可编程控制器PLC外文翻译.doc

晋 中 学 院本科毕业设计英文参考资料题 目 Programmable Logic Controller PLC 院 系 机械学院 专 业 机械设计制造及其自动化 姓 名 党佳明 学 号 1014312109 学习年限2010年09月至2012年07月 指导教师 王丽珍 职称 讲师 申请学位 工学 学士学位 2012年05月20日英文原文：Programmable Logic Controller PLC1 PLC IntroducePLC Introduction Programmable controller is the first in the late 1960s in the United States, then called PLC programmable logic controller (Programmable Logic Controller) is used to replace relays. For the implementation of the logical judgment, timing, sequence number, and other control functions. The concept is presented PLC General Motors Coroperation.PLC and the basic design is the computer functional improvements, flexible, generic and other advantages and relay control system simple and easy to operate, such as the advantages of cheap prices combined controller hardware is standard and overall. According to the practical application of target software in order to control the content of the user procedures memory controller, the controller and connecting the accused convenient target. In the mid-1970s, the PLC has been widely used as a central processing unit microprocessor, import export module and the external circuits are used, large-scale integrated circuits even when the PLC is no longer the only logical (IC) judgment functions also have data processing, PID conditioning and data communications functions. International Electro technical Commission (IEC) standards promulgated programmable controller for programmable controller draft made the following definition: programmable controller is a digital electronic computers operating system, specifically for applications in the industrial design environment. It used programmable memory, used to implement logic in their internal storage operations, sequence control, timing, counting and arithmetic operations, such as operating instructions, and through digital and analog input and output, the control of various types of machinery or production processes. Programmable controller and related peripherals, and industrial control systems easily linked to form a whole, to expand its functional design. Programmable controller for the user, is non-contact equipment, the procedures can be changed to change production processes. The programmable controller has become a powerful tool for factory automation, widely popular replication. Programmable controller is user-oriented industries dedicated control computer, with many distinctive features.high reliability, anti-interference capability; programming visual, simple; adaptability good; functional improvements, strong functional interface.Programmable Logic Controllers (PLC), a computing device invented by Richard E. Morley, have been widely used in industry including manufacturing systems, transportation systems, chemical process facilities, and many others. At that time, the PLC replaced the hardwired logic with soft-wired logic or so-called relay ladder logic (RLL), a programming language visually resembling the hardwired logic, and reduced thereby the configuration time from 6 months down to 6 days. Although PC based control has started to come into place, PLC based control will remain the technique to which the majority of industrial applications will adhere due to its higher performance, lower price, and superior reliability in harsh environments. Moreover, according to a study on the PLC market of Frost and Sullivan, an increase of the annual sales volume to 15 million PLC per year with the hardware value of more than 8 billion US dollars has been predicted, though the prices of computing hardware is steadily dropping. The inventor of the PLC, Richard E Morley, fairly considers the PLC market as a 5-billion industry at the present time. Though PLC are widely used in industrial practice, the programming of PLC based control systems is still very much relying on trial-and-error. Alike software engineering, PLC software design is facing the software dilemma or crisis in a similar way. Morley himself emphasized this aspect most forcefully by indicating: “If houses were built like software projects, a single woodpecker could destroy civilization.” Particularly, practical problems in PLC programming are to eliminate software bugs and to reduce the maintenance costs of old ladder logic programs. Though the hardware costs of PLC are dropping continuously, reducing the scan time of the ladder logic is still an issue in industry so that low-cost PLC can be used. In general, the productivity in generating PLC is far behind compared to other domains, for instance, VLSI design, where efficient computer aided design tools are in practice. Existent software engineering methodologies are not necessarily applicable to the PLC based software design because PLC-programming requires a simultaneous consideration of hardware and software. The software design becomes, thereby, more and more the major cost driver. In many industrial design projects, more than 50% of the manpower allocated for the control system design and installation is scheduled for testing and debugging PLC programs. In addition, current PLC based control systems are not properly designed to support the growing demand for flexibility and reconfigure ability of manufacturing systems.PLC is well-adapted to a range of automation tasks. These are typically industrial processes in manufacturing where the cost of developing and maintaining the automation system is high relative to the total cost of the automation, and where changes to the system would be expected during its operational life. PLC contains input and output devices compatible with industrial pilot devices and controls; little electrical design is required, and the design problem centers on expressing the desired sequence of operations. PLC applications are typically highly customized systems so the cost of a packaged PLC is low compared to the cost of a specific custom-built controller design. On the other hand, in the case of mass-produced goods, customized control systems are economic due to the lower cost of the components, which can be optimally chosen instead of a generic solution, and where the non-recurring engineering charges are spread over thousands or millions of units.For high volume or very simple fixed automation tasks, different techniques are used. For example, a consumer dishwasher would be controlled by an electromechanical cam timer costing only a few dollars in production quantities.A microcontroller-based design would be appropriate where hundreds or thousands of units will be produced and so the development cost (design of power supplies, input/output hardware and necessary testing and certification) can be spread over many sales, and where the end-user would not need to alter the control. Automotive applications are an example; millions of units are built each year, and very few end-users alter the programming of these controllers. However, some specialty vehicles such as transit busses economically use PLC instead of custom-designed controls, because the volumes are low and the development cost would be uneconomic.Very complex process control, such as used in the chemical industry, may require algorithms and performance beyond the capability of even high-performance PLC. Very high-speed or precision controls may also require customized solutions; for example, aircraft flight controls.Programmable controllers are widely used in motion control, positioning control and torque control. Some manufacturers produce motion control units to be integrated with PLC so that G-code (involving a CNC machine) can be used to instruct machine movements.PLC may include logic for single-variable feedback analog control loop, a proportional, integral, derivative or PID controller. A PID loop could be used to control the temperature of a manufacturing process, for example. Historically PLC was usually configured with only a few analog control loops; where processes required hundreds or thousands of loops, a distributed control system (DCS) would instead be used. As PLC has become more powerful, the boundary between DCS and PLC applications has become less distinct.PLC has similar functionality as Remote Terminal Units. An RTU, however, usually does not support control algorithms or control loops. As hardware rapidly becomes more powerful and cheaper, RTU, PLC and DCS are increasingly beginning to overlap in responsibilities, and many vendors sell RTU with PLC-like features and vice versa. The industry has standardized on the IEC 61131-3 functional block language for creating programs to run on RTU and PLC, although nearly all vendors also offer proprietary alternatives and associated development environments.2 The structure of PLC systemStructurally divides, PLC divides into the stationary type and the combined type (module type) two kinds. Stationary PLC including the CPU board, the I/O board, demonstrated the kneading board, the memory block, the power source and so on; these elements combine not a dismountable whole. Module type PLC including the CPU module, the I/O module, the memory, the power source module, the ledger wall or the rack, these modules may defer to certain rule combination disposition.1、CPU constitutionCPU is the PLC core, plays nerve centers role, wraps PLC to have CPU at least every time, it the function which entrusts with according to the PLC system program receives and stores the user program and the data, with scanning way gathering the condition or the data which sends by the scene input device, coexisting enters the stipulation in the register, simultaneously, diagnoses the power source and in the PLC internal circuit active status and the programming process grammatical error and so on. After enters the movement, one by one reads the instruction from the user program memory, the duty which stipulated according to the instruction produces the corresponding control signal again after the analysis, directs the related control circuit. CPU mainly by the operator, controller, register and implementation of data link between them, control and state BUS, CPU unit also includes peripheral chips, bus interface and related circuitry. Memory is mainly used for storing programs and data, is an integral unit PLC. In the user view, unnecessarily detailed analysis of the CPUs internal circuitry, but the working mechanism of the various parts, or should have sufficient understanding. CPU and the control work, which will read the instructions, directives and executive orders to explain. However, the pace of work from the vibration signals. Computing devices used for digital or logic operation, under the command of the controller work. CPU speed and memory capacity are important parameters for PLC, which determines the pace of work PLC, I/O number and software capacity, etc., thereby limiting the control of the scale.2、I/O modulesPLC interface with the electrical circuit is through the input and output section (I/O) completion. I/O module integrates the PLCs I/O circuits; the input register reflecting the input signal status, output point reflects the state of the output latch. Input module will transform electrical signals into digital signals into the PLC system, the output module opposite. I/O into digital input (DI), digital outputs (DO), analog input (AI), analog output (AO) modules.3、Common I/O as followSwitching capacity: voltage level by points, with 220VAC, 110VAC, 24VDC, by Way of isolation, there is isolation and transistor isolation relays.Analog: by type of signal, a current type (4-20mA ,0-20mA), voltage (0-10V ,0-5V,-10-10V) and so on, by the precision points are 12bit, 14bit, 16bit, etc. .In addition to these general-purpose IO, there are special IO modules, such as thermal resistance, thermocouple, pulse and other modules.By I/O module specifications and to determine the number of points, I/O modules can be more or less, but the maximum number of CPU can be the basic configuration management capabilities, which by the largest floor or rack slot limit.Power ModulesPLC power supply modules for the PLC to provide the power supply integrated circuits. Meanwhile, some of them for the work input circuit to provide 24V power supply. Power input types are: AC power (220VAC or 110VAC), DC power supply (commonly used to 24VDC).Most modular PLC to use floor or rack, its role is to: electrical, the realization of the modules, so that the CPU can access all the modules on the floor, machinery and realize the connection between each module, so that each module constitutes a overall.3 Installation and debugging Of PLC control system Programming device: development and application programmer is the PLC to monitor the operation, inspection, maintenance indispensable device for programming, some system settings, monitor the PLC and the PLC control system working conditions, but it is not directly involved in field control run. PLC programmers are generally small hand-held programmer, the current general by the computer (running programming software) as programmer. That is, our system PC.Human Machine Interface is the simplest indicators and buttons, the current LCD screen (or touch screen) type-one operator terminal has been widely applied by the computer (running the configuration software) as a very popular man-machine interface.PLC communication network rely on advanced industrial network technology can quickly and efficiently collect, transfer of production and management of data. Therefore, the network automation system integration projects in the importance of more and more significant, even been suggested that the network is the controllers point of view argument.PLC is a service specifically for the industrial production control device, usually do not need to take measures, it can be directly used in industrial environments. However, when the production environment is too harsh, especially strong electromagnetic interference, or improper installation, can not guarantee the normal operation of PLC, and therefore should pay attention to the following questions using the.First, the working environment1. PLC required temperature in the temperature 0 55 , heating installation, large components can not be placed below the space around the ventilation and cooling should be large enough, the basic unit and expansion unit interval between the need for more than 30mm; switch cabinet, the lower should be a ventilation shutters, to prevent too much direct sunlight; if the surrounding Stresses above 55 , to install electric fan forced ventilation.2. PLC humidity in order to ensure the insulation performance, air relative humidity should be less than 85% (no condensation).3. PLC should be made from a strong shock vibration source, to prevent the vibration frequency of 10 55Hz frequent or continuous vibration. When the environment is inevitable when using vibration, shock absorption to take measures, such as glue, such as using shock absorption.4. Air to avoid corrosion and flammable gases, such as hydrogen chloride, hydrogen sulfide, etc. The more the air of dust or corrosive gas environment can be installed in a closed PLC good control room or control cabinet, and install air cleaning devices.5. Power PLC power supply is 50Hz, 220 (1 10%) V AC, for the power cord to the interference, PLC itself has sufficient capacity to resist. Reliability requirements for high power interference is particularly serious situation or environment, you can install a shield with variable ratio of 1:1 isolation transformer to reduce the interference between the equipment and land. Power input can also be cascaded LC filter circuit Second, installation and wiring1. Power lines, control lines and power lines and PLC I/O lines should be split wiring, isolation transformer and PLC and I/O should be used between the cable connections.2. PLC should stay away from strong interference sources such as welding, high-power silicon rectifier devices and large power equipment, not with the high-voltage electrical switch installed in the same cabinet.3. PLC input and output separately from the best alignment, switch and analog should be laid separately. The transmission of analog signals should be shielded cable, one end or both ends of the shield should be grounding resistance should be less than the shielding layer 1 / 10.4. PLC basic unit and expansion modules and functional modules, connecting cables should be installed separately, to prevent interference from outside signals.5. AC output line and DC output lines do not use the same cable, the output line should be far from power lines and power lines, to avoid parallel.Third, I/O wiring terminal1. Input Connection(1) Input connection generally should not exceed 30 meters. But if the environment interfere with small, small voltage drop, the input terminalLonger be appropriate.(2) Input / output lines can not be used with a cable, input / output lines should be separated.(3) The extent possible, normally open contact form connected to the input in the establishment of the ladder and relay the same schematic2. Output connection(1) Output terminal is divided into separate output and public output. In different groups, using different types and voltage levels of output voltage. However, output in the same group can only use the same type, the same voltage level of power.(2) Since the PLCs output devices are packaged in printed circuit board and connected to the terminal board that if the load short-circuits connecting the output components, printed circuit boards will be burned, thus, applied fuse protected output devices.(3) The relay output, inductive load borne by the size, will affect the life of t