第1个回答 2013-05-09
High reliabilityis the keyperformanceof electrical control equipment.PLC due to the use of modernlarge scale integrated circuit technology,used the strict production craft manufacture,the internal circuit has adopted the advancedanti-jamming technology,with high reliability.For example,the Fseries PLCproduced by Mitsubishi Co,the mean time to failureof up to 300000hours.Some use theredundant CPUPLCmean time to failureis longer.From theexternalcircuit of PLC,the use of PLCcontrol system,compared with thesamescale relay system,the electrical wiring and the switch contacthas been reduced tohundreds or even thousandsof,the faultisgreatly reduced.In addition,self -detection functionwithPLC hardware failures,failure to issue timely warninginformation.In the application software,userscan alsofault self diagnosisprogramof peripheral devices,thesystemcircuitand equipmentexcept PLCaccess to the protection fault self-diagnosis.In this way,the reliability of the wholesystem with highis also not surprising.This paper focuses onthecontrol ofcrane,thecontrolmethod usingseries resistancehave been implementedto control the motor,so as to control thecrane.The working mode of PLCPLC sourceforcomputer controlinstead ofrelay contactor,so PLChassimilaritieswiththe general-purpose computer,such as with the samebasic structure andprinciple ofthe sameinstruction execution.However,the twoways of workinghaveimportant differences,the differences reflectthecircularscanning modein PLCCPU,focus on theinput sampling,focus on theoutputrefresh,I/Oimage areaseparately.Resultstheinput stateand process ofexecuting the programin the previousstate.The process ofcircularscanning modescanningmode of PLCPLCworkpackage,generallyfive stages,internal processingand self diagnosis,peripheralcommunicationprocessing,the input sample,the user program execution,the outputrefresh.
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第2个回答 2013-05-09
Hgh reliability is the key to the electrical control equipment performance.PLC as a result of the modern large scale integrated circuit technology, the strict production craft manufacture, the internal circuit adopted advanced anti-interference technology, has the very high reliability.
Such as mitsubishi F series PLC MTBF of up to 300000 hours.Some PLC using redundant CPU average trouble-free working time is longer.
From the closed circuit of PLC, the use of PLC control system, and compared to same size relay contactor system, electrical wiring and switch contacts have been reduced to hundreds or even thousands of points, one of fault is greatly reduced.
In addition, the PLC with a hardware fault self test function, failure can alert information in time.
In application, the user can also into the fault self-diagnosis procedures for the peripheral devices, besides the PLC in the system of the circuit and equipment also for the protection of fault self-diagnosis.
In this way, the whole system has high reliability, no wonder.
This article focuses on the crane control, through the use of series resistance speed control methods have been implemented for motor control, to control the crane.
The workings of a PLC PLC is the result of computer control instead of relay contactor, so PLC has in common with general computer, such as has the same basic structure and principle of instruction execution.
However, both on the way to work is an important difference, difference reflected in the PLC CPU adopts circular scanning method, focusing on the input sampling, focus on the output refresh, I/O image area respectively storing executable program before the state of each input in the implementation process and results.
PLC PLC scanning way of work process of circular scanning mode, regular package five stages, internal processing and self-diagnosis, peripherals communicate processing, input sampling, user program execution, output refresh.本回答被提问者和网友采纳