可编程控制器

Programmable controllerThe microcomputer technology already and continued in the change world.Is also changing the factory automatic control appearance take the microcomputer technology as the foundation programmable controller.Along with the science and technology swift and violent development, the programmable controller is extremely high by its reliability, can undergo the adverse circumstance the test, the use extremely convenient huge superiority, seizes the industry automatic control domain rapidly, becomes the industry automatic control the first choice product, with robot, CAD/CAM bingcheng for industrial production automation three big props.The programmable controller already became one kind importantly, most popular, the application situation most industry controller, might say only then the programmable controller was the true industry control computer.The initial period programmable controller only is uses in the logical control the situation, uses in replacing continues the electricity control panel, but the present programmable controller entered including situation and so on process control, position control all control domains. While retained original logical controller all merit, it absorbs has developed other control device (systematically for example process measuring appliance, collection and distribution, dispersion system and so on) the merit, only needs the programmable controller in many situations then to constitute including the logical control, the process control, the data acquisition and the control and the graph workstation economy worthwhile, the volume exquisite, the design debugging convenient integrated control system.In the international electrician committee (IEC)1987 year promulgation programmable controller standard draft has made the following definition to PLC: “The programmable controller is one kind of digital operation operation electronic system, for applies specially under the industry environment designs. It used has been possible the coding memory, used for in its internally stored program, to carry out the logic operation, the sequential control, fixed time, the counting and the arithmetic operation and so on face user's instruction, and through digital and the simulation -like input and the output, controlled each kind of type the machinery or the production process.The programmable controller and the related auxiliary equipment, all defer to easy with industry control system Lian Cheng a whole, easy to expand and the function principle designs.The so-called PLC system is uses in the present market each big industry to control the factory production the programmable controller, selects the different module according to the request, designs the procedure in this foundation to achieve designs function.This form is atpresent most widespread in the industry field application.Our company produces the GZPK100 series high speed rotary system pelletizer uses PLC the control mode.PLC reliability: Imports CPU which PLC uses all is the technical grade special-purpose processor which the manufacturer designs specially, other various parts also are directly to the manufacturer purchase, passes through the strict choice technical grade part, but moreover its power source module also is the collection each big company industry control experience designs specially, the anti-jamming is specially anti-power source disturbance ability has the very big enhancement, even if were very bad in the power source and under the frequency conversion velocity modulation disturbance still can the normal work.PLC extendibility: Must increase a function so long as increases the corresponding module and the revision correspondence procedure, but PLC programming relative quite simple, like this can reduce regarding the development cycle.PLC maintainability: PLC itself has very strongly from the diagnosis function, once the system appears the breakdown, according to is very easy from the diagnosis to diagnose crashes the part, even if the layman also can service, if breakdown because the programming causes not reasonably, because it provides the consummation the debugging aids da, must discover the breakdown to be also simple.Operation: The PLC operation uses the touching type to operate the terminal, the man-machine contact surface, the entire screen demonstrated, above has designed the very exhaustive operation manual, even if first use, also can act according to the prompt smooth operation, this reduced to operator's request, the common worker also can grasp very quickly.Moreover, once the phylogeny breakdown, the picture automatic cut over breakdown prompt picture, prompts the breakdown reason and the elimination method. Even may demonstrate the breakdown on the machine position, the serviceman may act according to the prompt very quick elimination breakdown.The PLC production had 30 remaining years of life histories, its development may divide into three stages approximately.20th century 70's PLC, its main function only is the execution originally the sequential control which completes by the black-white control installment, fixed time, the counting and so on.1980s, because the ultra large scale integrated circuit technology rapid development, the microprocessor market price falls largely, causes microprocessor scale universal enhancement which each kind of type PLC uses.In order to further enhance PLC the processing speed, many PLC manufacturer also in abundance developed develops the special-purpose logical processing chip, enabled PLC the function to have the huge change.1990s, the PLC trend of development has two major characteristics:First is to the volume small, a speed quicker function is stronger, the price cheaper small PLC direction develops; Second is to the large-scale network, the redundant reliability, the goodcompatibility, the programming to the IEC61131-3 standardization development.1990s Japan Mitsubishi Electrical machinery Company promotes A series PLC and the Siemens promotes S7-400 series PLC all belongs to large-scale PLC.21st century PLC will develop to a more open direction.Looking from the technology that, the computer technology new achievement can more applications in the PLC design and the manufacture, can have the operating speed to be quicker, the storage capacity is bigger, the intellectualized stronger product appearance.Our country PLC development and the production also has the near 30 year histories.At first in introduces in the equipment to use PLC massively.Through the technical introduction, the digestion absorption, the manufacture domestically PLC manufacturer had near 30 in 1990, the variety also has 20.At present domestically produced PLC had the suitable scale. The original Chinese-foreign joint venture silver coin electron (Wuxi) the limited company produces PLC has the subminiature machine PL series; Small machine SN series, SM series, SN series, SZ series, SR series; Molding machine series DL350, SU series.SU-5M/6M biggest I/O may reach 2048. Dalian aggregate machine-tool research production S series PLC, Hangzhou engine bed electrical equipment factory products and so on production DKK and D series PLC all had certain scale and have obtained the widespread application in the industry control.May anticipate that, along with our country industrialization, informationization advancement quickening, PLC will have a broader application in our country.According to the control type, its application may divide into following several aspects approximately.1st, uses in the switch quantity logic controllingthis is PLC is most basic, the most widespread application domain, it substitutes for traditional the black-white control electric circuit, realizes the logical control, the sequential control, then uses in the single Taiwan device control, also available Yu Duoji group control and automated assembly line.If aggregate machine-tool, grinder, injection molding machine, printer, stapler, packing assembly line.2nd, uses in simulating the quantity controlin the industrial production process, some many changes continuously the quantity, like the temperature, the pressure, the current capacity, the fluid position and the speed and so on all simulate the quantity, it measures the I/O module through the simulation, may realize between the simulation quantity and the digital quantity transformation, also is the A/D transformation and the D/A transformation.Each main PLC manufacturemanufacturer all has necessary A/D and the D/A module nearly, causes PLC to be possible to use in simulating the quantity control very conveniently.3rd, data processingmodern PLC nearly all has mathematics operation (including logic operation, function operation, a distance operation), functions and so on data transfer, data conversion, sorting, table look-up, position operation, may complete the data gathering, the analysis, processing and the demonstration.These data may with store up the reference value compare in the memory, complete certain control operation, also may transmit using the correspondence function to other intelligent installment, also may print them the scheduling. The data processing generally uses in the complex large-scale control system, like nobody control flexible manufacture system; Also may use in the process control system, like papermaking, metallurgy, chemical, food industry some large-scale control system4th, the movement controlsPLC to be possible to use in the translation or the circular motion control.It has the very strong data processing function, it may and in machine-finishing numerical control (NC) and the computer numerical control (CNC) close union, the realization numerical control.The early time directly measures the I/O module with the switch to connect the position transducer and the implementing agency, now general use special-purpose movement control module.If may actuate to step-by-step the electric motor either the servo motor single axle or the multiple spindle position control module. Each main PLC manufacture manufacturer all has the movement control function nearly.Widely uses in each kind of situations and so on engine bed, robot, elevator.5th, uses in corresponding networking control systemhigh function PLC to have the strong correspondence networking function, may realize PLC and PLC, PLC and long-distance I/O, PLC and on between the position computer correspondence, thus may form the multi-layer distributional control system or the factory automation (FA) network.Therefore, uses PLC to be possible to constitute the centralized management, the disperser control distributional control system very conveniently, realizes the factory automation ideal equipment.5.16.3 PLC characteristicPLC is faces the user the industry control computer, has many obvious characteristics.1. reliability are high, the antijamming ability strongindustrial production process set the very high request to the control device reliability, because the industrial production process often is the diurnal continuous production, the general production installs for several months, even several year only then overhaul one time.The industry scene each kind of electromagnetic interference is specially serious, in view of this situation, PLC has taken a series of measures, enables PLC to work reliably in the bad environment, mean time between failure (MTBF) is high, the breakdown restores the time to be short, in which mainly includes:The shield to the power transformer, the central processing element, the programmer and so on the major component and the module, uses the electric conduction good material to carry on the shield, prevents the radiated interference.The filter various input ends use the R-C filter, the filter time-constant generally are 10~20ms, uses the digital filter regarding some high speed input ends, its filter time-constant may use the instruction to establish.Isolates all input/output (below to use to be called I/O) the connection electric circuit to use the photoelectricity isolation, causes the industry scene the external circuit and between the PLC internal circuit on the electricity isolates, reduces the breakdown and the misoperation.The power source adjustment and the protection the 5V power source which needs regarding the microprocessor, uses the performance good switching power supply, the multistage filter and the adjustment, adapt exchange the electrical network undulation and the overvoltage, owe the voltage the influence.The part screens the primary device which PLC uses to carry on the strict aging and screening.The modular structure PLC modulation structure is helpful to in the breakdown situation the short-time repair, once finds out some module to appear the breakdown, can replace rapidly, causes the system rehabilitation.Simultaneously is also helpful in speeds up the search breakdown reason.Inspects the external environment regularly from the diagnosis function software, once discovered the unusual situation, CPU takes the effective action immediately, prevents the breakdown expansion.The information protects and restores when the accidental breakdown condition appears, does not destroy the PLC internal information; Once breakdown condition vanishing, may restore normally, continues the original work, therefore PLC is examining the breakdown condition, stores immediately the present condition the memory, the software coordination carries on to the memory the seal, forbids to memory any operation, guards against the canned data to flush out. Once breakdown condition vanishing, may restore normally, continues the original work, therefore PLC when examines the breakdown condition, stores immediately the present condition the memory, the software coordination carries on to the memory the seal, forbids to memory any operation, guards against the canned datato flush out.Once after examines the external environment normally, then may restore to the breakdown has before condition, continues the original work.Double CPU redundant system large-scale PLC also may use by the double CPU constitution redundant system or by three CPU constitution vote type system, causes the reliable further enhancement.Because has taken the above a series of measures, the PLC MTBF time has amounted to for several hundred thousand hours.2. Because the rich I/Ointerface module PLC is in an industrial production process automatic control system control main center, must realize to the industrial production process automatic control, it also must connect with each industry scene equipment, can complete the control task.Therefore, PLC besides has the computer major component, but also must have the rich I/O interface module. PLC in view of the different industry scene signal (for example exchange or cocurrent, switch quantity or simulation quantity, voltage or electric current, strong electricity or weak electricity and so on), has the corresponding I/O module and the industry scene component or the equipment (for example button, limit switch, close switch, photoelectricity switch, sensor and transmitting instrument, magnet coil, control valve and so on) the direct connection. In order to enhance the serviceability and intuitive, it also has a many kinds of person machine dialogue interface module; In order to compose the industry local network, it also has many kinds of correspondence networking interface module and so on.3. Programs simplePLC the trapezoidal chart programming language to be similar to the black-white control line trapezoidal chart, it inherited the tradition to control the line clearly direct-viewing, also considered the engineers and technicians interpreted drawings the custom, easy to accept, therefore received universal welcome. In the initial trapezoidal chart programming language, mainly has the normally opened contact and the coil which the people are familiar with, fixed time, mark compositions and so on counting, regarding the user, does not need to have the computer specialized knowledge, therefore very easily by general engineering technical personnel even technical worker understanding and grasping.Now, the PLC function big enhancement, the multitudinous function instruction also may use the trapezoidal chart language to describe, also very easy to cause at the beginning of the user to accept.4. Installs, the service simply facilitatesPLC not to need the special engine room, may move directly under each industry environment.When use only must looks carefully the connection scene each kind of equipment and PLC corresponding I/O, the system then may invest the movement.In PLC each kind of module is equipped with the movement and the failure indication equipment, is advantageous for the user to understand PLC the movement situation and the search breakdown.In order to meet each industry control need, besides unit -like small PLC, overwhelming majority PLC uses the modular structure.The PLC various parts all use the modular design, connects by the rack or the guide rail and the electric cable various modules.Because PLC uses the modular structure, once therefore some module breaks down, the user may through the replacement module method, make the system to restore the movement rapidly.5. Necessary complete, the function consummatesPLC to develop today, has formed the large, medium and small each scale serialized product, may be suitable for each scale industry control situation.PLC besides the logical function, modern PLC nearly all has the consummation data operational capability, available in each kind of numerical control domain.In recent years, as a result of the PLC intellectualization unit module massive emergences, caused PLC the application to seep the position control, the temperature control, CNC and so on in each industry control, in addition the PLC traffic capacity enhancement and the man-machine contact surface technology development, caused PLC to compose each kind of control system to become extremely easy.6. Volume small, weight light, energy consumption lowat present subminiature PLC, its base size is smaller than 100mm×100mm, the weight is smaller than 150g, the power loss only counts the tile.Because the PLC volume small very easy to load in the machinery, is the realization integration of machinery ideal control device.7. system designs, debugging cycle shortPLC replaces the wiring logic with the stored logic, with the traditional black-white control way compared to, greatly reduced the control device outside wiring; The PLC system hardware design duty is merely rests on the object the request disposition suitable module, caused the control system design and the construction cycle reduces greatly.5.16.4th, the PLC classifiedPLC product are very many, the model specification is not unified, usually may divide following three kind of situation classification: 1st, different may divide into the integral type and the module type according to the PLC structural style.2nd, may divide into the large, medium and small three ranks according to the PLC I//O points classification.3rd, is different according to the PLC function, has may divide into high, the low-grade three kinds.5.16.5th, PLC system compositionPLC is take CPU as the core electronic system, in the essence it is the special purpose computer which one industry control uses.PLC systemcomposition and microcomputer system basic same, it is two major part is composed by the hardware system and the software system. The general small PLC basic unit mainly by CPU, the memory, the input output module, the power source module, the I/O expansion connection, peripheral parts and so on I/O connection as well as programmer is composed PLC the software system also to include the system program and the user program.5.16.6th, the PLC principle of work1, PLC workingPLC uses is the periodic return scanning working.The user first must act according to some concrete request to establish the good procedure, then inputs to in the PLC user program memory.The user program is composed by certain instructions, instruction in memory step by step serial number arranged in order.When PLC movement work.CPU makes the cycle of motion scanning to the user program, in the non-skipping instruction situation, CPU starts the smooth one by one execution user program from the first instruction, finished until the user program, then has returns to the first instruction, starts to discuss one turn newly the scanning. In each time scans in the process, but also has completes and to outputs condition work and so on revolution to input signal gathering.PLC is this again and again repetition above scanning circulation.2nd, the PLC work processPLC work process may divide into the input sampling, the procedure execution, the output renovates three stages.In PLC work process according to such three stage periodic return scanning.3rd, PLC to inputs/the output outside principle principlebasis above PLC work process characteristic, may obtain PLC to input the output the outside principle rule:(1) input reflection register data, is decided by the input post panel various entrance points in the previous revolution period condition.(2) output part reflection register content the output order carries out the result decision by the procedure in.(3) outputs in the latch the data, by previous action cycle output revolution stage output reflection register data determination.(4) output terminal panel various out-ports ON/OFF condition, by outputs the latch the content to determine.In (5) procedure implementation must input, the output condition, by output reflection register and output reflection register reading.5.16.7th, the PLC procedure expression way1, trapezoidal chart (LD)2, smooth functional diagram (SFC)3, sentence table (IL) is called the instruction list, is similar in the computer assembly language form.4th, function block chart (FBD) uses for to express a sequentialcontrol process可编程控制器微机技术已经并继续在改变世界。