JPH07141002A - Positioner - Google Patents

Abstract

PURPOSE:To correct a characteristic curve based on an actually measured value when the difference between the actually measured value of a controlled system received in online made and a target value calculated from the built-in characteristic curve is larger than a prescribed value by calculating that difference at the time of correction. CONSTITUTION:At the time of correction, an operator sets an ultrasonic flow meter, actually measures a process flow rate F and imparts the actually measured value FIN of the process flow rate to an arithmetic part 1' of an electropneumatic positioner 100' in online mode. When the actually measured value FIN is inputted, the arithmetic part 1' reads an input electric signal IIN at that time. At input time, the input electric signal IIN is applied for 50%, a target value FOUT of the process flow rate corresponding to the read input electric signal IIN is calculated according to the built-in characteristic curve, the difference between the target value FOUT and the measured value FIN is calculated and when the difference is more than the fixed value, the built-in characteristic curve is corrected by the arithmetic part 1'. Thus, the accuracy of measurement from a present value at any adjacent position is improved, and the process flow rate F can be controlled with high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a positioner suitable for controlling a process flow rate.

[0002]

2. Description of the Related Art Conventionally, as this type of positioner,
An electropneumatic positioner configured as shown in FIGS. 4 and 5 is known. That is, FIG. 4 is a block diagram showing the operating principle of the electropneumatic positioner, 1 is an arithmetic unit having a CPU or the like, 2 is an electropneumatic conversion unit, and 3 is the nozzle back pressure P _N from the electropneumatic conversion unit 2. pilot relay to output air pressure P _out, 4 is a feedback sensor for detecting an output air pressure P _out.

The electro-pneumatic conversion section 2 has, for example, a permanent magnet 5 formed in a U-shape in plan view as shown in FIG. 5, and a permanent magnet 5.
The yoke 6 is attached to both ends of the upper and lower surfaces with one end facing each other, the coil 7 is disposed between the upper and lower yokes, and the yoke 5 is disposed with an appropriate gap. A flapper (iron piece) 9 penetrating through the center of 7 and having its lower end swingably supported by one of the lower yokes 6 by a fulcrum spring 8 and a counterweight 10 provided at the lower end of the flapper 9. A nozzle 11 is arranged at the upper end of the flapper 9 so as to closely face each other. Air having a predetermined pressure P _S is supplied to the nozzle 11 from an air pressure supply source through the throttle 12.

In the electropneumatic positioner 100 having such a structure, when the input electric signal I _IN (4 to 20 mA) is supplied from the controller (not shown), the arithmetic unit 1 has a characteristic curve C ( 6), a target value of the process flow rate (controlled object) F corresponding to the value of the input electric signal I _IN is obtained, and this target value is given to the electropneumatic converter 2 as an electric signal I _out . This electric signal I _out is applied to the coil 7 to change its magnetic field, so that the flapper 9 swings in the nozzle direction or in the counter nozzle direction. Therefore, the distance x between the nozzle 11 and the flapper 9 changes, and the nozzle 1
The back pressure of 1 (nozzle back pressure) P _N changes. Nozzle back pressure P
After being amplified by the pilot relay 3, _N is output air pressure P _out to the operating device that drives the valve shaft of the control valve (not shown).
As a result, the opening of the control valve, that is, the process flow rate F is controlled. Further, the output air pressure P _out is detected by the feedback sensor 4 and returned to the calculation unit 1 as the feedback signal I _FB , so that the control valve becomes stable when the deviation between I _out and I _FB becomes zero.

[0005]

However, according to such a conventional electro-pneumatic positioner 100, a characteristic curve between the input electric signal I _IN and the actual value of the process flow rate F is built in the arithmetic unit 1 due to secular change or the like. Characteristic curve C
Could not be corrected online if it changed.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a positioner capable of correcting a built-in characteristic curve on-line as necessary. It is in.

[0007]

In order to achieve such an object, the present invention is such that the above-mentioned positioner receives an actual measurement value of a controlled object online at the time of calibration.
The difference between the target value and the actual measurement value obtained from the built-in characteristic curve according to the value of the input electric signal at that time is obtained, and if the difference is larger than a predetermined value, the characteristic curve is corrected based on the actual measurement value. A characteristic curve correcting means is provided.

[0008]

Therefore, according to the present invention, when the measured value of the controlled object is provided online during calibration, the built-in characteristic curve is automatically corrected based on the measured value.

[0009]

EXAMPLES The present invention will now be described in detail based on examples. FIG. 2 is a block diagram of an electropneumatic positioner showing an embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 4 denote the same or equivalent components, and the description thereof will be omitted.
The electro-pneumatic positioner 100 'of this embodiment is different from the conventional electro-pneumatic positioner 100 shown in FIG. 4 in that the function of the computing unit 1'is different.

FIG. 1 shows an operation flow at the time of calibration of the arithmetic unit 1 '. During calibration, the operator sets an ultrasonic flow meter (not shown) and measures the process flow rate F. And
The measured value F _IN of this process flow rate is used as a portable communication device (SF
C) Online electro-pneumatic positioner 10 using 200
0'is given to the arithmetic unit 1 '.

When the measured value F _IN is input (step 10
1), the operation unit 1'reads the input electric signal I _IN at that time (step 102). Normally, at the time of calibration, the input electric signal I _IN is given as a 50% value. Then, a target value F _out of the process flow rate corresponding to the value I _in of the read input electrical signal I _IN is obtained according to the built-in characteristic curve C (FIG. 3) (step 103), and this target value F _out and actual measurement are obtained. The difference from the value F _IN is calculated (step 104).

If the difference between F _out and F _IN is not zero, that is, if F _out and F _IN are not equal (F _out ≠
F _IN ), in response to “YES” in step 105, the process proceeds to step 106, and the read input electrical signal I _IN (I
_in ) and F _IN to specify a coordinate point P _X1 on the characteristic curve C. Then, the process proceeds to step 107, and the specified coordinate point P _X1 and the previous polygonal line position P _n-1 (x _n-1 , y _n-1 ).
And the line where this line is connected and the next broken line place P _n (x
_n, y _n) of the X-coordinate position x of the intersection of the _n specified as a coordinate point P _X2, the specified coordinate point P _X2 and line location P
_{n + 1} (x _{n + 1} , y _{n + 1} ) is connected to obtain a new characteristic curve C ′.

In this way, by correcting the characteristic curve C built in the arithmetic unit 1'online,
The accuracy near the current value is improved, and the process flow rate F can be controlled with high accuracy.

In this embodiment, step 10
In step 5, if the difference between F _out and F _IN is not zero, the process immediately proceeds to step 106 and thereafter, but if the difference between F _out and F _IN is a certain value or more, step 106 is performed.
You may proceed to the following. Further, in the present embodiment, the characteristic curve C built in the calculation unit 1 ′ is the characteristic curve of the input electric signal I _IN and the process flow rate F.
The characteristic curve of the input electric signal I _IN and the opening θ of the control valve and the opening θ of the control valve and the process flow rate F may be used. That is, θ _out is obtained from the characteristic curve of I _IN and θ, and F _out corresponding to θ _out from the characteristic curve of θ and F.
Also in the case of obtaining, the characteristic curve can be similarly corrected. Also,
Although the control target is the process flow rate in the present embodiment, it goes without saying that it is not limited to the process resident bird.

[0015]

As is apparent from the above description, according to the present invention, when the measured value of the controlled object is provided online during calibration, the built-in characteristic curve is automatically calculated based on the measured value. As a result, the built-in characteristic curve can be corrected online if necessary.

[Brief description of drawings]

1 is a diagram showing an operation flow at the time of calibration of an arithmetic unit in the electropneumatic positioner shown in FIG.

FIG. 2 is a block diagram of an electropneumatic positioner showing an embodiment of the present invention.

FIG. 3 is a diagram showing a characteristic curve built in a calculation unit of this electropneumatic positioner and an on-line correction state of the characteristic curve.

FIG. 4 is a block diagram of a conventional electropneumatic positioner.

FIG. 5 is a side sectional view showing a configuration of an electropneumatic conversion section in this electropneumatic positioner.

FIG. 6 is a diagram showing a characteristic curve built in a calculation unit of this electropneumatic positioner.

[Explanation of symbols]

 1'Calculator 2 Electro-pneumatic converter 3 Pilot relay 4 Feedback sensor 100 'Electro-pneumatic positioner 200 Portable communication device

Claims (1)

[Claims] 1. A positioner having target value output means for obtaining and outputting a target value of a controlled object according to a value of an input electric signal according to a built-in characteristic curve, and providing a measured value of the controlled object during calibration. Is received online, the difference between the target value and the actual measurement value obtained according to the characteristic curve in accordance with the value of the input electric signal at that time is obtained, and if the difference is larger than a predetermined value, based on the actual measurement value. And a characteristic curve correcting means for correcting the characteristic curve.