1、 2012 届毕业设计说明书 外 文文献翻译 院 、 部： 电气与信息工程学院 学生姓名： 指导教师： 职称 副 教授 专 业： 班 级： 完成时间： PLC Theory And Applications A programmable logic controller, PLC, or programmable controller is a small computer used for automation of real-world processes, such as control of machinery on factory assembly lines. The PLC us
2、ually uses a microprocessor. The program can often control complex sequencing and is written by skilled engineers. The program is stored in battery-backed memory and/or EEPROMS. Definition is: a digital electronic computer operating system specifically designed for using in the industrial environmen
3、t. It adopts a category programmable memory for its internal storage procedures, the implementation of the logical operations, sequence control, timing, counting and arithmetic operations such as user-oriented instructions, and through digital or analog input / output control various types of machin
4、ery or production processes. 1 PLC Development Course In industrial production processes, a large number of switches in order to control it in a logical sequence of moves conditions, and in accordance with the logic of relations chain protection movements control, and a large number of discrete volu
5、me data collection. Traditionally, these functions are achieved through pneumatic or electrical control system. 1968 U.S. GM (General Motors) company replaced following electrical control devices, the second year, the U.S. company has developed a number of integrated circuits and electronic technolo
6、gy-based control devices, the first use of the means of the procedures applied to the electrical control, and this is the first generation programmable controller said Programmable Controller (PC) The functionality of the PLC has evolved over the years to include typical relay control, sophisticated
7、 motion control, process control, distributed control systems and complex networking. Personal computer (PC for short) has been developed, in order to facilitate, but also to reflect the functional characteristics of programmable controllers. Programmable controller is named Programmable Logic Contr
8、oller (PLC), now PC is often called PLC. 2 Programmable Controller Basic Tenets PLC is based on computers, and applies to industrial motor controlling work site. It originated from relay control devices, but it does relay devices, the physical process of controlling through circuits, and mainly reli
9、es on the operation of PLC memory stored in the procedures for the realization of their information into and out of control. PLCs were invented as less expensive replacements for older automated systems that would use thousands of relays and cam timers. Often, a single PLC can be programmed to repla
10、ce thousands of relays. Programmable controllers were initially adopted by the automotive manufacturing industry, where software revision replaced the re-wiring of hard-wired control panels. PLC-based computer, but can not be equated with ordinary computers. Information is transformed into a univers
11、al computer, and it is only considered by information itself. No matter information goes into and out of it； it can be a good human interface. And the PLC will also consider the reliability of information in and out, real-time, and the use of information and other issues. Special consideration must
12、be given to how to adapt to the industrial environment, such as the ease of installation, interference and other issues. 2.1 PLC Composition PLC is divided into two forms of fixed and modular (modular) in structure. Fixed PLC includes CPU boards, I/O boards, and panels shown, within blocks, electric
13、ity. All these elements into a portfolio as a whole are not detachable. Modular PLC includes CPU Modules, I/O module, memory, power supply module, or ill bed, these modules will be in accordance with the rules of portfolio allocation. 2.1.1 CPU Composition CPU is the core of PLC, and it plays a cent
14、ral role. At least one PLC has one CPU, the PLC system procedures is to receive and store the users functional procedures and data collection methods used by the scanning of the device or sent to the state data, and in the execution, at the same time, diagnostic power and the internal circuits PLC programming process and the work of the grammatical mistakes. During operation, from memory, the article retrieval user procedures is directively analyzed later by a corresponding directive mandates control signals to the command control circuits. For example:
