JPS60235213A - Detection for abnormality of digital control system - Google Patents

Abstract

PURPOSE:To find the abnormality in the early stage by judging input data to be abnormal if the difference between preceding input data and current input data of a digital control system exceeds a set value. CONSTITUTION:When a switch S1 is closed to take in data, a comparing circuit 2 compares preceding data in memory 1 with current data; and if the difference is within the set value, a switch S3 is closed to input current data to a PID arithmetic circuit 3. The switch S3 is opened, and the switch S2 is closed, and current data is stored in the memory 1 to prepare for the next sampling. If said difference exceeds the set value, data is not to the PID arithmetic circuit 3 by interlocking. Thus, the abnormality of input data is found in the early stage, and the abnormal control based on abnormal data is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for detecting an abnormality in input data of a digital control system.

[Background of the invention]

2. Description of the Related Art Digital control systems are well known in which data is input at regular intervals, a manipulated variable is calculated using the data, and a process is operated using the manipulated variable. For example, 1971
This is also clear in ``Digital Process Control'' published by Corona Co., Ltd. on October 20th.

Now, most of these digital control systems are PID
(proportional+integral-sufficient differential) control, and an example of the control formula in this case is shown on pages 84 to 87 of the above publication.

That is, △Po=Kp (Xn-+ X,,) + to + (Ro
-Xn)+I(D(2Xo-1-Xn-2)...
...(1) Here, △Pn: Total n: Correction amount KP of the operating end during current sampling - Proportional gain 1: Integral gain KD: Differential gain X, ,: Current sampling data X, ,: Previous Sampling data It is strongly influenced by large fluctuations in

There is no problem if the correct data is entered, but
For example, in the case where the measured value suddenly decreases due to a break in the signal system, etc., the operation correction amount ΔPo becomes abnormally large, which may adversely affect the process and make it impossible to operate.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for detecting abnormalities in a digital control system suitable for early detection of abnormalities in input data and preventing control based on abnormal data.

[Summary of the invention]

The present invention is characterized in that the input data is determined to be abnormal if the difference between the data input last time and the data input this time exceeds a set value.

[Embodiments of the invention] An embodiment of the present invention will be described below.

In FIG. 1, Sl is a switch that opens and closes every digitally controlled sampling. Memory 1 is switch S2
It has the function of retaining the data at that time by closing it.

First, when Sl is closed and data is taken in, comparison circuit 2 compares the previous data in memory 1 with the current data, and if the difference is within the set value, closes S3 and inputs it to PID calculation circuit 3. Enter data. Then open S3 and S
2 and store the current data in memory 1 in preparation for the next sampling.

On the other hand, if the difference with the previous data is larger than the set value, an interlock is performed to prevent data from being sent to the PID calculation circuit 3. In this case, an alarm can also be issued by an alarm circuit (not shown).

The tolerance between the previous data and the current data is determined by the sampling period and the response time of the process. That is, it should be set to a value that cannot be changed within that sampling interval and is as bulky as possible.

Although this embodiment has been described using a switch or a circuit, it is actually more practical to use it as software for a microcomputer.

〔Effect of the invention〕

As described above, according to the present invention, an abnormality in input data can be detected early, so that abnormal control based on abnormal data can be prevented.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention.

Claims (1)

[Claims] 1. In a digital control system that inputs data at regular intervals, uses the data to calculate a negative operation, and operates the process using the operation amount, the difference between the data input last time and the data input this time is set. A method for detecting an abnormality in a digital control system, characterized by detecting an abnormality in an input catenary when a certain value is exceeded.