可编程逻辑控制器-毕业设计外文翻译

1、毕业设计外文文献翻译毕业设计题目多车位轿车立体停车库PLC控制系统设计翻译题目可编程逻辑控制器专 业机械设计制造及其自动化姓 名XXX班 级 学 号XX指导教师XXX机械与材料工程学院二O一四年四月可编程逻辑控制器1 PLC介绍PLCS可编程逻辑控制器是用于各种自动控制系统和过程的可控网络集线器。他们包含多个输入输出，输入输出是用晶体管和其它电路，模拟开关和继电器来控制设备的。PLCS用软件接口，标准计算器接口，专门的语言和网络设备编程。可编程逻辑控制器I/O通道规那么包括所有的输入触点和输出触点，扩展能力和最大数量的通道。触点数量是输入点和输出点的总和。PLCS可以指定这些值的任何可能的组合

2、。扩展单元可以被堆栈或互相连接来增加总的控制能力。最大数量的通道是在一个扩展系统中输入和输出通道的最大总数量。PLC系统规那么包括扫描时间，指令数量，数据存储和程序存储。扫描时间是 PLC需要的用来检测输入输出模块的时间。指令是用于PLC软件例如数学运算的标准操作。数据存储是存储数据的能力。程序存储是控制软件的能力。用于可编程逻辑控制器的输入设备包括DC，AC，中间继电器，热电偶，RTD，频率或脉冲，晶体管和中断信号输入；输出设备包括DC，AC，继电器，中间继电器，频率或脉冲，晶体管，三端双向可控硅开关元件；PLC的编程设备包括控制面板，手柄和计算机。可编程逻辑控制器用各种软件编程语言来控制。

3、这些语言包括IEC61131-3，顺序执行表SFC，动作方块图FBD，梯形图LD，结构文本ST，指令序列IL，继电器梯形图RIL，流程图，C语言和Basic语言。IEC61131-3编程环境能支持五种语言，用国际标准加以标准，分别为SFC，FBD，LD，ST和IL。这便允许了多卖主兼容性和多种语言编程。SFC是一种图表语言，它提供了编程顺序的配合，就能支持顺序选择和并列选择，二者择其一即可。FBD用一种大的运行库，以图表形式建立了一些复杂的过程。标准数学和逻辑运行可以与用户交流和接口运行相结合。LD是适用于离散控制和互锁逻辑的图表语言。它在离散控制上与FBD是完全兼容的。ST是一种文本语言，用

4、于复杂的数学过程和计算，不太适用于图表语言。摘自：科学与工程期刊 Laurence BodelotIL是与组合编码相似的低级语言。它用在相比照拟简单的逻辑指令。继电器梯形图或梯形图是适用于可编程逻辑控制器的重要的编程语言。梯形图编程是设计成继电器逻辑程序的图表表示法。流程图是一种图表语言，用于在一个控制器或应用软件中描述顺序操作，它用于建立有标准组件的可循环使用的运行库。C语言是一种高级编程语言，适用于处理最复杂的计算，连续的数据采集任务。它典型地在PC机上运行调试。BASIC语言是用于处理数据的连续的数字采集和接口运行的高级语言。可编程逻辑控制器也标准了许多计算机接口设备，网络规那么和特色。

5、PLC能源设备和运行环境也是非常重要的。2 指令对于简单的编程，继电器型PLC是有效的。随着功能的复杂化，复杂的VonNeaman型PLC就必须被采用。一个VonNeaman计算机一次只能执行一个指令，他们是这样运行的，尽管许多计算机看上去一次在做许多事情。正如图1所示的计算机组成。图 1 简化个人计算机结构图 输入是通过键盘和鼠标得到的。输出被送到屏幕。磁盘和存储器用于输入和输出存储注意：这些箭头的方向对于设计者是非常重要的，要注意说明信息是流向哪里的。这个图表可以像图2那样能被重新拟订来说明输入设备和输出设备的作用。图2 输入输出方向图 在这个图表中数据通过输入设备进入左边。注意：大多数设

6、计图表都是左边输入，右边输出的。在进入CPU之前，它穿过缓冲电路。CPU通过其他回路输出数据。存储器和磁盘用语存储要输出的数据。如果我们把个人计算机看作一个控制器，它通过在屏幕上输出鼓励和输入来自鼠标和键盘的响应来控制用户。 PLC也是一个控制过程的计算机。当与应用程序完全结合起来时，类似之处变成：输入设备键盘与接近开关相类比。输入电路连续输入芯片就像一个直流24V的输入卡。计 算 机686CPU就像一个PLC的CPU模块。输出电路图形卡就像一个三相开关输出卡。输出设备监控器就像指示灯。存 储 器PLC的存储器与个人计算机的存储器相似。用普通个人计算机可以运行PLC，虽然那么并不被提倡做。就P

7、LC来说，输入和输出设备设计得更加可靠，更加粗糙，更适合恶劣的制造环境。3 运行顺序所有的PLC系统有每秒钟重复屡次的四种根本运行阶段。最初被第一次接通时，它会检测它的硬件和软件是否有错误。如果没有错误，它会把所有输入和输入值复制到存储器，这叫输入扫描。只用复制了输入值的存储器，梯形逻辑图将被解决一个，这叫逻辑扫描。在解决梯形图期间，输出值只在临时存储器中被改变。当梯形图扫描完成后，输出将用存储器中临时值修正，这叫做输出扫描。PLC此时将从自我检测开始重新启动这个过程，这个过程很明显地每秒钟重复10到100次，正如图3所示图3 PLC扫描循环自我检测检测是否所有的卡没有错误，把时间继电器复零等

8、。如果在很小一段时间内没有复零，时间继电器会引起错误，关闭PLC系统。这会说明梯形图没有被正常扫描。输入扫描从芯片上的输入卡读取输入值，并把输入值复制到存储器，这能使PLC更快速地运行，并且防止从程序开始到结束输入变化。例如：意外停止有一些特殊的PLC功能，能直接读取输入值，防止了输入表格。逻辑处理/扫描基于存储器的输入表格，程序被一次执行一步，同时输出值也被修正，这是其它节的集中。输出扫描输出表格从存储器复制到输出芯片，这些芯片然后驱动输出仪器。输入输出扫描经常会令初学者感到迷惑，但是他们是很重要的。输入扫描是输入值的快照，并且解决逻辑关系。在一个梯形图扫描期间，如果一个输入在梯形图的多个地

9、方被用到，它就会起变化，潜在问题就可能发生，而输入扫描却防止了这些问题。这个边境效应是如果在一段持续时间内如果一个输入变化太短，它可能在输入扫描之间会减少或者丧失。当PLC最初被启动时，通常的输出会被关闭，这不会影响输入值。3.1 输入输出扫描 当输入值被扫描到PLC时，自然输入值被复制到存储器。当输出值被扫描到PLC时，他们将从存储器复制到自然输出设备。当梯形图被扫描时，它将用存储器中的值，并不是实际的输入输出值。这样做的主要原因是如果一个程序在多个地方用一个输入值，那么输入值的变化将使其逻辑关系无效。而且，如果随着每块的变化，输出模块也变化，在扫描结束时PLC的运行速度将大大减慢。3.2

10、逻辑扫描梯形逻辑程序图是模仿继电器逻辑图的。在继电器逻辑图中，程序的每个元件将尽可能快地开关。但是在一个程序中，元件只能按固定的顺序一次检测一个。如图4所示，梯形图将按从左到右，从上到下的顺序被解释。在图中，梯形逻辑扫描将从最高层开始。在底层，它将先解释高层输出，然后输出它下面的分支。在第二层，沿着梯形逻辑图移动之前，将先解释分支。图4 梯形图逻辑执行顺序解决梯形逻辑程序时，逻辑扫描顺序会变得非常重要。梯形图输出作为输入，考虑输出应用时，它也变得非常重要。如图5所示，梯形图第一行将检测输入并把输出X置1，得到相同的值。第二行将检测输入B并把输出X置1，得到相反的值。因此，直到梯形图的第二行被扫

11、描时X值才能与A相等。在逻辑扫描期间，输出值只能在存储器中被改变，只有当梯形逻辑扫描完成时，实际的输出才能被修正。因此，在第二行的根底上，输出扫描将修正实际输出值。并且梯形图的第一行将无效。图5 错误重复输出4 PLC状态显示在一个PLC中，缺少键盘和其他的输入输出设备是非常值得注意的。在PLC前端通常有一定数量的状态指示灯。通常指示灯说明： 电源启动只要PLC带电，它将被启动。程序运行这将指示是否程序正在运行或是否没有程序正在运行。 错误显示当PLC有大的硬件或软件错误时，这将有显示。 这些灯通常用于调试。一定数量的按钮也将提供应PLC的硬件。最普通的按钮是一个运行/编程选择开关，当在保持状

12、态时，它将被调到编程；当在生产状态时，它将被调到运行。一个PLC系统几乎没有一个启动关闭开关或复位开关在前面。这需要被设计到系统剩余局部。PLC的状态也能被梯形逻辑图检测。检测程序是否第一次被执行是非常普遍的。如图6所示。first scan输入在梯形图被第一次扫描时，将是对的，而在其余的每次扫描时是错误的。这种情况下，PLC5的first scan的地址是S2：1/14。根据例子中的逻辑关系，第一次扫描将封上light，直到clear被启动。因此灯将在PLC被启动之后变亮，但在clear被启动之后，它将关闭并且保持在关闭状态。first scan 模块在first pass模块中被提到。图6

13、 核验PLC第一次扫描的程序5 存储器类型有几种根本的现在经常使用的计算机存储器类型：RAM随机存储器这种存储器速度很快，但是当没电时，它的内容将被丧失。这是一种不稳定存储器，每个PLC在运行时，都用这种存储器作为中央处理器 。ROM只读存储器这种存储器是永久性的不可擦除的。它通常用于存放PLC的操作系统。EPROM可擦除可编程只读存储器这是一种像ROM一样可编程的存储器，但是它能用紫外线光擦除并且可以重新编程。EEPROM电可擦除可编程只读存储器这种存储器能像ROM一样存放程序。它能被编程并且用电压擦除，因此它正变得比EPROM更加普遍。所有的PLC系统都用RAM做CPU，用ROM存储PLC

14、的根本操作系统。当有电时，RAM的内容被保存，但是问题在于当供应存储器的电源失去时会发生什么。原先PLC卖主用带有电池的RAM，这样如果不失电，存储器的内容就不会丧失。这种方法现在仍被使用，但变得不那么受欢送。EPROMS也是PLC编程的比拟好的选择。EPROM在PLC外部编程，然后被放入PLC。当PLC被启动时，在EPROM上的梯形逻辑程序被下载PLC并且运行。这种方法非常可靠，但是擦除和编程技术都是很消耗时间的。EEPROM存储器是PLC的永久局部，程序能EPROM一样被存放在他们中。存储器的价钱一直在下降，新类型正变得可被利用，这些变化将继续对PLC系统发生影响。6 检验和优化一个PLC

15、控制时间表混合的系统是快速地成长的重要一个研究领域。在系统中出现不连续的和连续的现象，激发了我们对特殊系统技术挑战和对我们能力的分析。这导致新的表达的模型开展，例如，计时的混合自动机械装置和新的方法，最特别地做模型检查技术包括即时方面。混合(嵌入的)系统的一个重要的例子是处理控制方案，包括处理系统的数传控制，举例来说，化学药品厂的控制系统是相当的重要的典型应用的程序控制器系统。令人失望的是PLC和他们组成的系统语言都没有好标准，不能用正式的模型来设计复杂可靠的控制器。欧盟研究方案VHS(混合的系统)有许多个案研究。其中一个研究为一个实验的化学工厂与PLC控制流程设计有关。在这个文章中，我们在两

16、个样板的检验员检测的根底上报告为给定的系统和最正确的控制引出预定。它是程序控制器的正确设计上的浓缩语。这个工具是一个很自然的备选者中支持即时的环境最正确的控制时间表引出的。这再一次给与我们实行个案研究的最正确化部份的时机，也是它自己功能的一种练习。收集数据并解释与之相比拟后获得的结果。这篇文章开始局部介绍PLC性质。7 基于软件的PLC系统个人计算机持续下降的价格增加了他们在控制系统中的应用，包括PLC的替代品。安装了软件就能用个人计算机解决梯形图逻辑.从传感器中读取输入，修改输出送到鼓励。这些对于维持是很重要的，因为他们不用遵守以前的计时模式.例如，计算机正运行一个游戏，就可能减慢或停止计算

17、机.这个以及其它问题现在正被研究，好的解决方案不久就会出现。8 概要PLC系统和计算机与输入设备，输出设备,存储器等很相似。PLC系统不断地执行系统检查，输入扫描,逻辑扫描和输出扫描这个循环。当逻辑图被扫描时，输入的变化没有被发现,输出也没有被修正。PLC系统用RAM，有时用EPROM存放永久程序。9 实际问题一个PLC系统通常包括RAM，ROM，EPROM和/或电池吗？PLC的指示灯用于什么？为什么一个PLC系统每秒钟只能扫描梯形图几次？如果一个PLC系统的扫描时间比输入脉冲长，会发生什么?为什么？一个PLC系统与一部台式计算机的不同是什么？为什么PLC系统每次扫描要做自我检查？PLC检测时

18、间会比简单程序所需时间长吗？10 实际问题解答每个PLC系统包括RAM和ROM，但是他们也包括EPROM或电池。诊断和保持。尽管程序是空的，PLC系统仍需扫描输入和输出，做自我检测。如果在两次输入扫描之间发生，脉冲就会丧失。主要的区别包括输入设备输出设备和应用。PLC系统是为工厂设计的，因此它没有鼠标键盘之类的输入设备。(虽然，一些较新型PLC能够到达)他们也没有屏幕声音之类的输出设备，.取而代之，他们有电压,电流这样的输入设备和输出设备。PLC使用户为专门的任务设计程序,然而在个人计算机上给系统编程是不常见的。这能帮助检测硬件和软件错误。如果一个错误发生了，PLC还继续运行,控制器就可能以一

19、种不可预见的方式运行，这对人和机器是非常危险的。自我检测那么帮助检查出这些错误，并且平安地关闭系统。是的，在许多PLC系统中，自检大约需要1ms，但一个单一程序需1mms。Programmable Logic Controllers (PLCs)1 About Programmable Logic Controllers (PLCs)PLCs (programmable logic controllers) are the control hubs for a wide variety of automated systems and processes. They contain multi

20、ple inputs and outputs that use transistors and other circuitry to simulate switches and relays to control equipment. They are programmable via software interfaced via standard computer interfaces and proprietary languages and network options. Programmable logic controllers I/O channel specification

21、s include total number of points, number of inputs and outputs, ability to expand, and maximum number of channels. Number of points is the sum of the inputs and the outputs. PLCs may be specified by any possible combination of these values. Expandable units may be stacked or linked together to incre

22、ase total control capacity. Maximum number of channels refers to the maximum total number of input and output channels in an expanded system. PLC system specifications to consider include scan time, number of instructions, data memory, and program memory. Scan time is the time required by the PLC to

23、 check the states of its inputs and outputs. Instructions are standard operations (such as math functions) available to PLC software. Data memory is the capacity for data storage. Program memory is the capacity for control software.Available inputs for programmable logic controllers include DC, AC,

24、analog, thermocouple, RTD, frequency or pulse, transistor, and interrupt inputs. Outputs for PLCs include DC, AC, relay, analog, frequency or pulse, transistor, and triac. Programming options for PLCs include front panel, hand held, and computer. Programmable logic controllers use a variety of softw

25、are programming languages for control.These include IEC 61131-3, sequential function chart (SFC), function block diagram (FBD), ladder diagram (LD), structured text (ST), instruction list (IL), relay ladder logic (RLL), flow chart, C, and Basic. The IEC 61131-3 programming environment provides suppo

26、rt for five languages specified by the global standard: Sequential Function Chart, Function Block Diagram, Ladder Diagram, Structured Text, and Instruction List. This allows for multi-vendor compatibility and multi-language programming. SFC is a graphical language that provides coordination of progr

27、am sequences, supporting alternative sequence selections and parallel sequences. FBD uses a broad function library to build complex procedures in a graphical format. Standard math and logic functions may be coordinated with customizable communication and interface functions. LD is a graphic language

28、 for discrete control and interlocking logic. It is completely compatible with FBD for discrete function control. ST is a text language used for complex mathematical procedures and calculations less well suited to graphical languages. IL is a low-level language similar to assembly code. It is used i

29、n relatively simple logic instructions. Relay Ladder Logic (RLL), or ladder diagrams, is the primary programming language for programmable logic controllers (PLCs). Ladder logic programming is a graphical representation of the program designed to look like relay logic. Flow Chart is a graphical lang

30、uage that describes sequential operations in a controller sequence or application. It is used to build modular, reusable function libraries. C is a high level programming language suited to handle the most complex computation, sequential, and data logging tasks. It is typically developed and debugge

31、d on a PC. BASIC is a high level language used to handle mathematical, sequential, data capturing and interface functions.Programmable logic controllers can also be specified with a number of computer interface options, network specifications and features. PLC power options, mounting options and env

32、ironmental operating conditions are all also important to consider.2 INTRODUCTIONFor simple programming the relay model of the PLC is sufficient. As more complex functions are used the more complex VonNeuman model of the PLC must be used. A VonNeuman computer processes one instruction at a time. Mos

33、t computers operate this way, although they appear to be doing many things at once. Consider the computer components shown in Figure 1.Figure 1 Simplified Personal Computer ArchitectureInput is obtained from the keyboard and mouse, output is sent to the screen, and the disk and memory are used for b

34、oth input and output for storage. (Note: the directions of these arrows are very important to engineers, always pay attention to indicate where information is flowing.) This figure can be redrawn as in Figure 2 to clarify the role of inputs and outputs.Figure 2 An Input-Output Oriented ArchitectureI

35、n this figure the data enters the left side through the inputs. (Note: most engineering diagrams have inputs on the left and outputs on the right.) It travels through buffering circuits before it enters the CPU. The CPU outputs data through other circuits. Memory and disks are used for storage of da

36、ta that is not destined for output. If we look at a personal computer as a controller, it is controlling the user by outputting stimuli on the screen, and inputting responses from the mouse and the keyboard.A PLC is also a computer controlling a process. When fully integrated into an application the

37、 analogies become;inputs - the keyboard is analogous to a proximity switchinput -circuits - the serial input chip is like a 24Vdc input cardcomputer - the 686 CPU is like a PLC CPU unitoutput - circuits - a graphics card is like a triac output cardoutputs - a monitor is like a lightstorage - memory

38、in PLCs is similar to memories in personal computersIt is also possible to implement a PLC using a normal Personal Computer, although this is not advisable. In the case of a PLC the inputs and outputs are designed to be more reliable and rugged for harsh production environments.3 OPERATION SEQUENCEA

39、ll PLCs have four basic stages of operations that are repeated many times per second. Initially when turned on the first time it will check its own hardware and software for faults. If there are no problems it will copy all the input and copy their values into memory, this is called the input scan.

40、Using only the memory copy of the inputs the ladder logic program will be solved once, this is called the logic scan. While solving the ladder logic the output values are only changed in temporary memory. When the ladder scan is done the outputs will be updated using the temporary values in memory,

41、this is called the output scan. The PLC now restarts the process by starting a self check for faults. This process typically repeats 10 to 100 times per second as is shown in Figure 3.Figure 3 PLC Scan CycleSELF TEST - Checks to see if all cards error free, reset watch-dog timer, etc. (A watchdog ti

42、mer will cause an error, and shut down the PLC if not reset within a short period of time - this would indicate that the ladder logic is not being scanned normally).INPUT SCAN - Reads input values from the chips in the input cards, and copies valuesmemory. This makes the PLC operation faster, and av

43、oids cases where an input changes from the start to the end of the program (e.g., an emergency stop). There are special PLC functions that read the inputs directly, and avoid the input tables.LOGIC SOLVE/SCAN - Based on the input table in memory, the program is executed 1 step at a time, and outputs

44、 are updated. This is the focus of the later sections.OUTPUT SCAN - The output table is copied from memory to the output chips. These chips then drive the output devices.The input and output scans often confuse the beginner, but they are important. The input scan takes a snapshot of the inputs, and

45、solves the logic. This prevents potential problems that might occur if an input that is used in multiple places in the ladder logic program changed while half way through a ladder scan. Thus changing the behaviors of half of the ladder logic program. This problem could have severe effects on complex

46、 programs that are developed later in the book. One side effect of the input scan is that if a change in input is too short in duration, it might fall between input scans and be missed.When the PLC is initially turned on the normal outputs will be turned off. This does not affect the values of the i

47、nputs.3.1 The Input and Output ScansWhen the inputs to the PLC are scanned the physical input values are copied into memory. When the outputs to a PLC are scanned they are copied from memory to the physical outputs. When the ladder logic is scanned it uses the values in memory, not the actual input

48、or output values. The primary reason for doing this is so that if a program uses an input value in multiple places, a change in the input value will not invalidate the logic. Also, if output bits were changed as each bit was changed, instead of all at once at the end of the scan the PLC would operat

49、e much slower.3 .2 The Logic ScanLadder logic programs are modelled after relay logic. In relay logic each element in the ladder will switch as quickly as possible. But in a program elements can only be examines one at a time in a fixed sequence. Consider the ladder logic in Figure 4, the ladder log

50、ic will be interpreted left-to-right, top-to-bottom. In the figure the ladder logic scan begins at the top rung. At the end of the rung it interprets the top output first, then the output branched below it. On the second rung it solves branches, before moving along the ladder logic rung.Figure 4 Lad

51、der Logic Execution SequenceThe logic scan sequence become important when solving ladder logic programs which use outputs as inputs. It also becomes important when considering output usage. Consider Figure 5, the first line of ladder logic will examine input A and set output X to have the same value

52、. The second line will examine input B and set the output X to have the opposite value. So the value of X was only equal to A until the second line of ladder logic was scanned. Recall that during the logic scan the outputs are only changed in memory, the actual outputs are only updated when the ladd

53、er logic scan is complete. Therefore the output scan would update the real outputs based upon the second line of ladder logic, and the first line of ladder logic would be ineffective.Figure 5 A Duplicated Output Error4 PLC STATUSThe lack of keyboard, and other input-output devices is very noticeable

54、 on a PLC. On the front of the PLC there are normally limited status lights. Common lights indicate;power on - this will be on whenever the PLC has powerprogram running - this will often indicate if a program is running, or if no program is running fault - this will indicate when the PLC has experie

55、nced a major hardware or software problem.These lights are normally used for debugging. Limited buttons will also be provided for PLC hardware. The most common will be a run/program switch that will be switched to program when maintenance is being conducted, and back to run when in production. This

56、switch normally requires a key to keep unauthorized personnel from altering the PLC program or stopping execution. A PLC will almost never have an on-off switch or reset button on the front. This needs to be designed into the remainder of the system.The status of the PLC can be detected by ladder lo

57、gic also. It is common for programs to check to see if they are being executed for the first time, as shown in Figure 6. The first scan input will be true on the very first time the ladder logic is scanned, but false on every other scan. In this case the address for first scan in a PLC-5 is S2:1/14. With the logic in the example the first scan will seal on light, until clear is turned on. So the light will turn on after the PLC has been turned on, but it will turn off and stay off after clear is turned on. The first scan bit is also referred to at the fir