数字阀门的PLC控制【优秀毕业设计答辩论文】

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关键词：: 数字阀门 plc 控制节制

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　　　一、题目及专题：
　　　1、题目　　基于PLC的数字阀门的控制　　
　　　2、专题　　
　　　二、课题来源及选题依据
随着科技的越来越发展，在机械类方面越来越向自动化方面靠拢，各种各种各样的技术如雨后春笋般冒出，而PLC就应运而生。就全世界自动化市场的过去、现在和可以预见的未来而言，PLC仍然处于一种核心地位。由此可见PLC的重要性，以及对其研究意义的肯定。
PLC是一种专门在工业环境下应用而设计的数字运算操作的电子装置。它采用可以编制程序的存储器，用来在其内部存储执行逻辑运算、顺序运算、计时、计数和算术运算等操作的指令，并能通过数字式或模拟式的输入和输出，控制各种类型的机械或生产过程。PLC及其有关的外围设备都应按照易于与工业控制系统形成一个整体，易于扩展其功能的原则而设计。目前，PLC在国内外已广泛应用于钢铁、石油、化工、电力、建材、机械制造、汽车、轻纺、交通运输、环保及文化娱乐等各个行业。
　　　
　　　三、本设计（论文或其他）应达到的要求：
　　　① 通过毕业设计培养学生综合运用所学的基础理论、基础知识、基本技能进行分析和解决实际问题的能力；
　　　②学会使用PLC系统开发的综合训练，达到能够进行PLC系统设计和实施的目的；
　　　③ 熟练掌握步进电机的工作方式及其电路分析；
　　　④ 掌握PLC的工作原理及其基本构造；
　　　⑤ 能够熟练编制梯形图编制；
　　　⑥ 熟练使用西门子S7系列提供的step7工具。
　　
摘要
　　　我们在各种场合看到了继电接触器控制，那个时代已经过去了，如今的继电器只能作为低端的基层控制模块或者简单的设备中使用，而PLC的出现也就成了划时代的主题，通过比较稳定的硬件和灵活的软件控制使得自动化走向了新的高潮。尤其是如今的互联网大潮下，可编程控制器和其它工业控制计算机组网构成大型的控制系统是可编程控制器技术的发展方向。目前的计算机集散控制系统DCS（Distributed Control System）。中已有大量的可编程控制器应用。伴随着计算机网络的发展，可编程控制器作为自动化控制网络和国际通用网络的重要组成部分，将在工业及工业以外的众多领域发挥越来越大的作用。本次毕业设计通过西门子S7-200（CPU　221）型PLC控制步进电机完成对阀门系统控制。根据数字阀门系统的电磁阀的动作要求和技术参数确定PLC的输入口和输出口的分配以及电气元件的选型，主电路和控制电路的设计。根据输入输出口和电磁阀的动作表利用西门子S7-200编译器V4.0 STEP 7 MicroWIN设计出控制系统主程序，自动运行和手动运行两个子程序的梯形图。最后根据控制系统的组成完成系统走线图和电气柜设计。
　　　
关键字：西门子PLC ；步进电机；STEP 7；梯形图
　　　
　　　
　　　
　　　　ABSTRACT
　　We saw the relay contactor control on various occasions. The time has passed, the relay can only use today as a low-end of the primary control module or a simple device. And the emergence of PLC has become the epoch theme, through a comparative stable hardware and flexible software control automation to a new climax. Especially in today's Internet tide, programmable controller and other industrial control computer network composed of large control system is the development direction of the programmable controller technology. DCS computer control system at present (Distributed Control System). Application of programmable controller in the already large number of. Along with the development of computer network, the programmable controller is an important part of automation and control network and international network, will be many outside the industry and industry play a more and more important role. The graduation design through the Siemens S7-200 (CPU 221) PLC to control the stepper motor to complete the valve control system. To determine the distribution of PLC input port and the output port and the selection of electrical components according to the movement requirements of digital valve solenoid valve system design and technical parameters, main circuit and control circuit. According to the input and output port and the electromagnetic valve action table by Siemens S7-200 compiler V4.0 STEP 7 MicroWIN to design the main program control system, ladder diagram of automatic and manual operation two subroutine. Finally, according to the control system to complete the system wiring diagram and electrical cabinet design.
　　　
Keywords: Siemens PLC; step motor; STEP 7; ladder diagram
　　　　　
　　　
目录
摘要 III
ABSTRACT IV
　　1绪论 1
　　　1.1 数字阀门的PLC控制研究内容和意义 1
　　　1.1.1 背景介绍 1
　　　1.1.2 研究内容和意义 1
　　1.2 国内外发展概况 1
　　　1.2.2 国外发展 2
　　　1.2.1 国内发展 3
　　　1.2.3 本课题应达到的要求 4
2数字阀门PLC控制的元件选择及其特点 5
　　2.1普通阀门电动装置的结构与功能特点 5
　　2.2 PLC阀门控制器总体设计方案 6
　　　2.2.1 调节型阀门控制器设计要求 6
　　　2.2.2 调节型阀门控制器功能分析 7
　　　2.2.3 PLC阀门控制器基本原理 7
　　2.3调节型阀门控制器中央处理单元 10
　　　2.3.1 PLC控制器的选择 10
　　　2.3.2 S7-200的优点 10
　　　2.3.3 硬件系统 11
　　　2.3.4 软元件 12
　　2.4步进电机的特点及其选择 12
　　　2.4.1 步进电机的特点 12
　　　2.4.2 步进电机的分类 13
　　　2.4.3 步进电机的选择 13
3 PLC步进电机工作方式的控制 15
　　3.1 常见的步进电机的工作方式 15
　　　3.1.1 常见的步进电机的工作方式有以下三种： 15
　　3.2 步进电机控制原理 16
　　　3.2.1 控制步进电机换向顺序 16
　　　3.2.2 控制步进电机的转向 16
　　　3.2.3 控制步进电机的速度 16
　　3.3 PLC控制步进电机的方法 16
　　　3.4 PLC控制步进电机的设计思路 17
　　　3.4.1 步进电机控制方式 17
　　　3.4.2 西门子PLC控制步进电机 19
　　　3.5 步进电机驱动电路设计 19
　　　3.5.1驱动器的选择 19
　　3.6控制原理和接线图 20
4 S7-200控制步进电机软件设计 21
　　4.1 STEP 7概述 21
　　　4.1.1 STEP 7的硬件接口 21
　　　4.1.2 STEP 7的编程功能 21
　　　4.1.3 STEP 7的诊断功能与硬件组态 22
　　4.2 程序的编写 22
　　4.3电机正反转接线图 24
　　4.4 梯形图程序设计 25
　　　4.4.1 CPU的选择 25
　　　4.4.3 PLC控制电机正反转I/O分配及硬件接线 25
　　　4.4.3 状态真值表 26
　　4.5 梯形图程序 26
5 总结 34
　　5.1 全文总结 34
　　5.2 不足之处及展望 34
致谢 35
参考文献 36
　　　
　　　
　　　
　　　
　

1绪论
1.1 数字阀门的PLC控制研究内容和意义
　　1.1.1 背景介绍
　　　可编程控制器ProgrammableController是计算机家族中的一员是为工业控制应用而设计制造的。早期的可编程控制器称作可编程逻辑控制器（ProgrammableLogicController）简称PLC，它主要用来代替继电器实现逻辑控制。随着技术的发展，这种装置的功能已经大大超过了逻辑控制的范围，因此，今天这种装置称作可编程控制器，简称PC。
　　　但是为了避免与个人计算机（PersonalComputer）的简称混淆，所以将可编程控制器简称PLC。
　　1.1.2 研究内容和意义
　　　本课题是在充分了解国内外调节型阀门电动执行机构技术现状和发展趋势的基础上，认真研究了其优点和不足之处，并结合国内用户的需求及应用环境而提出的。在国内现有的同类产品基础上，将单片机技术、电子技术、传感器技术应用在电动执行器中，开发了集执行机构、驱动单元、调节控制单元、现场显示仪表等为一体的机、电、仪一体化的调节型执行器。以西门子S7-200为中心对阀门电动执行装置进行控制。通过开关式控制机构在行程到位、过转矩或故障发生时直接切断该机构在电气控制回路中的对应常闭触点来断开电机电源的方式。由电机来带动阀门的开闭及整个过程。
　　　本课题由故障检测和开度控制两部分组成，故障检测包括相序检测及自动调整环节、断相检测环节、电机过热检测环节及极限位置检测等，开度控制包括控制电机正反转环节和开度显示环节等，主要功能包括本地控制和远程控制两个方面，本地控制使用旋钮控制电动执行器开度，远程控制使用4-20mA标准信号控制执行器开度，输出需要显示电机开度，同时使用指示灯显示电机状态。
　　　通过传感器实现行程和转矩控制机构实时采集行程和转矩信息并以电信号的形式传至西门子S7-200并分析处理，西门子S7-200根据处理结果实时刷新开度指示模块的开度显示，并通过电机驱动模块控制电机的正转、反转和停止；状态检测模块在系统上电后即对电机电源的相序正反、是否缺相、电机温度过热等状态实时监控，异常时向西门子S7-200发出相应的故障信号，西门子S7-200及时做出故障处理（如通过电机驱动模块使电机停止等），并通过开度指示模块显示故障报警信息。
1.2 国内外发展概况
　　　执行器是工业自动化系统中的执行单元，也是自动化系统中最重要的组成部分之一，电动执行器一般是以电动机作为动力源的阀门电动装置,其作用是将控制信号转换成相应的动作来控制阀内截流件的位置或其它调节装置。
　　1.2.2 国外发展
自1929年LIMITORQUE公司制造出了世界上第一台电动执行机构以来，国际上电动执行器技术水平发展迅速。20世纪80年代起，国外相继推出了符合各种现场总线标准的调节型执行器，在工业现场取得了较好的应用效果。由于高新技术的迅猛发展，目前国外己开发出新一代调节型化电动执行机构产品，电子计算机技术、微机控制技术己在阀门设计中得到广泛应用。这些调节型化电动执行器功能强大、简单可

内容简介：: 编号无锡太湖学院毕业设计（论文）相关资料题目：数字阀门的PLC控制信机系机械工程及自动化专业学号： 0923125 学生姓名：施赛峰指导教师：陈浩（职称：高工）（职称：）2012年5月25日目录一、毕业设计（论文）开题报告二、毕业设计（论文）外文资料翻译及原文三、学生“毕业论文（论文）计划、进度、检查及落实表”四、实习鉴定表无锡太湖学院毕业设计（论文）开题报告题目：数字阀门的PLC控制信机系机械工程及自动化专业学号： 0923125 学生姓名：施赛峰指导教师：陈浩（职称：高工）（职称：）2013年5月25日课题来源数字阀门的PLC控制科学依据（包括课题的科学意义；国内外研究概况、水平和发展趋势；应用前景等）（1）课题科学意义PLC是一种专门在工业环境下应用而设计的数字运算操作的电子装置。它采用可以编制程序的存储器，用来在其内部存储执行逻辑运算、顺序运算、计时、计数和算术运算等操作的指令，并能通过数字式或模拟式的输入和输出，控制各种类型的机械或生产过程。PLC及其有关的外围设备都应按照易于与工业控制系统形成一个整体，易于扩展其功能的原则而设计。目前，PLC在国内外已广泛应用于钢铁、石油、化工、电力、建材、机械制造、汽车、轻纺、交通运输、环保及文化娱乐等各个行业。（2）PLC现状与发展前景经过30多年的发展，PLC已十分成熟与完善，在国内外已广泛应用于钢铁、石油、化工、电力、建材、机械制造、汽车、轻纺、交通运输、环保及文化娱乐等各个行业。随着技术的发展，PLC的抗干扰能力将越来越强。PLC是专为工业生产自动化控制设计的，一般而言，无须任何保护措施就可以直接在工业环境中使用。然而，当生产环境过于恶劣，电磁干扰特别强烈，或安装使用不当，就可能造成程序错误或运算错误，从而产生误输入并引起误输出，这将会造成设备的失控和误动作，从而不能保证PLC的正常运行。因此，PLC控制系统可靠性将伴随PLC的抗干扰能力的增强而提高，未来PLC的抗干扰性会大大提高。另外，PLC的应用会朝网络化、数字化的趋势发展。PLC具有许多优越性能，如下：系统构成灵活，扩展容易使用方便编程简单，采用简明的梯形图、逻辑图或语句表等编程语言能适应各种恶劣的运行环境，抗干扰能力强，可靠性强，远高于其他各种机型研究内容通过毕业设计培养学生综合运用所学的基础理论、基础知识、基本技能进行分析和解决实际问题的能力；学会使用PLC系统开发的综合训练，达到能够进行PLC系统设计和实施的目的；熟练掌握步进电机的工作方式及其电路分析；掌握PLC的工作原理及其基本构造；能够熟练编制梯形图编制；熟练使用西门子S7系列提供的step7工具。拟采取的研究方法、技术路线、实验方案及可行性分析（1）实验方案研究分析各种PLC的接线方案来控制步进电机来找到最经济最合适的方案（2）研究方法作出几种电路分析，比较其优劣势。画出梯形图用仿真软件试运行研究计划及预期成果研究计划：2012年10月12日-2012年12月25日：按照任务书要求查阅论文相关参考资料，填写毕业设计开题报告书。2013年1月11日-2013年3月5日：填写毕业实习报告。2013年3月8日-2013年3月14日：按照要求修改毕业设计开题报告。2013年3月15日-2013年3月21日：学习并翻译一篇与毕业设计相关的英文材料。20103年3月22日-2013年4月11日：电路图设计。2013年4月12日-2013年4月25日：梯形图设计。2013年4月26日-2013年5月21日：毕业论文撰写和修改工作。预期成果：设计出PLC阀门控制系统特色或创新之处使用step7话梯形图，效果明显，简单易懂，易于判断。采用固定某些参量、改变某些参量来研究问题的方法，思路清晰，简洁明了，行之有效。已具备的条件和尚需解决的问题实验方案思路已经非常明确，已经具备使用PLC编程仿真的能力和图像处理方面的知识。使用STEP编程的能力尚需加强。指导教师意见指导教师签名：年月日教研室（学科组、研究所）意见教研室主任签名：年月日系意见主管领导签名：年月日英文原文PLC technique discussion and future developmentAlong with the development of the ages, the technique that is nowadays is also gradually perfect, the competition plays more strong; the operation that list depends the artificial has already cant satisfied with the current manufacturing industry foreground, also cant guarantee the request of the higher quantity and high new the image of the technique business enterprise.The people see in produce practice, automate brought the tremendous convenience and the product quantities for people up of assurance, also eased the personnels labor strength, reduce the establishment on the personnel. The target control of the hard realization in many complicated production lines, whole and excellent turn, the best decision etc., well-trained operation work, technical personnel or expert, governor but can judge and operate easily, can acquire the satisfied result. The research target of the artificial intelligence makes use of the calculator exactly to carry out, imitate these intelligences behavior, moderating the work through persons brain and calculators, with the mode that persons machine combine, for resolve the very complicated problem to look for the best pathWe come in sight of the control that links after the electric appliances in various situation, that is already the that time generation past, now of after use in the mold a perhaps simple equipments of grass-roots control that the electric appliances can do for the low level only; And the PLC emergence also became the epoch-making topic, adding the vivid software control through a very and stable hardware, making the automation head for the new high tide.The PLC biggest characteristics lie in: The electrical engineering teacher already no longer electric hardware up too many calculations of cost, as long as order the importation that the button switch or the importation of the sensors order to link the PLC up can solve problem, pass to output to order the conjunction contact machine or control the start equipments of the big power after the electric appliances, but the exportation equipments direct conjunction of the small power can.PLC internal containment have the CPU of the CPU, and take to have an I/ O for expand of exterior to connect a peoples address and saving machine three big pieces to constitute, CPU core is from an or many is tired to add the machine to constitute, mathematics that they have the logic operation ability, and can read the procedure save the contents of the machine to drive the homologous saving machine and I/ Os to connect after pass the calculation; The I/ O add inner part is tired the input and output system of the machine and exterior link, and deposit the related data into the procedure saving machine or data saving machine; The saving machine can deposit the data that the I/ O input in the saving machine, and in work adjusting to become tired to add the machine and I/ Os to connect, saving machine separately saving machine RAM of the procedure saving machine ROM and dates, the ROM can do deposit of the data permanence in the saving machine, but RAM only for the CPU computes the temporary calculation usage of hour of buffer space.The PLC anti- interference is very and excellent, our root need not concern its service life and the work situation bad, these all problems have already no longer become the topic that we fail, but stay to our is a concern to come to internal resources of make use of the PLC to strengthen the control ability of the equipments for us, make our equipments more gentle.PLC language is not we imagine of edit collected materials the language or language of Cs to carry on weaving the distance, but the trapezoid diagram that the adoption is original after the electric appliances to control, make the electrical engineering teacher while weaving to write the procedure very easy comprehended the PLC language, and a lot of non- electricity professional also very quickly know and go deep into to the PLC.Is PLC one of the advantage above and only, this is also one part that the people comprehend more and easily, in a lot of equipments, the people have already no longer hoped to see too many control buttons, they damage not only and easily and produce the artificial error easiest, small is not a main error perhaps you can still accept; But lead even is a fatal error greatly is what we cant is tolerant of. New technique always for bringing more safe and convenient operation for us, make we a lot of problems for face on sweep but light, do you understand the HMI? Says the HMI here you basically not clear what it is, also have no interest understanding, change one inside text explains it into the touch to hold or man-machine interface you knew, and it combines with the PLC to our larger space.HMI the control not only is reduced the control press button, increase the vivid of the control, more main of it is can sequence of, and at can the change data input to output the feedback with data, control in the temperature curve of imitate but also can keep the manifestation of view to come out. And can write the function help procedure through a plait to provide the help of various what lies in ones power, the one who make operate reduces the otiose error. Currently the HMI factory is also more and more, the function is also more and more strong, the price is also more and more low, and the noodles of the usage are wide more and more. The HMI foreground can say that think to be good very.At a lot of situations, the list is a smooth movement that cant guarantee the equipments by the control of the single machine, but pass the information exchanges of the equipments and equipments to attain the result that we want. For example fore pack and the examination of the empress work preface, we will arrive wrapping information feedback to examine the place, and examine the information of the place to also want the feedback to packing. Pass the information share thus to make both the chain connect, becoming a total body, the match of your that thus make is more close, at each other attain to reflect the result that mutually flick.The PLC correspondence has already come more body now its value, at the PLC and correspondence between PLCs, can pass the communication of the information and the share of the dates to guarantee that of the equipments moderates mutually, the result that arrive already to repair with each other. Data conversion the adoption RS232 between PLC connect to come to the transmission data, but the RS232 pick up a people and can guarantee 10 meters only of deliver the distance, if in the distance of 1000 meters we can pass the RS485 to carry on the correspondence, the longer distance can pass the MODEL only to carry on deliver.The PLC data transmission is just to be called a form to it in a piece of and continuous address that the data of the inner part delivers the other party, we, the PLC of the other party passes to read data in the watch to carry on the operation. If the data that data in the watch is a to establish generally, that is just the general data transmission, for example today of oil price rise, I want to deliver the price of the oil price to lose the oil ally on board, that is the share of the data; But take data in the watch for an instruction procedure that controls the PLC, that had the difficulty very much, for example you have to control one pedestal robot to press the action work that you imagine, you will draw up for it the form that a procedure combine with the data sends out to pass by.The form that information transport contain single work, the half a work and the difference of a workers .The meaning of the single work also is to say both, a can send out only, but a can receive only, for example a spy he can receive the designation of the superior only, but cant give the superior reply; A work of half is also 2 and can send out similar to accept the data, but cant send out and accept at the same time, for example when you make a phone call is to cant answer the phone, the other party also; But whole pair works is both can send out and accept the data, and can send out and accept at the same time. Be like the Internet is a typical example.The process that information transport also has synchronous and different step cent: The data line and the clock lines are synchronous when synchronous meaning lie in sending out the data, is also the data signal and the clock signals to be carry on by the CPU to send out at the same time, this needs to all want the specialized clock signal each other to carry on the transmission and connect to send, and is constrained, the characteristics of this kind of method lies in its speed very quick, but correspond work time of take up the CPU and also want to be long oppositely, at the same time the technique difficulty also very big. Its request lies in canting have an error margins in a dates deliver, otherwise the whole piece according to compare the occurrence mistake, this on the hardware is a bigger difficulty. Applied more and more extensive in some appropriative equipments, be like the appropriative medical treatment equipments, the numerical signal equipments.etc., in compare the one data deliver, its result is very good.And the different step is an application the most extensive, this receive benefit in it of technique difficulty is opposite and want to be small, at the same time not need to prepare the specialized clock signal, its characteristics to lie in, its data is partition, the long-lost send out and accept, be the CPU is too busy of time can grind to a stop sex to work, also reduced the difficulty on the hardware, the data throw to lose at the same time opposite want to be little, we can pass the examination of the data to observe whether the data that we send out has the mistake or not, be like strange accidentally the method, tired addition and eight efficacies method etc., can use to helps whether the data that we examine to send out have or not the mistake occurrence, pass the feedback to carry on the discriminator.A line of transmission of the information contains a string of and combine the cent of: The usual PLC is 8 machines, certainly also having 16 machines. We can be an at the time of sending out the data a send out to the other party, also can be 88 send out the data to the other party, an and 8 differentiations are also the as that we say to send out the data and combine sends out the data. A speed is more and slowly, but as long as 2 or three lines can solve problem, and can use the telephone line to carry on the long range control. But combine the ocular transmission speed is very quick of, it is a string of ocular of 25600%, occupy the advantage in the short distance, the in view of the fact TTL electricity is even, being limited by the scope of one meter generally, it combine unwell used for the data transmission of the long pull, thus the cost is too expensive.Under a lot of circumstances we are total to like to adopt the string to combine the conversion chip to carry on deliver, under this kind of circumstance not need us to carry on to deposited the machine to establish too and complicatedly, but carry on the data exchanges through the data transmission instruction directly, but is not a very viable way in the correspondence, because the PLC of the other party must has been wait for your data exportation at the time of sending out the data, it cant do other works.When you are reading the book, you hear someone knock on door, you stop to start up of affair, open the door and combine to continue with the one who knock on door a dialogue, the telephone of this time rang, you signal hint to connect a telephone, after connecting the telephone through, return overdo come together knock on door to have a conversation, after dialogue complete, you continue again to see your book, this kind of circumstance we are called the interruption to it, it has the authority, also having sex of have the initiative, the PLC had such function .Its characteristics lie in us and may meet the urgently abrupt affairs in the operation process of the equipments, we want to stop to start immediately up of work, the whereabouts manages the more important affair, this kind of circumstance is we usually meet of, PLC while carry out urgent mission, total will keep the current appearance first, for example the address of the procedure, CPU of tired add the machine data etc., be like to stick down which the book that we see is when we open the door the page or simply make a mark, because we treat and would still need to continue immediately after book of see the behind. The CPU always does the affair that should do according to our will, but your mistake of give it an affair, it also would be same to do, this we must notice.The interruption is not only a, sometimes existing jointly with the hour several inside break, break off to have the preferred Class, they will carry out the interruption of the higher Class according to persons request. This kind of breaks off the medium interruption to also became to break off the set. The Class that certainly break off is relevant according to various resources of CPU with internal PLC, also following a heap of capacity size of also relevant fasten.The contents that break off has a lot of kinds, for example the exterior break off, correspondence in of send out and accept the interruption and settle and the clock that count break off, still have the WDT to reset the interruption etc., they enriched the CPU to respond to the category while handle various business. Speak thus perhaps you cant comprehend the internal structure and operation orders of the interruption completely also, we do a very small example to explain.Each equipment always will not forget a button, it also is at we meet the urgent circumstance use of, which is nasty to stop the button. When we meet the Human body trouble and surprised circumstances we as long as press it, the machine stops all operations immediately, and wait for processing the over surprised empress recover the operation again. Nasty stop the internal I/ O of the internal CPU of the button conjunction PLC to connect up, be to press button an exterior to trigger signal for CPU, the CPU carries on to the I/ O to examine again, being to confirm to have the exterior to trigger the signal, CPU protection the spot breaks off procedure counts the machine turn the homologous exterior I/ O automatically in the procedure to go to also, be exterior interruption procedure processing complete, the procedure counts the machine to return the main procedure to continue to work. Have 1:00 can what to explain is we generally would nasty stop the button of exterior break off to rise to the tallest Class, thus guarantee the safety.When we are work a work piece, giving the PLC a signal, counting PLC inner part the machine add 1 to compute us for a day of workload, a count the machine and can solve problem in brief, certainly they also can keep the data under the condition of dropping the electricity, urging the data not to throw to lose, this is also what we hope earnestly.The PLC still has the function that the high class counts the machine, being us while accept some dates of high speed, the high speed that here say is the data of the in all aspects tiny second class, for example the bar code scanner is scanning the data continuously, calculating high-speed signal of the data processor DSP etc., we will adopt the high class to count the machine to help we carry on count. It at the PLC carries out the procedure once discover that the high class counts the machine to should of interruption, will let go of the work on the hand immediately. The trapezoid diagram procedure that passes by to weave the distance again explains the high class for us to carry out procedure to count machine would automatic performance to should of work, thus rise the Class that the high class counts the machine to high one Class.You heard too many this phrases perhaps: crash, the meaning that is mostly is a workload of CPU to lead greatly, the internal resources shortage etc. the circumstance cant result in procedure circulate. The PLC also has the similar circumstance, there is a watchdog WDT in the inner part of PLC, we can establish time that a procedure of WDT circulate, being to appear the procedure to jump to turn the mistake in the procedure movement process or the procedure is busy, movement time of the procedure exceeds WDT constitution time, the CPU turn but the WDT reset the appearance. The procedure restarts the movement, but will not carry on the breakage to the interruption.The PLC development has already entered for network ages of correspondence from the mode of the one, and together other works control the net plank and I/ O card planks to carry on the share easily. A state software can pass all se hardwires link, more animation picture of keep the view to carries on the control, and cans pass the Internet to carry on the control in the foreign land, the blast-off that is like the absolute being boat No.5 is to adopt this kind of way to make airship go up the sky.The development of the higher layer needs our continuous effort to obtain. The PLC emergence has already affected a few persons fully, we also obtained more knowledge and precepts from the top one experience of the generation, coming to the continuous development PLC technique, push it toward higher wave tide.Knowing the available PLC network options and their best applications will ensure an efficient and flexible control system design.The programmable logic controllers (PLCs) ability to support a range of communication methods makes it an ideal control and data acquisition device for a wide variety of industrial automation and facility control applications. However, there is some confusion because so many possibilities exist. To help eliminate this confusion, lets list what communications are available and when they would be best applied.To understand the PLCs communications versatility, lets first define the terms used in describing the various systems.ASCII: This stands for American Standard Code for Information Interchange. As shown in Fig. 1, when the letter A is transmitted, for instance, its automatically coded as 65 by the sending equipment. The receiving equipment translates the 65 back to the letter A. Thus, different devices can communicate with each other as long as both use ASCII code.ASCII module: This intelligent PLC module is used for connecting PLCs to other devices also capable of communicating using ASCII code as a vehicle.Bus topology: This is a linear local area network (LAN) arrangement, as shown in Fig. 2A, in which individual nodes are tapped into a main communications cable at a single point and broadcast messages. These messages travel in both directions on the bus from the point of connection until they are dissipated by terminators at each end of the bus.CPU: This stands for central processing unit, which actually is that part of a computer, PLC, or other intelligent device where arithmetic and logical operations are performed and instructions are decoded and executed.Daisy chain: This is a description of the connection of individual devices in a PLC network, where, as shown in Fig. 3, each device is connected to the next and communications signals pass from one unit to the next in a sequential fashion.Distributed control: This is an automation concept in which portions of an automated system are controlled by separate controllers, which are located in close proximity to their area of direct control (control is decentralized and spread out over the system).Host computer: This is a computer thats used to transfer data to, or receive data from, a PLC in a PLC/computer network.Intelligent device: This term describes any device equipped with its own CPU.I/O: This stands for inputs and outputs, which are modules that handle data to the PLC (inputs) or signals from the PLC (outputs) to an external device.Kbps: This stands for thousand bits per second, which is a rate of measure for electronic data transfer.Mbps: This stands for million bits per second.Node: This term is applied to any one of the positions or stations in a network. Each node incorporates a device that can communicate with all other devices on the network.Protocol: The definition of how data is arranged and coded for transmission on a network.Ring topology. This is a LAN arrangement, as shown in Fig. 2C, in which each node is connected to two other nodes, resulting in a continuous, closed, circular path or loop for messages to circulate, usually in one direction. Some ring topologies have a special loop back feature that allows them to continue functioning even if the main cable is severed.RS232. This is an IEEE standard for serial communications that describes specific wiring connections, voltage levels, and other operating parameters for electronic data communications. There also are several other RS standards defined.Serial: This is an electronic data transfer scheme in which information is transmitted one bit at a time.Serial port: This the communications access point on a device that is set up for serial communications.Star topology. This is a LAN arrangement in which, as shown in Fig. 2B, nodes are connected to one another through a central hub, which can be active or passive. An active hub performs network duties such as message routing and maintenance. A passive central hub simply passes the message along to all the nodes connected to it.Topology: This relates to a specific arrangement of nodes in a LAN in relation to one another.Transparent: This term describes automatic events or processes built into a system that require no special programming or prompting from an operator.Now that were familiar with these terms, lets see how they are used in describing the available PLC network options.PLC network optionsPLC networks provide you with a variety of networking options to meet specific control and communications requirements. Typical options include remote I/O, peer-to-peer, and host computer communications, as well as LANs. These networks can provide reliable and cost-effective communications between as few as two or as many as several hundred PLCs, computers, and other intelligent devices.Many PLC vendors offer proprietary networking systems that are unique and will not communicate with another make of PLC. This is because of the different communications protocols, command sequences, error-checking schemes, and communications media used by each manufacturer.However, it is possible to make different PLCs talk to one another; whats required is an ASCII interface for the connection(s), along with considerable work with software.Remote I/0 systemsA remote I/O configuration, as shown in Fig. 4A, has the actual inputs and outputs at some distance from the controller and CPU. This type of system, which can be described as a master-and-slave configuration, allows many distant digital and analog points to be controlled by a single PLC. Typically, remote I/Os are connected to the CPU via twisted pair or fiber optic cables.Remote I/O configurations can be extremely cost-effective control solutions where only a few I/O points are needed in widely separated areas. In this situation, its not always necessary, or practical for that matter, to have a controller at each site. Nor is it practical to individually hard wire each I/O point over long distances back to the CPU. For example, remote I/O systems can be used in acquiring data from remote plant or facility locations. Information such as cycle times, counts, duration or events, etc. then can be sent back to the PLC for maintenance and management reporting.In a remote I/O configuration, the master controller polls the slaved I/O for its current I/O status. The remote I/O system responds, and the master PLC then signals the remote I/O to change the state of outputs as dictated by the control program in the PLCs memory. This entire cycle occurs hundreds of times per second.Peer-to-peer networksPeer-to-peer networks, as shown in Fig. 4B, enhance reliability by decentralizing the control functions without sacrificing coordinated control. In this type of network, numerous PLCs are connected to one another in a daisy-chain fashion, and a common memory table is duplicated in the memory of each. In this way, when any PLC writes data to this memory area, the information is automatically transferred to all other PLCs in the network. They then can use this information in their own operating programs.With peer-to-peer networks, each PLC in the network is responsible for its own control site and only needs to be programmed for its own area of responsibility. This aspect of the network significantly reduces programming and debugging complexity; because all communications occur transparently to the user, communications programming is reduced to simple read-and-write statements.In a peer-to-peer system, theres no master PLC. However, its possible to designate one of the PLCs as a master for use as a type of group controller. This PLC then can be used to accept input information from an operator input terminal, for example, sending all the necessary parameters to other PLCs and coordinating the sequencing of various events.Host computer linksPLCs also can be connected with computers or other intelligent devices. In fact, most PLCs, from the small to the very large, can be directly connected to a computer or part of a multi drop host computer network via RS232C or RS422 ports. This combination of computer and controller maximizes the capabilities of the PLC, for control and data acquisition, as well as the computer, for data processing, documentation, and operator interface.In a PLC/computer network, as shown in Fig. 4C, all communications are initiated by the host computer, which is connected to all the PLCs in a daisy-chain fashion. This computer individually addresses each of its networked PLCs and asks for specific information. The addressed PLC then sends this information to the computer for storage and further analysis. This cycle occurs hundreds of times per second.Host computers also can aid in programming PLCs; powerful programming and documentation software is available for program development. Programs then can be written on the computer in relay ladder logic and downloaded into the PLC. In this way, you can create, modify, debug, and monitor PLC programs via a computer terminal.In addition to host computers, PLCs often must interface with other devices, such as operator interface terminals for large security and building management systems. Although many intelligent devices can communicate directly with PLCs via conventional RS232C ports and serial ASCII code, some dont have the software ability to interface with individual PLC models. Instead, they typically send and receive data in fixed formats. Its the PLC programmers responsibility to provide the necessary software interface.The easiest way to provide such an interface to fixed-format intelligent devices is to use an ASCII/BASIC module on the PLC. This module is essentially a small computer that plugs into the bus of the PLC. Equipped with RS232 ports and programmed in BASIC, the module easily can handle ASCII communications with peripheral devices, data acquisition functions, programming sequences, number crunching, report and display generation, and other requirements.Access, protocol, and modulation functions of LANsBy using standard interfaces and protocols, LANs allow a mix of devices (PLCs, PCs, mainframe computers, operator interface terminals, etc.) from many different vendors to communicate with others on the network.Access: A LANs access method prevents the occurrence of more than one message on the network at a time. There are two common access methods.Collision detection is where the nodes listen to the network and transmit only if there are no other messages on the network. If two nodes transmit simultaneously, the collision is detected and both nodes retransmit until their messages get through properly.Token passing allows each node to transmit only if its in possession of a special electronic message called a token. The token is passed from node to node, allowing each an opportunity to transmit without interference. Tokens usually have a time limit to prevent a single node from tying up the token for a long period of time.Protocol: Network protocols define the way messages are arranged and coded for transmission on the LAN. The following are two common types.Proprietary protocols are unique message arrangements and coding developed by a specific vendor for use with that vendors product only.Open protocols are based on industry standards such as TCP/IP or ISO/OSI models and are openly published.Modulation: Network modulation refers to the way messages are encoded for transmission over a cable. The two most common types are broadband and baseband.Network transmission interfacesThe vast majority of PLC communications is done via RS232C and twisted pair cables. Most PLCs have an RS232 port and are capable of handling communications with host computers, printers, terminals, and other devices. Maximum transmission speed is 19.2 Kbps.The distance and data transmission rates are standards for the various interfaces. Their actual performance is a function of the driving devices and varies significantly between manufacturers. As such, you should consult the manufacturers specifications for actual distance and data transmission rate capabilities.The only real limitation on RS232C is the 50-ft recommended distance between devices. While RS232C installations often can achieve cabling distances greater than this, the unbalanced design of the interface results in a greater susceptibility to surrounding electrical noise and reduced data integrity. This is particularly true where electromagnetic interference (EMI) and radio-frequency interference (RFI) are known to exist.When longer transmission distances are needed, RS422 is a better choice. Unlike the RS232C interface, RS422 is balanced. Each of its primary signals consists of two wires that are always at opposite logic levels, with respect to signal ground. As a result, the interface can achieve longer transmission distance (4000 ft) and higher data transmission rates (up to 90 Kbps). In shorter runs (less than 50 ft), data transfer can reach 10 Mbps.Fiber optic communications are gaining greater acceptance and are being used in more and more installations. Fiber optic cable is virtually impervious to harsh environmental conditions and electrical noise. Also, these links can span extremely long distances and transmit data at very high speeds. For example, in some LAN systems, these links can transmit at relatively high speeds and span long distances before requiring a repeater. When repeaters are used, virtually unlimited distances can be achieved.History of PLC:Programmable Logic Controllers (PLC), a computing device invented by Richard E. Morley in 1968, have been widely used in 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 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 superior 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 PLCs per year with the hardware value of more than 8 billion US dollars has been predicted, though the prices of computing hardware 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 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 programming are to eliminate software bugs and to reduce the maintenance costs of old ladder logic programs. Though the hardware costs of PLCs are dropping continuously, reducing the scan time of the ladder logic is still an issue in industry so that low-cost PLCs can be used.In general, the productivity 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 simultaneous 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 addition, 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 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 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, increasing 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.Now of PLC，From the structure is divided into fixed PLC 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 combination 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. Unit work under the controller command used in a digital or logic operation 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 for PLC, its determines the PLC speed of work, IO PLC number 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 youll 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 operation, 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 forma ladder diagram to a binary form. FLASH memory contents can 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 shortened. 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”in a specific memory bit/ 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 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. Todays transmission computers are ideal for reprogramming a PLC controller in factory itself. This 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 established 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 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 and 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 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 electrical energy to central processing unit. Most PLC controllers work either at 24 VDC or 220 VAC. On some PLC controllers youll 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 how 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 in starting PLC controller inputs because then you can ensure so called “pure” supply for the PLC 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 already incorporated into a PLC.中文译文可编程控制器技术随着时代的发展,当今的技术也日趋完善、竞争愈演愈烈;单靠人工的操作已不能满足于目前的制造业前景,也无法保证更高质量的要求和高新技术企业的形象. 人们在生产实践中看到,自动化给人们带来了极大的便利和产品质量上的保证,同时也减轻了人员的劳动强度,减少了人员上的编制.在许多复杂的生产过程中难以实现的目标控制、整体优化、最佳决策等,熟练的操作工、技术人员或专家、管理者却能够容易判断和操作,可以获得满意的效果.人工智能的研究目标正是利用计算机来实现、模拟这些智能行为,通过人脑与计算机协调工作,以人机结合的模式,为解决十分复杂的问题寻找最佳的途径我们在各种场合看到了继电器连接的控制，那已经是时代的过去，如今的继电器只能作为低端的基层控制模块或者简单的设备中使用到；而PLC的出现也成为了划时代的主题，通过极其稳定的硬件穿插灵活的软件控制，使得自动化走向了新的高潮。PLC的最大特点在于：电气工程师已不再电气的硬件上花费太多的心计，只要将按钮开关或感应器的输入点连接到PLC的输入点上就能解决问题，通过输出点连接接触器或继电器来控制大功率的启动设备，而小功率的输出设备直接连接就可以。PLC的内部包含了具有中央处理器的CPU，并带有外部I/O口扩展的I/O接口地址和存储器三大块组成，CPU的核心是由一个或者多个累加器组成，它们具有逻辑的数学运算能力，并能读取程序存储器的内容通过计算后去驱动相应的存储器和I/O接口；I/O口将内部累加器和外部的输入和输出系统连接起来，并将相关的数据存入程序存储器或者数据存储器中；存储器可以将I/O口输入的数据存入存储器中，并在工作时调转到累加器和I/O接口上，存储器分程序存储器ROM和数据存储器RAM,ROM可以将数据永久的存入存储器中，而RAM只能作为CPU计算时临时计算使用的缓冲空间。PLC的抗干扰是极其优秀的，我们根本不用去关心它的使用寿命和工作场合的恶劣，这些所有的问题已不再成为我们失败的主题，而留给我们的是关心如何来利用PLC的内部资源为我们加强设备的控制能力，使我们的设备更加的柔性。PLC的语言并不是我们所想象的汇编语言或C语言来进行编程，而是采用原有的继电器控制的梯形图，使得电气工程师在编写程序时很容易就理解了PLC的语言，而且很多的非电气专业人士也对PLC很快认识并深入。以上仅仅是PLC的优点之一，这也是人们比较容易理解的一部分，在很多的设备中，人们已不再希望看到太多的控制按钮，它们不但容易损坏而且极易产生人为的失误，小的并不是主要的失误也许你还能够接受；但过大的甚至是致命的失误是我们无法容忍的。新的技术总是为了给我们带来更安全和便捷的操作，使得我们面临的一大堆问题一扫而光，你有了解过HMI吗？这里说HMI你根本不清楚它是什么，也没有兴趣了解，换一个中文把它说明为触摸屏或者人机界面你就知道了，它和PLC的结合给了我们更大的空间。HMI控制不仅仅是减少了控制按钮，增加控制的灵活性，更主要的它是可顺序性的，而且在能够改变数据输入和数据输出反馈，在温度控制曲线的模拟也能直观的显示出来。并且能够通过编写功能帮助程序来提供各种力所能及的帮助，使得操作者减少不必要的失误。HMI的厂商目前也越来越多，功能也越来越强，价格也越来越低，使用的面越来越广。HMI的前景可以说十分的看好。在很多场合，单靠单机的控制是无法保证设备的顺畅运行，而通过设备与设备的信息交流达到我们想要的效果。比如在前包装和后工序的检测，我们就要将包装的信息反馈到检测处，而检测处的信息也要反馈到包装来。这样通过信息共享来使得两者之间链接起来，形成一个共体，从而使的两者间的配合更加的紧密，在彼此间达到映影相挥的效果。PLC的通信已经愈来愈体现它的价值，在PLC与PLC之间的通信，能够通过信息的沟通和数据的共享来保证设备之间的相互协调，已达到互补的效果。PLC之间的数据转换采用RS232接口来传送数据，而RS232接口只能保证10米的传输距离，如果在1000米的距离内我们可以通过RS485来进行通信，更长的距离只能通过MODEL来进行传输。PLC的数据传送只是将内部的数据传送到对方的一块连续的地址中，我们把它称为一个表，对方的PLC通过读取表中的数据来进行操作。如果表中的数据是一个一般设置的数据的话，那只是一般的数据传送，比如今天的油价上升了，我要把油价的价格传送到所有的输油机上，那就是数据的共享；而当表中的数据是一段控制PLC的指令程序，那就很有难度了，比如你要控制一台机器人来按你想象的动作工作，你会给它编制一段程序并以数据的形式发送过去。信息输送的形式有单工位、半双工位和全双工位的分别。单工位的意义也就是说两者之间，一个只能发送，而一个只能接收，比如一个特务他只能接收上司的指示，而无法给上司回复；半双工位也就是两个能都能发送和接受数据，但不能同时发送和接受，比如你打电话时是不能接电话,对方也一样；而全双工位是两者之间都能发送和接受数据，并可同时发送和接受。像互联网就是典型的例子。信息输送的过程也有同步和异步之分：同步的意义在于发送数据时数据线和时钟线是同步的，也就是数据信号和时钟信号同时由CPU进行发送，这需要彼此都要专门的时钟信号来进行传送和接送，并且是强制性的，这种方法的特点在于它的速度极快、但相应占用CPU的工作时间也相对的要长、同时技术难度也非常的大。它的要求在于在一帧的数据传送中不能有一位的误差，不然的话整个数据将发生错误，这在硬件上是一个比较大的难度。在一些专用的设备中应用的越来越广泛，像专用的医疗设备、数字信号设备等，在比较单一数据的传输中，它的效果非常的好。而异步是应用范围最广泛的，这得益于它的技术难度相对要小、同时不需要配制专门的时钟信号、它的特点在于，它的数据是间隔性的，离散性的发送和接受，当CPU太忙的时候可以停顿性去工作，在硬件上也减少了难度，同时数据的丢失相对要少，我们可以通过数据的检测来观察我们发送的数据是否有错误，像奇偶法、累加法和八位效验法等，都可以用来帮助我们检测发送的数据是否有错误发生，通过反馈来进行辨别。信息的传送口线有串口和并口之分：通常的PLC是8位机，当然也有16位机。我们在发送数据的时候可以是一位一位的发送给对方，也可以8位8位的将数据发送到对方，一位和8位区别也就是我们所说的串口发送数据和并口发送数据。串口速度比较慢，但只要两条或者三条口线就能解决问题，并能借用电话线来进行远程控制。而并口的传送速度是极快的，它是串口的256倍，在短距离占有优势，由于是TTL电平，一般限于1米的范围，它并不适用于长距离的数据传送，这样成本太昂贵了。很多的情况下我们总喜欢采用串并转换芯片来进行传输，这种情况下不需要我们进行过于复杂的寄存器设置了，而直接通过数据传送指令进行数据交流，但在通信中并不是一个十分可行的办法，因为在发送数据的时候对方的PLC必须一直等待你的数据输出，它不能去做其他的工作。当你在看书的时候，你听到有人敲门、你停下手上的事情、去打开门、并同敲门者对话、这个时候电话响了、你示意接个电话、在接完电话后、回过头来同敲门者继续对话、对话完毕后、你再继续看你的书，这种情况我们把它称为中断，它具有权威性，也具有优先性，PLC具备了这样的功能。它的特点在于我们在设备的操作过程中可能会遇到紧急的突发事件，我们要立刻的停下手上的工作，去处理更重要的事情，这种情况是我们经常所遇到的，PLC在去执行紧急的任务时，总会先保存目前的状态，比如程序的地址，CPU的累加器数据等，就像我们去开门时要记下我们看的书在第几页了或者干脆作个记号，因为我们待会还要继续接着看后面的书。CPU总是按照我们的意愿去做应该做的事情，但你错误的给它一件事情，它也会同样的去做，这一点我们必须注意。中断并不是只有一个，有时会同时存在几个中断，中断具有优先的级别，他们会根据人的要求去执行更高级别的中断。这种中断中的中断也就形成了中断嵌套。当然中断的级别根据各种PLC内部CPU的资源有关，同时也跟堆栈的容量大小也有关系。中断的内容有很多种，比如外部中断、通信中的发送和接受中断、定时和计数的时钟中断、还有WDT复位中断等，它们丰富了CPU在处理各种事务时响应种类。这样讲也许你并不能完全理解中断的内部结构和操作顺序，我们做一个小小的例子来说明.每一个设备总是不会忘记有一个按钮，它也是在我们遇到紧急情况时使用的，那就是急停按钮。当我们遇到人身事故和意外情况时我们只要按下它，机器立即停止所有的操作，并等待处理完意外后再恢复操作。急停按钮连接PLC内部CPU的内部I/O接口上，当按钮给CPU一个外部触发信号时，CPU对I/O进行再次检测，当确认有外部触发信号时，CPU保护现场并将程序计数器自动转到相应的外部I/O中断程序中去，当外部中断程序处理完毕，程序计数器返回到主程序继续工作。有一点可以说明的是我们一般会把急停按钮的外部中断升至最高级别，从而保证安全。当我们在工作完一个工件时，给PLC一个信号，将PLC的内部计数器加1来计算我们一天的工作量时，一个简单的计数器能解决问题，当然它们也能够在掉电的情况下保持数据，促使数据不丢失，这也是我们所渴望的。PLC还具有高级计数器的功能，当我们在接受一些高速的数据时，这里所说的高速是在在微秒级的数据，比如条码扫描机在不断的扫描数据，数据处理器DSP计算的高速信号等，我们就要采用到高级计数器来帮助我们进行计数。它在PLC执行程序时一旦发现高级计数器对应的中断，就会立即放下手上的工作。经过再次编程的梯形图程序说明我们在执行程序时高级计数器会自动的执行对应的工作，从而将高级计数器的级别升至高一级别。你也许听过太多的这个词:“死机”，大致的意思是CPU工作量过大，内部资源不足等情况造成程序无法运行。PLC也有类似的情况，在PLC内部有一个看门狗WDT，我们可以设置WDT一个程序运行的时间，当程序运行过程中出现程序跳转错误时或者程序繁忙时，程序的运行时间超过WDT的设置时间，CPU转而WDT复位状态。程序重新开始运行，但对中断不会进行破坏。PLC的发展已经从单一的模式进入了通信的网络时代，并同其它的工控网板和I/O卡板轻易的进行共享。组态软件可以将所有的这些硬件连接起来，通过更直观的动画图片来进行控制，并可以通过互联网在异地进行控制，像神舟五号的发射就是采用这种办法来使飞船升空。更高层次的发展需要我们不断的努力来取得。PLC的出现已经足足影响了几代人，我们也从上一辈的经验中获取了更多的知识和教训，来不断的发展PLC技术，将它推向更高浪潮。了解可用的PLC网络的最佳选择，其应用将确保有效率和灵活的控制系统设计。可编程逻辑控制器（PLC的）能够支持多种通信方法的范围，使之成为一个理想的控制和工业自动化和控制应用各种设施数据采集装置。然而，有一些混乱，因为这么多的可能性存在。为了帮助消除这种混乱，让我们的通讯名单，可什么时候他们会是最好的应用。为了了解PLC的通信多功能性，让我们首先定义描述的各种制度的用语：ASCII码：这代表着信息交换。1，当字母“A”是传播，例如，它会自动编码为“65由发送设备”。接收设备转换的“65”回答。因此，不同的设备可以相互通信既是使用ASCII代码的其他长。ASCII的模块：这个智能PLC模块是用于连接到PLC的通信也使用ASCII码作为车辆等设备的能力。总线拓扑结构：这是一个线性局部区域网络（LAN）的安排。 A条，其中个别节点成为窃听通讯电缆主要在单点和广播消息。这些消息对旅游的连接点从两个方向的巴士，直到它们被消耗在每个终端的巴士底。CPU：这代表“中央处理单元”，这其实就是一台计算机，可编程控制器，智能设备或其他地方的算术和逻辑运算的执行和指令被解码和执行的一部分。菊花链：这是对单个设备中的PLC网络，连接描述在那里，每个设备连接到下一个和通信信号从一个单位传递到下一个顺序的方式。分布式控制：这是一个自动化的概念，即一个自动化系统的部分是由单独的控制器，这是在位于其附近地区的直接控制（控制分散控制系统及遍布出）。主机电脑：这是一个被用来转移的PLC /计算机网络的数据，或接收从一个PLC数据的计算机。智能设备：这个术语描述了自己的CPU配备任何设备。I / O：这代表“输入和输出”，这些模块处理数据到PLC（输入），或从PLC（输出信号）至外部设备。Kbps：这代表“千比特每秒”，这是一个衡量的电子数据传输速率。Mbps：这第一个字母。“百万比特每秒”节点：本术语适用于任何立场或在网络电台之一。每个节点包含一个装置，可以与网络上的所有其他设备。议定书：数据的定义是怎样安排的编码和传输网络上。环形拓扑结构：这是一个局域网的安排，其中每个节点连接到两个其他节点，在一个连续的，封闭的，圆形的路径或导致邮件循环流通，通常在一个方向。有些环拓扑结构有一个特殊的“环回”功能，让它们继续发挥作用，即使主缆斩断。RS232：这是描述具体的线路连接，电压等级的串行通信IEEE标准，和其他经营通信电子数据参数。此外，还有其他一些遥感的标准。串行：这是一个电子数据传输计划，信息传输一次一个位。串行端口：这通讯上，它被设置为串行通讯设备接入点了。星型拓扑结构：这是一个局域网的安排方式，节点连接到彼此通过一个中央枢纽，它可以主动或被动。活跃的中心执行诸如路由和维护信息网络的职责。中央枢纽只是一个被动的传递沿线的所有连接到它的节点的信息。拓扑：这涉及到一个节点的具体安排在彼此的关系网络。透明：这个术语描述事件或过程的自动成一个系统，不需要特殊的编程或操作员提示兴建。现在，我们正在与这些条款熟悉，让我们看看它们是如何在现有的描述PLC网络选项。PLC网络方案PLC的网络提供一个网络方案，以满足特定的控制和通信需求的各种你。典型的方案包括远程I / O，同辈对同辈，和主机通信，以及局域网。这些网络可以提供可靠和成本之间的有效沟通少两个或几个100的PLC，计算机很多，和其他智能设备。许多PLC的厂商提供的专用网络系统，是独一无二的，不会与另一作出的PLC。这是因为不同的通信协议，命令序列，错误检查计划，并

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