DCS和PLC区别总结的比较好的一篇文章_dcs和plc区别
DCS和PLC区别总结的比较好的一篇文章由刀豆文库小编整理，希望给你工作、学习、生活带来方便，猜你可能喜欢“dcs和plc区别”。
河南理工大学2011届毕业设计中英文翻译
The Difference Between
DCS and PLC In the power plant automation in thermal field, DCS and PLC is two completely different and have something to the concept of contact.DCS and PLC is computer technology and industrial control technology, the combination of the power of the main engine control system, and is with DCS PLC is mainly applied in the power plant auxiliary workshop.DCS and PLC has operator station provides the means of human-computer interaction, rely on the controller based on computer technology to complete control operation, all through the I/O card finished and a component and execution of the device data exchange, has called network communications system.DCS and PLC so similar, why there is a completely different concept in engineering practice, we how to choose? This paper, from the historical evolution, technical features, development direction and so on several aspects are reviewed in this paper, the hope can be reference for the thermal profeionals.The DCS in NETWORK6000 + as an example, the paper tries to detailed clear examples.The history and core concept of DCS and PLC DCS for DISTRIBUTED CONTROL SYSTEM.Refers to the dangerous scattered and data set.70 s to enter the market, complete the analog control with PID operation, instead of the simulation mainly control instrument.First proposed a kind of such thoughts of DCS instrument manufacturers, at that time is mainly used in chemical industry.And in the 60 s PLC succefully developed, called the Logic 河南理工大学2011届毕业设计中英文翻译
operation of the PLC(Programmable Controller), based as PLC.Mainly is used in automobile manufacturing.DCS and design principle of large difference with PLC, PLC touch the relay copy from the control principle of the rise and development of the 70 s, only the switch quantity logic control of PLC.It’s to store to perform the logic operation, sequence control, timing, counting and operation of the operation instructions;And through the digital input and output operation, to control all kinds of mechanical or production proce.Users of the production proce control program to expre the proce requirement.Will it in the PLC program memory, the runtime users according to store the content of the program execution to complete ideally suited to proce the required action.DCS operational amplifier is in on the basis of the development of may.Put all the function, the relationship between the various proce variables are succeful design can block.In the mid 70's,the DCS only analog control.DCS and PLC controller is the main difference in the switch quantity and analog computing, even if later both mutual some penetration, but there are still differences.Since the 80 s, PLC logical operations outside, also in addition to adding some control circuit algorithm, but to complete some complex operation or more difficult with ladder-diagram programming, PLC, analog computing when programming in not too, intuitive, and programming is more troublesome.But in the solution in logic, show the advantages of fast.And DCS use function of packaging simulation calculation and logic operations, whether logic operation or complex simulation of operation forms of expreion are very clear, but relatively PLC for the expreion of the logical operation efficiency is low.DCS and PLC in the historical evolution differences is obvious, their subsequent had a great influence.However, the greatest impact on subsequent development, and not the difference in origin technology, but its origin, the 河南理工大学2011届毕业设计中英文翻译
difference between the concept.DCS of the core concepts of the danger is scattered data set, the computer control system, therefore the development of DCS, which is in the proce of continuous use of computer technology, the communication technology and the latest achievements of control technology, to set up a complete system of the distributed control, DCS offer users is a complete for industrial control of the safety and security of highly efficient and flexible solutions.And the core concepts of PLC programmable controller is, the purpose is used to replace relays, executing logic and time apart and control functions, establish the order of flexible program control device.So, PLC of the development of the main line is constantly improve the ability index, to users with a perfect function of flexible control device.DCS, PLC is a system is a device, this is both in the fundamental difference between the concept.This difference was the impact of the deep, it into the technology every aspect of the economy.DCS and PLC technology characteristics and mutual infiltration
Different conceptual basis, different path makes DCS and PLC have different technical characteristics, and the development of technology is not closed, learn from each other mutual infiltration has always throughout the development proce.2.1, control proceing power
We know, a PLC controller, often can deal with thousands of I/O point(up to 8000 DuoGe I/O).But the controller, normally only DCS deal with hundreds of I/O point(no more than 500 I/O).Is it DCS developers technical level is so bad? I'm afraid not.From the distribution system requirements for, are not allowed to have control of the situation appears on the controller, too many points in practical 河南理工大学2011届毕业设计中英文翻译
application is usele and DCS developers no development zones many I/O points of the controller, they need to drive the main focus of the system is to provide the reliability and flexibility.And is not the same as the PLC, as an independent flexible control device, with a stronger ability of course means its technical level higher, as to the whole control system? And the application level of the main is project traders and user's things, not the core target of PLC manufacturers.Control ability to handle another index, speed, in people of impreion faster than DCS PLC many.From one perspective, indeed, PLC executive logic operation efficiency is very high, executive 1 K logic programming le than 1 milliseconds, the control cycle(input directly to DI sent as an example)can DO output control in within 50 ms;And DCS in dealing with logic operation and the simulation computation of the same way, the control cycle in more than 100 ms often.We use PID algorithm to compare, can find PLC executive a PID operation in a few milliseconds, and NETWORK6000 + DCS T2550 controller for calculating a PID also need a millisecond, show that the PLC and DCS and actual operation ability is pretty, some of this type of DCS controller even better.And the differences between the control cycle of main and controller scheduling design relevant.Large PLC often use CPU to complete the analog quantities of the operations, the CPU to complete high speed switch quantity operations, so even if the simulation calculation speed in general, switch quantity control aspects of the speed performance or very good.And DCS at the same speed to deal with the switch quantity and analog computing, control cycle of the index does not ideal.New type of DCS controller studied the design of the large PLC in the control cycle, performance won a dramatic increase.To NETWORK6000 + DCS T2550 controller for example.The controller can set up four different priority task, the minimum operation cycle can be set to 10 ms, cooperate with the I/O card parts, control cycle can achieve the 15 ~ 20 ms.And analog computing set in other cycle long miions.河南理工大学2011届毕业设计中英文翻译
2.2 data communication exchange
Data communication exchange is mainly refers to the control system network and its data exchange form.And in this respect DCS have innate advantage.Distribution system “scattered” shows in independent controller, “focus on” shows in a complete data of human-computer interaction device, and will be dispersed and concentration distribution system is connected to the network.Therefore, from the early days of DCS, the network will become the DCS manufacturers the core technology of the direction, redundant technology, narrowband transmiion technology is the earliest development or application of DCS manufacturer of succe.PLC is mainly according to the independent device to design, the “network” is in fact a serial communication.Industrial Ethernet technology development and the widespread application, in the form of DCS and PLC network levels the gap.From apparently look a lot of DCS and PLC is applied, but the industrial Ethernet is gap but still exists.With a lot of PLC used MODBUS-with an example.TCP MODBUS is serial communication protocol, not network, everyone have no doubt;MODBUS-TCP is network? Many people have questions.Careful analysis, MODBUS-TCP is will MODBUS communication protocols of the TCP protocol to load the Ethernet on a method of communication, it is the appearance of the network, but is still more than the Lord from management, the data table transmiion structure.And DCS, to NETWORK6000 + DCS ELIN network as an example, although also be based on industrial Ethernet, but the application layer protocol is European company accumulated almost 30 years of statele token LIN nets agreement, in the 1 M OLIN, 2.5 M and 20 M ARCNET have long-term succeful applications.ELIN online, equality, not every are mainly a enterprise.And the data communication modules for the unit is structured data, data management ability the data table way comparable.河南理工大学2011届毕业设计中英文翻译
With PID module for example, one of the basic data have PV, SP, using the data table of OP, transmiion, you must first define the PV, SP, OP data for, 02, addre the other station also, by the way the data table receiving data, but what is the data? 02 is what data? Through the data defined table to restore.The data table management way cumbersome fallible, a large system of data points of this way, tile in data table for the management, and is very terrible.And NETWORK6000 + DCS to module for units of structured management, will be a PID as a module, to deal with acce to its PV value, first visit the module, the form of PID.PV is management.This will be all tile data, claification on each one small box belonging to the module.The way of weight management, the management efficiency is greatly increased.PLC, data communication exchange mainly comes from PLC for a long time as a independent device in development, no system concepts;And is mainly applied in small control system, the problem is exposed to was not obvious, so low.At present some large PLC in this aspect somewhat improve, but to reach the level of the DCS need quite a long proce.2.3, configuration maintenance functions
Configuration maintenance functions including logic configuration, download modification, operation commiioning, remote diagnosis, etc.Early, PLC to ladder diagram is given priority to, DCS to module function chart is given priority to.After DuoNian development, the international electrotechnical commiion through the IEC1131-3 standard specifies the five kinds of programming language, at present the mainstream of DCS and PLC said the accord with the standard, to support some of them or all of the programming language.From a development efficiency and procedures to consider and readability module function chart and order has become a more and more of the main function 河南理工大学2011届毕业设计中英文翻译
diagram, trapezoidal logic and structured programming way text became the custom module development tools.Large PLC in the configuration way more and more like DCS, reduced gradually, and the gap and small PLC is still the ladder diagram to give priority to.Through the development of DCS DuoNian, accumulated the maive advanced algorithm modules.For example NETWORK6000 + have the device level modules in a module on the face of the equipment to complete basic control and fault alarm functions, in the network communication in this module for the unit also has to convey, greatly improving the efficiency of software development.A device a module is equivalent to 0.5 K ladder diagram of logic, to complete the same function of PLC, will more troublesome.In the download modification, operation commiioning, remote diagnosis, PLC lack of solutions.From a design and DCS at the beginning of the system is from the Angle of the need of, with DuoNian accumulation of the perfect solution.To NETWORK6000 + DCS, for example, the system can be modified online, also can control strategy online download control strategy, modify and download proce, to the normal operation of the system have no effect.NETWORK6000 + DCS has perfect virtual DCS function, not only can be used for configuration validation logic, and can build into complete virtual DCS and the model is linked together, complete system simulation test.NETWORK6000 + DCS has the perfect safety measures, provided based on the wan's remote debugging plan.2.4, hardware package structure
PLC general for soles format frame, enclosed the I/O module, closed structure favorable and improve the I/O module, the reliability of rf, antistatic, fight damage.PLC module I/O points are 8, 16 points, 32 points.河南理工大学2011届毕业设计中英文翻译
DCS for 19 inches most standard case and plug-in type I/O module, the I/O module for bare type structure.Each module of I/O points are 8 and 16 points, rarely used by 32 module.The structure of DCS stems from its main use the field in large control object, 19 inches standard case for intensive decorate, the le I/O points is due to dispersion requirements.PLC bottoms, enclosed format frame module structure in management and configuration of a single device more flexible, higher reliability.Therefore, many DCS also absorbed in the structure of PLC in advantage, using and PLC similar package structure, such as I/A metal shell, the NETWORK-6000 + the conductive plastic shell.2.5, man-machine interactive device
In the early days, DCS as a system, the man-machine interactive device is the special device manufacturers with DCS.And manufacturers don't usually provide PLC man-machine interactive device, often by project traders independent by the universal surveillance software to finish(such as ifix, intouch, configuration king).DCS integrated man-machine interactive devices often have the function is more profeional, stability good characteristics, but the price is high.With the rapid development of the PC technology, some general monitoring software development soon, functions and performance is outstripping the special device manufacturers with DCS.So a lot of DCS manufacturers gradually give up the dedicated human-computer interaction device, and also used to PLC used as the monitoring software.DCS manufacturers use general monitoring software and not simply aembled, but in general the monitoring software, and on the basis of development through cooperation, DuoNian myself the accumulation of network communication technology, the system since the diagnosis technology with special form of the package to retain and inherited.河南理工大学2011届毕业设计中英文翻译
For example, NETWORK-6000 + early once used special operating system based on the T1000 human-computer interaction system, and the current main use based on IFIX or INTOUCH don/T3500 of human-computer interaction system.One of the LINPOLL network communication bag is the integration of European company by development.DCS and PLC market conditions and development direction
In the thermal automation field, main workshop of control system basically no exception to the use of DCS.And in auxiliary workshop to use PLC.The main reason is the early DCS system is very expensive, people think auxiliary workshop operation can be discontinuous, reliability requirement is not very high, and analog control requirements le, from the point of view of cost reduction, often choose to construct the PLC control system.And boiler, turbine and generator control system, require long-term stable reliable operation, signal contains a significant proportion of the analog, from the performance of the system, people have to choose on expensive DCS.In addition, analyze main workshop of DCS and auxiliary workshop control system market competition, we will find an interesting phenomenon.Main building of DCS in different brand competition often the supplier or agent, competition is intense, developed between the prices have cut DCS.And the auxiliary workshop control system in the same brand competition often PLC all project between busine and low threshold, more competitive, but the price of PLC declines but is not as obvious DCS.The main reason is the DCS producers compete directly, in the huge market preure, and constantly cut equipment manufacturing costs and project implementation costs.And the producers do not directly involved in PLC, each project traders can only competition cut their own limited engineering cost, limited 河南理工大学2011届毕业设计中英文翻译
space.From now seems, DCS and high-grade PLC price gap has not obvious, the auxiliary workshop still more used PLC, is due to the inertia of the market.Domestic power plant with an installed capacity of the continued expansion of and power system reform, the auxiliary workshop control requirements improve continuously, in this environment, DCS system into the auxiliary workshop control has become the trend.NETWORK6000 + DCS for its comprehensive technical economic advantage, has and will continue to aist in control of the workshop is playing a greater role.In auxiliary workshop widely used PLC will not exit in the historical stage of thermal automation, unprecedented preure of competition, will force a PLC technology firms in the DCS standard draws close, is in the price to greater efforts.The results of the competition in the market, which was more benefit.The Conclusion
DCS and PLC as computer technology and control technology, the combination of thermal automation for the power plant to raise the level of their respective contributions are made.Because both in applications are many of the larger, at various times, their respective technical or price advantage, will directly affect the market position.And the response of the market will quickly or slowly to reflect to their technology development and price adjustment.On the general trend of DCS and PLC technology, in the fusion and promote competition will be the mainstream, and in price-performance, you come to me to to increasing, also will be the theme of development.河南理工大学2011届毕业设计中英文翻译
DCS PLC区别
在火电厂热工自动化领域，DCS和PLC是两个完全不同而又有着千丝万缕联系的概念。DCS和PLC都是计算机技术与工业控制技术相结合的产物，火电厂主机控制系统用的是DCS，而PLC主要应用在电厂辅助车间。DCS和PLC都有操作员站提供人机交互的手段、都依靠基于计算机技术的控制器完成控制运算、都通过I/O卡件完成与一次元件和执行装置的数据交换、都具备称之为网络的通信系统。DCS和PLC如此相似，为什么会有完全不同的概念，我们在工程实践中如何进行选择？本文从历史沿革、技术特点、发展方向等几个方面作一综述，希望能够对热工专业人员有所借鉴。其中的DCS的情况以NETWORK6000+为例，力求例举详实阐述清晰。
1、DCS和PLC的历史沿革及核心概念
DCS为分散控制系统的英文（TOTAL DISTRIBUTED CONTROL SYSTEM）简称。指的是危险分散、数据集中。70年代中期进入市场，完成模拟量控制，代替以PID运算为主的模拟控制仪表。首先提出DCS这样一种思想的是仪表制造厂商，当时主要应用于化工行业。而PLC于60年代末研制成功，称作逻辑运算的可编程序控制器（Programmable Logic Controller），简称PLC。主要应用于汽车制造业。
DCS和PLC的设计原理区别较大，PLC是从摸仿原继电器控制原理发展起来的，70年代的PLC只有开关量逻辑控制。它以存储执行逻辑运算、顺序控制、定时、计数和运算等操作的指令；并通过数字输入和输出操作，来控制各类机械或生产过程。用户编制的控制程序表达了生产过程的工艺要求。将其存入PLC的用户程序存储器，运行时按存储程序的内容逐条执行，以完成工艺流程要求的操作。
DCS是在运算放大器的基础上得以发展的。把所有的函数、各过程变量之间的关系都设计成功能块。70年代中期的DCS只有模拟量控制。
DCS和PLC控制器的主要差别是在开关量和模拟量的运算上，即使后来两者
河南理工大学2011届毕业设计中英文翻译
相互有些渗透，但是仍然有区别。80年代以后，PLC除逻辑运算外，也增加了一些控制回路算法，但要完成一些复杂运算还是比较困难，PLC用梯形图编程，模拟量的运算在编程时不太直观，编程比较麻烦。但在解算逻辑方面，表现出快速的优点。而DCS使用功能块封装模拟运算和逻辑运算，无论是逻辑运算还是复杂模拟运算的表达形式都非常清晰，但相对PLC来说逻辑运算的表达效率较低。
DCS和PLC在历史沿革上的差异是明显的，对它们后续的发展产生了重大影响。然而，对后续发展影响最大的，并不是起源技术上的差别，而是其起源概念的差别。DCS的核心概念是危险分散，数据集中的计算机控制系统，因此DCS的发展过程，就是在不断的运用计算机技术、通讯技术和控制技术的最新成果，来构建一个完整的集散控制体系，DCS给用户提供的是一个完整的面向工业控制的安全可靠高效灵活的解决方案。而PLC的核心概念是可编程序控制器，目的是用来取代继电器，执行逻辑、计时、计数等顺序控制功能，建立柔性程序控制装置。所以，PLC不断发展的主线是在不断地提高各项能力指标，给用户提供一个完善的功能灵活的控制装置。
DCS是一个体系，PLC是一个装置，这是两者在概念上的根本区别。这个区别的影响是深刻，它渗透到了技术经济的每一个方面。
2、DCS和PLC的技术特点与相互渗透
不同的概念基础、不同的发展道路使得DCS和PLC有着各自不同的技术特点，而技术的发展也不是封闭的，相互学习相互渗透也始终贯穿在发展过程之中。2．
1、控制处理能力
我们知道，一个PLC的控制器，往往能够处理几千个I/O点（最多可达8000多个I/O）。而DCS的控制器，一般只能处理几百个I/O点（不超过500个I/O）。难道是DCS开发人员技术水平太差了吗？恐怕不是。从集散体系的要求来说，不允许有控制集中的情况出现，太多点数的控制器在实际应用中是毫无用处的，DCS开发人员根本就没有开发带很多I/O点数控制器的需要驱动，他们的主要精力在于提供体系的可靠性和灵活性。而PLC不一样，作为一个独立的柔性控制装置，带点能力越强当然也就代表其技术水平越高了，至于整个控制体系的应
河南理工大学2011届毕业设计中英文翻译
用水平呢，这主要是工程商和用户的事情，而不是PLC制造商的核心目标。
控制处理能力的另一个指标，运算速度，在人们印象当中PLC也比DCS要快很多。从某一个角度来看，情况也的确如此，PLC执行逻辑运算的效率很高，执行1K逻辑程序不到1毫秒，其控制周期(以DI输入直接送DO输出为例)可以控制在50ms以内；而DCS在处理逻辑运算和模拟运算时采用相同的方式，其控制周期往往在100ms以上。我们用PID算法来比较时，可以发现PLC执行一个PID运算在几个毫秒，而NETWORK6000+DCS的T2550控制器解算一个PID也需要1个毫秒，这说明PLC和DCS和实际运算能力是相当的,某此型号的DCS控制器甚至更强。而控制周期上的差异主要与控制器的调度设计有关。大型PLC往往使用副CPU来完成模拟量的运算，主CPU高速地完成开关量运算，所以即使模拟运算速度一般，在开关量控制方面的速度表现还是非常优秀的。而DCS以同样的速度来处理开关量和模拟量运算，控制周期的指标确实不理想。新型的DCS控制器学习了大型PLC的设计，在控制周期方面的表现获得了大幅度的提高。以NETWORK6000+DCS的T2550控制器为例。控制器可以设置四个不同优先级的任务，最小运算周期可以设为10ms，配合高速I/O卡件，控制周期能够达到15~20ms。而模拟量运算设置在其它周期较长的任务中。
2．2数据通讯交换
数据通讯交换主要是指控制系统网络及其数据交换形式。在这个方面DCS有着先天的优势。集散系统的“分散”主要体现在独立的控制器上，“集中”主要体现在具有完整数据的人机交互装置上，而将分散和集中连接成集散系统的正是网络。因此，从DCS发展的早期，网络就成为了DCS生产厂家的核心技术方向，冗余技术、窄带传输技术都是DCS厂家最早研发或应用成功的。PLC主要是按照独立装置来设计的，其 “网络”实际上是串行通讯。
工业以太网技术的发展和广泛应用，从形式上拉平了DCS和PLC网络方面的差距。从表面上看很多DCS和PLC都应用了工业以太网，但是其实质上的差距却依然存在。以很多PLC采用的MODBUS-TCP以例。MODBUS是串行通讯协议，不是网络，大家都没有疑问；MODBUS-TCP是网络吗？很多人就有疑问了。仔细分析，MODBUS-TCP是将MODBUS通讯协议加载到以太网的TCP协议之上的一种通
河南理工大学2011届毕业设计中英文翻译
讯方式，它虽然具有了网络的外形，但依然是一主多从的管理方式，数据表的传输结构。而DCS呢，以网络6000+DCS的ELIN网为例，虽然也是基于工业以太网的，但其应用层协议是欧陆公司积累了近30年的无主令牌LIN网协议，在1M的OLIN，2.5M和20M的ARCNET上都有长期成功的应用。ELIN网上，各站平等，不存在主要管理站。而且数据通讯是以模块为单位的结构化数据，数据管理能力非数据表方式可比。
以PID模块为例，其中的基本数据有PV、SP、OP，采用数据表的传输方式，你必须先定义PV、SP、OP的数据地址为01、02、03，其它的站也以数据表的方式接收数据，但是01是什么数据？02是什么数据？必须通过数据定义表才能还原。数据表的管理方式烦琐易错,一个大型系统的上万点数据采用这个方式,平铺在数据表中进行管理，是非常可怕的。而NETWORK6000+DCS以模块为单位的结构化管理，将一个PID作为一个模块进行处理，要访问其PV值，首先访问其模块，以PID.PV的形式来管理。这就将所有平铺的数据，分类归属集中到一个个小盒子中，按模块.分量的方式进行管理，管理的效率大大提高。PLC数据通讯交换的问题，主要源于PLC长期以来做为一个独立装置在发展，没有系统概念；而且主要应用在小型控制系统中，问题暴露得并不明显，所以发展较慢。目前也有一些大型PLC在这个方面有所提高，但是要达到DCS的水平还需要一个相当长的过程。
2．3、组态维护功能
组态维护功能包括逻辑组态、下载修改、运行调试、远程诊断等。
早期，PLC以梯形图为主，DCS以模块功能图为主。经过多年的发展，国际电工委员会通过IEC1131-3标准规定了五种编程语言,目前主流的DCS和PLC都表示符合这个标准，支持其中的几种或全部编程语言。从开发效率和程序可读性来考虑，模块功能图和顺序功能图越来越成为主要的编程方式，梯形逻辑和结构化文本成为了自定义模块的开发工具。大型PLC在组态方式上越来越像DCS，差距在逐渐缩小，而小型PLC仍然以梯形图为主。
DCS经过多年的发展，积累了大量的高级算法模块。例如NETWORK6000+具有的设备级模块，在一个模块中集中完成了面向设备的基本控制和故障报警功
河南理工大学2011届毕业设计中英文翻译
能，在网络通讯中也已此模块为单位进行传递，大大提高了软件开发的效率。一个设备极模块相当于0.5K的梯形图逻辑量，PLC要完成同样的功能，就要烦琐得多了。
在下载修改、运行调试、远程诊断方面，PLC缺乏解决方案。而DCS从一设计之初就是从系统需要的角度出发的，有着多年积累的完善的解决方案。以NETWORK6000+DCS为例，系统既可以在线修改控制策略，也可以在线下载控制策略，修改和下载过程中，对系统的正常运行没有影响。NETWORK6000+DCS有完善的虚拟DCS功能，不但可以用于组态逻辑的验证，而且能够构建成完整的虚拟DCS与模型相连，完成系统的仿真调试。NETWORK6000+DCS具有完善的安全措施，提供基于广域网的远程调试方案。
2．4、硬件封装结构
PLC一般为大底版式机架，封闭式I/O模件，封闭式结构有利与提高I/O模件的可靠性，抗射频、抗静电、抗损伤。PLC模件的I/O点数有8点、16点、32点。
DCS大部分为19英寸标准机箱加插件式I/O模件，I/O模件为裸露式结构。每个模件的I/O点数有8点和16点，很少使用32点模件。
DCS的这种结构源于其使用领域主要在大型控制对象，19英寸标准机箱便于密集布置，较少的I/O点数则是由于对分散度的要求。PLC的大底版式机架，封闭式模件结构在管理和配置上更加灵活，单个设备的可靠性更高。因此，不少DCS也吸收了PLC在结构上的优点，采用了和PLC相似的封装结构，如I/A采用金属外壳，NETWORK-6000+采用导电塑料外壳。
2．5、人机交互装置
在早期，DCS作为一个系统，其人机交互装置是DCS厂家提供的专用装置。而PLC厂家一般不提供人机交互装置，往往由工程商自主采用通用的监控软件来完成(如ifix、intouch、组态王)。DCS集成的人机交互装置往往有着功能较专业、稳定性较好的特点，但是其价格也很高。随着PC技术的快速发展，一些通用监控软件发展很快，功能和性能逐渐超过了DCS厂家提供的专用装置。因此不少DCS厂家逐步放弃了专用的人机交互装置，转而和PLC一样也使用了通
河南理工大学2011届毕业设计中英文翻译
用的监控软件。DCS厂家使用通用监控软件并不是简单地拼装，而是在通用监控软件的基础上，通过合作开发，将自已多年积累的网络通讯技术、系统自诊断技术以专用软件包的形式保留和继承下来了。
例如，NETWORK-6000+早期曾经使用过基于专用操作系统的T1000人机交互系统，而目前主要使用基于FIX/IFIX或INTOUCH的T3500人机交互系统。其中的LINPOLL网络通讯包是由欧陆公司开发集成的。
3、DCS和PLC的市场情况和发展方向
在热工自动化领域，主厂房控制系统基本上毫无例外地使用DCS。而在辅助车间才使用PLC。其主要原因是早期的DCS系统非常昂贵，人们认为辅助车间的运行可以间断，可靠性要求不是很高，且模拟量控制要求较少，从降低成本的角度出发，往往选择PLC来构建控制系统。而锅炉、汽机和发电机的控制系统，要求长期稳定可靠地运行，信号中含有相当比例的模拟量，从系统的性能出发，人们不得不选择了昂贵的DCS。
另外，分析一下主厂房DCS和辅助车间控制系统的市场竞争情况，我们会发现一个有趣的现象。主厂房DCS的竞争往往在不同品牌的供应商或代理商之间展开，竞争激烈,DCS的价格不断下调。而辅助车间控制系统的竞争往往在同一品牌PLC的各个工程商之间进行，门槛较低，竞争更加激烈，但是PLC的价格下调幅度却并不如DCS明显。主要原因是DCS的生产商直接参与竞争，在巨大的市场压力下，不断下调设备制造费用和工程实施费用。而PLC的生产商不直接参与竞争，各个工程商只能下调自身有限的工程费用，空间有限。从现在情况看来，DCS与高档PLC的价格差距已不明显，辅助车间仍然较多地采用PLC，是市场的惯性使然。
随着国内电厂装机容量的不断扩大及电力系统改革的推进，对辅助车间控制的要求也不断提高，在这个大环境，DCS系统进入辅助车间控制已成为趋势。NETWORK6000+DCS因其综合的技术经济优势，已经并将继续在辅助车间控制方面发挥越来越大的作用。在辅助车间应用广泛的PLC也并不会就此退出热工自动化的历史舞台，前所未有的竞争压力，将会促使PLC厂商在技术上向DCS标准靠拢，在价格上作出更大的努力。市场竞争的结果，将使用户获获得更大的利
河南理工大学2011届毕业设计中英文翻译
益。
4、结论
DCS和PLC作为计算机技术和控制技术结合的产物，为火电厂热工自动化水平的提高都作出了各自的贡献。由于两者在应用上有较大的相通性，在不同的时期，其各自的技术或价格优势，都会直接影响到其市场地位。而市场的反应也会或快或慢地反映到各自的技术发展和价格调整上。从总的趋势来看，DCS和PLC在技术上的融合和促进将会是竞争的主流，而在性价比方面，你来我往地不断攀升，也将是发展的主旋律。
