英汉翻译文献.doc

2011届毕业设计（论文） 外文翻译 系 、 部： 电气与信息工程系 学生姓名： 吴龙军 指导教师： 罗雪莲 职 称： 教授 专 业： 自动化 班 级： 自本0703班 学 号： 410070331 2011 年6月PLC control technology Programmable logic controller (PLC) is in the program controller and microcomputer controller is developed on the basis of microcomputer technology and relay conventional control the combination of the concept. With the development of science and technology, the application of PLC in industrial control more and more widely. PLC produced so far only 30 years since the history, but have developed rapidly and the widespread application, become the contemporary industrial automation, one of the main pillars of industrial production in future, PLC technology and robots and CAD/CAM technology will become production of industrial automation tied, since the three pillars of the new industrial control device of PLC in industrial application in importance and universality, in order to adapt to the needs of the development of the industrial production automation, namely to PLC automatic control system design and reliability is of great significance to the discussion.1 The development and application of PLCPLC is in the program controller and microcomputer controller developed on the basis of microcomputer technology and relay conventional control the combination of the concept. Broadly speaking, PLC is a computer system, computer has stronger than average of industrial process connected with the input/output interface, and has become the basic device automation control system. PLC has been used widely in machinery, metallurgy, chemical industry, automobile, light industries, has basic replaced traditional relays and contactor logic control. Use PLC to control the system reliability of the equipment, its than mere relays and contactor controlling is greatly increased.In computer technology as the core of PLC general industrial automation devices. It will traditional relay control system and computer technology together, high reliability, flexible gm, easy to programming, use convenient wait for a characteristic, therefore in recent years in the industrial automatic control, electromechanical integration, transform traditional industries been widely used.1.1 traditional relay control and PLC control advantages and disadvantagesIn industrial automation field, PLC as automatic control, to become the most of the automation system, but also to the equipment foundation of industrial control has brought an unprecedented special changes. The use of PLC control system and the traditional industry with relays, compared the industrial control system in operation, control, efficiency and precision and other aspects have incomparable advantages. Although in industrial control system which used in the relay control equipment will not be eliminated, but because the PLC appear have changed industrial control the designers design thought.(1) control relay the shortcomings of:Today already applied to the family and relay to the industrial control in various fields. They than the previous product has higher reliability. However, this also is then cause some problems. Like most control relay are long-term wear and fatigue working conditions, easily damaged. And relay contact easy to produce the arc, even will melt together produce false operation, cause serious consequence. Moreover, for a specific use the equipment with hundreds of relays, and its control box will be large and heavy. In all the load carrying cases, big relay will produce large amounts of heat and noise, also consumes vast quantities of electricity. And relay control system must be manual connection, installation, if there are simple change, also need to spend a lot of time and manpower and material resources to restructuring, installation and commissioning.(2) programmable controller advantage, characteristics and functions:Programmable controller to small volume powerful is known for, it not only can easily finish order logic, motion control, timing control, count control, digital computing, data processing, and other functions, and can be established through input/output interface with various production machinery digital quantity and analogue connection, so as to realize the automatic control production process. Especially now, due to the arrival of the era of information, network, expanded the PLC function, make it strong network communication ability, thus the more widely used in many industries.Compared with the traditional relays have a few big notable features: high reliability and anti-interference is strong; Powerful, cost-effective; Easy programming, field can be changed; Necessary is complete, easy to use; Life is long, small volume, low consumption; System design, installation, commissioning, maintenance less workload, convenient maintenance, etc.1.2 PLC automatic control system development present situationProgrammable controller to appear first in the United States, in 1968, the American general motors (GM) proposed a new controller developed from the user requirements, and put forward the new generation controller should have put forward ten condition, the condition immediately after caused development boom. In 1969, the United States digital equipment corporation (DEC) developed the worlds first programmable controller, and applied to gms line. When called programmable logic controller (PLC), the purpose is used to replace relays to execute logical judgment, timing, count etc sequence control function.Along with the semiconductor technology, especially the microprocessor and miniature computer technology development, to after the mid 1970s, especially in the 1980s, PLC has widely used 16 even 32bit mpu as the central processor. Input/output module and peripheral circuit are adopted, large-scale even in large scale integrated circuits, make PLC in concept, design, performance to price and applications have new breakthrough. At this time of PLC has not only has the logic function, also has the data processing, PID regulation and data communication function, called the programmable controller is more appropriate.PLC is microcomputer technology and traditional relays - contactor controlling techniques, its basic design thought is the perfect function and the computer advantages and flexible, general the relay control system, convenient operation, simple, easy to combine cheap price advantages, the hardware is a standard, general. For users, programmable controller is a non-contact equipment, change can change the production process, the program at the preliminary design stage therefore if it chooses programmable controller, can make the design and debug is easily. From manufacturing production programmable controller manufacturers perspective, in the manufacturing stage dont need according to users request specifically designed controller, suitable for mass production.Due to these characteristics, the programmable controller by industrial control was soon after, and get the welcome of bounded rapid development. At present, the programmable controller has become the powerful tools, industrial automation has been widely used.PLC have vitality, is it more suitable for industrial site and market demands, PLC after decades of development, realize the start from scratch, from the simple logic control to the present motion control, process control, data processing and network communication, along with the science and technology progress, PLC will also have greater development, mainly in the following respects.(1) technically, along with the computer technology to more use of new achievements in the design and manufacture of PLC, PLC will provide faster and more large storage capacity, function more wider and more stable performance, more cost-effective way.(2) from the scale on look, with PLC application domain expands unceasingly, in order to adapt to the demand of the market, PLC will further to mini and super-large two direction.(3) look from sex, with PLC function continues to expand, PLC products will more rich, scale to breed more complete direction.(4) from the standard on look, along with the birth of IEC1131 standard, each manufacturer PLC or same manufacturers to different types of PLC mutually exclusive format will be broken, and will make the PLC general information, equipment characteristics, such as IEC1131 standard programming language to the direction of development.(5) from the perspective of network communication, along with PLC and other industrial control computer networking constitute a large control system and the development of the fieldbus, PLC will be simplified to network and communication direction.1.3 Presently influenced promotion PLC applicationPLC not only can easily finish order logic, motion control, timing control, count control, digital computing, data processing, and other functions, and can be established through input/output interface with various production machinery digital quantity and analogue connection, so as to realize the automatic control production process. Especially now, due to the arrival of the era of information, network, expanded the PLC function, make it strong network communication ability, thus the more widely used steel, petroleum, chemical industry, electric power, building materials, machinery manufacturing, automotive, textile, transportation, environmental protection, and other industries. And as their performance to price rise ceaselessly, its utility to roughly the following several aspects:(1) sequence control(2) closed-loop process control(3) sports position control(4) production process monitoring and management(5) network characteristics2 PLC automatic control system to study the effect factors of reliability and SuggestionsAs PLC application occasions more and more widely, and application environment more and more complicated, by the interference more and more, all of these may cause PLC control system reliability is reduced, can not work normally, which cause irreparable economic loss. Therefore, analyzes the influential factors of reliability PLC control system, studies its measures to improve the reliability PLC control system has an important role for the PLC further popularized also has the universal significance.Therefore, from the two aspects to consider:(1) PLC peripherals to consider the reliability analysis of PLC(2) PLC software program to consider the reliability analysis control systemAccording to these factors, and put forward reasonable Suggestions for improving the reliability of PLC as possible. PLC is for industrial and set control equipment. But the factors that influence the reliability of also pretty is much, such as electromagnetic interference, peripheral humidity, the power supply voltage, input and output connections and I/O circuit, some actuator switch ah, mechanical contactor ah, in-house software system ah etc are susceptible to interfere, can make the control system reliability affected. Below the reliability for PLC affect large some Suggestions:(1) for power requirements: PLC low-pressure operations shall be directly from the mistress of online using private sidings power supply, in order to reduce motor start-stop and other factors to PLC a direct result of; Different PLC for power requirements of products, including power supply is different also, here the voltage grade, frequency, communication ripple coefficient and input and output of power-supply modes, and strong electromagnetic interference of PLC reliability requirements and higher occasions, PLC power supply should and power supply and control circuit power supply separate; When necessary, can use belt shielding isolation transformer power supply, series LC filter circuit, etc.; In the design, external dc power should adopt manostat, power should stay have 20% 30% headroom. By controller itself to provide dc power, should understand it can provide the maximum current, prevent over-current cause equipment damage.(2) the requirements and wiring dock:1. PLC good the normal operation of the ground is a prerequisite. In the design, PLC grounding should and power equipment grounded apart, using special grounding; If cannot separate grounding, should use common grounding; It is prohibited to adopt common grounding method. As shown in figure 1 shows, connect a site should as far as possible the grounding wires near PLC, 4mm2 should be greater than line diameter, grounding resistance generally should be less than 10 .2. PLC wiring including input wiring and output wiring. The length of the input connection shoulds not be too long, generally no greater than as; In line distance is long, can use the conversion between signal relays. Input wiring the COM end and output wiring the COM end cannot meet together. Input wiring and output connection cables shall be set separately. When necessary, field set respectively junction boxes. Integrated circuit or transistor equipment output signal and the input signal wiring must use shield cable; Shielding layer grounding end should pick site appropriate one-point earthing, in controller side.(3) installation and wiring to take certain antijamming measures: PLC power supply, I/O power typically use the belt shielding layer isolation transformer power supply, PLC, I/O the power cord, input and output signal, ac, dc lines should try to separate wiring, some still need shielding wire, or even grounded.(4) to the I/O circuit and input and output terminals signal protection:1. To improve on-site input to the reliability of PLC signal, the first to choose high reliability transmitter and all kinds of switch, prevent various causes transmit signal short-circuit, open circuit or contact undesirable;2. In programming increases with the increase of digital filter procedures, the credibility of the input signal;3. When the input signal source and load of the output driver as perceptual component, for dc road should be at its free-wheeling diode; both ends parallel For the circuit, should be at its absorbing circuit parallel resistance capacity at both ends. 4. PLC is through the input circuit input signals, thus input circuit components quality stand or fall and connection mode directly affect the reliability of the control system.(5) to actuators reliability research: when the signal accurately input to PLC, PLC program execution, will the results through actuators on the field devices to adjust and control. When load by contactor controlling, starting or stopping this kind of load of contactor to coil, start-up contactor is reliable suction close, stops contactor is reliable, this is should understand release. When open or closed electric valves, open valve, closing time according to different, set delay time, after delay test drive in place or off in place signals, if these signals cant accurately in time that returns to PLC, do a fault valves can fault alarm processing. The Even design perfect fault alarm system in the design of the automatic control system, we designed a tier 3 fault display alarming system, grade 1 set in the control field each control cabinet panel, use the normal operation and indicator lights instructions equipment fault condition normal operation, when equipment corresponding indicator, when the equipment operation failure in the frequency of 1Hz flashing lights. To prevent light bulb is damaged cant correctly reflect equipment work situation, set up specifically fault reset/lamp test button, the system running any time duration, according to this button 3s shall all be lit all lights, such as if this has instructions to illustrate the bright lights have been bad, should be replaced immediately, changing the button reattachment still presses the original working status indicator lights display device working state. Level 2 fault display Settings in central control room monitors, large screen when equipment malfunction, have text indicate that the fault type, process flow diagram on the corresponding device shine, historical events will record the breakdown. Watch Level 3 fault display Settings in central control room signal cabinet and when the equipment malfunction, signal box will use sound and light alarm means hint staff, deal with failure. In dealing with fault, and fault classification, some fault is the requirement of the system to a halt, but some fault run of system, the system can work with little impact, fault fault running out in operation, thus greatly reducing the entire system to stop running time, and improve the system reliability operation level.PLC interference problems very complex, therefore the reliability design of PLC control system in system design, occupies an important position in the actual design of the application system only according to the characteristics and application environment of specific conditions, the theory with practice, the concrete analysis, flexible to choose effective reliability design technology and anti-jamming method, overall, reasonable to consider the system software and hardware design, from the overall improve the system of anti-jamming and reliability.June 2011PLC控制技术可编程序控制器（PLC）是在程序控制器和微机控制器的基础上发展起来的微机技术和继电器常规控制概念相结合的产物。随着科学技术的发展，PLC在工业控制中的应用越来越广泛。PLC 自产生至今只有30 多年的历史,却得到了迅速发展和广泛应用,成为当代工业自动化的主要支柱之一，未来的工业生产中,PLC 技术和机器人以及CAD/ CAM技术将并列成为实现工业生产自动化的三大支柱，鉴于PLC 这种新型工业控制装置在工业应用中的重要性和广泛性,为适应工业生产自动化发展的需求，即对PLC自动控制系统设计及可靠性的探讨有着重要的意义。1 PLC的发展与应用PLC是在程序控制器和微机控制器的基础上发展起来的微机技术和继电器常规控制概念相结合的产物。从广义上讲，PLC是一种计算机系统，比一般计算机具有更强的与工业过程相连接的输入输出接口，并已成为自动化控制系统的基本装置。PLC已经广泛应用于机械、冶金、化工、汽车、轻工等行业中，已基本取代了传统的继电器和接触器的逻辑控制。用PLC来控制系统设备，其工作的可靠性要比单纯继电器和接触器控制大大提高。PLC是以计算机技术为核心的通用工业自动化装置。它将传统的继电器控制系统与计算机技术结合在一起，具有高可靠性、灵活通用、易于编程、使用方便等特点，因此近年来在工业自动控制、机电一体化、改造传统产业等方面得到了广泛的应用。1.1 传统继电器控制与PLC