JPS5952307A - Controller provided with alarm function - Google Patents

Abstract

PURPOSE:To detect the minute leakage, etc. of a plant pipeline, by comparing the normal operation signal generated from a function generator with an actual control signal. CONSTITUTION:The pressure in a tank 1 is detected as a process signal 201 by a pressure transmitter 2 and supplied to a deviation operator 43 together with the target value of a setter 42 via a filter 41 within a controller 4. The deviation detected by the operator 43 is turned into an operation signal by a PID operator. This operation signal controls a control valve 3 via an up-down limiter 45 to control the pressure in the tank 1. The signal 201 is applied via a time delay element 47 to a function generator 48 which approximates the static characteristics between the operation signal of the controller 4 and the signal 201. The normal operation signal given from the generator 48 and the actual operation signal given from an operator 44 are applied to a comparator 5 via a subtrator 49 in the form of a difference signal. The comparator 50 decides the generation of minute leakage when said difference signal exceeds a fixed level and delivers an alarm 403.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a control system that performs a predetermined control operation on a control deviation between a target value and a process value, outputs an operation signal, and controls a process to be controlled using this operation signal. In addition to this function, the present invention relates to a controller with an alarm function that has an alarm function to notify of abnormalities in this process.

[Technical background of the invention and its problems]

Do controllers used to control plants, etc. have various functions in addition to control functions? There are many things it has.

One such feature is an alarm function that alerts users when a process variable deviates from a predetermined range.

The 11F4 section shown in FIG. 1 is equipped with a function to detect changes in pressure and flow in a plant and to warn against leaks in plant piping. The pressure in the tank 1 is detected by a pressure transmitter 2, for example.

Moreover, this pressure is controlled by opening and closing the pressure regulating valve 3. The controller 4 processes the process signal 201 from the pressure transmitter 4 and outputs it as an operation signal 4, and at the same time outputs an alarm signal 402. The process signal 201 is first filtered by a digital filter 41, and the deviation from the set value signal of the target value setter 42 is calculated by a deviation calculator 43. The deviation signal from the deviation calculator 43 is controlled and calculated by the PID processor 44 to be used as an operation signal, which is input to the pressure regulating valve 3 via 45 upper and lower limit limiters as required. In addition to this control function, this controller 4 also has process signals? It has a monitoring function. For example, when a leak occurs from a pipe in a plant, the process signal 201 falls below the normal pressure range, so this is detected by the lower limit alarm setting device 46 and an alarm signal 402 is output.

However, in the case of such conventional controllers, if there is a minute leak in the plant piping, the controller's own control function compensates for the pressure drop, so even though there is a leak, , Lower (3) may not be detected by the alarm setting device 46.

In other words, there was a problem in that the conventional controller with an alarm function could not detect minute leaks.

[Purpose of the invention]

The present invention has been made in consideration of the above-mentioned circumstances, and is a controller with an alarm function that can detect process abnormalities that were previously undetectable, such as leaks from micrometers in piping in tanks, and issue an alarm. ? The purpose is to provide.

[Summary of the invention]

In order to achieve this objective, the controller according to the invention with %-1 → function is equipped with a time lead/lag element for compensating for the dynamic time deviation between the process value and the operating signal.

a function generator that converts the process into a normal operation signal assuming that the process operates normally; and a function generator that converts the normal operation signal into a normal operating signal assuming that the process operates normally; (4) A comparator that compares the operation signal and the actual operation signal and outputs an 11 signal when the difference between these normal operation signals and the actual operation signal is greater than or equal to a predetermined value. Be prepared.

[Embodiment of the Invention] A controller with an alarm function according to an embodiment of the present invention is characterized in that the alarm signal outputted by the comparator does not notify an abnormality in the process. 201 is filtered by a digital filter 41, and a deviation from the set value signal of the target value setter 42 is calculated by a deviation calculator 43. The deviation signal generated by the deviation calculator 43 is controlled and calculated by the vPID calculator 44 and used as an operation signal, and the upper and lower limit limiters 45V
Upper and lower limits are set from c and the pressure regulating valve 3 is operated. Further, when the process signal 201 deviates from the normal pressure range, it is detected by the lower limit setter 46 and an alarm signal 402 is output.

The controller according to this embodiment further includes a time delay element 47.
, function generator 48. A subtractor 49 and a suggestor are added to provide a function for detecting minute calculations. The process signal 201 is subjected to a time delay operation by a time delay element 47. This is to compensate for the dynamic time delay between the process signal 201 and the operation of the pressure regulating valve 3 due to the operation signal 401, and is composed of a second delay element and a dead time element.

The output signal of time delay element 47 is converted by function generator 48 and output to subtracter 49 . This function generator 48
is obtained by a static characteristic polygonal line approximation between the operation signal of the controller when the plant is normal and the process signal 201 which is the process pressure, and the process signal 20 which is the input signal
1V Converts to an operation signal when the plant is normal. Subtractor 49
The output signal of the PID calculator 44 is inputted to the other input terminal of the , and the difference between the output signal and the output signal of the function generator 48 is calculated.

This difference signal is compared with a predetermined value between the comparators, and if it is greater than or equal to the predetermined value, it is determined that a small amount of leak has occurred, and an alarm signal 403 is generated.

In this way, according to this embodiment, even a slight failure can be reliably detected. In the first embodiment, the primary delay element and wasted time element were used as time delay elements, but Depending on the process, an integral element or a higher-order delay element may be required. Also, is the process signal time delay element 47? via function generator 4
8, but the order of processing is reversed and the input is to function generator 4.
8 and may be input to the time delay element 47. Furthermore, the time delay element 47 does not necessarily need to be placed on the function generator 48 side; it is only necessary to compensate for the time difference between the two signals input to the subtracter 49, so %P
A time advance element may be inserted on the ID calculator 44 side. Further, the function generator 48 may be expressed by a mathematical expression instead of the polygonal line approximation.

Also, is this the target of control in the example in the trench? Although the process signal has been explained as a pressure signal of a tank, it goes without saying that the target process may be other equipment. That is, the controller with an alarm function according to the present invention is very effective for processes that require detection of minute changes in operating signals.

〔Effect of the invention〕

According to the present invention, it is possible to detect a slight abnormality in a process that was previously undetectable, such as a small leak in a tank pipe (7). A serious abnormality like? Can such abnormalities be detected in advance? It can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional controller with an alarm function. FIG. 2 is a block diagram of a controller with an alarm function according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Tank, 2... Pressure transmitter, 3... Pressure control valve, 4... Controller with good news function, 41... Digital filter, 42... Target value setter, 43 ... Deviation calculator, 44... PID calculator, 45... Upper and lower limit limiter, 46... Lower limit alarm setter, 47... Time delay element, 48... Function generator, 49 ...Subtractor, Seki...
・Comparator. Applicant's agent Kiyoshi Inomata (8)

Claims (1)

[Claims] Predetermined control operation for control deviation between target value and process value? In addition to the control function of outputting operation signals from the trunk and controlling the process to be controlled using these operation signals,
In this controller with an alarm function having a function to notify abnormalities in the process, a time lead/delay element is provided to compensate for an automatic time difference between the process value and the operation signal. A function generator converts the process value into a normal operating signal assuming that the process is operating normally, and the time lead/lag element compensates for dynamic time shifts. Compare the normal operation signal converted by the function generator with the actual operation signal, and output an alarm signal when the difference between the normal operation signal and the actual operation signal is greater than or equal to a predetermined value. A controller with an alarm function, characterized in that the controller is equipped with a comparator, and notifies an abnormality in the process by an alarm signal output from the comparator.