JPS63191201A - Automatic plant controller - Google Patents

Abstract

PURPOSE:To realize the automatic operation of a plant by using the output of an operating means or the output of another correlative detector as a substitute signal when the abnormality of the output of a certain detector lasts longer than a prescribed period of time. CONSTITUTION:The value corresponding to the sampling value of this time and the prescribed value are calculated by the minimum square method using the paste detector outputs and the regression linear approximation and in consideration of the dynamic properties. These calculated value and prescribed value are compared with the current sampling value for detection of the abnormality of the detector output. If the abnormality of output lasts longer than a prescribed period of times with detectors 4-7, an abnormality detecting means functions to substitute the abnormal detector output for the outputs of operating means 2 and 3 serving as the substitute signals decided normal or the output of another correlative detector. For this purpose, the signals undergone the advance/delay compensation and the correlative compensation processing are changed to the bumpless states by bumpless switches 16 and 26 as long as the deviations of those signals are kept under the prescribed value. Thus it is possible to prevent the influence given to a control system owing to the continuation of the automatic control especially the malfunctions of the control system and also to avoid the increase of the operator load and misoperations.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for detecting an abnormality in a detector in various plants, maintaining a signal, and switching to an alternative signal, and in particular, continues automatic control even in the event of an abnormality in a detector. This invention relates to a plant automatic control device that enables automatic control of plants.

[Conventional technology]

The conventional device locks the operating device when a detector or the like becomes abnormal, as described in Japanese Patent Laid-Open No. 51-33201.

Alternatively, a means of switching to manual control by an operator was used. There is also a method of multiplexing the detectors and switching to a normal detector if one detector becomes abnormal.

On the other hand, the abnormality detection means of the detector diagnoses that the upper limit value, lower limit value, and rate of change of the output of the detector are within specified values. In particular, diagnosis of the rate of change is performed using the previous sampling value (DN-1) and the current sampling value (DN), as shown in Figure 2.
The diagnosis is made by determining whether dN, which is the difference between the two, is within a specified value. Also, use the first-order lag function shown in Figure 3 to calculate the value corresponding to the current sampling value from the current sampling value and the previous sampling value, and check whether the difference between the calculated value and the current sampling value is within a specified value. Diagnosis was made by determining the

Further, the signal holding means holds the signal at the previous sampling value, which is one time before the abnormality in the detector output is detected.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology does not take into consideration the continuation of automatic operation or the dynamic characteristics of plant state quantities, and therefore has the following problems.

First of all, in recent years, locking of operating devices and switching to manual control by operators has become more difficult due to the type of operating devices and
As the number of operators increases and the load on operators increases, there are problems such as further increasing the load, which is likely to lead to operator errors.

Additionally, multiplexing of detectors increases the maintenance of the detectors, detector piping, signal cables, and detectors, leading to increased plant construction and maintenance costs, and multiple detectors detecting exactly the same plant state quantity. Since it is not easy to do so, there is a problem that it can only be applied to limited plant state quantities.

On the other hand, among abnormality detection methods, regarding diagnosis of rate of change,
The diagnosis method using the current sampling value and the previous sampling value has a problem in that the dynamic characteristics of the plant state quantities are known and the specified value cannot be determined unless the upper limit of the difference between each sampling value can be predicted. Further, in the method of diagnosing the rate of change using a first-order lag function, there is a problem that the dynamic characteristics of the plant state quantity are limited to the detector power that can be approximated by the first-order lag function.

Regarding the signal holding means, holding the value at the sampling value one time before the time when an abnormality in the detector output was detected is important because there is no difference in the detector output within one sampling period or there is no effect on the control system. There was a problem in that it would only be valid if there was no such thing.

The purpose of the present invention is to provide a detector output abnormality detection means and holding means that take into account the dynamic characteristics of plant state quantities, and to enable continuation of automatic operation by switching to an alternative signal if the detector output continues to be abnormal. It's about doing.

[Means for solving problems]

The above purpose is to calculate a calculated value and a specified value corresponding to the current sampling value, taking into account dynamic characteristics, using the past detector output using the least squares method and one regression linear approximation, and to detect by comparing with the current sampling value. Detects abnormality in device output,
If the detector output is abnormal, the detector output is held at the above calculated value, and if the abnormality of the detector output continues for a predetermined period of time or more, the output of the actuator as an alternative signal or other correlated signal is This is achieved by switching to the detector output.

[Operation] The abnormality detection means adds the amount of change obtained by regression line approximation using the past detector output to the calculated value corresponding to the previous sampling value obtained by the least squares method using the past detector output. The calculated value corresponding to the current sampling value is calculated, and the difference between this calculated value and the current sampling value is
An abnormality is detected depending on whether the amount of change is within the above range. Thereby, there is no need to understand the dynamic characteristics of the plant state quantities in advance, and the method can be applied to detector outputs of plant state quantities that cannot be approximated to a first-order lag function. In addition, by holding the calculated value corresponding to the current sampling value as described above instead of the detector output when the detector is abnormal, the influence on the control system can be reduced.
In particular, malfunctions can be prevented. Furthermore, if the abnormality of the detector output continues for a predetermined period of time or more, the operation device output, which is an alternative signal determined to be normal by the above-mentioned abnormality detection means, or another correlated detector output is determined to be abnormal. Lead/lag compensation is applied to correspond to the detector output, and if the deviation of the processed signal is within a specified value, the signal is switched to bumpless mode, thereby preventing the effects of continuous automatic control on the control system, especially malfunctions. This also prevents an increase in operator workload and erroneous operation.

〔Example〕 An embodiment of the present invention will be described below with reference to the drawings.

First, FIG. 1 shows an outline of a plant automatic control system. The plant automatic control system 1 includes a control circuit 1o that outputs a control signal 52 for an operating device 2, and an abnormality detection means.

The outputs of the detectors 4 and 5 are 54° and 55°, respectively.
Diagnosis circuits 11 and 12 perform signal diagnosis and retention. The signal 62 diagnosed by the diagnosis circuit 12 is inputted, and lead/lag compensation and correlation function compensation calculations are performed to make the signal correspond to the output 54 of the detector 4. Alternative signal 63 for output 54 of detector 4
A comparator 13 that outputs a compensator 13 that checks the deviation between the signal 61 diagnosed by the diagnostic circuit 11 and the alternative signal 63, and sets the switching permission signal 34 to '1' if the deviation is within a specified value.Diagnostic circuit 14 Signal switching request signal 3 output from 11
1, the switching permission signal 34 output from the comparator 14, and the alternative signal normal signal 32 output from the diagnostic circuit 12, and the AND element 15 outputs the switching signal 35, and the switching signal 35 is "1". ”, the post-diagnosis signal 61 is changed to the alternative signal 63, and conversely, if the switching signal 35 is “0”, the alternative signal 6 is changed.
3, a bumpless switch 16 that switches the output signal 66 from the post-diagnosis signal 61 to the bump press, a control circuit 20 that similarly outputs the control signal 53 of the operating device 3, and a diagnosis that diagnoses and holds the signals of the detectors 6 and 7, respectively. Circuit 21.22 Signal 7 after diagnosis
The compensator 23 performs compensation to make the signal corresponding to the output 56 of the detector 6 into a signal corresponding to the output 56 of the detector 6, and outputs the alternative signal 73. The compensator 23 compares the post-diagnosis signal 71 and the alternative signal 73, and outputs the switching permission signal 4.
a comparator 24 which outputs a switching signal 45; It is constituted by a bumpless switch which switches the post-diagnosis signal 71 and the alternative signal 73 bumplessly using the switching signal 45 to produce an output signal 76.

Next, the 1 diagnostic circuit 11 will be explained with reference to FIG. Since the circuits of the other diagnostic circuits 12, 21, and 22 are the same as the diagnostic circuit 11, only the first diagnostic circuit 11 will be explained.The first diagnostic circuit 11 has an abnormality detection means and a holding means. Certain detector outputs 54 and alternative signals 63.
The abnormality reset signal 170 is input, and the post-diagnosis signal 61. The switching request signal 311 and the alternative signal normal signal 165 are output.

As shown in FIG. 5, the least squares filter element 111 uses the past values LN-1 to LN-6 of the detector output 54 to
．． Y = (3X
LM-1+ 2 X LN-z+Ls-a
-LN-Is) Calculate 15 and output. The change amount calculation element 112 uses RN-a from the past value Rs-t of the detector output 54 and calculates the change amount Y (fourth
152) in the figure is Y=2XRs-1+RN-z RN-
4RN-6) and output. The addition element 113 in FIG. 4 adds the output 151 of the least squares filter 111 corresponding to the previous sampling value and the calculated change value 152,
A calculated value 153 corresponding to the current sampling value is output. The addition element 115 is a signal generation element 114 that outputs the calculated change value 152 and a margin corresponding to the error of the detector.
The outputs 154 of are added to output the specified value 155 of the comparison elements 117 and 120. The limiting element 116 limits the upper and lower limits of the calculated value 153. The upper and lower limit values correspond to the signal range of the detector output 54. Comparator $117 is the current sampling value of detector output 54 and limit plate calculated value 156
The deviation is compared with a specified value 155, and when the deviation is larger than the specified value, the large deviation signal 157 is set to "1".

The comparison element 119 checks the upper and lower limits of the detector output 54, and sets the upper and lower limit abnormality signal 159 to "1" when the detector output 54 is larger than the specified upper limit value or smaller than the specified lower limit value.
''.The specified value for the upper and lower limit check is the detector output 54.
Compatible with the range. OR element 126 is large deviation signal 1
57 and the upper and lower limit abnormality signal 159 are calculated, and a holding signal 166 is output. Switching element 118 provides hold signal 166
is “1”, the detector output 54 is set to the limit plate calculated value 156
is switched to, held, and output as post-diagnosis output 61. The delay time element 123 sets the switching request set signal 163 to "1" when the holding signal 126 continues to be "1" for a predetermined period of time.The flip-flop element 124 has a set signal priority function, and sets the switching request set signal 163 to "1". 163 becomes "1", the switching request signal 31 is held at "1" until the switching request reset signal 162 becomes "1". Logical negation element 125
performs a logical NOT operation on the switching request signal 31 and outputs the 1 alternative signal normal signal 165. The comparison element 120 compares the difference between the detector output 54 and the alternative signal 63 with a specified value 155;
If the difference is greater than the specified value 155, the large deviation signal 160 is
1'', the logical negation element 121 calculates the logical negation of the large deviation signal 160 and outputs the switching request reset permission signal 161. Calculate,
A switching request reset signal 162 is output.

According to this embodiment, after the detector output becomes abnormal and switches to an alternative signal, there is a function to confirm and permit that the detector output has become normal, and a function for the operator to confirm and permit.
The return to the detector output from the alternative signal also has the effect of preventing influence on the control system and malfunction.

〔Effect of the invention〕

According to the present invention, first, the past value of the detector output is
Since the calculated value and specified value corresponding to the current sampled value can be calculated using multiplicative regression linear approximation, even if the dynamic characteristics of the plant state quantities are not known in advance, or the dynamic characteristics of the plant state quantities can be approximated to a first-order lag function. This has the effect that effective detection of abnormalities in the detector can be performed even if the detection is not possible. In addition, when the detector output is abnormal, the detector output can be held at the above calculated value corresponding to the detector output at the time of abnormality detection, rather than the detector output one sampling before the time of abnormality detection, which has a negative impact on the control system. This is especially effective in preventing malfunctions. Furthermore, if an abnormality in the detector output continues for more than a predetermined time, the detector output is switched to an alternative signal to prevent a negative impact on the control system, and automatic control can be continued without increasing the burden on the operator. , which is effective in preventing operator errors.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a plant automatic control system according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of a change rate check, FIG. 3 is a characteristic diagram of a first-order lag function, and FIG. 4 is a diagnostic port. 5 is an explanatory diagram of the least squares method, and FIG. 6 is an explanatory diagram of regression line approximation. 1... Plant automatic control device, 2, 3... Operator,
4 to 7...Detector, 11,12,21.22...Diagnostic circuit, 13.23...Compensator, 16.26...Bumpless switch, 111...Least squares filter element,
112... Change amount calculation element.

Claims (1)

[Claims] 1. An abnormality has occurred in the detector in the control device that outputs a signal to automatically control the operating device according to the output of the detector that detects the plant state quantity to be controlled and the operating device that controls the plant state quantity. an abnormality detection means for detecting the abnormality detection means; a holding means for calculating a signal corresponding to the output at the time of abnormality from the past output of the detector based on the output of the detector according to the output of the abnormality detection means; and holding the output at the calculated signal; Plant automation characterized by comprising a switching means that automatically switches the output of the holding means to the output of the operating device or the output of another correlated detector when the output of the abnormality detection means continues for a predetermined time or more. Control device.