JPS61148502A - Process controlling system - Google Patents

Abstract

PURPOSE:To suppress an opposite polarity deviation, and to return a system to a stable process control state without giving a disturbance by confirming a state of a deviation, in case when tracking has been applied to a process control system, and increasing or decreasing precedently before the deviation becomes the opposite polarity. CONSTITUTION:A deviation epsilon always passes through the maximum deviation epsilonP and decreases, therefore, the maximum deviation epsilonP is stored in advance. In this state, when tracking is applied, a time t1 of a deviation epsilon=0 can be set before the time t1 virtually by subtracting or adding a deviation epsilonX of X[%] of the maximum deviation epsilonP, from or to the deviation epsilon, and a process control system is made to have a precedent control.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention uses a process control system to control the setting of the valve opening degree after a commonly used control valve is fully closed or fully opened in a power generation plant. It relates to process control systems.

[Questions and questions about how to get used to the invention] Normally, the process control system in a plant is roughly shown in Figure 4, where the inflow is q1 and the outflow is Q! In order to set tank water level 2 of tank 1 to the water level specified by setting device 3, set tank water level 2 of tank 1.
is detected by the detector 4. Then, the water level specified by the setting device 3 (hereinafter abbreviated as set water level WL) and the tank water level 2 of the detector 4 are input to the control device 50, and the control valve 6 is controlled as a calculation output signal of the calculation device 5 to control the inflow amount Q. .

The structure is such that it can be adjusted. The characteristics of the control device 5 are that if the evening water level is higher than WL, the control valve 6 is closed, and if it is lower than WL, it is opened. Conventionally, a control device 5 having such characteristics has a configuration as shown in FIG.

The control device 5 extracts the difference between WL7 and tank water level 2 as deviation ε using a detection device 8 which receives WL7 and tank water level signals from two people. This deviation C is calculated by the proportional calculation device 9 and the integral calculation device 1.
0 (there is also a differential calculation device as a component of the control device 5, but for the sake of explanation, the integral calculation device 10 will be explained as an example), the proportional output P which is the output of each calculation device, and the integral ratio crab. are added by the adding device 1, and the output of the control device 5 is set as Mo.

Furthermore, the integral calculation device 10 has a characteristic that if there is a deviation ε, the integral ratio K continues to increase or decrease depending on the amount of deviation. In other words, the upper limit output Mo at which the control valve 6 is fully opened at the control output M0
, and the integral ratio is above or below the lower limit output Moc that becomes fully closed. The control output becomes Mo.

To prevent this, the upper and lower limit outputs are monitored by an upper limit detector 12 and a lower limit detector 13, respectively. That is, when the output of the upper limit detection device 12 turns ON, the AND circuit AN
It is input to D1.

At this time, when the polarity of the deviation ε is positive, the output of the polarity detection device 14 is ON, so ANDl is turned ON.

If ANDJ or AND2 output turns ON, ORI turns ON.
becomes. Since the ORI output turns ON, the integral calculation device 1
The result of equation (1) calculated by the adder 15 excluding the input of 0 is (integral ratio crab.) = (control output MO) - (proportional output P
6)...(1) Integral output I, is forcibly input to the integral calculation device 10 as:

The control output M0 is expressed by equation (2).

(Control output MO) = (Proportional output po) + (Integral ratio crab.) = (Proportional output P(1) + (Response output MO) - Example output I0 Also, the output of the lower limit detection device 13 is The same applies when it is turned ON.Here, it is called tracking in which the control output M0 is balanced as shown in equation (2).

The conventional control device 15 has the following problems. FIG. 6 is for explaining this problem, and plots deviation 6 and control output M0 on the vertical axis and time t on the horizontal axis. A case is shown in which an external EL occurs in the process system and the control output M0 is in a tracking state at the upper limit output MOF.

As the deviation ε increases with positive polarity, the control output M0 increases in an attempt to correct the deviation C, and when it reaches the upper limit value, tracking is performed at the upper limit output M, . The deviation 8 is corrected little by little and decreases after the maximum deviation has elapsed, since the opening degree of the control valve 6 becomes fully open at the upper limit output MOF in the fully open direction as the control output M0 increases. And time t,
After becoming 0 at , a deviation C occurs on the negative polarity side. This reverse polarity deviation is the maximum deviation ε.

Although it varies depending on the magnitude of the deviation, the cause of this is due to tracking, and the repetition of positive polarity deviation and negative polarity deviation causes disturbance to the process control system, resulting in an unfavorable state for the plant.

[Purpose of the invention]

Therefore, the purpose of the present invention has been made in view of the above circumstances, and when tracking is applied to the process control system, the situation of the deviation e is checked and the deviation e is proactively detected before the deviation e becomes reverse polarity. It is an object of the present invention to provide a process control system that can suppress reverse polarity deviation and return to a stable process control state without causing disturbance by increasing or decreasing control output M#.

[Summary of the invention]

, to achieve this purpose, the deviation blur must be the maximum deviation
Since it passes through and decreases, the maximum deviation e.

Let me remember it. When tracking is applied, the deviation g in Fig. 6 can be calculated by subtracting or adding the deviation 81 of X(S,) of the maximum deviation ε, from the deviation C.
= The time t of Q can be made apparently earlier than the time t1, and the process control system is characterized by having advance control.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to FIG. FIG. 1 shows the configuration of the present invention. The maximum deviation ε is stored in the maximum deviation detection storage device 16. Also, deviation e
The direction of the deviation ε is confirmed by the change rate device 17, which confirms whether the deviation ε is increasing or decreasing. Rate of change device 17
turns ON in the deviation-decreasing direction. When the output of the rate of change device 17 is ON, the Δt detection device 18 is activated. The Δt detection device 18 measures and stores the appropriate time Δt during which the deviation C decreases from, for example, 2/3 to 1/2 of the maximum deviation C.

After the measurement is completed, that is, when the deviation is -6, the output is turned on and output to ANDJ. The detection dead band device 19 turns on the output if the deviation g is greater than the normal deviation since there is no problem even if tracking is applied in the normal operating state.

AND3 turns on the output of the detection dead band device 19.

This is an AND circuit that turns the output ON when the output of the rate of change device 12 is ON, the output of the Δt detection device 18 is ON, and the OR2 output is ON. OR2 is when the output of ORI is ON or A
When the output of NDJ is ON, the output is turned ON.

The arithmetic unit 20 inputs the maximum deviation and the passing time Δt from the deviation detection device 16 and the Δt detection device 18, respectively, by AND and 9 being turned on.

The values determined by patterning by the two persons are outputted to the bias group gL21.

Bias device 2111: By turning on AND3,
The output of the arithmetic device 20 and the current deviation ε are compared. This is because if tracking is applied while the deviation e is decreasing, the output of the arithmetic unit 20 may be large. Therefore, in this device, if the output of the arithmetic device 20 is smaller than the deviation ε, the output of the arithmetic device 20 is set as the bias value ε''.

In the opposite case, the bias value ε" is set to, for example, 60 (%) of the deviation ε, and the bias value ε" is always 0 when ANDJ is OFF. The bias amount ε"· determined by the bias device 21 is input to the adding device 22, and the adding device 22 turns the deviation C into the deviation ε' obtained by subtracting the bias value 6".

(deviation ε') = (deviation e) - (bias value ε")...
...(3) This deviation e' is calculated by the proportional calculation device 9. It becomes an input to the integral calculation device 10.

The patterned operation of the arithmetic device 20 of the present invention performed by two people will be explained with reference to FIG. In FIG. 2, the maximum deviation gp is plotted on the vertical axis and the transit time Δt is plotted on the horizontal axis. Then, the area is divided into ε□ to εx4. For example, the maximum deviation ε.

When the intersection point X of and transit time Δt is within the region εx1, the bias value ε is 11 g, and when it is within the region ε1, the bias value C is eXl. Also, the bias value C" has a value of 4 or less, which is the maximum deviation, because the passing time Δt is measured between - and 1/2 of the maximum deviation ε.

Now that the configuration of the present invention has been described above, the operation will be described next. The operation of the present invention will be explained based on the embodiment of the present invention shown in FIG. 1 in the case where a deviation occurs as shown in FIG. When the deviation ε starts to increase from time t0, time t.

The output of the detection dead band device 18 is ON, but AND3 is OFF'F. Control output M at time t1.

When becomes the upper limit, ORz is 0NL) racking is applied,
OR2 turns ON. Then the maximum deviation ε.

After a period of time, when the difference ε starts to decrease, the rate of change device 17 changes to O.
It becomes N. After that, the difference e is the maximum side difference ε.

When the Δt detection device 18 reaches 3/4 of the deviation, the Δt detection device 18 counts the passing time Δt until the time t4 when the maximum deviation becomes 14.
It is stored and output to ANDJ. This results in AN
All D3 inputs are turned ON, and the output is turned ON. AND
When j is established, the maximum deviation e and the transit time Δt are input to the arithmetic unit 2o, and the arithmetic unit 20 outputs the bias value e' to the bias device 2. At this time, the bias value ε“
is smaller than the deviation ε, so the output of the bias device 21 is directly the output of the arithmetic device 2o as the bias value ε" and is outputted to the adder 22. At this time, the input of the proportional arithmetic device 9 and the integral arithmetic device 10 is abrupt. It shifts to the value shown by equation (3) and shifts to BK from the actual deviation ε curve.However, since Hiro tracking is applied at this time, the control output M
.

is kept constant by equation (2). Then time t.

When the polarity of the deviation ν is reversed at
I turns OFF. At this point, the re-tracking is canceled and the control output M begins to decrease.

Even if ORI turns OFF, ANDl is self-held by OR2, so it will not turn OFF'. Thereafter, the time t when the preparation difference C becomes within the dead zone of the detection dead zone device 18
・It turns OFF at , so ANDl turns OFF.
becomes. When ANDJ turns OFF, NO'l',?
is ON1, and the SS circuit output is ON for a certain period of time. This SS
Tracking is applied again at the circuit output.

When tracking is applied, OFT changes from ON to OFF.
F, so the bias value e of the bias device 2o
" becomes 0 and becomes the same as the deviation 87 company deviation ε. However, since it is in a tracking state at this time, the control output M0 does not change and obtains a constant value. When the SS circuit output turns OFF, tracking is canceled and normal operation resumes. Return to

〔Effect of the invention〕

As described above, according to the present invention, tracking is performed at the upper and lower limits of the control output M. In other words, it is possible to provide a control device 5 that can proactively perform automatic control operations based on the state of the deviation C even when the control valve is fully open or fully closed (tracking is applied). The present invention can be applied to process control systems of power plants, steel plants, water and sewage plants, etc.
The control device can be configured with a sequence controller, and can also be configured with a combination of relay circuits or analog circuits0

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a control device according to the present invention, Figure 2 is a pattern diagram of a bias value l'' according to the present invention, Figure 3 is an explanatory diagram of the circuit according to the present invention + when deviation ε occurs, and Figure 94 is A block diagram of a conventional process control system, No. 5riA is a block diagram of a conventional control device, and Fig. 6 is a state characteristic diagram of the control output M6 when a conventional deviation e occurs. 1...tank, 2...・Tank water level, 3... Setting device, 4... Detector, 5... Control device, 6... Control valve, ?... Setting water level, 8... Detector Rs y... Proportional calculation device, IQ... Integral calculation device, 11... Addition device, 12... Upper limit detection device, 13... Lower limit detection device, 14 Polarity detection device, 15... Addition device, 16.
... Deviation detection storage device, 17... Rate of change device, 18.
.DELTA.t detection device, 19. Detection dead zone device, 2o river calculation device, 21.. Bias device 1.22.. Addition device. (7317) Agent Patent Attorney Noriyuki Chika (and 1 other person) No. 21! 1 ”lie PJf

Claims (1)

[Claims] A maximum deviation detection storage device that stores the maximum deviation of the deviation between the input signal and the set value, a rate of change device that confirms the rate of increase or decrease in the deviation, a Δt detection device that stores the passing time of the increase or decrease in the maximum deviation, and a deviation a detection dead band device having a detection sensitivity of
In a process control system comprising a bias device that inputs and calculates a signal from a t-detection device, a calculation signal from a rate-of-change device, and a detection dead band device signal, an addition device inputs the deviation input signal and a calculation output signal from the bias device. A process control system characterized in that when a process signal reaches an upper and lower limit value and enters a tracking state based on the difference between the signals, the amount of deviation is automatically controlled in advance to stabilize the control system.