JPH0350155B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an improvement in a pneumatically actuated control valve control system.

(Prior Art) As an example of a conventional air-operated control valve control device, there is a one-to-one relationship between an opening command signal and a valve lift signal of an air-operated control valve.
Monitors the deviation between the opening command signal and the valve lift signal,
Some devices are designed to determine that there is an abnormality when a set value is exceeded. However, the valve has a delay in operation,
Even if it is normal, deviations occur transiently. Figure 1 shows the relationship, where a is the opening command signal, b
indicates the valve lift signal. For this reason, in order to avoid misdiagnosis, the conventional configuration has been to increase the set value, but if a failure occurs, there will be a delay in detecting the failure.

(Problems to be Solved by the Invention) The present invention has been made to solve these problems, and provides an air-operated control valve control device that can quickly detect failures without causing erroneous valve diagnosis. The purpose is to provide.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a deviation detector for detecting a deviation between an opening command signal and a valve lift signal of an air-operated control valve, and an output from this deviation detector. a time constant setter that receives a signal and sets a predetermined time constant; a first-order lag processing circuit that applies first-order lag processing to the opening command signal using the time constant of the time constant setter; This air-operated control valve control device includes a determining device that determines an abnormality when the deviation between the output signal of the processing circuit and the valve lift signal exceeds a specified value.

[Operation] According to the present invention, the deviation between the opening command signal and the valve lift signal is detected, and a predetermined time constant is set based on this detection output. In this case, for example, if the deviation is positive, an increasing time constant is set, and if the deviation is negative, a decreasing time constant is set. And with this set time constant,
The opening command signal is subjected to first-order delay processing, and when the deviation between the opening command signal subjected to the first-order delay processing and the valve lift signal exceeds a specified value, an abnormality is determined.
Because of this, it is possible to prevent erroneous diagnosis due to a delay in the operation of the control valve, and to quickly detect a failure.

(Example) The present invention will be described below with reference to the drawings.
FIG. 2 is a schematic diagram showing an embodiment of the apparatus of the present invention. Reference numeral 20 denotes a control valve for adjusting the flow rate of a desired fluid, and this control valve 20 can be opened by a predetermined opening degree by a diaphragm 21 provided in a diaphragm chamber (not shown). Pressurized air is supplied to the diaphragm 21 from an air pressure control mechanism 23, which will be described later, in accordance with an opening command signal 24 of the control valve 20. The opening command signal 2
4 is supplied not only to the air pressure control mechanism 23 but also to an abnormality diagnostic device 27, which will be described later. The pneumatic control mechanism 23 includes an electropneumatic converter 23a, a positioner 23b, and a booster relay 23c. A valve lift signal 26, which is an outlet of the diaphragm 21, is detected by a lift meter, and the detected valve lift signal 26 is supplied to an abnormality diagnostic device 27. On the other hand, the valve lift signal 26 is transmitted to the positioner 2 via the feedback link 22.
3b.

The abnormality diagnostic device 27, as shown in FIG.
It consists of a deviation detector 100, a time constant setting device 101, a first-order delay circuit 102, and a determining device 103, and the valve lift signal 26 and opening command signal 24 supplied to this abnormality diagnostic device 27 are inputted and calculated to detect abnormalities. It is now possible to diagnose whether it is present or not.

Hereinafter, the operation of the air-operated control valve control device configured as described above will be explained. The opening degree control of the control valve 20 is performed as follows. Normal opening adjustment is performed by an opening command signal 24 supplied from the outside.
is converted into an air signal by the electro-pneumatic converter 23a. In a steady state, the relationship between this air pressure signal and the opening command signal 24 is a linear function as shown in FIG. The positioner 23b is adjusted to satisfy the following equation (1), where the control valve lift is L, the air pressure signal is P, and a and b are constants.

L=aP+b...(1) If L>aP+b, positioner 2
The outlet air pressure of the positioner 23b is increased, and if L<aP+b, the outlet air pressure of the positioner 23b is decreased. Booster relay 23c is an amplifier that makes the diaphragm pressure match the outlet pressure of positioner 23b. If the diaphragm pressure is higher than the outlet pressure of the positioner 23b, the air in the diaphragm 21 is exhausted to the atmosphere and the pressure in the diaphragm 21 is lowered. Also, diaphragm 21
If the pressure is low, air is sent into the diaphragm 21. As the pressure in the diaphragm 21 increases, the valve lift signal 26 increases, and as the pressure decreases, it decreases.
In this way, the positioner 23b valve lift signal 26
A linear function relationship as shown in FIG. 5 is established between the opening command signal 24 and the opening command signal 24.

Now, booster relay 2 to diaphragm 21
Supplying and exhausting the required amount of air by 3c is not instantaneous and takes time. Therefore, when the opening command signal 24 changes, the diaphragm pressure will have a time lag. This means that the valve lift signal 26 satisfies the relationship shown in FIG. 5 with a time lag. At this time, the time lag between the valve lift signal 26 and the opening command signal 24 can be described as a first-order lag as shown in FIG. Therefore, in order to cope with the case where the opening command signal 24 changes, the signal passed through the first-order delay processing circuit 102 of the opening command signal 24 and the valve lift signal 26 are used.
Compare. Furthermore, the amount of air supplied to the diaphragm 21 and the amount of air exhausted from the diaphragm 21 per unit time are different, and therefore, the time delay in the opening direction and the time delay in the closing direction of the valve lift signal 26 are also different. . Figure 7 shows the relationship. Therefore, when the opening command signal 24 increases, that is, when the valve lift signal 26 is in the opening direction, and when the opening command signal 24 decreases, that is, when the valve lift signal 26 is in the closing direction, the first-order lag in FIG. The time constant of processing circuit 102 must be changed. Here, when the opening command signal 24 is increasing, the deviation obtained by subtracting the valve lift signal 26 from the opening command signal 24 is a positive value, and when the opening command signal 24 is decreasing, the deviation is a negative value. Therefore, the time constant of the first-order delay processing circuit 102 may be set based on the sign of the deviation.

The deviation detector 100 of the abnormality diagnostic device 27 in FIG. 3 calculates the deviation by subtracting the valve lift signal 26 from the opening command signal 24, and if the deviation is positive, it will increase; if the deviation is negative, it will be determined to decrease. Time constant setter 101
is the time constant T 1 if the signal from the deviation detector 100 is increasing, and if it is decreasing, the time constant T ₁ is
Set _T2 . The first-order delay processing circuit 102 uses the time constant set by the time constant setter 101 to perform first-order delay processing on the opening command signal 24. Judgment device 1
03 is determined to be normal if the difference between the output of the primary lag processing circuit 102 and the valve lift signal 26 is within a specified value, and determined to be abnormal if it exceeds the specified value. In FIG. 8, the shaded area is a normal area, and the other areas are areas determined to be abnormal.

(Effects of the Invention) According to the present invention described above, there is provided a deviation detector that detects the deviation between the opening command signal of the air-operated control valve and the valve lift signal, and a time constant setting device for setting a constant; a first-order lag processing circuit for performing first-order lag processing on the opening command signal using the time constant of the time constant setting device; and an output signal of the first-order lag processing circuit. The structure is equipped with a determination device that determines an abnormality when the deviation of the valve lift signal exceeds a specified value, so the abnormality diagnosis is more accurate than conventional devices, and air-operated adjustment that does not cause misdiagnosis. A valve control device can be provided.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the opening command signal and valve lift signal of a conventional air-operated control valve control device, and FIG. 2 is a schematic configuration diagram showing an embodiment of the air-operated control valve control device of the present invention. Fig. 3 is a schematic diagram of the abnormality diagnostic device shown in Fig. 2, and Figs. 4 and 5 show the relationship between the opening command signal and the outlet air pressure of the electro-pneumatic converter to explain the operation of the same embodiment. 6 and 7 are diagrams showing the relationship between the valve lift signal and the opening command signal to explain the operation of the embodiment. , 8th
The figure is a diagram showing the relationship between the output signal of the first-order lag processing circuit and the valve lift signal for explaining the operation of the same embodiment. 20...Control valve, 21...Diaphragm, 22
...Feedback link, 23...Pneumatic control mechanism, 23a...Electro-pneumatic converter, 23b...Positioner, 23c...Booster relay, 24...Opening command signal, 26...Valve lift signal, 27... ... Abnormality diagnostic device, 33 ... Valve lift meter, 100 ... Deviation detector, 101 ... Time constant setting device, 102 ... 1
Next delay processing circuit, 103...determiner.

Claims (1)

[Claims] 1. A deviation detector that detects the deviation between the opening command signal and the valve lift signal of the air-operated control valve, a time constant setting device that receives the output signal from this deviation detector and sets a predetermined time constant, and 1. Performing first-order delay processing on the opening command signal using a time constant of a constant setting device.
A pneumatic control valve control device comprising: a second-order delay processing circuit; and a determining device that determines that an abnormality occurs when the deviation between the output signal of the first-order delay processing circuit and the valve lift signal exceeds a specified value.