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dq073油漆烘干自动线控制系统设计,毕业设计
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湖北汽车工业学院电气工程系毕业答辩 题目：东风康明斯发动机烘干自动线系统设 计 姓名：杨功强 班级： T423-5 指导老师：文元雄 nts课题来源 本课题来自康明斯发动机烘干车间现场。 nts课题意义 本课题以 PLC控制技术为依托 , 结合触摸屏和网络技术成功地实现了远程监控和无人操作。解决了老生产线需要投入人工成本大、事故率高、不能及时反应故障等问题。 有效降低了生产成本，提高了产品在市场上的生存能力和竞争能力，为企业带来了更大的经济效益。 nts课题简介 本课题主要进行的设计是围绕着温度控制系统来进行的。通过 PLC来实现对生产过程的全程监控，有效的对温度进行实时的检测和调节。 nts系统结构图 nts课题的主要内容 传统烘干炉 红外烘干炉 故障的判断与显示 nts传统烘干炉工作流程 返回 nts红外烘干炉的提出 远红外加热的优点： 加热速度快、新产品质量好、设备占地面积小、生产费用低和加热效率高 红外烘干对发动机面漆内部进行很好的烘干，在传统烘干炉之前加一个红外烘干，可以得到一个很好的的烘干效果。 nts红外烘干炉的硬件组成 3组红外加热器， 3组风机 调压器 温度检测模块 A/D、 D/A转换模块 nts红外烘干系统硬件流程 nts测试与调节的实现 nts电压的计算 当温度为 20 时，电压实际以调到最大，为方便计算，在 0的位置取最大电压值。得到如下公式： Y=380-17/38X 在这里 X为测得的温度值，根据公式可计算相应的电压，再通过调压器对加热器进行控制，实现温度的调节。 nts红外烘干相关程序 nts返回 nts触摸屏主画面 nts故障显示画面 nts触摸屏程序 )1( f60n sp nts现场 现场图片 现场录像 nts现场相关内容 nts nts nts现场录像 nts结论 经经过三个月的紧张工作，按时完成了该系统的设计和安装调试，通过生产检验，证明该系统运行安全可靠设计符合要求。 nts致谢 在这里我特别感谢我的指导老师的耐心指导；感谢和我一道完成课题的同学东风康明斯公司烘干车间的全体职工，在项目的设计和安装中，他们给予了我很大帮助。 在此也要感谢在座的各位老师。 nts 谢 谢 大 家！ nts电气工程系毕业设计开题报告 课题名称 ： 东风康明斯油漆烘干自动线控制系统设计 姓 名 ： 杨 功 强 班 级 ： T423-5 学 号： 20040230536 指导老师 ： 文元雄 2008 年 3 月 5 日 nts 一、课题来源 采用欧姆龙 PLC控制康明斯发动机油漆烘干自动线，通过悬链完成对输送线的控制，完成对发动机油漆烘干设备及温度控制，以及与其他设备联锁控制，当设备出现问题时进行异常状态判定，通过触摸屏显示故障信息。 二、国内外 PLC的的发展与现状 1.可编程 控制器的发展历史。可编程控制器从 1969年诞生，当时主要由分立元件和中小规模集成电路组成，后经微处理器的引人直到进人实用化发展阶段，是一步一步的走过来的。可编程控制器的进人成熟阶段的标志是大规模、高速度、高性能、产品系列化。 2.可编程控制器的总体概况。 20世纪末期，可编程控制器的发展特点是更加适应于现代工业的需要。随着系统能力的提高， PLC提供系统通信的能力，构成了可编程控制系统，人机界面逐步完善，具有离散量和模拟量数据采集系统的监控能力。从控制规模上来说，这个时期发展了大型机和超小型机 ;从控制能力上来说，诞生了各种各样的特殊功能单元，用于压力、温度、转速、位移等各式各样的控制场合 ;从产品的配套能力来说，生产了各种人机界面单元、通信单元，使应用可编程控制器的工业控制设备的配套更加容易。目前，可编程控制器在机械制造、石油化工、冶金钢铁、汽车、轻工业等领域的应用都得到了长足的发展。 3.我国可编程控制器的现状。我国可编程控制器的引进、应用、研制、生产是伴随着改革开放开始的。最初是在引进设备中大量使用了可编程控制器。接下来在各种企业的生产设备及产品中不断扩大了 PLC的应用。目前，我国自己已可以生产中小型可编程 控制器。上海东屋电气有限公司生产的 CF系列、杭州机床电器厂生产的 DKK及 D系列、大连组合机床研究所生产的 5系列、苏州电子计算机厂生产的 Yz系列等多种产品已具备了一定的规模并在工业产品中获得了应用。此外，无锡华光公司、上海乡岛公司等中外合资企业也是我国比较著名的 PLC生产nts厂家。可以预期，随着我国现代化进程的深人， PLC在我国将有更广阔的应用天地。 三、 PLC的发展趋势 1.向高速度、大容量方向发展 为了提高 PLC的处理能力，要求 PLC具有更好的响应速度和更大的存储容量。目前，有的 PLC的扫描速度可达 0.1ms/k步左右。 PLC的扫描速度已成为很重要的一个性能指标 。 在存储容量方面，有的 PLC最高可达几十兆字节。为了扩大存储容量，有的公司已使用了磁泡存储器或硬盘。 2.向超大型、超小型两个方向发展 当前中小型 PLC比较多，为了适应市场的多种需要，今后 PLC要向多品种方向发展，特别是向超大型和超小型两个方向发展。现已有 I/O点数达 14336点的超大型 PLC，其使用 32位微处理器，多 CPU并行工作和大容量存储器，功能强。 小型 PLC由整体结构向小型模块化结构发展，使配置更加灵活，为了市场需要已开发了各种简易 、经济的超小型微型 PLC，最小配置的 I/O点数为 8 16点，以适应单机及小型自动控制的需要，如三菱公司 系列 PLC。 3.PLC大力开发智能模块，加强联网通信能力 为满足各种自动化控制系统的要求，近年来不断开发出许多功能模块，如高速计数模块、温度控制模块、远程 I/O模块、通信和人机接口模块等。这些带CPU和存储器的智能 I/O模块，既扩展了 PLC功能，又使用灵活方便，扩大了 PLC应用范围。 加强 PLC联网通信的能力，是 PLC技术进步的潮流。 PLC的联网通信有两类：一类是 PLC之间联网通信，各 PLC生产厂家 都有自己的专有联网手段；另一类是 PLC与计算机之间的联网通信，一般 PLC都有专用通信模块与计算机通信。为了加强联网通信能力， PLC生产厂家之间也在协商制订通用的通信标准，以构成更大的网络系统， PLC已成为集散控制系统（ DCS）不可缺少的重要组成部分。 nts4.增强外部故障的检测与处理能力 根据统计资料表明：在 PLC控制系统的故障中， CPU占 5%， I/O接口占 15%，输入设备占 45%，输出设备占 30%，线路占 5%。前二项共 20%故障属于 PLC的内部故障，它可通过 PLC本身的软、硬件实现检测、处理 ；而其余 80%的故障属于 PLC的外部故障。因此， PLC生产厂家都致力于研制、发展用于检测外部故障的专用智能模块，进一步提高系统的可靠性。 5.编程语言多样化 在 PLC系统结构不断发展的同时， PLC的编程语言也越来越丰富，功能也不断提高。除了大多数 PLC使用的梯形图语言外，为了适应各种控制要求，出现了面向顺序控制的步进编程语言、面向过程控制的流程图语言、与计算机兼容的高级语言（ BASIC、 C语言等）等。多种编程语言的并存、互补与发展是 PLC进步的一种趋势。 四、课题研究的进度安排 2008年 3月 -2008年 4月，收集资料 , 并对温度控制技术 ,触摸屏应用技术 ,变频控制技术进行系统的学习。 2008年 4月 -2008年 5月，研究课题 ,整理出具体思路 ,对毕业设计所需的程序进行编写、调试。 2008年 5月 -2008年 6月，将所需程序进行完善 ,通过软件实现课题所要求的功能。 2008年 5月 -2008年 6月，整理资料，完成论文。 五、课题研究内容及方案论证 （一）研究内容 1. PLC原理与应用 nts 2. 触摸屏应用技术 3. 变频控制技术 4. 温度控制技术 （二） 方案论证 1. 自动烘干 系统的硬件设计要求 1) 要 求 每台加热臂都要有自己独立的控制台，控制台选用国家标准柜体 ; 2) 每 台 加热臂要有感测元件 (热电偶 )，实现模拟信号的采集，并且可把采集的模拟信号送往 PLC处理 ; 3) 此 系 统要有手动和自动两种工作模式 (通过控制面板实现 ); 4) 自 动 控制系统要设有紧急停车功能 ; 5) 通 过 控制柜面板仪表，可以监测系统点火启动情况 ; 6) 对 混 合气体风扇的电机和液压驱动风扇的电机，要有短路保护和接地保护 . 7) 系 统 本身要有自动点火装置，该装置由 PLC控制 ; 8) 控 制 台面板上应安装有急停按钮、给电按钮、燃烧臂上升和下降等控制按钮 ; 9) 控 制 柜导线的引人和引出要通过端子板 ; 10) 柜 体 内的接线采用不同的颜色，以区别不同的作用 ; 11) 柜 体 内要用标签标明元汽件的标号，以便维修 ; 12) 系 统 应带有气动阀、电动阀、空气 /煤气比较控制器等器件来控制混合气体和氮气 。 2. 可编程控制器选型 在系 统 硬 件设计中要有充分的 /10点数作为备用 .在系统硬件设计时一般根据实际 vo点数留有 10%一 15%的余量 .(或根据实际系统的需要来确定 )如果是为了实现单机自动 化，或机电一体化的产品，可选用小型的 PLC.如果控制系统较大，输人、输出点数多，被控设备分散就可选用大型 PLC.同时还应初步确定用户程序存储器的容量 .一般粗略的估算的方法是“输人点数 +输出点数 x (10 - 12)=指令步数” .特别要注意控制功能复杂，数据处理量较大，就可能出现存储容量不够nts的问题 PLC 的 主 要功能包括逻辑运算、算术运算、计时、计数和通信等功能 .如果仅用于实现继电器功能的系统，如报警连锁、顺序动作，时序控制等仅有开关量的场合，可选择一般具有开关量输人输出的 PLC.若被控对象以开关量为主， 并有少量的模拟量信号，需要实现算术运算， A/D,D/A转换， PID控制等，就要选择具有以上功能的 PLC. 六、参考文献 1林小峰 .可编程控制器原理及应用 M北京 :高等教育出版社 . 1994. 2汪志峰 .可编程控制器原理与应用 M陕西 :西安电子科技大学 .2004. 3田瑞庭 .可编程控制器应用技术 M北京 :机械工业出版社 .1994. 4何衍庆，俞金寿 .可编程控制器原理及应用技巧 M北京 :化学工业出版社 .1998. 5张万忠 .可编程控制器应用技术 M北京 :化学工业出版社 . 2001,12. nts电气工程系毕业设计中英文翻译课题名称:东风康明斯油漆烘干自动线控制系统设计系 部:电气工程系专 业:电气工程及其自动化班 级:T423-5姓 名:杨功强学 号:20040230536指导教师:文元雄 湖北汽车工业学院毕业设计（开题报告）Introductions to PLC And Intelligent ControlA PLC (i.e. Programmable Logic Controller) is a device that was invented to replace the necessary sequential relay circuits for machine control. 1 The PLC works by looking at its inputs and depending upon their state, turning on/off its outputs. The user enters a program, usually via software or programmer, that gives the desired results.PLCs are used in many “real world” applications. If there is industry present, chances are good that there is a PLC present. If you are involved in machining, packaging, material handling, automated assembly or countless other industries, you are probably already using them. If you are not, you are wasting money and time. Almost any application that needs some type of electrical control has a need for a PLC.For example, lets assume that when a switch turns on we want to turn a solenoid on for 5 seconds and then turn it off regardless of how long the switch is on for. 2 We can do this with a simple external timer. But what if the process included 10 switches and solenoids? We would need 10 external timers. What if the process also needed to count how many times the switch individually turned on? We need a lot of external counters.As you can see, the bigger the process the more of a need we have for a PLC. We can simply program the PLC to count its inputs and turn the solenoids on for the specified time. We will take a look at what is considered to be the “top 20” PLC instructions. It can be safely estimated that with a firm understanding of these instructions one can solve more than 80% of the applications in existence.Thats right, more than 80%! Of course well learn more than just these instructions to help you solve almost ALL your potential PLC applications.The PLC mainly consists of a CPU, memory areas, and appropriate circuits to receive input/output data, as shown in Fig. 19.1. We can actually consider the PLC to be a box full of hundreds or thousands of separate relays, counters, timers and data storage locations. Do these counters, timers, etc. really exist? No, they dont “physically” exist but rather they are simulated and can be considered software counters, timers, etc. These internal relays are simulated through bit locations in registers.INPUT RELAYS-(contacts) These are connected to the outside world. They physically exist and receive signals from switches, sensors, etc. Typically they are not relays but rather they are transistors.INTERNAL UTILITY RELAYS-(contacts) These do not receive signals from the outside world nor do they physically exist. They are simulated relays and are what enables a PLC to eliminate external relays. There are also some special relays that are dedicated to performing only one task. Some are always on while some are always off. Some are on only once during power-on and are typically used for initializing data that was stored.COUNTERS-These again do not physically exist. They are simulated counters and they can be programmed to count pulses. Typically these counters can count up, down or both up and down. Since they are simulated, they are limited in their counting speed. Some manufacturers also include high-speed counters that are hardware based. We can think of these as physically existing. Most times these counters can count up, down or up and down.TIMERS-These also do not physically exist. They come in many varieties and increments. The most common type is an on-delay type. Others include off-delay and both retentive and non-retentive types. Increments vary from 1ms through 1s.OUTPUT RELAYS-(coils) These are connected to the outside world. They physically exist and send on/off signals to solenoids, lights, etc. They can be transistors, relays, or triacs depending upon the model chosen.DATA STORAGE-Typically there are registers assigned to simply store data. They are usually used as temporary storage for math or data manipulation. They can also typically be used to store data when power is removed from the PLC. Upon power-up they will still have the same contents as before power was removed. Very convenient and necessary!A PLC works by continually scanning a program. We can think of this scan cycle as consisting of 3 important steps, as shown in Fig. 19.2. There are typically more than 3 but we can focus on the important parts and not worry about the others. Typically the others are checking the system and updating the current internal counter and timer values. Step 1-CHECK INPUT STATUS-First the PLC takes a look at each input to determine if it is on or off. In other words, is the sensor connected to the first input on? How about the second input? How about the third It records this data into its memory to be used during the next step.Step 2-EXECUTE PROGRAM-Next the PLC executes your program one instruction at a time. Maybe your program said that if the first input was on then it should turn on the first output. Since it already knows which inputs are on/off from the previous step, it will be able to decide whether the first output should be turned on based on the state of the first input. 3 It will store the execution results for use later during the next step.CHECK INPUT STATUSEXECUTE PROGRAMUPDATE OUTPUT STATUSFig. 19.2 The work process of PLCStep 3-UPDATE OUTPUT STATUS-Finally the PLC updates the status of the outputs. It updates the outputs based on which inputs were on during the first step and the results of executing your program during the second step. Based on the example in step 2 it would now turn on the first output because the first input was on and your program said to turn on the first output when this condition is true.After the third step the PLC goes back to step one and repeats the steps continuously. One scan time is defined as the time it takes to execute the 3 steps listed above. Thus a practical system is controlled to perform specified operations as desired.Intelligence and intelligent systems can be characterized in a number of ways and along a number of dimensions. There are certain attributes of intelligent systems, common in many definitions, which are of particular interest to the control community.In the following, several alternative definitions and certain essential characteristics of intelligent systems are first discussed. A brief working definition of intelligent systems that captures their common characteristics is then presented. In more detail, we start with a rather general definition of intelligent systems, we discuss levels of intelligence, and we explain the role of control in intelligent systems and outline several alternative definitions. We then discuss adaptation and learning, autonomy and the necessity for efficient computational structures in intelligent systems, to deal with complexity. We conclude with a brief working characterization of intelligent (control) systems. We start with a general characterization of intelligent systems:An intelligent system has the ability to act appropriately in an uncertain environment, where an appropriate action is that which increases the probability of success, and success is the achievement of behavioral subgoals that support the systems ultimate goal. In order for a man-made intelligent system to act appropriately, it may emulate functions of living creatures and ultimately human mental faculties. An intelligent system can be characterized along a number of dimensions. There are degrees or levels of intelligence that can be measured along the various dimensions of intelligence. At a minimum, intelligence requires the ability to sense the environment, to make decisions and to control action. Higher levels of intelligence may include the ability to recognize objects and events, to represent knowledge in a world model, and to reason about and plan for the future. In advanced forms, intelligence provides the capacity to perceive and understand, to choose wisely, and to act successfully under a large variety of circumstances so as to survive and prosper in a complex and often hostile environment. Intelligence can be observed to grow and evolve, both through growth in computational power and through accumulation of knowledge of how to sense, decide and act in a complex and changing world.The above characterization of an intelligent system is rather general. According to this, a great number of systems can be considered intelligent. In fact, according to this definition, even a thermostat may be considered to be an intelligent system, although of low level of intelligence. It is common, however, to call a system intelligent when in fact it has a rather high level of intelligence.There exist a number of alternative but related definitions of intelligent systems and in the following we mention several. They provide alternative, but related characterizations of intelligent systems with emphasis on systems with high degrees of intelligence.The following definition emphasizes the fact that the system in question processes information, and it focuses on man-made systems and intelligent machines:A. Machine intelligence is the process of analyzing, organizing and converting data into knowledge; where (machine) knowledge is defined to be the structured information acquired and applied to remove ignorance or uncertainty about a specific task pertaining to the intelligent machine. This definition leads to the principle of increasing precision with decreasing intelligence, which claims that: applying machine intelligence to a database generates a flow of knowledge, lending an analytic form to facilitate modeling of the process. Next, an intelligent system is characterized by its ability to dynamically assign subgoals and control actions in an internal or autonomous fashion:B. Many adaptive or learning control systems can be thought of as designing a control law to meet well-defined control objectives. This activity represents the systems attempt to organize or order its “knowledge” of its own dynamical behavior, so to meet a control objective. The organization of knowledge can be seen as one important attribute of intelligence. If this organization is done autonomously by the system, then intelligence becomes a property of the system, rather than of the systems designer. This implies that systems which autonomously (self)-organize controllers with respect to an internally realized organizational principle are intelligent control systems. A procedural characterization of intelligent systems is given next:C. Intelligence is a property of the system that emerges when the procedures of focusing attention, combinatorial search, and generalization are applied to the input information in order to produce the output. One can easily deduce that once a string of the above procedures is defined, the other levels of resolution of the structure of intelligence are growing as a result of the recursion. Having only one level structure leads to a rudimentary intelligence that is implicit in the thermostat, or to a variable-structure sliding mode controller.The concepts of intelligence and control are closely related and the term “Intelligent Control” has a unique and distinguishable meaning. An intelligent system must define and use goals. Control is then required to move the system to these goals and to define such goals.Consequently, any intelligent system will be a control system. Conversely, intelligence is necessary to provide desirable functioning of systems under changing conditions, and it is necessary to achieve a high degree of autonomous behavior in a control system. Since control is an essential part of any intelligent system, the term “Intelligent Control Systems” is sometimes used in engineering literature instead of “Intelligent Systems” or “Intelligent Machines”. The term “Intelligent Control System” simply stresses the control aspect of the intelligent system.Below, one more alternative characterization of intelligent (control) systems is included. According to this view, a control system consists of data structures or objects (the plant models and the control goals) and processing units or methods (the control laws) :D. An intelligent control system is designed so that it can autonomously achieve a high level goal, while its components, control goals, plant models and control laws are not completely defined, either because they were not known at the design time or because they changed unexpectedly.There are several essential properties present in different degrees in intelligent systems. One can perceive them as intelligent system characteristics or dimensions along which different degrees or levels of intelligence can be measured. Below we discuss three such characteristics that appear to be rather fundamental in intelligent control systems.Adaptation and Learning. The ability to adapt to changing conditions is necessary in an intelligent system. Although adaptation does not necessarily require the ability to learn, for systems to be able to adapt to a wide variety of unexpected changes learning is essential. So the ability to learn is an important characteristic of (highly) intelligent systems.Autonomy and Intelligence. Autonomy in setting and achieving goals is an important characteristic of intelligent control systems. When a system has the ability to act appropriately in an uncertain environment for extended periods of time without external intervention, it is considered to be highly autonomous. There are degrees of autonomy; an adaptive control system can be considered as a system of higher autonomy than a control system with fixed controllers, as it can cope with greater uncertainty than a fixed feedback controller. Although for low autonomy no intelligence (or “low” intelligence) is necessary, for high degrees of autonomy, intelligence in the system (or “high” degrees of intelligence) is essential.Structures and Hierarchies. In order to cope with complexity, an intelligent system must have an appropriate functional architecture or structure for efficient analysis and evaluation of control strategies. This structure should be “sparse” and it should provide a mechanism to build levels of abstraction (resolution, granularity) or at least some form of partial ordering so to reduce complexity. An approach to study intelligent machines involving entropy emphasizes such efficient computational structures. Hierarchies (that may be approximate, localized or combined in heterarchies) that are able to adapt, may serve as primary vehicles for such structures to cope with complexity. The term “hierarchies” refers to functional hierarchies, or hierarchies of range and resolution along spatial or temporal dimensions, and it does not necessarily imply hierarchical hardware. Some of these structures may be hardwired in part. To cope with changing circumstances, the ability to learn is essential, so these structures can adapt to significant, unanticipated changes.In view of the above, a working characterization of intelligent systems (or of (highly) intelligent (control) systems or machines) that captures the essential characteristics present in any such system is:An intelligent system must be highly adaptable to significant unanticipated changes, and so learning is essential. It must exhibit high degree of autonomy in dealing with changes. It must be able to deal with significant complexity, and this leads to certain sparse types of functional architectures such as hierarchies.译文PLC和智能控制简介PLC(即可编程逻辑控制器)是机械控制中为替代必要的继电器时序电路而发明的一种设备。PLC 工作时通过查询输入端并根据其状态打开或关闭输出。用户通常用软件或编程器输入程序，从而获得期望的结果。很多实际应用都采用PLC。工业生产中应用PLC的可能性很高。如果你正在进行机械制造、产品包装、材料处理、自动化装配及无数其他工业生产，你可能已经用到了PLC。如果没有用到，那就是在浪费金钱和时间。几乎所有需要电气控制的地方都需要PLC。例如，假定在开关闭合时我们需要一个线圈接通5 秒，然后不管开关接通多长时间都将线圈断开。我们可以通过一个简单的外部定时器来实现。但是假如该过程有十个开关和线圈呢？我们就需要十个外部定时器。如果这个过程需要分别记录每个开关开启的次数呢？我们又需要很多外部计数器。由此可见，系统越大，我们就越需要PLC。我们可以简单地用PLC编程来对输入信号进行计数，并在规定的时间接通线圈。我们考察一下哪些是PLC 中最常用的20 条指令。保守地估计一下，如果真正地掌握了这些指令，就能解决80%以上现存的应用问题。是的，80%以上！当然，我们要学习的指令比这些更多，以帮助你解决几乎所有潜在的PLC应用问题。PLC 主要由中央处理器(CPU)、存储器和输入、输出电路构成，如图19.1 所示。我们可以将PLC看成是一个装满了成百上千个独立的继电器、计数器、定时器以及数据存储器的盒子。这些计数器、定时器等是不是真的存在呢？不，它们都是模拟的，物理上并不存在，但可以将它们看成是软计数器、软定时器等。这些内部继电器是用寄存器中的位单元模拟出来的。各个部分是如何工作的呢？输入继电器(触点)这些继电器连接外部电路。它们是实际存在的，并接收来自开关、传感器等的信号，通常是晶体管而非继电器。内部通用继电器(触点)它们不从外部设备接收信号，也非物理上存在的。它们是模拟的继电器，用以消除PLC的外部继电器。此外还有一些特殊继电器，专门执行一项任务。其中一些是常开的，一些是常闭的。有一些仅在电源上电时导通一次，通常用来初始化存储的数据。计数器 它们也非物理上存在的，而是模拟的计数器，可通过编程来对脉冲进行计数。通常它们可进行加计数、减计数或同时进行加减计数。因为它们是用软件模拟的，计数速度就有限。一些制造商提供了基于硬件的高速计数器。这样的计数器可以认为是物理上存在的。这些计数器多数情况下可以进行加计数、减计数或同时进行加减计数。定时器 它们也非物理上存在的，分为多种类型和定时单位。最常用的一种类型是延时导通型。其他类型还有延时断开型、记忆和非记忆型。定时单位的范围是1ms 到1s。输出继电器(线圈) 该部分连接到外围电路。它们是物理上存在的，并给线圈、灯等发送开关信号。输出继电器可以是晶体管、继电器或可控硅，取决于选择的型号。数据存储器 它们通常是用来存储数据的寄存器，一般作为运算或数据处理的暂存器。在PLC断电时通常还可用来存储数据。再次接通电源后，其内容与断电前相同，非常方便且必要。PLC 是通过连续扫描一个程序来工作的。我们可以认为扫描周期是由3 个主要阶段组成的，当然有多于三个阶段的情况，但我们可关注重要的环节，忽略其他环节。其他阶段通常正在检查系统及更新内部计数器和定时器的当前值。第一步检查输入状态首先PLC检查每一个输入是否接通。换句话说就是，与第一个输入端连接的传感器接通了吗？第二个输入呢？第三个输入呢？ 将这些数据记录到存储器中，以便在下一阶段使用。第二步执行程序然后PLC一次一条指令地执行程序。你的程序可能要求第一个输入接通时，就接通第一个输出。因为在上一步已经知道输入端的开关状态，根据上一步中第一个输入端的状态，就可以确定是否应接通第一个输出。PLC将执行结果存储起来，以供下一步使用。第三步更新输出状态最后PLC更新输出状态。PLC根据第一步中接通的输入和第二步中程序执行的结果更新输出状态。由于第一个输入接通了，程序要求在该条件满足时就接通第一个输出，根据第二步的情况，PLC就接通第一个输出。PLC 在执行完第三步后就返回到第一步，并反复循环。一次扫描时间定义为执行上面的三步所花的时间。因此，一个实际的系统应根据要求去执行特定的操作。智能与智能系统能用许多方式和从许多方面来描述。通常包含智
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