JPH01237805A - Flow rate controller - Google Patents

Abstract

PURPOSE:To reduce the number of times of control by performing the inverse operation of the targeted divergence of a valve from a targeted flow rate, and approaching a flow rate to the targeted flow rate in advance by performing initial control action based on the divergence. CONSTITUTION:On a flow rate controller equipped with the valve 1 and a flow meter 2, a targeted divergence arithmetic means 3, a valve divergence control means 4, and a valve flow rate control means 5 are provided. And at this time, the flow rate controller finds the targeted divergence of the valve 1 by performing the inverse operation by using a flow rate calculation equation at the targeted divergence arithmetic means 3. At the time of performing the initial time of control, the flow rate is controlled to a value nearer to the targeted flow rate in advance by controlling the divergence of the valve 1 from the targeted divergence and the present divergence. Afterwards, the divergence of the valve 1 can be controlled by a prescribed control system such as a PID control system or an ON/OFF control system, etc., by the valve flow rate control means 5. In such a way, it is possible to reduce the number of times of control due to hunting.

Description

[Detailed description of the invention] [Summary] Correction function using flow rate calculation formula! The purpose of this system is to reduce the number of hunting controls required even when the flow rate is slow to follow, and we have developed a valve that adjusts the flow rate of the fluid applied to the flow path, and a flow rate controller that measures the flow rate. a flow control device for controlling flow i according to a target flow rate, comprising: a target opening calculation means for back calculating a target opening of a valve using a flow rate calculation formula when a target flow rate is given; and a valve flow control means for controlling the opening and closing of the valve according to a predetermined control method from the target flow rate and the current flow rate. After the initial control is performed by the flow rate control means, subsequent control is performed by the valve flow rate control means.

[Industrial application field]

The present invention relates to a flow rate control device for controlling the flow rate of a fluid, and particularly to a flow rate control device for controlling the flow rate of a fluid. The present invention relates to a flow rate control device that has a correction function using a calculation formula.

In a valve control device that controls the flow rate of a fluid, it is necessary to be able to quickly and accurately adjust the required target flow rate. On/off control, PI
Various control methods such as D-control have been put into use, and the time required for control is gradually being reduced.

In the future, it is desired that such a flow rate control device be able to further reduce the number of adjustment steps at the time of introduction and the time required for control.

[Conventional technology]

Fig. 5 shows the configuration of a conventional flow rate control device, in which 11 indicates a valve, 12 a pipe, 13 a flow meter, 14 a controller, 15 an operator, and 16 a water tank. It is.

The flow meter 16 measures the flow rate of water flowing out through the pipe line 12'e, and sends a signal indicating a flow rate value to the controller 14.

When the controller 14 receives control command values such as a target flow rate and a dead zone, it generates a control signal according to the error pressure between these values and the flow command value, and supplies it to the operating device 15 . The operating device 15 drives the valve 11 in the open or close direction in response to a control signal, thereby changing the flow rate of water flowing out from the water tank 16 through the pipe 12. The flow meter 13 changes the flow rate instruction value in accordance with this, and as a result, a loop feedback control is performed and the flow rate instruction value approaches the target flow rate.

Conventionally, as an adjustment method in this case, an on-off control method and a PID control method are used. In the on-off control method, when the flow rate instruction value is outside the dead zone, control 7 is performed to change it to within the Z dead zone, and the follow-up delay of the flow rate is not considered at all. The PID control method is
The valve opening operation amount obtained from the difference between the flow rate instruction value and the target flow rate, the follow-up speed of the flow rate when the valve is operated, and the offset when the flow rate instruction value enters the dead zone.
The control is performed by considering the following thi.

[Problem to be solved by the invention]

In conventional flow rate control devices, whether the on-off control method or the PID control method is used, only flow rate information is used as a control amount. Depending on the characteristics of the system, so-called hunting may occur and a stable state will be achieved after multiple control operations, but if the flow rate is slow to follow, it will take time to reach the target value.
The number of times the control is performed until the adjustment becomes stable! Even if you try to reduce it, there are limits. Furthermore, even if the number of times of control can be reduced, in this case there is a problem in that it takes a lot of time and effort to determine the control parameters.

The present invention aims to solve the problems of the prior art, and by performing the initial operation with the valve opening calculated back from the target flow rate as the target, even when the flow rate is slow to follow, the To be able to reduce the number of times of control by pinching! The purpose is

[Means to solve the problem]

FIG. 1 shows the basic configuration of the present invention, which includes a valve 1 that adjusts the flow rate of fluid in a flow path, and a flow meter 2 that measures the flow rate, and adjusts the flow rate according to a target flow rate. In the flow rate control device to be controlled, a target opening calculation means 3;
A valve opening control means 4 and a valve flow rate control means 5 are provided, and after the valve opening degree control means 4 performs initial control, the valve flow rate control means 5 performs subsequent control.

The target opening degree calculation means 3 calculates the target opening degree of the valve 1 by using a flow rate calculation formula when the target flow rate 'jk is given.

The valve opening control means 4 controls the opening of the valve 1 based on the target opening and the current opening.

The valve flow rate control means 5 controls the opening and closing of the valve 1 according to a predetermined control method based on the target flow rate and the current flow rate.

[For production]

In the flow control device, the fluid flow tht in the flow path
The flow meter 2 is equipped with a flow meter 2 that measures the flow rate, and the flow rate is controlled to approach the target flow rate by adjusting the opening and closing of the valve 1 according to the target flow rate and the measured flow rate. In such a flow rate control device, when a target flow rate is given, the target opening degree calculation means 6 calculates the target opening degree of the valve 1 using a flow rate calculation formula. During the first control, the valve opening degree control means 4 controls the opening degree of the valve 1 based on the target opening degree and the current opening degree, thereby controlling the flow rate to a value close to the target flow rate in advance. Thereafter, the valve flow rate control means 5 controls the opening and closing of the valve 1 according to a predetermined control method such as a PID control method or an on-off control method.

In this way, in the present invention, initial control is performed by setting the valve to the target opening degree calculated backward from the target flow rate, and then the flow rate control is performed using a predetermined control method. Even if the flow rate is slow to follow, the number of controls by hunting can be reduced. Further, by updating and optimizing the parameters of the flow rate calculation formula when back calculating the target opening degree every time the actual flow rate is sampled, the number of times of control can be further reduced.

〔Example〕

FIG. 2 shows an embodiment of the present invention, 21
indicates a valve control device, and central processing unit (CPU) 2
2, a memory section 22A, and a digital input/output section 23. 24 is a water tank, and is equipped with a water level gauge 25. Reference numeral 26 denotes a valve, which has a valve drive device 27 that opens and closes the valve, and an opening gauge 28 that indicates the opening degree. 29 is a flow meter, and a water tank 24. It is provided on the pipe line 30 connecting the valve 26 and indicates the flow rate of water flowing through the pipe line 30.

In the valve control device 21, the CPU 22 inputs the target flow rate (Qo), the water level (H) of the water tank 24 obtained by the water level gauge 25, and the opening degree of the valve 26 obtained by the opening gauge 28 via the digital input/output unit 23. (G), data such as the flow f (Q) obtained by the flowmeter 29 are taken in, the necessary arithmetic processing is performed, and a signal instructing the opening and closing of the valve 26 is output. The valve driving device 27 drives the valve 26 in the open or close direction according to this signal, thereby changing the flow rate and changing the magnitude of the flow rate (Q) measured by the flow meter 26.

FIG. 3 is a flowchart of control in the valve control device shown in FIG. 2.

The operation of the valve control device shown in FIG. 2 will be explained below according to the flowchart shown in FIG.

First, the target flow rate (Qo) for this system is read into the valve control device 21 via the digital input/output section 23 (step S1) and stored in the memory section 22A. Read the flow rate (Q) obtained in the Jichi flowmeter 29,
It is checked whether the flow rate is within the dead zone above the target flow rate (step 82). The width of the dead zone is given in advance as a system parameter.

When the flow rate f (Q) is not within the specified range, the target flow rate (Qo
) and the water level (H) of the water tank 24, the target opening degree (G) of the valve 26 is calculated backwards (step 83). The method of back calculation will be explained in detail later. Then, the valve driving device 27 is controlled using the obtained opening degree as a target value. The valve driving device 27 thereby drives the valve 26 in the opening or closing direction until the opening matches the target opening (step 84). Thereafter, the process waits until the flow rate indication value of the flow meter 29 becomes stable (step S5).

This time varies depending on the characteristics of the system.

Next, it is checked again whether the flow rate (Q) is within the target flow rate earthwork distortion range (step S6). When the flow rate is not within the predetermined range, the valve control device 21 drives the valve 26 in the opening or closing direction via the valve drive device 27 using a predetermined PID control method or on/off control method (step 87 ). and step S
Return to step 5 and repeat this control thereafter.

If the flow rate (Q) is within the range of the target flow rate earthwork sensitivity in step S2 or step S6, this control ends and the next target flow rate (Qo) is read.

Note that the above-mentioned back calculation of the target opening degree is performed in more detail as follows. Flow rate Q detected by flow meter 29
is Q” Fq (H, G, FC(G))
...+11 where Q: Flow rate passing through the valve (
m”/5) Fq: Flow rate calculation function (m/s
) H: Water level of water tank (m) G: Valve opening (%) FC (G): Valve flow coefficient (function of opening G) (1)
Calculating the formula for determining the valve opening GV by setting Q = Qo from the formula, G = Fg (Qo, H)...
-+2) As is clear from equation (2), the valve opening degree G can be determined from the target flow rate Q0 and the water level H.

However, equation (1) is an experimental equation, and there is an error between it and the actual flow rate. In order to reduce this error, it is necessary to actually measure the valve flow rate and calculate the valve flow coefficient F in equation (1).
It is necessary to correct c(G).

Therefore, step S2 or S in the flowchart of FIG.
The coefficient F is determined by the least squares method using the flow rate Q used in step 6, the target flow fQo, and the valve opening degree G.

CG).

For example, if the coefficient FC (G) can be expressed by parameters a, b, c and opening degree G, then Fc (G) = F (a, b, c, G)
=-(31 If the target opening is G, if the actual flow rate is repeatedly sampled, MIN(Σ(Q! Qol)") 1=1 where N: the number of times the actual flow rate is sampled. However, the sampling timing is At step 82.86 on the flowchart shown in FIG. 3, parameters a, b, and c are obtained by minimizing the values of Ql and QoitFqt: i-th data of equation (4).

FIG. 4 explains the data flow in the valve control method shown in FIG. 3, and the step numbers in the diagram correspond to those in FIG. 3.

That is, in step S3, the target opening degree back calculation program 31 performs calculations from the target flow rate Qo, the water level H, and the data in the valve flow rate calculation parameter table 32 to determine the target opening degree Go.

In step S4, the valve opening control program 33 calculates from the target opening Go and the current opening G to generate and output a control signal for the valve driving device 27. In step S7, the valve flow control program 34
Accordingly, calculations are performed from the target flow it Qo and the current flow iQ, and a control signal for the valve driving device 27 is generated and output by PID control or on/off control.

Furthermore, by the valve flow rate calculation formula correction program 35,
The parameters in the valve flow rate calculation parameter table 32 are updated by performing calculations from the target flow rate 1tQo, target opening degree Gee, and current flow rate tQ. This parameter is the target opening G0 in the target opening back calculation program 31 as described above.
This is used for decision calculations.

In this way, in the present invention, when the target flow rate value l4 is obtained, the target opening degree of the valve is calculated backwards using the flow rate calculation formula and initial control is performed based on this, so that the target flow rate value can be sufficiently approached by the first control. Therefore, it is possible to reduce the number of times hunting control is performed until the control end state is reached. Furthermore, the parameters of the flow rate calculation formula that back-calculates the target opening are updated and corrected for each control, so as the number of operations increases, the back-calculated target opening value becomes more accurate, and the control can be completed with fewer controls. You will be able to do this.

〔Effect of the invention〕

As explained above, according to the flow rate control device of the present invention, the target opening degree of the valve can be calculated backward from the target flow rate, and the initial control operation 7 can be performed based on this opening degree to bring the flow rate close to the target flow rate in advance. Even when the flow rate in the system is slow to follow, the number of hunting control operations can be reduced. Furthermore, by updating and optimizing the flow rate calculation parameters for back calculating the target opening degree every time the actual flow rate is sampled, it is possible to further reduce the number of times of control.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the principle configuration of the present invention, Fig. 2 is a diagram showing an embodiment of the present invention, Fig. 3 is a diagram showing a control flowchart of a valve control device, and Fig. 4 is a diagram showing a valve control system. A diagram showing a data flow. FIG. 5 is a diagram showing the configuration of a conventional flow rate control device. 21... Valve control device 22... Central processing unit (CPU) 25... Water level gauge 26... Valve 28... Openness gauge 29... Flow meter Rational configuration of the present invention? Fig. 1: g, Fig. 2 showing an embodiment of the invention.

Claims (1)

[Claims] A flow rate control device that controls the flow rate according to a target flow rate, comprising a valve (1) that adjusts the flow rate of fluid in a flow path and a flow meter (2) that measures the flow rate. Target opening calculation means (3) for calculating the target opening of the valve (1) using a flow rate calculation formula when the flow rate is given; the valve opening control means (4) for controlling the opening and closing of the valve (1) according to a predetermined control method from the target flow rate and the current flow rate; A flow rate control device characterized in that after initial control is performed by an opening degree control means (4), subsequent control is performed by a valve flow rate control means (5).