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编号无锡太湖学院毕业设计（论文）相关资料题目： 定量给料机控制系统设计 信机 系 机械工程及自动化专业学 号： 0923153 学生姓名： 盛阳阳 指导教师： 黄敏 （职称：副教授 ） 2013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： 定量给料机控制系统设计 信机 系 机械工程及自动化 专业学 号： 0923153 学生姓名： 盛阳阳 指导教师： 黄敏 （职称：副教授 ） 2012年11月25日 课题来源自拟题目科学依据（1）课题科学意义随着工业生产的迅速发展，导致了定量给料机的需求量日益增大。定量给料设备已广泛应用于冶金、建材、电力、化工、食品等各种行业中。比如药物的生产，机械浇铸生产。定量给料机是对散状物料进行连续称量给料的理想设备，是集输送、称重计量和定量控制为一体的高科技产品，是根据我国现有工艺工况改进后的新一代产品，它以技术先进、稳定可靠、性价比高、经久耐用而著称。能适应各种生产环境，对各种块、粒状物料（如石灰石、铁粉、粘土）和粉状物料（如粉煤灰、水泥）等进行连续给料、计量，为各种工业现场的生产控制、管理提供准确的计量数据。配有RS485上位机通讯接口，可与中央控制机组成DCS系统。定量给料机的出现解放了人工劳动力，使给料更加智能化，更加精确。促进了工业的发展。（2） 定量给料机的研究状况及其发展前景在的日常生活中，已经很少见到纯单体的物质了，复合材料在工业、农业、日常生活中起着越来越重要的作用。如常见的家电、汽车、飞机制造过程中用的塑料，是由 PP 或 PE 等原材料以一定的配方和工艺制成的；食品中的巧克力、高档饼干等等是由多种食品按照一定的配比，经过一定的工艺制成的；医药领域中的多种中西药都是由多种药材按照一定的配比，制造成特殊功效的药品；日用品中用的洗发液，洗衣粉/剂，灭虫剂等等均为配方产品。研究内容 熟悉定量给料机的发展历程，使用领域； 熟练掌握定量给料机的基本工作原理； 熟练掌握并且完成系统的硬件选型、接口电路设计； 掌握并完成控制软件设计；拟采取的研究方法、技术路线、实验方案及可行性分析实验方案:通过参阅借来的参考资料，网上的介绍以及对定量给料机进行实体观察，了解定量给料机的工作原理。提出任务分析对控制系统需求确定任务要求，完成设计任务书。选定最优方案该阶段目标为提出原理性的设计方案。技术设计阶段明确系统控制要求完成硬件选型、接口电路设计，控制软件设计,并画出电气图、写出使用说明书、标准明细表、其他技术文件等。实验通过通过自行设计控制系统，从而达到预期的控制。研究计划及预期成果研究计划：2012年11月12日-2013年12月2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；完成一篇英文文献翻译；2012年12月3日-2013年2月17日： 进行专业实训，填写毕业实习实训报告；2013年2月18日-3月9日： 进行需求分析和可行性分析。构建论文框架完成第一章节绪论部分,按格式要求确定参考文献和四篇英文文献；2013年3月10日： 将在此之前做的所有的相关资料交给导师检查，填写中期进表；2013年3月10日- 3月20日： 对定量给料机机械部分做一个简单的设计、描述；2013年3月21日- 4月9日： 对控制系统做初步的设计、介绍，选择好系统的硬件选型，接口电路；2013年4月10日- 4月24日： 完成系统全部设计，并提供一份控制软件；2013年4月24日-5月5日： 进行实验检验，撰写毕业论文和相关资料。2013年5月6日-5月20日：完善毕业论文以及相关资料，为答辩做好充分的准备。预期成果：照计划安排进行本设计，对给料机设计的系统能良好的完成需要的动作。完成控制系统总体方案设计、控制系统的硬件选型、接口电路设计；写出控制软件1套。完成设计说明书的撰写，并翻译外文资料1篇。特色或创新之处 主题明确，有针对性,稳定, 易操作, 通用性强。 使用简易，功能完善。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，已经确定总目标，策略。 给料机控制部分的设计，plc电气方面的硬件选择，所需软件。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 control system design elementsSubmitted: -; Accepted: March 27, 2002; Published: September 25, 2002Pavan K. Heda 1 , Kapiamba Muteba 2 and Larry L. Augsburger 21 Personal Products Company, Division of McNeil-PPC, Skillman, NJ 085582 Department of Pharmaceutical Sciences, University of Maryland, School of Pharmacy, Baltimore, MD 21201ABSTRACTOriginally, the PLC was represented by the acronym PC. There was some confusion with using this acronym as it is commonly accepted to represent personal computer. Therefore, PLC is now commonly accepted to mean programmable logic contoller.A PLC is a user-friendly, microprocessor-based specialized computer that carries out control functions of many types and leves of complexity. Its purpose is to monitor crucial process parameters and adjust process operations accordingly. It can be programmed, controlled, and operated by a person unskilled in operating computer. Essentially, a PLCs operator draws the lines and devices of ladder diagrams with a keyboard onto a display screen. The resulting drawing is converted into computer machine language and run as a user program1.The computer takes the place of much of the external wiring required for control of a process. The PLC will operate any system that has output devices that go on and off (known as discrete, or digital, outputs). It can also operate any system with variable (analog) outputs. The PLC can be operated on the input side by on-off devices (discrete, or digital) or by variable (analog) input devices.KEYWORDS: PLC, programmable logic contoller.In the automated control domain, PLC is one kind of important control device. At present, in the world has more than 200 factories to produce more than 300 varieties PLC product, applies in the automobile (23%), the grain processing (16.4%), chemistry/drugs manufacture (14.6%), the metal/mine (11.5%), the paper pulp/papermaking (11.3%) and so on the profession. In order to make fellow beginners conveniently to understand PLC, this article to the PLC development, the basic structure, the disposition, using and so on the elementary knowledge makes a synopsis.First, PLC development courseIn the industrial production process, the massive switches quantity sequential control, it carries on the smooth movement according to the logical condition, and defers to the logical relations to carry on the chain-like protection movement the control, and massive data acquisition. In the tradition, these functions are realize through air operated or the electricity control system. In 1968 American GM (general automobile) the company proposed the substitution continues the electricity control device the request, the second year, the American numeral company developed based on the integrated circuit and the electronic technology control device, used sequenced the method to apply for the first time to the electrical control, this was the first generation of programmable foreword controller, called Programmable Controller (PC)2. After the personal computer (is called PC) to develop, in order to be convenient, also in order to reflect the programmable controller the function characteristic, the programmable foreword controller chooses a name is Programmable Logic Controller (PLC), now, still frequently was called PLC PC. The PLC definition has many kinds. The international electrician committee (IEC) to PLC the definition is: The programmable controller is one kind of digital operation operation electronic system, specially for applies under the industry environment designs3. It uses the programmable foreword the memory, uses for to carry out the logic operation, the sequential control in its internal storage, fixed time, counts with operation the and so on arithmetic operation instruction, and through digital, the simulation input and the output, controls each kind of type the machinery or the production process. The programmable foreword controller and its the related equipment, all should according to easy form a whole with the industry control system, is easy to expand its function the principle design.On the century 80s to the 90s intermediate stages, are PLC develop the quickest time, the yearly rate continuously maintenance are 30-40%. In this time, PLC in the processing simulation quantity ability, the digital operation ability, the man-machine connection ability and the networking capability obtains the large scale enhancement, PLC gradually enters the process control domain, substituted in certain applications has been at the dominant position in the process control domain the DCS system.PLC has the versatility strongly, the easy to operate, the adaption surface broad, the reliability high, the antijamming ability strong, the programming is simple and so on the characteristic. PLC in the industrial automation control specially is in the sequential control status, in future which may foresee, is unable to substitute.Second, PLC constitution From the structure the minute, PLC divides into the stationary type and the combined type (module type) two kinds. Stationary PLC including the CPU board, the I/O board, demonstrated the kneading board, the memory block, the power source and so on, these element groups synthesize a not dismantable whole. Module type PLC including the CPU module, the I/O module, the memory, the power source module, the ledger wall or the rack, these modules may defer to the certain rule combination disposition. Second, PLC constitution4.Third, CPU constitutionCPU is the PLC core, plays nerve centers role, every time wraps PLC at least to have CPU, it function receive and storage user program and data which entrusts with according to the PLC system program, with scanning way gathering the condition or the data which sends by the scene input device, and stores the stipulation in the register, simultaneously, diagnoses the power source and in the PLC internal circuit active status and the programming process grammatical error and so on. After enters the movement, reads from the user program memory by the strip takes the instruction, the duty which stipulated according to the instruction produces the corresponding control signal again after the analysis, directs the related control circuit5. CPU mainly by the logic unit, the controller, the register and realizes the data, the control and the condition main line constitution which between them relates, the CPU unit also includes the periphery chip, the main line connection and the related electric circuit. The memory mainly uses in the stored routine and the data, is the PLC essential composition unit.Looked like in the user, nonessential multianalysis CPU internal circuit, but or should have the enough understanding to each part of work mechanism. The CPU controller controls the CPU work, reads by it takes the instruction, the interpretive order and carries out the instruction. But the work rhythm by shakes the signal control. The logic unit uses in to carry on the numeral or the logic operation, works under the controller direction. The register participation operation, coexists stores the operation the intermediate result, it also is works under the controller direction. The CPU speed and the memory capacity are the PLC important parameter, they are deciding the PLC working speed, the IO quantity and the software capacity and so on, therefore is limiting the control scale.Fourth, I/O modulePLC and the electrical return route connection, is (I/O) completes through the input output unit. The I/O module integrated the PLC I/O electric circuit, its input temporary storage device reflection input signal condition, output point reflection output latch condition. The load module transforms the electrical signal the digital signal to enter the PLC system, the output module is opposite. I/O divides into the switch quantity input (DI), switch quantity output (DO), simulation quantity input (AI), simulation quantity output (AO) and so on module.The switch quantity is refers has and closes (or 1 and 0) two kind of conditions signals, the simulation quantity is only a quantity which refers continuously changes. Commonly used I/O classifies as follows:Switch quantity: Divides equally according to the voltage water, has 220VAC, 110VAC, 24VDC, divides according to the isolation way, has the relay isolation and the transistor isolation. Simulation quantity: Divides according to the signal type, has the electric current (4-20mA,0-20mA), the voltage (0-10V,0-5V, -10-10V) and so on, divides according to the precision, has 12bit,14bit,16bit and so on. Besides above general I/O, but also has the special I/O module, like module and so on thermal resistance, thermo-element, pulse. According to the I/O points determination module specification and the quantity, the I/O module may be many may be few, but its biggest number the basic disposition ability which can manage CPU, namely biggest ledger wall or rack Key slot number limit.Fifth, power source moduleThe PLC power source uses in is the PLC various modules integrated circuit provides the work power source. At the same time, some also provides 24V for the input circuit the work power source. The mains input type includes: (What the alternating current supply (220VAC or 110VAC), the direct-current power supply is commonly used is 24VAC).Sixth, ledger wall or rackThe majority module type PLC use ledger wall or the rack, its function is: On the electricity, realizes during various modules relation, enables CPU to visit on the ledger wall all modules, on the machinery, realizes during various modules connection, enable various modules to constitute a whole.Seventh, PLC system other equipment1st, programs the equipment: The programming is the PLC development application, the monitor movement, the inspection maintains the essential component, uses in to program, makes some hypotheses to the system, monitors the system working condition which PLC and PLC controls, but it not directly participates in the scene control movement. Small programming PLC generally has the grasping programming, at present generally (movement programming software) acts as the programming by the computer. 2nd, man-machine contact surface: The simplest man-machine contact surface is the indicating lamp and the button, at present the liquid crystal screen (or touches screen) a formula writing style operator terminal application to be more and more widespread, (movement configuration software) acts as the man-machine contact surface by the computer extremely to popularize. 3rd, input-output device: Uses in permanently the memory user data, like EPROM, EEPROM reading in, bar code microreader, input simulation quantity potentiometer, printer and so on.Eighth, PLC correspondence networkingDepends upon the advanced industry network technology to be allowed rapidly effectively to collect, the transmission produces and manages the data. Therefore, the network is more and more remarkable in the automated system integration project importance, even some people proposed the network is the controller viewpoint view. PLC has the correspondence networking the function, it causes between PLC and PLC, PLC and on between the position computer and all that intelligent equipment can exchange the information, forms a unified whole, the realization disperser common control. Most PLC has the RS-232 connection, but also has some in sets has supports respective correspondence agreement the connection.PLC correspondence, but also the realization mutually has not been operational, IEC had stipulated the many kinds of field bus standard, the PLC various factories have the use. (Specially is center large-scale control system) says regarding an automated project, the choice network count for much. First, the network will have to be open, facilitates the different equipment the integration and the future system scale expansion; Next, in view of the different network level transmission performance requirement, the choice network form, this must in thoroughly understand this network standard the agreement, under the mechanism premise carries on; Once more, the synthesis considered system cost, equipment compatibility, scene environment serviceable and so on concrete question, determined the different level uses network standard.Today, the big unit growth in the PLC industy is at the low end-where small keeps getting smaller. When a few years ago the micro PLC entered the market, some thougt that these devices had “bottomed out”. Now,nano PLCs-generally defined as those with 16 or fewer I/O-are spreading. Some can fit into your shirt pocket, being no larger than a deck of cards and at the time of this writing, PLC Direct plants to introduce a PLC the size of a box of Tic-Tac candy that will include many features of current micro models.The first PLC systems evolved from conventional computers in the late 1960s and early 1970s. These first PLCs were installed primarily in automotive plants. Traditionally, The auto plants had to be shut down for up to a month at model changeover time. The early PLCs were used along with other new automation techniques to shorten the changeover time. One of the major time-consuming changeover procedures had been the wiring of new or revised relay and control panels. The PLC keyboard reprogramming procedure replaced the rewiring of a panel full of wires, relays, timers and other components. The new PLCs helped reduce changeover time to a matter of few days.There was a major problem with these early 1970s computer/PLC reprogramming procedures. The programs were complicated and required a highly trained programmer to make the changes. Through the late 1970s, improvements were made in PLC programs to make them somewhat more user friendly; in 1978, the introduction of the microprocessor chip increased computer power for all kinds of automotion systems and lowered the computing cost. Robotics, automotion devices, and computers of all types, including the PLC, consequently underwent many improvements. PLC programs, written in high-level language, became more understandable to more people, and PLCs became more affordable.In the 1980s, with more computer power per dollar available, the PLC came into exponentially increasing use. Some large electronics and computer companies and some diverse corporate electronics divisions found that the PLC had become their greatest volume product. The market for PLCs grew from a volume of $80 million in 1978 to $1 billion per year by 1990 and is still growing. Even the machine tool industry, where compute numerical controls (CNCs) have been used in the past, is using PLCs. PLCs are also used extensively in building energy and security control systems. Other nontraditional uses of PLCs, such as in the home and in medical equipment, haved exploded in the 1990s and will increase as we enter the new millennium.A person knowledgeable in relay logic systems can master the major PLC functions in a few hours, These functions might include coils, contacts, timers and counters. The same is true for a person with a digital logic background. For persons unfamiliar with ladder diagrams or digital principles, howere, the learning process takes more time.A person knowledgeable in relay logic can master advanced PLC functions in a few days with proper instruction. Company schools and operating manuals are very helpful in mastering these advanced functions. Advanced functions in order of learning might include sequence/drum controller, register bit use, and more functions.Following are 8 major advantages of using a programmable controller.Flexibility. In the past, each different electronically controlled production machine required own controller; 15 machines might require 15 different controllers. Now it is possible to use just one model of a PLC to run any one of the 15 machines. Implementing Change and Correcting Errors. With a wired relay-type panel, any program alterations require time for rewriting of panels and devices. When a PLC program circuit or sequence design change is made, the PLC program can be changed from a keyboard sequence in a metter of minutes. No rewiring is required for a PLC-controlled system.Large quantities of contacts. The PLC has a large number of contacts for each coil available in its programming.suppose that a panel-wired relay has four contacts and all are in use when a design change requiring three more contacts is made. Time would have to be taken to procure and install a new relay or relay contact block. Using a PLC, howere, only three more contacts would be typed in. the three contact would be automatically available in the PLC. Indeed, a hundred contacts can be used from one relay-if sufficient computer memory is available. Lower cost. Increased technology makes it possible to condense more functions into smaller and less expensive packages. Now you can purchase a PLC with numerous relays, timers and counters, a sequencer, and other function for a few hundred dollars.Pilot Running. A PLC programmed circuit can be evaluated in the office or lab. The program can be typed in, tested, observed, and modified if needed, saving valuable factory time. In contrast, conventional relay systems have been tested on the factory floor, which can be very time consuming.Visual Observation. A PLC circuits operation can be seen during operation directly on a CRT screen. The operation or misoperation of a circuit can be observed as it happens. Logic paths light up on the screen as they are energized. Troubleshooting can be done more quickly during visual observation. In advanced PLC systems, an operator message can be programmed for each possible malfunction.In advanced PLC systems, an operator message can be programmed for each possible malfunction. The malfunction description appears on the screen when the malfunction is detected by the PLC logic. Advanced PLC systems also may have descriptions of the function of each circuit component. Speed of Operation. Relays can take an unacceptable amount of time to actuate. The operational speed for the PLC program is very fast. The speed for the PLC logic operation is determined by scan time, which is a matter of milliseconds.Ladder or Boolean Programming Method. The PLC programming can be accomplished in the ladder mode by an electrician or technician. Alternatively, a PLC programmer who works in digital or Boolean control systems can also easily perform PLC programming. In modern industrial production equipment, and large numbers of simulations of the control devices, such as the cease electrical, electromagnetic devices to turn, the number of products, temperature, Ap power, and set the flow control, the automatic control of the industrial site, If a programmable controller (PLC) to resolve the issue has become a cybernetic one of the most effective tools, this article describes Plc control system design should be noted. Hardware purchase many products currently on the market Plc, with the exception of domestic brands, foreign : Japan Omron, Mitsubishi, FUJJ, ANASONIC, Germany Siemens, Korean LG. In recent years, Plc greater decline in the prices of products, increasing its performance cost rate. This is a technical staff chosen Plc important reasons. Then, how to purchase Plc products? First, the system should first determine the size of single control system with Plc or using Plc networking, thus calculating Plc importing, exporting. Few, and in some Plc to be in real need have a certain cushion Second, determine the type of load under Plc export-led type of load is the DC or exchange-type, big or small currents, and Plc export points such as the frequency of movements, the use of relays to determine export-export, or transistor output, or goods of export gates. Different load choose different ways to export to the operating systems stability is very important. Third, the storage capacity and speed while foreign manufacturers of Plc products essentially the same, but there are some differences. Currently the company has not yet found full compatibility between products. The development of software companies are not the same, and users of storage capacity and procedures to implement the Directive speed are two important indicators. General greater storage capacity, faster speed on the Plc higher prices, but should be based on system size reasonable choice Plc products.Fourth, programming devices Plc programming can purchase three ways : Using hand-held programming device programming in general, it can provide businesses phrases programming language table. This approach inefficient, but the capacity of small systems, the products more suitable for small consumption, and small size, ease of debugging scene, but also lower costs. Using graphical programming device programming, the programming device used Trapezoid Chart programming for visual and general electrical personnel shortly be applied easily, but the programming device prices higher. Using IBM personal computers and software packages using Plc programming, this approach is the most efficient way, but most of the companys Plc development software packages expensive, and that means not at the scene debugging. Therefore, the system should be based on the size and level of difficulty, the length of the development cycle and reasonable funding of the purchase Plc products.Fifth, And large companies to choose their quality guaranteed products, and good technical support, after sales services are generally better, but also help expand your product and software upgrades.For small systems, such as 80 points within the system. Generally do not need expansion; When a larger system, we must expand. Different companies products to the total points system and the expansion of the number of modules have limitations when expansion can not meet the requirements, can network structure; At the same time, some manufacturers of individual products do not support the expansion module directives, in software development, we must pay attention to. When using such simulation module temperature, some of the manufacturers, see related technical manuals. Many types of companies expansion modules, such as single-input modules, single output modules, input output modules, temperature modules, high-speed input module. This modular design Plc product development provided for the convenience of users.When using a Plc network design, its much more difficult to control than single Plc. First you should choose their own more familiar type, its basic instructions and a more in-depth understanding of the functional commands, and the speed and direction of the implementation of storage capacity users should also be careful about the procedure. Otherwise, you can not adapt to the real-time requirements, resulting in the collapse of the system. In addition to communications interfaces, communication protocols, data transmission speed should also be considered. Finally, we must seek to Plc businessmen network design and software technical support and detailed technical information for the selection of several workstations in your system size.In the preparation of the software, should first become familiar with the use of Plc software products specification, the question skilled later programming. If using graphical programming device or software package programming may direct programming, if using hand-held programming device programming, should be painted Trapezoid Chart before programming, so can less mistakes speed was fast. After the first air conditioning programming procedures to be normal functioning of all, again in equipment debugging.References:1 G.C. Beolchini, V. Gattulli, R. Ghanem, Data fusion in bridge health monitoring for management, Proceedings of the First International Conference on Bridge Maintenance,Safety and Management, IABMAS 2002, Barcelona, 1417,July, 2002,2002. 2 Fu Dawei and Liu Ruisu, in: The System edited by Fu Dawei and Liu Ruisu,Open System,chapter,10,Chemical Industry Press (2005) 3 Yang Delin,in:Machine tool servo system and electrical control,edited by Li Qingxin,Stepping Servo System,chapter,5,Machinery Industry Press (1999) 4 Zhang Heng and Cao Shukun: Research on Processing Path-oriented Open System (University of Jinan, China 2009)中文翻译PLC控制系统设计的要点摘要 可编程序控制器 (可设计的控制器) 本来应简称个人计算机，为了与个人计算机的简称个人计算机相区别,一般将它简称为 PLC(可设计的逻辑控制器)。PLC 是一个方便使用，是实行许多类型和复杂层的控制功能的基于微处理器的特殊计算机. 它的目的是适当地检测决定性的程序叁数并且调整程序操作。在操作计算机方面不熟练的人能对它进行规划，控制, 而且操作。 本质上, 一个 PLC 的操作员在一个展览荧屏之上用一个键盘画梯图表的线和装置. 产生的图画转换成计算机机器语言和作为一个用户程序运行。计算机代替了一个过程控制所需的许多外部配线。 PLC 将会操作有开或关的输出装置的任何系统 (已知不连续的，或数字的, 输出) 。 它也能操作任何输出为变量 (模拟) 的系统. PLC 能通过开关装置 (不连续的, 或数字的) 或输入变量 (模拟) 的装置在输入端进行操作。关键词：PLC，可设计的逻辑控制器在自动化控制领域，PLC是一种重要的控制设备。目前，世界上有200多厂家生产300多品种PLC产品，应用在汽车（23%）、粮食加工（16.4%）、化学/制药（14.6%）、金属/矿山（11.5%）、纸浆/造纸（11.3%）等行业。为了使各位初学者更方便地了解PLC，本文对PLC的发展、基本结构、配置、应用等基本知识作一简介。一、PLC的发展历程在工业生产过程中，大量的开关量顺序控制，它按照逻辑条件进行顺序动作，并按照逻辑关系进行连锁保护动作的控制，及大量离散量的数据采集。传统上，这些功能是通过气动或电气控制系统来实现的。1968年美国GM（通用汽车）公司提出取代继电气控制装置的要求，第二年，美国数字公司研制出了基于集成电路和电子技术的控制装置，首次采用程序化的手段应用于电气控制，这就是第一代可编程序控制器，称Programmable Controller（PC）。 个人计算机（简称PC）发展起来后，为了方便，也为了反映可编程控制器的功能特点，可编程序控制器定名为Programmable Logic Controller（PLC），现在，仍常常将PLC简称PC。PLC的定义有许多种。国际电工委员会（IEC）对PLC的定义是：可编程控制器是一种数字运算操作的电子系统，专为在工业环境下应用而设计。它采用可编程序的存贮器，用来在其内部存贮执行逻辑运算、顺序控制、定时、计数和算术运算等操作的指令，并通过数字的、模拟的输入和输出，控制各种类型的机械或生产过程。可编程序控制器及其有关设备，都应按易于与工业控制系统形成一个整体，易于扩充其功能的原则设计。上世纪80年代至90年代中期，是PLC发展最快的时期，年增长率一直保持为30-40%。在这时期，PLC在处理模拟量能力、数字运算能力、人机接口能力和网络能力得到大幅度提高，PLC逐渐进入过程控制领域，在某些应用上取代了在过程控制领域处于统治地位的DCS系统。PLC具有通用性强、使用方便、适应面广、可靠性高、抗干扰能力强、编程简单等特点。PLC在工业自动化控制特别是顺序控制中的地位，在可预见的将来，是无法取代的。二、PLC的构成从结构上分，PLC分为固定式和组合式（模块式）两种。固定式PLC包括CPU板、I/O板、显示面板、内存块、电源等，这些元素组合成一个不可拆卸的整体。模块式PLC包括CPU模块、I/O模块、内存、电源模块、底板或机架，这些模块可以按照一定规则组合配置。 三、CPU的构成CPU是PLC的核心，起神经中枢的作用，每套PLC至少有一个CPU，它按PLC的系统程序赋予的功能接收并存贮用户程序和数据，用扫描的方式采集由现场输入装置送来的状态或数据，并存入规定的寄存器中，同时，诊断电源和PLC内部电路的工作状态和编程过程中的语法错误等。进入运行后，从用户程序存贮器中逐条读取指令，经分析后再按指令规定的任务产生相应的控制信号，去指挥有关的控制电路。CPU主要由运算器、控制器、寄存器及实现它们之间联系的数据、控制及状态总线构成，CPU单元还包括外围芯片、总线接口及有关电路。内存主要用于存储程序及数据，是PLC不可缺少的组成单元。在使用者看来，不必要详细分析CPU的内部电路，但对各部分的工作机制还是应有足够的理解。CPU的控制器控制CPU工作，由它读取指令、解释指令及执行指令。但工作节奏由震荡信号控制。运算器用于进行数字或逻辑运算，在控制器指挥下工作。寄存器参与运算，并存储运算的中间结果，它也是在控制器指挥下工作。CPU速度和内存容量是PLC的重要参数，它们决定着PLC的工作速度，IO数量及软件容量等，因此限制着控制规模。四、I/O模块PLC与电气回路的接口，是通过输入输出部分（I/O）完成的。I/O模块集成了PLC的I/O电路，其输入暂存器反映输入信号状态，输出点反映输出锁存器状态。输入模块将电信号变换成数字信号进入PLC系统，输出模块相反。I/O分为开关量输入（DI），开关量输出（DO），模拟量输入（AI），模拟量输出（AO）等模块。开关量是指只有开和关（或1和0）两种状态的信号，模拟量是指连续变化的量。常用的I/O分类如下：开关量：按电压水平分，有220VAC、110VAC、24VDC，按隔离方式分，有继电器隔离和晶体管隔离。 模拟量：按信号类型分，有电流型（4-20mA,0-20mA）、电压型（0-10V,0-5V,-10-10V）等，按精度分，有12bit,14bit,16bit等。除了上述通用I/O外，还有特殊I/O模块，如热电阻、热电偶、脉冲等模块。按I/O点数确定模块规格及数量，I/O模块可多可少，但其最大数受CPU所能管理的基本配置的能力，即受最大的底板或机架槽数限制。五、电源模块PLC电源用于为PLC各模块的集成电路提供工作电源。同时，有的还为输入电路提供24V的工作电源。电源输入类型有：交流电源（220VAC或110VAC），直流电源（常用的为24VAC）。六、底板或机架大多数模块式PLC使用底板或机架，其作用是：电气上，实现各模块间的联系，使CPU能访问底板上的所有模块，机械上，实现各模块间的连接，使各模块构成一个整体。七、PLC系统的其它设备1、编程设备：编程器是PLC开发应用、监测运行、检查维护不可缺少的器件，用于编程、对系统作一些设定、监控PLC及PLC所控制的系统的工作状况，但它不直接参与现场控制运行。小编程器PLC一般有手持型编程器，目前一般由计算机（运行编程软件）充当编程器。2、人机界面：最简单的人机界面是指示灯和按钮，目前液晶屏（或触摸屏）式的一体式操作员终端应用越来越广泛，由计算机（运行组态软件）充当人机界面非常普及。3、输入输出设备：用于永久性地存储用户数据，如EPROM、EEPROM写入器、条码阅读器，输入模拟量的电位器，打印机等。八、PLC的通信联网依靠先进的工业网络技术可以迅速有效地收集、传送生产和管理数据。因此，网络在自动化系统集成工程中的重要性越来越显著，甚至有人提出网络就是控制器的观点说法。PLC具有通信联网的功能，它使PLC与PLC 之间、PLC与上位计算机以及其他智能设备之间能够交换信息，形成一个统一的整体，实现分散集中控制。多数PLC具有RS-232接口，还有一些内置有支持各自通信协议的接口。PLC的通信，还未实现互操作性，IEC规定了多种现场总线标准，PLC各厂家均有采用。对于一个自动化工程(特别是中大规模控制系统)来讲，选择网络非常重要的。首先，网络必须是开放的，以方便不同设备的集成及未来系统规模的扩展；其次，针对不同网络层次的传输性能要求，选择网络的形式，这必须在较深入地了解该网络标准的协议、机制的前提下进行；再次，综合考虑系统成本、设备兼容性、现场环境适用性等具体问题，确定不同层次所使用的网络标准。今天, 在PLC工业中的大单位增长就要结束-因为小的变得越来越小。 微 PLC 数年以前进入了市场，一些人认为这些装置降到最低点。 现在,十亿分之一 PLCs-通常定义了 16 或者较少的输入输出-正在广泛应用。 一些能装在你的衬衫口袋，没
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