PLC外文文献翻译.docx

1、PLC外文文献翻译 外文翻译题目Programmable Logic Controller 目 录Programmable Logic Controller (PLC) 11. About Programmable Logic Controller (PLC) 12. INTRODUCTION 23. OPERATION SEQUENCE 43 .1 The Input and Output Scans 53.2 The Logic Scan 54 PLC STATUS 65. MEMORY TYPES 76. SOFTWARE BASED PLCS 87. SUMMARY 88. PRACT

2、ICE PROBLEMS 89. PRACTICE PROBLEM SOLUTIONS 9中文翻译 111. PLC介绍 112指令 123运行顺序 133.1 输入输出扫描 1432 逻辑扫描 144PLC状态显示 155存储器类型 166基于软件的PLC系统 167概要 178实际问题 179实际问题解答 17Programmable Logic Controller (PLC)1. About Programmable Logic Controller (PLC)PLC (programmable logic controllers) is the control hubs for a

3、wide variety of automated systems and processes. They contain multiple 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 networ

4、k options.Programmable logic controllers I/O channel specifications 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. PLC may be specified by any possible combination of these va

5、lues. Expandable units may be stacked or linked together to increase 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,

6、 and program memory. Scan time is the time required by the PLC to 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.Ava

7、ilable inputs for programmable logic controllers include DC, AC, analog, thermocouple, RTD, frequency or pulse, transistor, and interrupt inputs. Outputs for PLC include DC, AC, relay, analog, frequency or pulse, transistor and triac. Programming options for PLC include front panel, hand held and co

8、mputer.Programmable logic controllers use a variety of software 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 B

9、asic. The IEC 61131-3 programming environment provides support 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

10、 is a graphical language that provides coordination of program 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 com

11、munication and interface functions. LD is a graphic language 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

12、 a low-level language similar to assembly code. It is used in relatively simple logic instructions. Relay Ladder Logic (RLL), or ladder diagrams, is the primary programming language for programmable logic controllers (PLC). Ladder logic programming is a graphical representation of the program design

13、ed to look like relay logic. Flow Chart is a graphical language 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, an

14、d data logging tasks. It is typically developed and debugged 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 specificatio

15、ns and features. PLC power options, mounting options and environmental 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.

16、A VonNeuman computer processes one instruction at a time. Most 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 both input and output for storage.