Method for diagnosing input signal fault of PLC system using counter

Abstract

The invention relates to a method for diagnosing an input signal fault of a PLC system by using a counter, and belongs to the technical field of automatic control. The method comprises the steps of assigning the fault diagnosis CTU counter to each input signal causing a controlled device to stop running; using a fault state of the input signal as an enable bit of the CTU counter, setting a presetvalue of the counter as 1, wherein a completion bit (.DN) of the counter is communicated with corresponding signal fault lock; determining the fault cause of the controlled device to stop running by checking the completion bit (.DN) of the fault diagnosis CTU counter and the corresponding signal fault lock. The method has the advantages that a PLC system input signal fault is diagnosed by using acounter programming program in the PLC controller, and the input signal fault can be quickly and accurately locked, thereby saving the fault processing time and improving the response speed of the fault processing.

Description

technical field [0001] The invention relates to a method for diagnosing input signal faults of a PLC system by using a counter, and belongs to the technical field of automatic control. technical background [0002] PLC controller is an electronic device specially designed for digital operation in industrial environment. It uses a memory that can be programmed to store instructions for performing operations such as logic operations, sequential operations, timing, counting, and arithmetic operations, and can control various types of devices through digital or analog inputs and outputs. machinery or production process. PLC controllers have been widely used in various industries such as steel, petroleum, chemical industry, electric power, building materials, machinery manufacturing, automobiles, textiles, transportation, environmental protection, cultural entertainment, etc. It has high reliability, strong anti-interference ability, powerful functions, Flexible, easy to learn ...

AI Technical Summary

Problems solved by technology

In practical applications, the external input signal of the PLC system often has a "jitter" fault phenomenon, that is, the frequency of the normal signal and the fault is less than 1 second, so because a scan cycle of the PLC system is generally tens of milliseconds, it can capture the signal fault and make it The control equipment stops running. However, since the data communication rate between the HMI monitoring system and the PLC is greater than or equal to 1 second, the signal failure cannot be captured, and the operator cannot be prompted about the cause of the equipment failure. The method of replacing the input signal of the input signal or fastening the terminal block for investigation and processing takes a long time to deal with the fault, which greatly reduces the production efficiency

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