电气工程 自动化 外文翻译 外文文献 英文文献 PLC未来发展趋势

1、4th international daaam conference industrial engineering innovation as competitive edge for sme 29 - 30th april 2004, tallinn, estonia programmable logic controllers in process automation ahti mikkor, lembit roosimlderdepartment of product development, institute of machinery, tallinn technical univ

2、ersity, ehitajate tee 5, 19086 tallinn, estonia ahti.mikkor abstract: nowadays, control problems are solved using operating components from a wide variety of technologies: electronics, hydraulics, pneumatics and mechanics. functio-nality, reliability and price of the controlled system are deter-mine

3、d by the quality of the solution made. the paper concentrates on practical use of programmable logic controllers (plc) that is based on the five years project development experience in this area. successful solutions and problems are under focus. specific hardware, controller programming problems, d

4、ata/signals exchange and human machine interfaces are considered. as a result the method for selecting programmable controllers according to specific needs is developed. practical suggestions, possible hazards and warnings are proposed that could help to avoid mistakes. key words: programmable contr

5、ollers, plc, automation, automation systems, process automation. 1. introduction modern machinery consists of both mechanical and electronic parts. overall functionality is determined by “balance” between these components. initial planning and solution selection plays critical role in final result.

6、in control methods the selection has to be made between relay-based circuits, special devices, programmable logic controllers (plc) and new development electronics. this article is concentrated on plc-s and experience that has collected over 5-year practical work with plc-s. strong and weak sides, p

7、ositive and negative practices are discussed. suggestions weather to use programmable controllers or not have been formed to help decision making. the most important decision in planning plc-based system is selecting processor type. mistakes mean extra costs for modifications or even need for comple

8、tely new devices. the most common error is overestimating programming possibilities of small-sized processors. there are several methods for selecting plc. unfortunately most of them focus on electrical side of plc-s and maximum count of signals allowed. they dont involve analysis to determine possi

9、ble special needs for user program or communications. based on several existing methods, practical experience and future trends a new method for selecting plc was developed. ahti mikkor has gained his experience by taking part in more than 15 big-scale automation projects. these projects include dev

10、elopment of power consumption monitoring system in as kunda nordic cement factory, renewing testing rig for flowmeters, building ahtme powerplant turbine safety systems, water treatment plants in towns rakvere and plva, waste water treatment plant in town jgeva and development of monitoring system f

11、or central heating network in tartu.2. pros and cons in using programmable logic controllers 2.1 positive arguments the main advantage that programmable controllers provide is flexibility (jack, 2003). behaviour of the system can be easily changed via program without any other alterations. special d

12、evices for example make any changes in control algorithm very hard to implement. flexibility makes plc-s well suitable for frequently changed applications, for example in robotics. in plc-s the relations between inputs and outputs are determined by user program. by using advanced programming technol

13、ogies it is much easier to implement complex control algorithms than in any hard-wired solutions. it makes plc-s very competitive for complex tasks, for example in controlling chemical processes. special modules allow vast amount of different signals to be connected to the plc system. use of plc-s s

14、hould be considered in applications that require some “special” input or output signals. typical example would be positioning using reference data from high-speed input. typically pc visualization software packages are made for plc-s. some special devices have also pc software packages. wide range o

15、f communication options between plc-s makes it possible to gather all information from field devices into one central control point. communication lines between plc-s allow using information collected from other parts of the system in local process control. modern communication technologies enable r

16、emote diagnostics and configuration (jack, 2003). these two significantly reduce overall maintenance costs of the system. 2.2 negative arguments programmable controllers are not equipped with enough memory to store big amounts of data. although future trends show growth in plc memory sizes, special

17、devices (recorders) are still better suited for standalone datalogging applications. for networked solutions there is possibility to use visualization software packages together with plc-s to archive collected data in any database format necessary. if logged data amounts are small or there are also

18、control functions included, its reasonable to still use plc-s. about visualization software packages its good to know that in standard versions most of them do not support offline recording so that after communication breakdown it is not possible to acquire data backwards from plc. modern communicat

19、ion options for plc-s include standard protocols for example ethernet. it is tempting to use existing office networks also as data carrier for automation system communications. time has shown that it is better practice to keep these two separated if there is a need for constant online communication.

20、 hardly traceable temporal network overloads can cause problems also in automation system communications all plc-s need be programmed. all programming works include risk for accidental errors in control algorithm. special devices are well tested and generally free of this kind of problems. if availa

21、ble, its economically thoughtful to use special devices. safety applications that require highest degree of reliability should contain simplest devices and circuits possible. there is a rule that every new link in chain decreases overall reliability. in small applications its often cost saving to us

22、e relay-based circuits instead of plc-s. 3. future trends progress in process automation systems is aiming at so called complete automation when all the human has to do is to enter the parameters of the product wanted and everything else is carried out by machines (rosin, 2000). although the destina

23、tion lies far ahead, trends indicate movement in that direction. firstly, systems become more and more standardized. big manufacturers organize their products into families. the aim is to reduce amount of knowledge needed for configuration and maintenance works of different devices from same company

24、. its also important that this way built applications are easily expandable. secondly, importance of communication is rising (hughes, 2000). there are many reasons, some of more essentials are: better collaboration of different parts of the system. cutting costs on cabling. less cabling results fall

25、 in fault probability, but also increases severity of ones that occur. sensors and actuators can be at longer distances from the processor module than if using conventional methods. increased scalability of the systems. new devices can be added at minimal costs. at some cases it is better to make ar

26、chitecture of many small independent modules and network them. this solution enables system to keep working although some parts have failed. communication networks ease fault diagnostics and provide remote management possibilities. central operating stations can be formed relatively easy. possibilit

27、y to connect devices form different manufacturers (opc foundation, 2003). third important tendency is spreading use of so called software controllers or soft plc-s (siemens ag, 2003). these are pc software-based solutions that relate with field devices via communication networks. there is no need fo

28、r processor module, resources of pc are used. some soft plc-s are still formed as processor cards for pc (figure 1). reliable communication networks are essential. soft plc-s are well suited for data acquisition applications because of data storage possibilities of pc-s. figure 1. siemens simatic wi

29、nac slot plc 412fourthly, combo-devices (figure 2) that contain both operator panel and medium size processor module gain popularity (siemens ag, 2002). in this solution possibility of disturbances is low and reuse of some components make whole package cheaper. figure 2. combo device siemens simatic

30、 c7-613 fifthly, processor software takes over properties from pc software. data collected from production can be easily transferred into office applications (siemens ag, 2000). 4. method for selecting programmable controller a method for forming an application specific list of required properties f

31、or selecting programmable controller was developed. there are nine criterions and the results are presented in table 1. selection is made by comparing results table with controllers technical data. following is short description of every criteria involved. nature of solution determines weather it is

32、 expanding of old system or completely new development. in first case the architecture of system and hardware requirements are limited by already existing solution. using hardware from same company makes servicing easier and avoids integration problems that would occur when using products form diffe

33、rent manufacturers. for example many hardware producers integrate their own specific communication interfaces directly into processor module and for every universal protocol a special module is needed (siemens ag, 2003). it is also possible to reduce spare part stock amounts when using same type har

34、dware all over the system. maximum number of electrical inputs-outputs allowed is classical criteria to determine processor class. if complex control algorithms and non-standard functions are needed, its not the most important parameter any more. generally it is money saving to use one bigger proces

35、sor module for input-output signals that originate from nearby locations than several smaller ones. in this case there will be no need for communication network and programming will be easier too. special signals and modules are usually available for medium and large controller families only. many m

36、icrocontrollers do not even have possibility to add analogue output (siemens ag, 2003). in some cases using special modules is the only way, in other ones (positioning) it is just an opportunity to save money. layouts of sensors and actuators can be very different, sometimes the sensors are located

37、several kilometres away from the actuator (pumping liquids in long pipes). in this case special communication network (profibus, as-inteface) might be the only solution. if not, it can at least save costs by reducing cabling works. not all programmable controllers have interfaces for communication p

38、rotocols. properties of processor have important role in complex applications. most common problem is lack of programming memory, sometimes also data memory. memory requirements can be estimated by number of input and output signals. but in practice 100 digital input-output points system often has 3

39、 times smaller program than 10 digital input-output points system. the only way to estimate program size exactly is using previous experience. program specialities include special program functions needed. different areas of applications have some typically used functions, for example temperature co

40、ntrol in building automation. programming is much simpler if these functions are already built into system software of processor. in process automation 2 digital output (up-down) closed loop pid regulation is quite often used. it might be a surprise but its not included in most of the microcontrolle

41、rs (siemens ag, 2003) and for average programmer its too complicated task to create his own regulator using standard functions. basically there are 2 solutions: either to avoid this construction or to use applicable controller. table 1. table for method results communication is becoming more importa

42、nt in nowadays automation systems. in some cases non-standardised devices as barcode readers or electronic weights have to be included into the system. then its vital to have functions for protocol programming (freeport programming). standardised protocols demand existence of specific modules. worki

43、ng conditions can usually be overcome by using special cabinets, but there are also specific series of programmable controllers that have improved resistance for electromagnetic disturbances, humidity and vibrations. in very dusty environments all cooling ventilators have to be equipped withfilters.

44、5. conclusions main benefits of programmable controllers are: flexibility communication possibilities realisation of complex control algorithms reliability alternative solutions should be considered if: system is very simple special devices are available data recording is necessary initial selection

45、 of appropriate solution and hardware has great influence on final result. mistakes in this step significantly increase overall budget of project as some programs might have to be changed and some hardware replaced. based on his practical experience the author has formed a method for selecting progr

46、ammable controller. it has 9 criterias: nature of solution (new or existing) maximum number of electrical inputs-outputs allowed (digital, analogue, inputs, outputs) need for special modules (high-speed digital outputs) layout of sensors and actuators (local or periphery) properties of processor (pr

47、ogram and data memory) program specialities (special functions) communication needs (profibus, ascii) working conditions (humidity, temperature, vibration, dust) method is not guaranteed to always point out the best selection, but using it certainly avoids mistakes. 6. references hughes, t. a. progr

48、ammable controllers, third edition. isa the instrumentation, systems, and automation society, 2000, 334 p. jack, h. automating manufacturing systems with plc-s, 828 p., available: /jackh/books/plcs/pdf/plcbook4_2.pdf, accessed: 3.10.2003 logo! manual. siemens ag, 2003

49、, 312 p. opc foundation homepage: /, accessed: 9.11.2003 rosin, a. programmable controllers simatic s7. tallinn, ttu, 2000, 120 p. master thesis in estonian. berger, h. automating with simatic. siemens ag, 2003, 214 p. simatic programming with step 7 v 5.2: manual. siemens

50、 ag, 2002, 610 p. simatic s7-200 programmable controller system manual. siemens ag, 2003, 474 p. simatic hmi wincc configuration manual. volume 1, 2, 3. siemens ag 2000, 468 p. 摘自可编程控制器在过程自动化中的应用ahti mikkor,lembit roosimolderdepartment of product development,institute of machinery,tallinn technical

51、university,ehitajate tee 5,19086tallinn.摘要：目前，控制问题解决了各种各样的技术操作部分：电子，液压，气动和机械。函数- nality，可靠性和控制系统的价格是阻止开发的理由。本文集中于可编程逻辑控制器（plc），以五年在这方面的发展经验为基础。成功的解决方案是问题重点。具体的硬件，控制器编程的问题、数据/信号的交换和人机界面进行审议。实际的建议，需要根据具体的方法来开发可编程控制器。对于可能出现的错误和警告，提出可以帮助避免方法。关键词：可编程控制器、自动化、自动化系统、过程自动化1引言现代的机器包括电子和机械两部分。平衡两方面因素，初步规划和方案选择

52、对最终结果起着至关重要的作用。在控制方法的选择，继电器，专用设备，可编程逻辑控制器（plc）和电子制造技术的发展。这篇文章是基于plc集中- s的经验，拥有超过5年的plc - s的实际工作经验中收集的。双方强弱，积极和消极的做法进行了讨论。建议使用可编程控制器帮助解决。在规划基于plc系统中最重要的决定是选择处理器类型。误区是意味着修改额外费用或扩展完全新设备的需要。最常见的错误是高估小型处理器编程的可能性。有选择plc的几种方法。不幸的是，他们大多集中在电气方面的plc - s和允许的最大计数信号。他们不涉及分析，以确定用户程序或通信可能的特殊需要。基于几个现有的方法，实践经验和未来趋势的

53、选择为开plc的开发提供新的方法。阿赫蒂瓦尔mikkor已获得通过采取在超过15个大范围的自动化项目的一部分，以他的经验，这些项目包括电力消耗在as昆达北欧水泥工厂监控系统的开发，更新测试流量计钻机，建设城镇rakvere和普亚，污水处理厂在城里jogeva和发展动力涡轮安全系统，污水处理厂在塔尔图监测网络系统的集中供热。2可编程控制器在投票站的使用2.1正面论据主要优势是灵活性提供可编程控制器（杰克，2003年）该系统的行为可以很容易地通过计划，没有任何其他的改动。例如特殊装置使控制算法很难实现任何改变。灵活性使得plc的- s经常更换适合应用在机器人的例子。在plc - s的投入和产出之间

54、的关系是由用户程序决定。通过使用先进的编程技术比任何硬连接解决方案容易得多，以实现复杂的控制算法。它使plc在复杂的任务很有竞争力。例如，在控制化学过程，特别模块，让大量不同的信号被连接到plc系统。plc - s的使用，应考虑应用，需要一些“特殊”的输入或输出信号。典型的例子是利用定位高速输入参考的数据。通常个人电脑的可视化软件是由可编程序控制器plc- s控制，也有一些特殊设备的pc软件包。宽的plc - s的通信选择范围使得它能够收集到一个中央控制点。搜集现场的所有设备的信息。窄的plc - s的通讯线路允许使用从本地过程控制系统的其他部分中收集信息。现代通讯技术实现远程诊断和配置（杰克

55、，2003年）。这两方面显着降低了系统的总体维护成本。2.2没有配备足够的内存来存储数据虽然未来的趋势在plc内存大小，（录像机）专用设备的增长仍然是更适合于独立的数据记录应用。对于网络解决方案，有可能使用可视化软件包一起与plc - s到存档于任何数据库格式收集必要的数据。如果记录的数据量小或者有控制功能也包括在内，采用plc - s是合理的。关于它的可视化软件，知道他们在标准版本的大多数不支持脱机录音通讯故障后，使我们无法获得向后从plc的数据。对plc的现代通讯选项包括，例如以太网标准协议。人们很容易用数据自动化系统的通信运营商中获得。时间已经证明，最好的做法是保持这两方面分离的，如果有

56、一个经常上网的通信需求。几乎没有时间可追溯网络超载问题，也可能在自动化系统的通信。所有的plc - s的需要进行编程，所有的编程作品包括在控制算法和意外错误的风险。特种设备是行之有效的，并且通常解决这类问题的。如果有的话，它是经济的使用特殊设备。安全应用需要最高的可靠性程度，应该包含最简单的设备和电路。有一个规则，每一个链的新环节可能降低整体的可靠性。在小型系统应用中，经常节省成本使用中继电路，而不是使用plc的- s的。3今后的趋势过程自动化系统的进展是针对所谓的完全自动化，所有的人所要做的就是进入该产品的参数和其他一切工作由机器（松香，2000年）协调。虽然目标遥遥领先，表明在这个方向的趋

57、势运动。首先，系统变得越来越规范。从大型制造商组织到家庭的产品。其目的是减少对来自同一公司不同的设备配置和维护工作所需的知识量。同样重要的是这种方式构建的应用程序很容易扩展。其次，沟通的重要性正在上升（休斯，2000）。有很多原因，更多的要领有：更好的系统是不同部分的合作。 降低成本的布线。减布线结果增加了故障率，也增加了那些发生的严重程度。 传感器与驱动器可以在从传统方法相比，如果使用的处理器覆盖更长的距离。 提高了系统的可扩展性。在增加新设备时以最低的成本。 在某些情况下，最好是让许多小型的独立模块和网络架构。该解决方案使系统继续工作，尽管一些地区已经失败。 方便的通信网络故障诊断为远程管

58、理提供了可能性。中央操作站，可形成相对容易。 可将设备连接形式（opc基金会，2003）不同的生产厂家。第三个重要趋势是散布所谓的软件控制器或软plc - s的（西门子股份公司，2003年）的使用。这些都是电脑软件为基础的解决方案，通过通信网络与现场设备。有没有需要的处理器模块，使用的pc资源。有些软plc - s仍然为pc处理器卡（图1）。可靠的通信网络是必不可少的。软plc - s是非常适合于个人电脑的数据存储数据采集应用的。图1。西门子的simatic winac插槽式plc 412第四，组合装置（图2）同时包含操作员面板和中等规模的处理器模块得到普及（西门子股份公司，2002）。这个解决方案的可能性很低，一些组件的重用使整个包便宜。西门子simatic组合设备的c7 613第五，处理器软件接管从pc软件性质。收集的数据可以很容易地从生产到office应用程序转移（西门子股份公司，2000）。4 可编程控制器的控制