JPH08305444A - Flow rate controller - Google Patents

Abstract

PURPOSE: To provide the flow rate controller for which any valve aperture detector is not required and the accuracy and stability of flow rate control are extremely improved. CONSTITUTION: Concerning the flow rate controller, a valve manipulated variable computing element 5 for calculating a manipulated variable at one time of sampling with PID arithmetic considering a correction loop gain based on flow rate deviation from a target flow rate 11 of a measured flow rate 10 and flow rate control valve aperture/flow rate characteristics, valve operating time computing element 6 for finding the opening or closing command output time of the valve from the manipulated variable 12, and valve opening/closing outputter 9 for outputting the valve opening/closing command are provided inside a controller 4 and the command for opening or closing the valve is outputted to a valve driving device 7 so that a flow rate control valve 2 can be driven.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow control device, and more particularly to a flow control device having a flow control valve.

[0002]

2. Description of the Related Art Conventionally, a flow rate control device for controlling the flow rate of a fluid flowing through a flow path without including an opening detector of a flow rate control valve is disclosed in Japanese Patent Laid-Open No. 4-47416 and Japanese Patent Laid-Open No. 59-47416.
It is disclosed in Japanese Patent Laid-Open No. 103116. Further, Japanese Patent Application Laid-Open No. 6-19556 discloses a flow rate control device that controls the flow rate of a fluid flowing through a flow path by operating a flow rate control valve by on / off control, and uses a PID without a valve opening detector. It is disclosed that the flow rate can be controlled.

[0003]

The conventional flow rate control device calculates the opening of the flow rate control valve at the time of flow rate measurement from the measured flow rate and the flow rate control valve opening-flow rate characteristic, and calculates the flow rate control valve. When the opening deviation of the opening from the target opening exceeds a set value, a command to open or close the flow control valve is output, and when the opening deviation falls within the set value,
The flow shifts to PID calculation flow control.

However, the amount of change in the flow rate with respect to the amount of change in the opening of the flow control valve is not constant at any opening of the flow control valve. Therefore, based on the deviation of the measured flow rate from the target flow rate, P
One sampling calculated by the ID calculation, that is, the valve operation amount in the calculation cycle needs to be corrected for each valve opening. That is, it is necessary to adjust the PID calculation loop gain to be constant regardless of the opening degree of the flow control valve.

An object of the present invention is to facilitate flow rate control by PID calculation in a flow rate control device for controlling a flow rate by operating a flow rate control valve by outputting an open or close signal to a valve drive device. In addition to maintaining the control stability, the flow rate control method that conventionally required two detectors, that is, a flow rate detector and a valve opening degree detector, enables flow rate control without the valve opening degree detector. It is to provide a possible flow control device.

[0006]

The above object can be achieved as follows.

(1) A flow control valve for controlling the flow rate of the fluid flowing through the flow path and a flow meter for measuring the flow rate are provided,
A flow control device that reduces the deviation of the measured flow rate from the target flow rate by controlling the opening of the flow rate control valve with an open or closed output signal. Output the valve open or close output signal continuously until the flow deviation is within the set value.
If the flow rate deviation is within the set value, the flow rate control valve opening at the time of the measured flow rate is calculated from the relationship between the measured flow rate and the flow rate control valve opening-flow rate characteristics, and From the relationship of the flow rate change amount to the valve opening change amount, a loop gain constant that makes the PID calculation loop gain constant in flow rate control is calculated, and the PID calculation using this loop gain constant is performed during one sampling in the flow control valve. A valve target opening calculator that calculates the opening operation amount, and a valve operation that calculates the opening or closing operation time of the flow control valve from the opening operation amount for one sampling in the flow control valve when the flow deviation is within the set value. The flow control valve based on the command for the operation time of the judgment device and the flow control valve output from this valve operation judgment device. A valve driving device for driving, without requiring the opening detector of the flow control valve allows the flow control by PID operation, to improve the accuracy of flow rate control.

(2) In (1), the correction curve of the relationship curve in which the inclination angle of the tangent line of the relationship curve of the flow rate control valve opening-flow rate characteristic is constant irrespective of the flow rate control valve opening is the PID Use for correction of calculation, and keep PID calculation loop gain constant.

[0009]

In the present invention, the flow rate control device comprises a flow rate detector for measuring the flow rate of the fluid flowing through the flow path, a flow rate control valve for controlling the flow rate, a valve drive device for changing the opening of the flow rate control valve, and a controller. The flow rate signal from the flow rate detector is input to the controller. In addition,
The valve drive device is an on-off control type that operates according to a command from a digital output signal to open or close the opening of the flow control valve from the opening at the time of flow measurement.

Inside the controller, the opening of the flow control valve at the time of flow measurement is calculated from the measured flow rate and the flow-opening characteristic of the flow control valve, and the valve opening at the opening of the flow control valve at the time of flow measurement is calculated. Valve opening based on the flow rate deviation from the target flow rate of the measured flow rate, which calculates the open loop gain to be given to the valve operation amount calculation unit from the relationship of the flow rate change amount to the degree change amount. A valve operation amount calculator that calculates the amount of change, a valve operation time calculator that calculates the opening or closing command output time of the flow control valve, that is, the valve operation time from the calculated valve operation opening change amount, and a valve operation amount calculator A valve opening / closing output device for outputting an opening or closing signal from the valve or valve operating time calculator to the valve driving device is provided.

The valve operation amount calculator calculates a flow rate deviation of the input measured flow rate from a preset target flow rate, and outputs a continuous open or closed output signal when the flow rate deviation exceeds a set value. When it is output to the valve opening / closing output device and the flow rate deviation is within a certain value, the valve opening operation amount operated during one sampling is calculated by PID calculation and is output to the valve operation time calculator. Furthermore, when the valve manipulated variable calculator calculates the valve opening manipulated variable, the valve manipulated variable calculator corrects the valve opening manipulated variable in one sampling by the loop gain calculated by the open loop gain calculator. There is.

The valve operation time calculator stops the PID calculation if the flow rate deviation exceeds a set value, but if the flow rate deviation is within a certain value, the valve opening control amount given from the valve control amount calculator. Thus, based on the valve opening amount operated during one sampling time, the time width for outputting the opening or closing command is calculated and output to the valve opening / closing output device.

The valve open / close output device outputs the opening or closing command output from the valve operation amount calculator or the valve operation time calculator to the valve drive device for the calculated time to operate the valve. There is.

In the present invention, as described above, when the flow rate deviation exceeds the set value, the valve opening / closing output device is operated so as to be within the set value. Further, when the valve operation amount calculator calculates the valve opening operation amount, at the same time, the valve operation amount calculator uses the loop gain calculated by the open loop gain calculator to operate the valve opening amount in one sampling. Since the amount is corrected, the flow control accuracy in the flow control valve is improved.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an explanatory view of a flow rate control device of this embodiment, and FIG.
Is a flow rate control valve opening-flow rate characteristic diagram, FIG. 3 is an explanatory diagram of a method of determining the loop gain α of the present embodiment, FIG. 4 is a relational diagram of a minute operation amount and valve operation time in the present embodiment,
FIG. 5 is an explanatory diagram of a valve operation time chart of the present embodiment.

In this embodiment, as shown in FIG.
The flow rate of the flowing fluid was detected by the flow meter 3, and the measured flow rate 10 was input to the controller 4. In the valve operation amount calculator 5, based on the flow rate deviation of the measured flow rate 10 from the target flow rate 11, the measured flow rate 10 is PV _f , the target flow rate 11 is SV _f , the flow rate deviation upper limit value is DH, and the flow rate deviation lower limit value is DL.
, PV _f −SV _f = EN, and
The following two calculations were performed.

[I] When the flow rate deviation exceeds the set value, that is, when EN> DH or EN <DL is satisfied, the following processing is performed.

(1) When EN> DH is satisfied, the switching command 15 is used to switch the switching switch 16 and the switching switch 17 inside the valve opening / closing output device 9 to the terminal 19 side. 9
Then, the valve closing command 13 is continuously output.

(2) When EN <DL is satisfied, the switching command 15 is used to switch the switching switch 16 and the switching switch 17 inside the valve opening / closing output device 9 to the side of the terminal 19, thereby opening / closing the valve opening / closing output device. 9
The valve open command 14 was continuously output to the.

[II] When the flow rate deviation is within a certain value, that is, when DH ≧ EN ≧ DL is satisfied, the following processing is performed. That is, the valve operation amount calculator 5 inputs the operation amount of the flow rate control valve 2 that operates during one sampling to the valve operation time calculator 6, but at the same time,
By the switching command 15, the switching switch 16 and the switching switch 17 installed inside the valve opening / closing output device 9 are switched to the terminal 18 side, so that the valve opening / closing output device 9 receives a command from the valve operating time calculator 6. Received.

Further, the valve operation amount calculator 5 calculates the operation amount of the flow control valve 2 which is operated during one sampling as follows using the flow rate deviation of the measured flow rate 10 from the target flow rate 11. It was

First, based on the flow control valve opening-flow rate characteristic as shown in FIG. 2, the flow control valve opening at the time of flow rate measurement is calculated. As shown by the convex curve in which the central portion of FIG. 2 projects upward, the flow rate change amount with respect to the change amount of the flow control valve opening differs depending on the flow control valve opening. That is, the inclination angle K of the tangent line of this convex curve differs depending on the opening of the flow control valve.

Therefore, the valve opening manipulated variable obtained by the PID calculation based on the deviation of the measured flow rate from the target flow rate does not provide a stable loop gain at any valve opening degree. That is, in order that the flow rate change amount with respect to the change amount of the flow rate control valve opening is constant, the relationship between the flow rate control valve opening degree and the flow rate is represented by a straight line, and a constant tilt angle such as the tilt angle C is shown. Need to have.

In this embodiment, in order to correct such a defect, the following means are used. That is, with respect to the tilt angle K described above,

[0025]

[Equation 1] α = C / K ………………………………………………………………………………………………………………………………………………………… 1. Here, C is a constant, and the relationship between these K, C, and α is as shown in FIG.

Next, in the open loop gain calculator 8, the loop gain α is obtained from the measured flow rate 10 using the equation (1), and this value is output to the valve operation amount calculator 5.

In this case, P is calculated by the following equation.
ID calculation was used. The following equation is a commonly used equation.

[0028]

MV = KP * EN + 1 / TI * ∫ENdt + KD * dEN / dt (2) where MV is the manipulated variable, KP is the proportional gain, TI is the integration time, KD is the differential time, and , EN = P
V _f −SV _f and PV _f are measured flow rates, and SV _f is a target flow rate.

Here, the equation in which the loop gain α is added to the equation (2) is obtained as follows.

[0030]

MV = α (KP * EN + 1 / TI * ∫ENdt + KD * dEN / dt) (3) From the equation (3), a difference equation such as the following equation is derived.

[0031]

## EQU00004 ## .DELTA.MV = .alpha. (KP * .DELTA.EN + 1 / TI * EN + KD * .DELTA..DELTA.EN) ... (4) where .DELTA.EN = EN (n) -EN (n-1), .DELTA..DELTA.E
N = ΔEN (n) −ΔEN (n−1).

The MV obtained by the equation (3) is the manipulated variable 0.
It corresponds to the valve opening when the opening of the flow control valve 2 is operated within the range of up to 100%. ΔMV calculated by the equation (4) is a value calculated by the valve operation amount calculator 5, and is the operation amount 12 for operating the valve opening during one sampling.

Further, the flow control valve 2 is opened from 0% to 1
When the time required to operate up to 00% is Tb,
The valve operation time calculator 6 calculates the opening operation time T corresponding to the manipulated variable 12 of ΔMV by the following equation.

[0034]

(5) T = Tb * ΔMV / 100 …………………………………… (5) where T is the valve opening command 14 if ΔMV is positive.
Is output time, and if it is negative, it is output time of the valve closing command 13. This opening or closing command was output to the valve opening / closing output device 9.

Further, in the valve operating time calculator 6, a dead zone as shown in FIG. 4 is provided in order to reduce the frequency of operation of the valve driving device 7 with respect to the minute operation amount ΔMV.

Even if the operating speed of the flow rate control valve 2 changes with time, since the PID calculation feedback control by the flow rate is performed, the state of the flow rate deviation is not maintained continuously, and the small operation amount is not maintained. The valve operating time gain could be adjusted with respect to ΔMV. Note that G is the tilt angle of the relational straight line between the minute operation amount ΔMV and the operation time T.

FIG. 5 is a time chart showing the operation as described in [I] and [II]. When the flow rate deviation is larger than DH, the valve closing command 13 is continuously output, and when it is small. Is a valve closing command 13 for a time corresponding to the operation amount of the flow control valve 2 operated during one sampling.
Was output intermittently.

Further, since the amount of change in the flow rate with respect to the amount of change in the valve opening differs depending on the size of the opening of the flow rate control valve 2, the open loop gain calculator 8 opens the flow rate control valve 2 from the measured flow rate 10. Predicting degree, formula (3) and formula
By changing the loop gain α in (4), the open loop gain is always kept constant and the control stability is improved.

As described above, the flow rate control by PID calculation could be carried out with high accuracy without providing the valve opening detector.

[0040]

According to the present invention, PID due to flow rate deviation
When the calculation is used to obtain the command output time for opening or closing the valve drive device, make sure that the inclination angle of the tangent line of the relationship curve of the flow rate control valve opening-flow rate characteristic becomes constant regardless of the flow rate control valve opening. The correction curve of the relationship curve
By making the PID calculation loop gain constant for use in correction of calculation, the stability of flow control is significantly improved, and a flow control device that does not require a valve opening detector can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a flow rate control device according to an embodiment of the present invention.

FIG. 2 is a flow rate control valve opening-flow rate characteristic diagram.

3 is an explanatory diagram of a loop gain determination method of the flow rate control device of FIG.

4 is a relationship diagram of a minute operation amount and a valve operation time of the flow rate control device of FIG.

5 is an explanatory diagram of a valve operation time chart of the flow rate control device of FIG.

[Explanation of symbols]

1 ... Flow path, 2 ... Valve, 3 ... Flow rate detector, 4 ... Controller, 5 ... Valve operation amount calculator, 6 ... Valve operation time calculator, 7 ... Valve drive device, 8 ... Open loop gain calculator, 9 ... valve opening / closing output device, 10 ... measured flow rate, 11 ... target flow rate, 12 ... manipulated variable, 13 ... valve closing command, 14 ... valve opening command, 15 ... switching command, 16 ... switching switch, 17 ... switching switch, 18 ... Terminal, 19 ... Terminal.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masayuki Koike 3-2-1, Sachimachi, Hitachi City, Ibaraki Prefecture Hitachi Engineering Co., Ltd. (72) Mitsuaki Nakamura 2-3-2, Saiwaicho, Hitachi City, Ibaraki Prefecture No. 1 within Hitachi Engineering Co., Ltd.

Claims (2)

[Claims] 1. A flow control valve for controlling a flow rate of a fluid flowing through a flow path, and a flow meter for measuring the flow rate,
In the flow rate control device that reduces the flow rate deviation from the target flow rate of the measured flow rate by controlling the opening degree of the flow rate control valve by the open or closed output signal, if the flow rate deviation exceeds a set value, The output signal for opening or closing the flow rate control valve is continuously output until the flow rate deviation is within a set value, and when the flow rate deviation is within the set value, the measured flow rate and the flow control valve opening-flow rate characteristic The flow control valve opening at the time of the measured flow rate is calculated from the relationship with, and the PID calculation loop gain in the flow control is constant from the relationship of the flow rate change amount to the valve opening change amount in the vicinity of the flow control valve opening. PID using this loop gain constant
A valve target opening degree calculator for calculating the opening operation amount for one sampling in the flow control valve by calculation, and the opening operation amount for one sampling in the flow control valve when the flow rate deviation is within a set value. A valve operation determiner that calculates the opening or closing operation time of the flow control valve, and drives the flow control valve based on a command of the opening or closing operation time of the flow control valve output from the valve operation determiner. A flow rate control device comprising a valve drive device, enabling flow rate control by PID calculation without requiring an opening detector of the flow rate control valve, and improving accuracy. 2. A correction curve of the relational curve, wherein the inclination angle of the tangent line of the relational curve of the flow rate control valve opening-flow rate characteristic is constant regardless of the flow rate control valve opening,
The flow rate control device according to claim 1, wherein the PID calculation loop gain is made constant by using the correction for the PID calculation.