可编程控制器中英文翻译@外文翻译@外文文献翻译

外文原文： Introduction to PLC In order to use the advantages of all those controllers and eliminate the difficulties, the programmable logic controllers were invented. programmable logic controllers (PLCs), also referred to as programmable controllers, are in the computer family.A PLC was replacement for relay devices. They are programmed using a ladder diagram,which is standard electric wiring diagram. As PLC become more flexible, high-level as well as low-level languages are available to PLC programmers. PLC have the flexibility of computers as well as a standard and ersy interface with processes and other devices. They are used in commercial and applications. They are widely acceped in industry for controlling from a single device to a complex manufacturing facility. programmable logic controllers were first introduced in 1968 as a substitute for hardwired relay panels. The original intent was to replace a mechanical switching device (relay modules).However,since 1968, the capabilities of the PLC were to replace relay panels,modern PLC have many more functions. Their use extends from simple process control to manufacturing system controls and monitoring. They are used for high-speed digital processing, high-speed digital communication, high-level computer-language support, and, of course, for basic control. PLC vary in size and power. A large PLC can have up to 10000 I/O points and support all the functions discussed earlier. There are expansion slots to accommodate PC and oter communitions decices. For many applications, a small PLC is sufficient. The speed of PLC is constantly improving, even the low-end PLC perform at high speed. One to two microsec / kbyte of memory speed is very common. Programmable logic controllers Architecture The basic components in a relay panel circuit and the design of a relay ladder diagram have been discussed. In the implementation of such a circuit, not only doesthe logic problem have to be thought out, but alse the electrical compatibility and wiring layout have to be considered. Breadboarding a relay panel circuit is a tedious task； it requires a lot of careful planning and work. The debugging and changing of a circuit is even more difficult. Programmable logic controllers replace most of this wiring by software programming. Therefore, the task is made much easier, because the wires and the moving mechanical components (relay contacts) are mostly replaced by software, the system is much more reliable. Like a general-purpose computer, a programmable controller consists of five major parts； CPU (processor), memory, input/out (I/O), power supply, and peripherals. Programmable logic controllers Functions and Configurations. 1 Basic PLC Operation PLC consist of input modules or poits, a Central Processing Unit (CPU), and output modules or points. An input accepts a variety of digital oranalog signals from various field devices (sensors) and converts them into a logic signal that can be used by the CPU. The CPU makes decisions and executes control instructions based on program instructions in memory. Output modules convert convert control instructions from the CPU into a digital or analog signal that can be used to control various field devices (actuators). A programming device is used to input the desired instructions. These instructions determine what the PLC will do for a specific input. An operator interface device allows process information to be displayed and new control paramenters to be entered. Pushbuttons (sensors), connected to PLC inputs, can be used to start and stop a motor connected to a PLC through a motor starter (actuator). 2 Hard-Wired Control Prior to PLC many of these control tasks were solved by contactors or relay controls. This is often referred to as hardwired control. Circuit diagrams had to be designed. Electrical components specified and installed, and wiring lists created. Electricians would then wire the components necessary to perform a specific task. If an error was made the wires had to be reconnected correctly. A change in function or expansion required wxtensive component changes and rewiring. 3 Advantages of PLC The same, as well as more complex tasks, can be done with a PLC. Wiring between devices and relay cintacts is done in the PLC program. Hard-wiring, though still required to connect field device, is less intensive. Modifying the application and correcting errors are easier to handle. It is easier to create and chang a program in a PLC than it is to wire and rewire a circuit. Following are just a few of the advantages of PLC: Smaller physical size than hard-wire solution. Easier and faster to make changes. PLC have integrated diagnostics and override dunction. Applications can be immediately documented. Applications can be duplicated faster and less expensively. 4 Siements PLC Siements makes several PLC product lines in the SIMATIC S7 family. They are: S7-200, S7-300, S7-400. (1) S7-200 The S7-200 is referred to as a micro-PLC because of its small size. The S7-200 has a brick design which means that the power supply and I/O terminal are on-board. The S7-200 can be used on smaller, stand-alone applications such as elevators, car washes, or mixing machines. It can also be used on more complex industrial applications such as bottling and packaging machines. (2) S7-300 and S7-400 The S7-300 and S7-400 PLC are used in more complex applications that support a greater number of I/O poits. Both PLC are modular and expandable. The power supply and I/O consist of separate modules connected to be the CPU. Choosing either the S7-300 or S7-400 depends on the complexity of the task and possible future expansion. Your Siemens sales representative can provide you with additional information on any of the Siemens PLC. 5 CPU CPU is a microprocessor system that contains the system memory and is the PLC decision-making unit. The CPU monitors the inputs and makes decisions based on instructions held in the program memory. The CPU performs relay, couting, timing, data comparison, and sequential operations. 6 Programming Devices The program is created in a programming device (PG) and then transferred to the PLC. The program for the S7-200 can be created using a dedicated Siemens SIMATIC S7 programming device, such as a PG 720 or PG 740, if STEP 7 Micro/WIN software is installed. A personal computer (PC), with STEP 7 Micro/WIN installed, can also be used as a programming device with the S7-200. 7 Software A software program is required in order to tell the PLC what instructions it must follow. Programming software is typically PLC specific. A software package fo r one PLC ,or one family of PLC ,such as the S7 family, would not be useful on other PLC. The S7-200 uses a Windows-based software program called STEP -7 Micro/WIN32, The PG 720 and PG 740 computer in a similar manner to any other computer software. 8 Connector Cables PPI (Poit-Poit Interface) Connector cables are required to transfer data from the program the programming device to the PLC. Communication can only take place when the two device speak the same language or protocol. Communication between programming device and the S7-200 is referred to as PPI protocol. An appropriate cable is required for a programming device such as a PG 720 or PG 740. The S7-200 uses a 9-pin,D-connector. This is a straight-through serial device that is compatible with Siemens programming devices (MPI port) and is a stangard connector for other serial interface. A special cable,referred to as a PC/PPI cable, is needed when a personal computer is used as a programming device. This cable allows the serial interface of the PLC to communicate with the RS-232 serial interface of a personal computer. DIP switched on the PC/PPI cable are used to select an appropriate speed (bit rate) at which information is passed between the PLC and the computer. 译文： 可编程控制器 为了利用那些控制器的优势，消除弊端，可编程逻 辑控制器（ PLC）应运而生，可编程逻辑控制器（ PLC），也就是可编程控制器，是计算机家族的一员。一个 PLC 就是能代替整个继电器控制装置，它们用梯形图（梯形图是标准的电路图）。由于 PLC 的编程灵活性逐渐增强，既可使用高级语言也可使用低级语言。PLC 不仅具有计算机的灵活性，同时也具有与处理过程及其他装置连接的界面标准简易的特点。它们被应用于商业和工业领域，在工业上，从单一设备到复杂的制造设备都广泛使用 PLC 控制。 可编程逻辑控制器（ PLC）于 1968 年被首次使用，用来替代一个硬接线的继电器控制板。最初目的是替代 机械开关装置（继电模块）。然而，自从 1968 年以来， PLC 的功能逐渐代替了继电器控制板，现代 PLC 具有更多的功能。其用途从单一过程控制延伸到整个制造系统的控制和监控。 可编程控制器也可用在高速数字处理、高速数字通信以及高级计算机语言的支持方面，当然也可用于基本的过程控制。 PLC 在尺寸和功率上不尽相同，一个大型 PLC 可以有高达 10000 个输入输出点，具有前面讨论过的所有功能。 PLC 有连接 PC 机和其他通信设备的扩展槽，在很多场合下，一个小的 PLC 就足够了。 可编程控制器的构造 我们已经讨论了继电器装置面板电 路中的基本部件和继电器梯形图的设计。在这样的电路设计过程中，我们不仅要认真思考逻辑问题，而且还要对电气兼用型和布线加以考虑。设计继电器的面板电路是一项乏味的任务，它需要周密计划和大量的工作。电路的调试和修改变得容易很多。因为导线和运动的机械部件（继电器出头）几乎全部被软件所替代，所以整个系统更加可靠。 像通用计算机一样，可编程控制器由以下 5 个主要部分组成： CPU(处理器 )、内存、输入输出（ I/O）、电源和外设。 可编程控制器的功能和配置 1 PLC 的基本操作 PLC 包括输入模块或输入点、一个中央处理单元（ CPU）以及输出模块或输出点。输入单元可以接受来自不同现场设备（传感器）的各种数字或模拟信号，然后将它们转换为 CPU 可以使用的逻辑信号。 CPU 根据存储器中的程序指令做出判断，然后执行指令。输出模块将来自 CPU 的控制指令转换为现场控制的各个设备（执行机构）所能使用的数字或逻辑信号。编程设备用于输入期望指令，由这些指令来决定对于特定的输入 PLC 做什么。操作界面能够显示过程信息及输入新的控制参数。连接到 PLC 输入端的按钮 ,通过电动机的启动器可以启动和停止与 PLC 连接电动机。 2 硬接线控制 使用 PLC 之前，许多控制 人为是通过接触器和继电器来完成的。这就是经常所说的硬接线控制。必须先设计电路图，确定元件，并且进行安装以及建立接线表，电工再连接需要执行特定任务的元件。如果接线中有一个错误，就必须重新连接来纠正。如果改变功能或扩充系统，元件就需要大量变化，并且线路要重接。 3 PLC 的优势 同样或更加复杂的任务，可以用 PLC 来做。设备同继电器出典之间的连接由PLC 中的程序完成。硬接线虽然依然需要连接到现场设备，但这一要求已经很少了。修改应用软件或纠正错误要容易些。在 PLC 中建立或修改程序比起连接或重新连接电路要容易。 下面 列出的知识 PLC 的一小部分优点： 比通过硬接线方式的物理尺寸小 修改时更简单且更快速 PLC 有综合诊断和忽略功能 应用软件能被立即生成文件 应用程序能够被更快并且费用更低的复制 4 西门子 PLC 西门子制造了几种属于 SIMATIC S7 产品系列的 PLC。它们是 S7-200， S7-300，S7-400。 （ 1） S7-200 S7-200 由于尺寸小，被称为微型 PLC。 S7-200 是块状设计结构，即它的电源和 I/O 都在一块板上。 S7-200 可以被使用在小型的、独立的应用设备中，