1、 1 毕业 设计 （ 论文 ）外文 文献 翻译 （本科学生用） 题 目： Plc based control system for the music fountain 学 生 姓 名： _ _学号 ： 060108011117 学 部 （系） : 信息学部 专 业 年 级 : _06 自动化（ 1）班 _ 指 导 教 师： _职称 或学位 ： 助教 _ 20 年 月 日 2 外文文献翻译（译成中文 1000 字左右）： 【 主要阅读文献不少于 5 篇 ， 译文后附注 文献信息 ，包括 ： 作者、 书名（或论文题目）、出 版 社（或刊物名称）、出版时间（或刊号）、页码 。 提供 所译外文资料附
2、件（印刷类含封面、封底、目录、翻译部分的复印件等，网站类的请附网址及原文 】 英文节选原文： Central Processing Unit (CPU) is the brain of a PLC controller. CPU itself is usually one of the microcontrollers. Aforetime these were 8-bit microcontrollers such as 8051, and now these are 16-and 32-bit microcontrollers. Unspoken rule is that youll fi
3、nd mostly Hitachi and Fujicu microcontrollers in PLC controllers by Japanese makers, Siemens in European controllers, and Motorola microcontrollers in American ones. CPU also takes care of communication, interconnectedness among other parts of PLC controllers, program execution, memory operation, ov
4、erseeing input and setting up of an output. PLC controllers have complex routines for memory checkup in order to ensure that PLC memory was not damaged (memory checkup is done for safety reasons).Generally speaking, CPU unit makes a great number of check-ups of the PLC controller itself so eventual
5、errors would be discovered early. You can simply look at any PLC controller and see that there are several indicators in the form. of light diodes for error signalization. System memory (today mostly implemented in FLASH technology) is used by a PLC for a process control system. Aside form. this ope
6、rating system it also contains a user program translated forma ladder diagram to a binary form. FLASH memory contents can be changed only in case where user program is being changed. PLC controllers were used earlier instead of PLASH memory and have had EPROM memory instead of FLASH memory which had
7、 to be erased with UV lamp and programmed on programmers. With the use of FLASH technology this process was greatly shortened. Reprogramming a program memory is done through a serial cable in a program for application development. User memory is divided into blocks having special functions. Some par
8、ts of a memory are used for storing input and output status. The real status of an input is stored either as “1”or as “0”in a specific memory bit/ each input or output has one corresponding bit in memory. Other parts of memory are used to store variable contents for variables used in used program. F
9、or example, time value, or counter value would be stored in this part of the memory. PLC controller can be reprogrammed through a computer (usual way), but also through manual programmers (consoles). This practically means that each PLC controller can programmed through a computer if you have the so
10、ftware needed for programming. Todays transmission computers are ideal for reprogramming a PLC controller in factory itself. This is of great importance to industry. Once the system is corrected, it is also important to read the right program into a PLC again. It is also good to check from time to t
11、ime whether program in a PLC has not changed. This helps to avoid hazardous situations in factory rooms (some automakers have established communication networks which regularly check programs in PLC controllers to ensure execution only of good programs). Almost every program for programming a PLC co
12、ntroller possesses various useful options such as: forced switching on and off of the system input/outputs (I/O lines), 3 program follow up in real time as well as documenting a diagram. This documenting is necessary to understand and define failures and malfunctions. Programmer can add remarks, nam
13、es of input or output devices, and comments that can be useful when finding errors, or with system maintenance. Adding comments and remarks enables any technician (and not just a person who developed the system) to understand a ladder diagram right away. Comments and remarks can even quote precisely
14、 part numbers if replacements would be needed. This would speed up a repair of any problems that come up due to bad parts. The old way was such that a person who developed a system had protection on the program, so nobody aside from this person could understand how it was done. Correctly documented
15、ladder diagram allows any technician to understand thoroughly how system functions. Electrical supply is used in bringing electrical energy to central processing unit. Most PLC controllers work either at 24 VDC or 220 VAC. On some PLC controllers youll find electrical supply as a separate module. Th
16、ose are usually bigger PLC controllers, while small and medium series already contain the supply module. User has to determine how much current to take from I/O module to ensure that electrical supply provides appropriate amount of current. Different types of modules use different amounts of electri
17、cal current. This electrical supply is usually not used to start external input or output. User has to provide separate supplies in starting PLC controller inputs because then you can ensure so called “pure” supply for the PLC controller. With pure supply we mean supply where industrial environment
18、can not affect it damagingly. Some of the smaller PLC controllers supply their inputs with voltage from a small supply source already incorporated into a PLC. 中文翻译： 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
19、置。 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。 PLC 使用系统存储器 （现在大部分采用闪存技术了）用于过程控制系统。除了这个操作系统之外，它还包括一个由梯形图翻译成而进制形式的用户程序。快擦型存储器（ FLASH memory）的内容只有在改变用户程序的时候可以被改变。 PLC 控制器比快擦型存储器使用得更早， EPROM存储器比快擦型存储器也更早，快擦型存储器必须用紫外线（ UV， Ultra-Violet Ray）灯擦除，并在编程器上进行编程。由于快擦型存储器技术的应用，使得这个过程大大缩短了。在应用程序开发中，通过一个串行电缆可以对程序存储器进行重新编程。 用户存储器被分 成具有特殊功能的块。一部分存储器用来存储输入和输出状态。一个输入的实际状态存储状态存储在专用存储器位上，为 “1” 或者 “0” 。每一个输入和输出在存储器
