JP3389066B2 - Calculation method of valve opening of electropneumatic positioner - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has an electropneumatic converter for converting an input electric signal into air pressure, and an electropneumatic valve for controlling a valve opening degree of a control valve for opening and closing a passage through which a fluid flows by the converted air pressure. The present invention relates to a positioner valve opening calculation method.

[0002]

2. Description of the Related Art An electropneumatic positioner having a positioner function, which is a type of pneumatic servo mechanism, and an electropneumatic converter is provided with a feedback lever connected between a valve shaft of a control valve and an angle sensor. An angle sensor detects a change in the rotation angle of the feedback lever according to the lift position of the shaft, and the actual opening of the control valve is calculated from the detected force of the angle sensor.

FIG. 2 shows the positional relationship between the angle sensor of the electropneumatic positioner and the control valve. In the figure, 1 is a control valve, 2
Is the angle sensor (position sensor) of the electro-pneumatic positioner,
The control valve 1 includes a drive unit 1A, a valve shaft 1B and a valve 1C. The drive unit 1A has a diaphragm, and moves the valve shaft 1B up and down according to the introduced air pressure from an electropneumatic conversion unit (not shown) of the electropneumatic positioner to adjust the opening of the valve 1C.

A feedback lever 3 is connected between the angle sensor 2 and the valve shaft 1B in order to detect the lift position of the valve shaft 1B, that is, in order to detect the actual opening of the valve 1C. The feedback lever 3 uses the center O of the angle sensor 2 as an axis center according to the lift position of the valve shaft 1B.
Rotate. By detecting the change in the rotation angle of the feedback lever 3 according to the lift position of the valve shaft 1B with the angle sensor 2, the actual opening degree of the control valve 1C can be detected from the detected force of the angle sensor 2.

Conventionally, in detecting the actual opening, when the detected force of the angle sensor 2 is v, the rotation angle of the feedback lever 3 from the horizontal position is θ, and the constant is k, v
The angle sensor 2 having the characteristic of = k · θ is used. In this case, the horizontal distance from the center O of the angle sensor 2 to the valve shaft 1B is L, and from the horizontal position of the feedback lever 3 to the valve shaft 1B.
When the vertical distance to the connection position P with B is x, x =
The vertical distance x is calculated from the equation L · tan θ, and the actual opening of the valve 1C is calculated from the calculated vertical distance x.

[0006]

However, according to such a conventional method for calculating the valve opening, a trigonometric function is included in the formula for calculating the vertical distance x, and an approximate formula is used. It will be limited.

The present invention has been made in order to solve such a problem, and its object is to prevent the trigonometric function from being included in the calculation formula, and to simply and accurately control the actual opening degree of the control valve. It is to provide a method for calculating the valve opening of an electropneumatic positioner capable of calculating

[0008]

In order to achieve such an object, the first invention (the invention according to claim 1) is the detection method of an angle sensor in the above-described method for calculating the valve opening of an electropneumatic positioner. When the force is v, the rotation angle of the feedback lever from the horizontal position is θ, and the constant is k, v = k · si
with use of an angle sensor having a characteristic of N2shita, angle
The horizontal distance from the center of the sensor to the valve shaft is L, and the feed bar is
Vertical from the horizontal position of the lock lever to the connection position with the valve shaft
When the distance is x, x = v · L / {k + (k ² −
v ² ) ^1/2 } and calculate the vertical distance x.
The actual opening of the control valve is calculated from the vertical distance x . According to the present invention, the detected force of the angle sensor v = k · sin2θ does not include the trigonometric function x = v · L
^{/ {K + (k 2 -v} 2) 1/2} is obtained by substituting the equation, it is possible to calculate the actual opening of the regulating valve.

[0009]

The second invention (the invention according to claim 2 ) is as described above.
In the method for calculating the valve opening of the electro-pneumatic positioner,
Sensor detection force v, feedback lever horizontal position
Where θ is the rotation angle from and the constant is k, v = k · s
In addition to using an angle sensor with in2θ characteristics, the horizontal distance from the center of the angle sensor to the valve shaft is L, the vertical distance from the horizontal position of the feedback lever to the connection position with the valve shaft is x, and the electro-pneumatic positioner mounting error The angle is ε, e =
When tan ε, x = L · [e · {k + (k ² −v
² ) ^1/2 } + v] / {k + (k ² −v ² ) ^1/2 −e · v}
The vertical distance x is calculated by the following equation, and the actual opening of the control valve is calculated from the calculated vertical distance x. According to the present invention, the detected force of the angle sensor is v = k.
sin2θ does not include trigonometric functions x = L ・ [e ・ {k +
^{(K 2 -v 2) 1/2}} + v ] ^{/ {k + (k 2 -v} 2) 1/2
The actual opening of the control valve can be calculated by substituting it into the equation −e · v}.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail based on embodiments. In this embodiment, instead of the conventional angular velocity sensor 2 (FIG. 2) having the characteristic of v = k · θ, v
= K · sin2θ angle sensor 2 '(Fig. 1)
To use. When the mounting error angle of the electropneumatic positioner is ε and e = tan ε = x ₀ / L, x = L · [e · {k + (k ² −v ² ) ^1/2 } + v] / {k + (K ² −v ² ) ^1/2 −e · v} (1) The vertical distance x is calculated from the equation, and the actual opening of the control valve 1C is calculated from the calculated vertical distance x.

According to this embodiment, the vertical distance x can be obtained simply by substituting the detected force v = k.sin2.theta. Of the angle sensor 2'in the above equation (1) in which k, e and L are expressed as constants.
Is calculated, that is, the calculation of the trigonometric function is unnecessary, so that the actual opening of the control valve 1C can be calculated easily and with high accuracy.

In the present embodiment, the above (1)
The formula is derived as follows. That is,
In FIG. 1, x / L = tan (θ + ε) = (tan θ + tan ε) / (1-tan θ · tan ε) ... (2) Here, if tan ε = x ₀ / L = e, then x / L = (tan θ + e) / (1−e · tan θ) (3)

Detection force v = k.sin of the angle sensor 2 '.
2θ is represented as v = 2k · sin θ · cos θ,
v ² = 4k ² · sin ² θ · cos ² θ = 4k ² (1-
can be transformed into cos ² θ) · cos ² θ. Where co
When s ² θ = X, v ² = 4k ² (1-X) · X. This equation can be modified as 4k ² X ² -4k ² X + v ² = 0 X ² -X + v ² / 4k ² = 0 X ² -X + (v / 2k) ² = 0, and X = [1 ± {1- ( v / k) ² } ^1/2 ] / 2 ... (4) is obtained.

Here, if −π / 4 <θ <π / 4, then
1/2 <X = cos ² θ <1, and X = cos ² θ = [1+ {1- (v / k) ² } ^1/2 ] / 2 (5).

Tan θ = sin θ / cos θ = sin θ · cos θ · (1 / cos ² θ) (6) and s obtained from v = 2k · sin θ · cos θ
Substituting in θ · cos θ = v / 2k into the equation (6), tan θ = (v / 2k) · (1 / cos ² θ) = (v / k) · 1 / [1+ {1- (v / k) ² } ^1/2 ] = v / {k + (k ² −v ² ) ^1/2 } ... (7).

[0017] (3) and (7) from equation, x / L = [e + v / {k + ( k 2 -v 2) 1/2} ] / [1-e · v / {k + (k 2 -v ² ) ^1/2 }] = [e · {k + (k ² −v ² ) ^1/2 } + v] / {k + (k ² −v ² ) ^1/2 −e · v} ... (8 ). From this, x = L · [e · {k + (k ² −
The above formula (1) is obtained as v ² ) ^1/2 } + v] / {k + (k ² −v ² ) ^1/2 −e · v}.

In the formula (1), the feedback lever 3 has a mounting error. However, if the mounting error of the electropneumatic positioner is so small as to be negligible, e in the formula (1) can be obtained as e = 0. Even if the following formula (9) is used, a sufficiently accurate result can be obtained. x = v · L / {k + (k 2 -v 2) 1/2} ···· (9)

[0019] (1) by transforming the equation, x = L · [(e / k) · {k + (k 2 -v 2) 1/2} + (v / k) ] / {(k / ^{k) + (k 2 -v 2} ) 1/2 / k-e · (v / k)} = L · [e + e {1- (v / k) 2} 1/2 + (v / k) ] / [1+ {1- (v / k) ² } ^1/2 −e · (v / k)] and V0 = v / k, x = L · [e · {1+ (1-V0 ² ) ^{1 /} 2} + V0] ^{/ {1+ (1-V0 2} ) is expressed by ^{1/2 -e · V0} ····} (10). Further, when e = 0, x = L · V0 / {1+ (1-V0 ² ) ^1/2 } ... (11)

The angle sensor 2'may be a potentiometer or an MR sensor that uses magnetism to detect an angle.

[0021]

As is apparent from the above description,
According to the first invention, the angle sensor having the characteristic of v = k · sin2θ is used , and the mounting error of the electropneumatic positioner is increased.
Assuming that there is no
・ Sin2θ does not include trigonometric functions x = v ・ L / {k +
(K ² −v ² ) ^1/2 }
The actual opening of the control valve can be calculated independently and with high accuracy.
Like According to the second aspect of the invention, the detected force of the angle sensor v = k · sin2θ does not include a trigonometric function x = L · [e
^{· {K + (k 2 -v} 2) 1/2} + v ] / {k + (k ² -
v ² ) ^1/2 −e · v}, the actual opening of the control valve can be calculated easily and with high accuracy even if there is an error in the installation of the electropneumatic positioner. .

[Brief description of drawings]

FIG. 1 is a diagram showing a positional relationship between an angle sensor of an electropneumatic positioner and a control valve for explaining a valve opening calculation method of the present invention.

FIG. 2 is a diagram showing an arrangement relationship between an angle sensor of an electropneumatic positioner and a control valve for explaining a conventional valve opening calculation method.

[Explanation of symbols]

1 ... Control valve, 1A ... Drive part, 1B ... Valve shaft, 1C ... Valve,
2 '... Angle sensor (VTD sensor), 3 ... Feedback lever.

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields investigated (Int.Cl. ⁷ , DB name) F15B 5/00 G01D 5/00-5/252 G01D 5/39-5/62 G01D 7/00-7 / 34 G01D 21/00-21/32

Claims (2)

(57) [Claims] 1. A feedback lever connected between a valve shaft of a control valve and an angle sensor, wherein a change in the rotation angle of the feedback lever according to a lift position of the valve shaft is detected by the angle sensor. In the valve opening calculation method of the electropneumatic positioner for calculating the actual opening of the control valve from the detected force of the angle sensor, the detected force of the angle sensor is v, and the rotation angle of the feedback lever from the horizontal position is θ. , Where k is a constant, an angle sensor having a characteristic of v = k · sin2θ is used.
And the horizontal distance from the center of the angle sensor to the valve shaft is L,
The feedback lever is connected from the horizontal position to the valve shaft.
When the vertical distance to the forming position and the x, calculates x = v · L / {k + (k 2 -v 2) 1/2} becomes perpendicular distance x from the equation, the adjustment from the calculated perpendicular distance x Calculate the actual valve opening
The method for calculating the valve opening of the electro-pneumatic positioner is characterized in that 2. A control valve connected between a valve shaft and an angle sensor.
Equipped with a feedback lever
Rotation angle change of the feedback lever according to position
Is detected by the angle sensor, and the detected force of this angle sensor is
Electropneumatic positioner valve that calculates the actual opening of the control valve from
In the calculation method of the opening, the detected force of the angle sensor is v, and the feedback level is
If the rotation angle from the horizontal position of the bar is θ and the constant is k
Using an angle sensor with the characteristics of v = k · sin2θ
In addition, the horizontal distance from the center of the angle sensor to the valve shaft is L, the vertical distance from the horizontal position of the feedback lever to the connection position with the valve shaft is x , and the installation error of the electropneumatic positioner is
When the angle is ε and e = tan ε, x = L · [e · {k + (k ² −v ² ) ^1/2 } + v] / {k + (k ² −v ² ) ^1/2 −e · v } The vertical opening x is calculated by the following formula, and the actual opening of the control valve is calculated from the calculated vertical opening x.