科技论文-Application of Programmable Logic Controller.doc

科技论文题 目 application of programmable logic controller 系 别 尚德光伏学院 专 业 计算机控制技术 班 级 0801 学生姓名 学 号 指导教师 蒋鹏 2010年 11 月28application of programmable logic controllerabstract: this paper introduces the plcs history, structure, uses, applications, characteristics and future prospects related to plc. this can be through a corresponding understanding of the plc.it will be helpful to plc applications .key words: plc、application、featuresbrieflyprogrammable controller is the late 60s in the united states first, and then called programmable logic controller plc (programmable logic controller), aims to replace the relay in order to implement the logic to determine, timing, counting and other sequential control functions. plc basic design idea is the computer fully functional, flexible, universal and other advantages and relay control system, easy to understand, easy to operate, cheap and combine the advantages of the controller hardware is standard, generic. based on the actual application objects, the software will control the content compiled into the controller user program memory. controller and the controlled object to connect easily. as the semiconductor technology, in particular microprocessors and micro-computer technology, to 70 after the mid, plc has been widespread use of microprocessors as the cpu, input and output modules, and peripheral circuits are also used in large-scale even very large scale integrated circuits, when the plc is no longer logical to determine function, also has a data-processing, pid regulator, and data communication capabilities. programmable controller is a digital computing operation of an electronic system designed for industrial environment applications. it uses a programmable memory, used in its internal memory implementation of the logical, sequential control, timing, calculation and arithmetic operations such as instruction, and through digital an inputs and outputs to control various types of mechanical or the production process. plc is a computer technology with traditional relay contact with the product of a combination of control technology, which overcomes the relay contacts control system wiring complexity of the mechanical contacts, reliability and low power consumption and high, versatility and flexibility of the shortcomings of poor, full the advantages of using a microprocessor. programmable logic controller for users, is a non-contact device, to change the program can change the production process, so you can use in the preliminary design stage programmable controller, in the implementation phase to determine whether or process. on the other hand, from the programmable controller manufacturers manufacturing point of view, in the manufacturing phase of the users order request does not require specially designed controllers, suitable for mass production. because of these characteristics, programmable controllers came soon after the welcome by the industrial control sector, and rapid development. at present, the programmable controller, factory automation has become a powerful tool, has been widely used. plc part of the structure and the role of each part programmable controller structure varied, but its composition is basically the same general principles are based on the microprocessor as the core structure. usually by the central processing unit (cpu), memory (ram, rom), input and output unit (i / o), power supply and programmer, and several other components. central processing unit (cpu) plc-core cpu as a whole, plays the role of commander in chief. cpu generally by the control circuit, an arithmetic logic unit and register form. these circuits are often encapsulated in an integrated circuit chip. cpu through the address bus, data bus, control bus and storage units, input-output interface circuit to connect. cpu features are the following: from memory to read instructions, implementation of the instruction, remove an instruction to deal with interrupts. memory (ram, rom) memory is mainly used for storage of system programs, user procedures and data. memory storage system software, known as the system program memory; application memory store known as the user program memory; repositories of data storage is called data memory. commonly used memory are ram, eprom, and eeprom. ram is a read-write operation can be random access memory storage of user program to generate user data area, stored in the ram in the user program can be easily modified. ram memory is a high-density, low power, inexpensive semiconductor memory that can be used to do backup power lithium batteries. power-down, it can effectively maintain the stored information. eprom, eeprom are read-only memory. curing with these types of storage systems management processes and applications. input-output unit (i / o unit) i / o unit is actually passed between the plc and the controlled object interface to input and output signal components. i / o module has a good electrical isolation and filtering effect. plc input interface receives the input devices are a variety of switches, buttons and sensors. plc, the output control device is often the solenoid valves, contactors, relays, but relays are ac and dc type, high voltage type and low-voltage type, voltage-and current-mode. power plc power supply unit includes power supply and battery backup systems, power supply units role is to convert the inner workings of an external power supply voltage. plc has a regulated power supply is used to plcs cpu unit and i / o module power supply. programmer plc programmer is the most important peripherals. programmer using the user program into the plc memory, you can also check with the programmer program, modify the program to monitor plcs working condition. in addition, a personal computer to add the appropriate hardware interface and software packages, you can use a personal computer to the plc program. the use of computers as a programmer, you can direct the preparation and display the ladder.over the years, programmable controller (hereinafter referred to as plc) from its birth, is now to realize the logical connection to the storage logical leap; its function from weak to strong, and achieved a logic control to digital control progress; its applications from small to large, simple control device to achieve a monomer to a qualified motion control, process control and distributed control across a variety of tasks. plc in dealing with todays analog and digital computing, human-computer interfaces, and networks in all aspects of power have been greatly improved, to become the mainstream of industrial control field control equipment, in all walks of life playing an increasingly important role.plc applicationsat present, plc at home and abroad have been widely used in iron and steel, petroleum, chemical, electric power, building materials, machinery manufacturing, automobile, textile, transportation, environmental protection and culture and entertainment in various industries, the use of mainly divided into the following categories.switch the amount of logic controlto replace the traditional relay circuit, logic control, sequential control, both for the control of a single piece of equipment can also be used for multi-cluster control and automation lines. such as injection molding machines, presses, stapler machine, combination machine tool, grinding, packaging and production lines, plating lines and so on.industrial process controlin the industrial production process, there are some such as temperature, pressure, flow, level and speed, the amount of continuous change (ie, analog), plc, with the corresponding a / d and d / a converter module and a variety of control algorithm program to deal with analog to complete the closed-loop control. pid regulation is a general closed-loop control system using a lot about the kind of adjustment. process control in metallurgy, chemical industry, heat treatment, boiler control situations have a very wide range of applications.motion controlplc can be used in a circular motion or linear motion control. generally use a dedicated motion control modules such as may drive a stepper motor or servo motor single-axis or multi-axis position control module, are widely used in all kinds of machinery, machine tools, robots, elevators and other occasions.data processingplc with mathematics (including matrix operations, functions, operation, logic operation), data transmission, data conversion, sorting, look-up table, bit manipulation functions, you can complete the data collection, analysis and processing. data processing is generally used, such as paper making, metallurgy, food industry, some of the large-scale control system.communication and networkingplc communication with the communication between plc and the plc and other communication between intelligent devices. with the development of factory automation network, now have a plc communication interface, communication is very convenient.plc application characteristicshigh reliability, strong anti-interference abilityhigh reliability is the key to performance of electrical control equipment. plc due to the use of modern large scale integrated circuit technology and strict manufacturing process, the internal circuitry to take the advanced anti-jamming technology, with high reliability. constitute the use of plc control systems, and on the same scale as compared relay contactor systems, electrical wiring and switch contacts have been reduced to a few hundred or even a few thousandths of the failure thus greatly reduced. in addition, plc hardware failures with a self-testing features, failure to issue timely warning information. in the application software, application of those peripheral devices can also be incorporated into the fault self-diagnosis procedure,the system, in addition to plc circuits and equipment other than access to the protection fault self-diagnosis. in this way, the entire system will be extremely high reliability.supporting complete, fully functional applicabilityplc development today, has formed a series of all sizes, product can be used for occasions of all sizes to industrial control. in addition to the logical processing functions other than, plc most computing power has improved the data can be used for a variety of digital control areas. a wide variety of functional units in large numbers, so that plc penetrated into the position control, temperature control, cnc and other industrial control. enhanced communication capabilities coupled with plc and human-machine interface technology, the use of the composition of a variety of plc control systems very easily.to learn to use, well received by engineers and technicians welcomeplc-oriented industrial control equipment, industrial and mining enterprises. it is easy to interface, the programming language easily acceptable for the engineering and technical personnel. ladder language, graphic symbols and expressions and the relay circuit is very close to, in order not familiar with electronic circuits, computer principles and do not understand assembly language to engage in industrial control to open the door.system design, the workload is small, easy to maintain, easy to transformplc logic with memory logic, instead of wiring, greatly reducing the control equipment external wiring, so that control system design and construction of the cycle is much shorter, while routine maintenance is also easier up and, more importantly, is to make the same equipment have been changes in procedures to change the the production process possible. this is particularly suitable for multi-variety and small batch production of occasions. power lines, control lines, as well as plc power lines and i / o lines should be split wiring, isolation transformers and plc and i / o should be used between shuangjiao cable. the plcs io lines and power lines separate the alignment, such as to be in the same groove, the separation of bundled communication lines, dc lines, if conditions allow, the best sub-slot alignment, which will not only enable them the greatest possible spatial distance, and can interfere to a minimum. plc should stay away from strong interference sources such as welding, high power silicon rectifier devices and large-scale power equipment, high-voltage electrical installation can not be a switch in the same cabinet. plc in the cabinet should stay away from power lines (the distance between the two should be more than 200mm). with the plc installed in the same cabinet within the inductive load, such as the power of the larger relays, contactor coil should be parallel rc circuit arc. plc input and output separately from the best alignment, quantity and analog switches must be laid separately. the transmission of analog signals should be shielded wire, one end or both ends of the shield should be grounded, grounding resistance should be less than shield resistance 1 / 10. ac output line and dc output lines do not use with a cable, the output lines should be away from the high-voltage lines and power lines, to avoid parallel.(3) i / o side of the wiringinput wiring input connection general rule, not too long. however, if the environment interfere with smaller, less voltage drop when the input wiring can be properly longer. input / output lines can not be used with a cable, input / output lines should be separated. normally open contact form as far as possible connected to the input side, so that the establishment of the ladder in line with the relay schematic, easy to read.output connection output wiring is divided into separate output and the public output. in different groups, using different types and voltage levels of output voltage. however, the output in the same group can only use the same type, the same voltage level of power. as the plcs output components are encapsulated in the printed circuit board, and connected to the terminal board that if the load short-circuit by connecting the output components, printed circuit boards will be burned. when using relay outputs, the inductive load to bear the size will affect the life of the relays, therefore, the use of inductive load should be a reasonable choice, or add isolation relays. plc may interfere with the output load, so to take measures to control, such as the dc output of the continued flow of control protection, the exchange of the output rc snubber circuit, transistors and resistors triac output bypass the protection.plc applications that need attentionplc is an industrial automation control equipment, general do not need to take what measures can be used directly in industrial environments. however, despite the higher reliability described above, a strong anti-interference ability, but when the production environment is too bad, especially strong electromagnetic interference, or improper installation on the procedure may cause error or operator error, resulting in incorrect input and cause false output, which will result in loss of control and misuse of equipment, movement, and thus can not guarantee the normal operation of plc, plc control system to improve reliability, on the one hand require plc equipment manufacturers to improve anti-jamming capability; the other hand.to design, install and use of maintenance caused a high degree of attention, multi-party cooperation in order to improve problem-solving, effectively enhance the anti-jamming performance of the system. therefore, in use should be aware of the following issues:1. the work environmenttemperatureplc require environmental temperature is 0 55oc, installation can not be placed in a large heat components below the space around the ventilation cooling should be enough.humidityto ensure the plc, insulation, air relative humidity should be less than 85% vibrationplc should be made from a strong vibration source, to prevent the vibration frequency of 10 55hz frequent or continuous vibration. when the inevitable use of environmental vibration, the damping must be taken measures, such as use of damping glue and so on.airto avoid corrosion and flammable gases such as hydrogen chloride, hydrogen sulfide and so on. for more dust in the air or corrosive gases in the environment, can be installed in a closed plc good control room or control cabinet.power supplyplc for the power line disturbance caused by a certain ability to resist. demanding in terms of reliability or power supply interference is particularly serious circumstances, you can install a isolation transformer with a shield in order to reduce interference between equipment and ground. general plc has a 24v dc output provided to the input, when using an external dc power input, we should use dc power supply. because an ordinary rectifier filter power supply, because of ripple effects, easy to make plc received an error message.2. control system interference and its sourceon-site plc control system for electromagnetic interference is the most common and most likely one of the factors affecting system reliability, the so-called root of the problem symptoms first, identify the problems in order to propose solutions to the problem. must therefore be aware of on-site sources of interference. the source of interference and the general classification.plc control system affect the sources of interference, most produce dramatic changes in the current or voltage of the area, the reason is the current changes in magnetic field, the equipment produces electromagnetic radiation; the magnetic field change generated currents, electromagnetic waves generated high-speed. is usually different modes of electromagnetic interference by jamming is divided into common-mode interference and diffe