Using PLC automatic control principle, solve the problem of control acquisition slow -

1 introduction

is well known, since the advent of PLC in automatic control of various industries play a difficult to replace the core control function. PLC reliable operation, suitable for all kinds of bad industrial environment, PLC and industrial control ( IPC） Compared to its reliable operation, good scalability, convenience of electrical connections, control, more professional, but industrial good man-machine interface, convenient high-level language is can't be matched by PLC controller.

is applied to control configuration software in many situations, but the entire control center, often still PLC, configuration software ( PC) The control of the role is very small. Human-machine interface is generally used in simple motion control, process parameters, set of formula and so on, although conceptually belong to the category of control, but it does not really have core control effect, because the real long-term automatic control is performed by PLC. We don't often use industrial computer as core control part for two reasons: first, industrial PC is not suitable for running in a very dirty environment; Second, the industrial computer often use Windows system does not reassuring, its long-term effect is not good.

although PLC, IPC plays different roles in automation control, in many continuous running time is shorter, the environment is relatively good place, people still want to use the IPC control core. There are many kinds of way using the IPC for core control, of course one of the most simple way is to use configuration software.

this paper use configuration software to do users frequently encountered problems in control are discussed. In many users use configuration software to control, especially when using a serial port connection to control, found that automatic control configuration software will affect the speed of data collection, this paper focuses on how to solve this problem, a solution to this is - — The application of the control mode of imitation of PLC to the PC serial port control.

after 2 users using configuration software control, the cause of slow data acquisition

this is a lot of configuration software users in writing problems encountered in computer automatic control program, what is the reason? Can have a good way to solve?

let's a brief description of the principle of data acquisition control configuration software. Under normal circumstances, configuration software timing down a machine a read command to wait for a response to intercept want to query data, the circulation of the cycle, the data of the dynamic display in the upper machine, realize the data real-time acquisition '. So when we need to control the hypogyny machine, configuration software can write command, accordingly to achieve the upper machine under the real-time control of a machine.

on the surface looks reasonable, but why there will be a slow data acquisition this kind of situation? All the original 'blame' mechanism of configuration software, speaking, reading and writing. Control of the configuration software to realize fast, so to write command the highest priority executive power, that is to say, when you have to write, Control) Command, configuration software executed first write command, until there is no written ( Control) Command is resumed normal configuration software to read ( Acquisition) Cycle.

as a result, it is easy to find the user often appear slow data acquisition. If users frequently will control command issued, the system will be allocated very little time for data collection, resulting in data acquisition slow or interrupted. Users in the cycle instruction repeated to a variable assignment ( Such as y0 = 1) , will cause the above problems, so our solution is the need to control control, don't need to control when to let go. In order to achieve this control way, we can refer to the mode of the PLC.

3 PLC works

without interruption, PLC adopts 'sequential scan, cycle' way of working. 4 summary

as mentioned above, in the control configuration software, we adopt the method of operation and then output, that is, to the IO variable cycle complex arithmetic operations, we use the intermediate variable calculation, to calculate the results when we again to IO variable assignment, this will solve the problem of control acquisition slow.

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