory which had to be erased with UV lamp and programmed on programmers. With the use of FLASH technology this process was greatly sho

21、rtened. Reprogramming a program memory is done through a serial cable in a program for application development. User memory is divided into blocks having special functions. Some parts of a memory are used for storing input and output status. The real status of an input is stored either as“1”or as “0

22、”in a specific me each input or output has one corresponding bit in memory. Other parts of memory are used to store variable contents for variables used in used program. For example, time value, or counter value would be stored in this part of the memory. PLC controller can be reprogrammed through a

23、 computer (usual way), but also through manual programmers (consoles). This practically means that each PLC controller can programmed through a computer if you have the software needed for programming. Today s transmission computers are ideal for reprogramming a PLC controller in factory itself. Thi

24、s is of great importance to industry. Once the system is corrected, it is also important to read the right program into a PLC again. It is also good to check from time to time whether program in a PLC has not changed. This helps to avoid hazardous situations in factory rooms (some automakers have es

25、tablished communication networks which regularly check programs in PLC controllers to ensure execution only of good programs). Almost every program for programming a PLC controller possesses various useful options such as: forced switching on and off of the system input/outputs (I/O lines), program

26、follow up in real time as well as documenting a diagram. This documenting is necessary to understand and define failures and malfunctions. Programmer can add remarks, names of input or output devices, and comments that can be useful when finding errors, or with system maintenance. Adding comments an

27、d remarks enables any technician (and not just a person who developed the system) to understand a ladder diagram right away. Comments and remarks can even quote precisely part numbers if replacements would be needed. This would speed up a repair of any problems that come up due to bad parts. The old

28、 way was such that a person who developed a system had protection on the program, so nobody aside from this person could understand how it was done. Correctly documented ladder diagram allows any technician to understand thoroughly how system functions. Electrical supply is used in bringing electric

29、al energy to central processing unit. Most PLC controllers work either at 24 VDC or 220 VAC. On some PLC controllers you ll find electrical supply as a separate module. Those are usually bigger PLC controllers, while small and medium series already contain the supply module. User has to determine ho

30、w much current to take from I/O module to ensure that electrical supply provides appropriate amount of current. Different types of modules use different amounts of electrical current. This electrical supply is usually not used to start external input or output. User has to provide separate supplies

31、in starting PLC controller inputs because then you can ensure so called“pure ” supply for the PL controller. With pure supply we mean supply where industrial environment can not affect it damagingly. Some of the smaller PLC controllers supply their inputs with voltage from a small supply source alre

32、ady incorporated into a PLC. Four ：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 mod

33、eled by formal languages or, equivalently, 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 p

34、rovides a structured representation 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 contr

35、ollers can reduce programming lead-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 requir

36、ements. A major challenge is therefore 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 i

37、ndustrial practice. Studies have 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 PLC still relies on a conventional programming style with ladder logic diagrams. As a result, the del

38、ays and resources in programming 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

39、to fix and disseminate state-of-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

40、 make large-scale system design 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

41、 as a performance destructor and 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 o

42、ther hand. Secondly, software proliferates 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 wi

43、th a similar number of 1/O points. 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%

44、of these costs are going into software 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

45、 of design theory and methodology 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

46、way. Furthermore, building a bridge 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 soft

47、ware design is similar to the hardware 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

48、 design stage, single functions 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 progra

49、m design may impact the logical hardware design. 可编程控制器 一、PLC 概述 可编程控制器是 60 年代末在美国首先出现的，当时叫可编程逻辑控制器 PLC (Programmable Logic Controller )，目的是用来取代继电器。以执行逻辑 判断、计时、计数等顺序控制功能。 提出 PLC 概念的是美国通用汽车公司。 PLC 的基本设计思想是把计算机功能完善、 灵活、通用等优点和继电器控制系统的简 单易懂、操作方便、 价格便宜等优点结合起来， 控制器的硬件是标准的、 通用的。 根据实际应用对象，将控制内容编成软件写入控制器的用户程

50、序存储器内,使控 制器和被控对象连接方便。 70 年代中期以后， PLC 已广泛地使用微处理器作为中央处理器， 输入输出模 块和外围电路也都采用了中、大规模甚至超大规模的集成电路，这时的 PLC 已 不再是仅有逻辑(Logic)判断功能，还同时具有数据处理、PID调节和数据通信功 能。国际电工委员会(IEC)颁布的可编程控制器标准草案中对可编程控制器作了 如下的定义： 可编程控制器是一种数字运算操作的电子系统， 专为在工业环境下 应用而设计。 它采用了可编程序的存储器， 用来在其内部存储执行逻辑运算， 顺 序控制、定时、 计数和算术运算等操作的指令， 并通过数字式和模拟式的输入和 输出，控制各

51、种类型的机械或生产过程。 可编程控制器及其有关外围设备， 易于 与工业控制系统联成一个整体，易于扩充其功能的设计。 可编程控制器对用户来说，是一种无触点设备，改变程序即可改变生产工艺。 目前，可编程控制器已成为工厂自动化的强有力工具， 得到了广泛的普及推广应 用。 可编程控制器是面向用户的专用工业控制计算机，具有许多明显的特点。 可靠性高，抗干扰能力强； 编程直观、简单； 适应性好； 功能完善，接口功能强 二、PLC 的历史 1968 年， Richard E. Morley 创造出了新一代工业控制装置可编程逻辑控制 器(PLC),现在，PLC已经被广泛应用于工业领域，包括机械制造也、运输系统

52、、 化学过程设备、 等许多其他领域。 初期可编程控制器只是用一种类似于语言的软 件逻辑于代替继电器硬件逻辑，并且使开发时间由 6个月缩短到 6天。 虽然计算机控制技术已经产生，但是 PLC 控制因为它的高性能、成本低、 并且对恶劣的环境有很强的适应能力而在工业控制的广泛应用中保持优势。而 且，尽管硬件的价格在逐渐下跌，据估计，根据Frost和Sullivan对PLC市场 的调查研究表明，每年销售硬件的价格要比销售 PLC 的价格（一千五百万）至 少多出八十亿美元。 PLC 的创造者 Richard E. Morley 十分肯定的认为目前 PLC 市场是一个价值五十亿的工业 虽然 PLC 广泛应

53、用于工业控制中， PLC 控制系统的程序依然和语法有关。 和软件过程一样， PLC 的软件设计也以同样的方式会遇到软件错误或危机。 Morley 在演讲中着重强调了这个方面。 如果房子建造的像软件过程一样， 那么仅仅一只啄木鸟就可以摧毁文明。 特 别的， PLC 程序要解决的实际问题是消除软件错误和减少老式梯形逻辑语言的 花费。尽管 PLC 的硬件成本在继续下降，但是在工业控制上减少梯形逻辑的扫 描时间仍然是一个问题，以至于可以用到低耗时的 PLC 。 一般来说，和其他领域相比生产 PLC 的周期要短很多。例如，在实践中， VISI 设计是一种有效的计算机辅助设计。 PLC 不需要使用目前的以

54、软件设计为 基础软件工程方法论，因为 PLC 程序要求对软件和硬件搜都要考虑到。因此， 软件设计越来越成为花费动力。 在许多的工业设计工程中， 多数人力分配给了控 制系统设计和安装，并且他们被要求对 PLC 进行程序测试和错误排除。 再者， PLC 控制系统不适合设计对适应性和重构有越来越多要求的生产系 统。一个更深入的问题是在大规模的工程中软件越来越复杂， 促使要有一个系统 化的设计方法论。 主题的客观性是为 PLC 自动控制系统建立一个系统化的软件设计方法论。 这个设计方法论包括以状态转换模型为基础的精确的描述， 这个转台转换模型是 自动控制系统的抽象系统。 方法论还包括一个逐步的设计过程

55、， 并且要设置一个 设计规则， 这样才能为一个成功的设计提供导向和方法。 这项研究的真正目的是 找到一个减少控制软件发展过程的不稳定性的方法， 也就是说， 减少程序和调试 时间以及他们的变化， 以增强自动控制系统的适应性， 并且通过调整软件使得软 件可以再度使用。 这样的目的是为了克服目前程序策略的不足之处， 而目前的程 序策略是以个人软件开发者的经验为基础的。 三、现今的 PLC 从结构上分，PLC分为固定式和模块式两种。固定式PLC包括CPU板、I/O 板、显示面板、内存块、电源等，这些元素组合成一个不可拆卸的整体。模块式 PLC 包括 CPU 模块、 I/O 模块、内存、电源模块、底板或

56、机架，这些模块可以 按照一定规则组合配置。 在使用者看来，不必要详细分析 CPU 的内部电路，但对各部分的工作机制 还是应有足够的理解。 CPU 的控制器控制 CPU 工作，由它读取指令、解释指令 及执行指令。但工作节奏由震荡信号控制。 运算器用于进行数字或逻辑运算，在控制器指挥下工作。寄存器参与运算， 并存储运算的中间结果，它也是在控制器指挥下工作。 CPU 速度和内存容量是 PLC 的重要参数，它们决定着 PLC 的工作速度， IO 数量及软件容量等，因此限 制着控制规模。 中央处理器（CPU）是PLC控制器的大脑。通常CPU本身就是一个微控制器。 起先是 8位微控制器例如 8051,现在

57、发展为 16位和 32 位微控制器。你会发现 大部分由日本制造商制造的PLC中是日立和Fujicu的微控制器,西门子的微控制 器多应用在欧洲的 PLC 中,摩托罗拉生产的微控制器则独占美国市场。 CPU 同样 关注通信 , PLC 控制器,操作程序的执行 ,监督记忆设置的输入和输出等部分的关 联性。 PLC 使用系统存储器（现在大部分采用闪存技术了）用于过程控制系统。 除了这个操作系统之外，它还包括一个由梯形图翻译成而进制形式的用户程序。 快擦型存储器（ FLASH memory ）的内容只有在改变用户程序的时候可以被改 变。 PLC 控制器比快擦型存储器使用得更早， EPROM 存储器比快擦

58、型存储器 也更早，快擦型存储器必须用紫外线（ UV，Ultra-Violet Ray ）灯擦除，并在编 程器上进行编程。 由于快擦型存储器技术的应用， 使得这个过程大大缩短了。 在 应用程序开发中，通过一个串行电缆可以对程序存储器进行重新编程。 用户存储器被分成具有特殊功能的块。一部分存储器用来存储输入和输出状 态。一个输入的实际状态存储状态存储在专用存储器位上，为“1或”者“0。”每一 个输入和输出在存储器中都有一个相应的位。 另外一部分存储器用来存储用户程 序中的变量的内容。例如，定时器值，或者记数器值存放在存储器的这个部分。 PLC 控制器可以通过计算机（通常方式）重新编程，但是也可以通

59、过人工编 程器 9 控制台）编程。实际上，这意味着，如果你有编程所需要的软件，早期 PLC 控制器可以通过计算机进行编程。今天的传输计算机是工厂自己对 PLC 控 制器进行重新编程的理想设备。 这对于工业企业来说是非常重要的。 一旦系统修 改结束，将正确的程序重新读入 PLC 控制器也是非常重要的。 定期检查 PLC 中 的程序是否改变是非常好的事情。 这有助于避免车间发生危险情况 （一些汽车制 造商已经建立了通信网络，可以定期检查 PLC 中的程序，以保证运行的程序都 是正确的）。 几乎所有用于为 PLC 控制器编程的程序都拥有各种不同的选项，例如系统输 入/输出（I/O线）的强制开关，程序实时跟踪以及图表验证。图表验证对于理解、 定义失败和故障非常必要。 程序员可以添加标记， 书日和输出设备名称， 以及对 于查找错误或者对于系统维护很有用的注释。添加注释和标记可以使技术人员 （不仅仅是开发人员） 很快理解梯形图。 注释和标记甚至还可以准确地引用零件 号，如果需要更换零件的话。 这将加快由于损坏零件而引起的任何问题的修理速 度。响应的旧方法是这样的， 开发系统的人必须保护这个程序， 他旁边再没有人 知道系统是怎样完成