JPH03240801A - Cascade flow rate controller - Google Patents

Abstract

PURPOSE:To control properly the cascade flow rate by providing a proportion control part for the secondary constant value negative feedback control of a secondary control system and changing the proportion gain in accordance with the instantaneous flow rate to be controlled. CONSTITUTION:A controller main body 13 and a proportion gain setter 14 are provided to a secondary controller 15 of a control system 17 contained in a cascade flow rate controller 16 including a primary control system 10 and the system 17. Then a valve opening amount measuring signal 5a and a valve opening amount setting signal 7a are inputted via the main body 13. The main body 13 performs the PID control and outputs an operating signal 13a. In such a case, the setter 14 inputs a flow rate measuring signal 6a received from a flow rate transmitter 6 set at the downstream side of a flow rate control valve 2. Then the setter 14 sets the proportion gain for the proportion control action of the main body 13 in accordance with the instantaneous flow rate shown by the signal 6a. This proportion gain is sent to the main body 13 for execution of the control of the cascade flow rate.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a device for controlling the instantaneous flow rate of a fluid such as water to a predetermined value using a flow rate control valve in a water treatment facility. , relates to a device that can obtain appropriate instantaneous flow rate control results.

[Conventional technology]

FIG. 2 is an explanatory diagram of the configuration of a conventional cascade flow rate control device 1. As shown in FIG. In FIG. 2, a fluid 3 flows through 2. Conduit 4
5 is attached to the valve 2, and is an electric flow control valve that changes the instantaneous flow fiQ of the fluid 3 by changing the valve opening θ according to the contents of the input operation signal 9a. It's been a long time since I've been in the middle of a long time.

A 5K valve opening transmitter that constantly detects the opening θ of the valve 2 and outputs a valve opening measurement signal 51 according to θ.

6 is installed in the pipe line 4 on the downstream side of the valve 2, and the instantaneous flow rate Q
&7 is a flow rate transmitter configured to detect the flow rate and output a flow rate measurement signal 61 according to the detection result, and &7 receives the flow rate measurement signal 6- and the flow rate setting signal 8 outputted by the flow rate setting 68. A primary adjustment that performs a predetermined primary control calculation so that the flow rate Q represented by Hatake coincides with the instantaneous flow rate set value QsK represented by the signal 8-, and outputs a valve opening setting signal 7m according to the calculation result. It is a vessel. Then, the valve opening setting signal 7- and the valve opening measuring signal 51 are inputted to 9, and a predetermined signal is set so that the valve opening θ represented by the signal 5a matches the valve opening 4sK represented by the signal 7a. A secondary regulator that performs secondary control calculations and outputs the above-mentioned operation signal 9a according to the calculation results.
1 is made up of the parts shown in the figure except for the pipe line 4. Furthermore, in this control device [1], at least a proportional control operation is always performed in the above-mentioned secondary side (goods) calculation performed by the secondary regulator 9.

Since each part of the flow rate control device I is configured as described above, in this case, the flow rate transmitter 6, the regulator 7, and the flow rate setter 8 control the instantaneous R*Q of the fluid 3 controlled by the valve 2.
A primary control system 10 is configured that performs primary constant value negative feedback control on the VC and outputs a signal 7a that indicates the opening degree of the valve 2 to be ◇0, and the valve 2, the opening degree transmitter 5, and the regulator 9, signal 7a
A secondary control system 11 is configured that performs a secondary constant value negative feedback side for the opening degree θ of the valve 2 using the
It is clear that systems 11 and 10 perform a cascade of interactions for fiffiQff. In the case of the control device 1, if the signal 7a is input directly to the valve 2 instead of the signal 9a, the valve opening degree θ may be changed due to the resistance of the pipe 4 to the fluid 3, the density change of the fluid 3, etc. Since the change in flow rate Q is slow at 6° C., and therefore an appropriate instantaneous flow rate constant value control result cannot be obtained, the above-mentioned cascade control configuration is adopted.

C Problems to be Solved by the Invention] Since the flow rate control device l is configured as described above, the operation signal 9a is the signal 7a of the valve opening measurement value θ represented by the signal 5a.
Control deviation (θ3-θ) with respect to the valve opening set value θS represented by
The signal has a value Mv corresponding to
Since the opening degree θ and the flow rate Q usually have a one-to-one correspondence as shown in characteristic linework 2 in FIG. 3, the operation signal 9
This means that a is a signal having a value MY regardless of the magnitude of fijtQ.

However, it is clear from the above custom-made 11j12 that it is 5K.

In this case, θ and Q are not in a directly proportional relationship, and the amount of change in Q per unit amount of change in θ varies depending on the value of Q.

For this reason, in the control equipment engineer, if there are many Qs, the operation signal 9a
There is a problem in that the change in Q with respect to the value MY is too small, and when Q is small, the change in Q with respect to MVc is too large, and an appropriate control result cannot be obtained.

An object of the present invention is to provide a crab x Kate flow control device that can obtain appropriate control results by changing the value MY of the operation signal 9a not only depending on the control deviation (θ, -〇) but also depending on the flow rate QVC. There is a particular thing.

[Means for resolving divisions]

In order to achieve the above objects, 1 according to the present invention, primary constant value negative feedback control is performed on the instantaneous fffK of the fluid controlled by the flow control valve, and a valve opening setting signal is provided that specifies the valve opening of the flow control valve. and a secondary side system that performs secondary constant value negative feedback control on the valve opening of the flow control valve using the valve opening setting signal, The feedback control includes at least proportional control, and the proportional gain in the proportional control IVc changes depending on the instantaneous flow rate, thereby forming a cascade flow rate subsidiary device.

[Effect]

With the above configuration, the proportional gain on the second-order constant value negative feedback side is set to, for example, the characteristic line 12 in Figure 3. By reducing , even if the control deviation in the secondary control system is the same, the value MY of the operation signal output by the secondary control system will be adjusted depending on the amount of R, so that appropriate control can be achieved. A cascade flow side (2) device is obtained which can obtain results.

[Embodiment] FIG. 1 is an explanatory diagram illustrating the configuration of an embodiment of the present invention.
The difference between this figure and FIG. 2 is that there is a regulator main body 13 which receives a valve opening measurement signal 5a and a valve opening setting signal 7a, performs a PID control operation and outputs an operation signal 13a, and a flow rate measurement signal. 6a is input, and a proportional gain setter 14 sets the proportional gain of the proportional control operation performed by the regulator main body 13 according to the instantaneous flow tQ represented by the signal 6a.

The operation signal 13a is applied to the flow rate control valve 2 to adjust the valve opening θ of the valve 2. A secondary regulator 15 corresponding to the aforementioned secondary regulator 9 is provided.

16 in Figure 1 is a cascade Rfr NIJ device consisting of each part shown except for the pipe line 4, and 17 is a valve 2.
, a valve opening transmitter 5, and a secondary regulator 15.

A secondary control system corresponding to the secondary leg system 11 described above.

Therefore, in FIG. 1, the flow rate control device [16 is the control system 10
and 17 (become).

In FIG. 1, a proportional gain setter 14 is shown.

For example, the valve opening-flow rate characteristic # of the R1 control valve 2 shown in FIG. 3! 12, the signal 6 input to the setting device 14
When the flow rate Q represented by a is large, the proportional gain ν is set large, and when the flow rate Q represented by the signal 6a is small, the gain is set small. Therefore, according to the flow rate control device 16, the control of the valve opening degree θ is as follows: fi:tQ
Secondary regulator 1 whose proportional gain Kp changes depending on the amount of
Based on the PID combat control of No. 5 (as it is performed by the operation signal 138, the R4U-control device li in FIG.
A more appropriate R'j# control result can be obtained than by relying on e.

〔Effect of the invention〕

As described above, in the present invention, primary constant value negative feedback control is performed on the instantaneous flow rate of the fluid controlled by the flow rate control valve, and a valve opening setting signal that commands the valve opening of the flow rate control valve is output. with the primary control system.

and a secondary control system that performs secondary constant value negative feedback control on the valve opening of the flow control valve using the valve opening setting signal, and the secondary constant value negative feedback control includes at least a proportional system, and The cascade flow rate control device was configured such that the proportional gain in the control lc changes depending on the instantaneous flow rate.

Therefore, with the above configuration, the proportional gain on the secondary constant value negative feedback side flJK is set to be large when the instantaneous flow rate Q of the fluid is large, or Q When the flow rate Q is small, by reducing Kp, the value MY of the operation signal output by the secondary control system will be adjusted depending on the flow rate Q even if the peak deviation in the secondary control system is the same. The invention has the effect of providing a cascade flow rate control device that can obtain appropriate control results.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the configuration of an embodiment of the present invention. FIG. 2 is an explanatory diagram of the configuration of a conventional cascade flow rate control device. FIG. 3 is a valve opening-instantaneous flow rate characteristic diagram of the flow control valve shown in FIGS. 1 and 2. FIG. 1.16... Cascade flow control device, 2...
...Flow control valve, 3...Fluid, 10.
...-Secondary control system, 11°17...Secondary control system, Q... Instantaneous flow rate. P@1 Note 2 Tsuta torture

Claims (1)

[Claims] 1) a primary control system that performs primary constant value negative feedback control on the instantaneous flow rate of the fluid controlled by the flow control valve and outputs a valve opening setting signal that commands the valve opening of the flow control valve;
a secondary control system that performs secondary constant value negative feedback control on the valve opening of the flow control valve using the valve opening setting signal,
A cascade flow rate control device, wherein the secondary constant value negative feedback control includes at least proportional control, and a proportional gain in the proportional control changes depending on the instantaneous flow rate.