JP3295885B2 - Zero / span adjustment method for 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 pneumatic pressure, and controls the valve opening of a control valve that opens and closes a passage through which fluid flows with the converted air pressure. It concerns the positioner.

[0002]

2. Description of the Related Art In an electro-pneumatic positioner having a function of a positioner, which is a kind of pneumatic servo mechanism, and an electro-pneumatic converter, a zero point position and a span point position are used as references when controlling a valve opening of a control valve. Must be determined in advance (zero / span adjustment). Therefore, in the conventional electropneumatic positioner, a person directly operates a knob for zero / span adjustment on site to perform zero / span adjustment.

[0003]

However, since such conventional electropneumatic positioners are often used in process control systems such as plants, there is a danger when humans perform zero / span adjustments on site. (For example, explosion-proof area). Further, the operation of the knob for zero / span adjustment is troublesome, and it takes time to adjust the zero / span. That is, since the zero adjustment and the span adjustment must be performed separately and interfere with each other, the zero adjustment and the span adjustment are repeated several times. In addition, a mechanism such as a knob for zero / span adjustment is required, which causes an increase in cost. Also, only one electropneumatic positioner can perform zero / span adjustment at a time.

The present invention has been made in order to solve such a problem, and an object of the present invention is to eliminate the need for a mechanism such as a zero / span adjustment knob and to automatically perform a zero / span adjustment automatically and remotely. An object of the present invention is to provide a zero / span adjustment method for an electropneumatic positioner that can be performed. Also,
An object of the present invention is to provide a zero / span adjustment method for an electropneumatic positioner that can perform zero / span adjustment for a plurality of electropneumatic positioners at a time.

[0005]

In order to achieve the above object, a first invention (an invention according to claim 1) is to provide an electropneumatic positioner, which receives a zero / span automatic adjustment command and controls a control valve. the zero point as a reference for controlling the valve opening degree position LRV (alpha) and span point position URV a ([theta] s),
For the zero point position LRV (α), shut off the control valve
From the horizontal position of the feedback lever when
About the span point position URV (θs) obtained from the angle α
Is the span angle θs from the center of the angle sensor to the valve shaft.
Θs = α + t from the horizontal distance l and the nominal stroke S of
an ^-1 (S / l-tan α) . According to the present invention, zero /
When a span automatic adjustment command is given, the zero point position L
RV (α) and span point position URV (θs) are zero
For point position LRV (α), close off pressure is marked on the control valve
Angle from the horizontal position of the feedback lever when applied
About span point position URV (θs) obtained from α
Is that the span angle θs is θs = α + tan ⁻¹ (S / l−
tan α) .

[0006]

A second invention (invention according to claim 2 ) is an electropneumatic positioner, which receives a zero / span automatic adjustment command and controls a valve opening of a control valve in a zero point position LRV ( α) and the span point position URV (θs)
The zero point position LRV (α) is obtained from the angle α from the horizontal position of the feedback lever when the closing pressure is applied to the control valve, and the span angle θs of the span point position URV (θs) is θs = 2 · α. It is something to ask for. According to the present invention, when a zero / span automatic adjustment command is given to the electropneumatic positioner, the zero point position LRV (α) and the span point position URV (θs) are automatically set.
However, the zero point position LRV (α) is obtained from the angle α from the horizontal position of the feedback lever when the closing pressure is applied to the control valve, and the span point position URV (θs)
Is obtained as θs = 2 · α. However, in the present invention, it is assumed that the valve opening of the control valve is adjusted to 50% at the horizontal position of the feedback lever.

[0008] The third invention (the invention according to claim 3 ) is the second invention.
In the present invention, when the zero point position LRV (α2) is obtained in response to the next zero / span automatic adjustment command, the angle α2 of the zero point position LRV (α2) is obtained in response to the previous zero / span automatic adjustment command. Zero point position LRV (α1)
Is larger than the angle α1, the span point position URV
For (θ _s2 ), the span angle θ _s2 is given by θ _s2 = tan
^-1 ｛2tanα1 / (1 + tan ² α2-2tanα1
• tanα2)｝.
According to this invention, when the next zero / span automatic adjustment command is given to the electropneumatic positioner, the zero point position LRV (α2) is obtained in the same manner as in the previous zero / span automatic adjustment command. If the angle α2 of the point position LRV (α2) is larger than the previous angle α1, the span point position URV
(Θ _s2 ), the span angle θ _s2 is θ _s2 = tan
^-1 ｛2tanα1 / (1 + tan ² α2-2tanα1
Tan α2) It is obtained as｝.

The fourth invention (the invention according to claim 4 ) is the first invention.
In any one of the inventions to the third invention, a plurality of electropneumatic positioners are connected in series by two wires, a zero / span automatic adjustment command is common to each electropneumatic positioner, and a predetermined line current is determined.
It is designed to be transmitted in the specified pattern. According to the present invention, a predetermined pattern of the line current ( for example, a repetition of 20 mA and 4 mA every 2 seconds is performed)
A zero / span automatic adjustment command is sent in common to a plurality of electropneumatic positioners connected in series by two wires, and the electropneumatic positioner receiving the zero / span automatic adjustment command resets the zero / span at one time. The point position LRV (α) and the span point position URV (θs) are obtained.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments. FIG. 2 is a system configuration diagram of a control valve control system to which the present invention is applied. In the figure, 1 is a controller, 2-1 and 2-2 are control valves, and 3-
Reference numerals 1 and 3-2 denote electropneumatic positioners for controlling the valve openings of the control valves 2-1 and 2-2, and reference numerals L1, L2 and L3 denote communications for connecting the controller 1 and the electropneumatic positioners 3-1 and 3-2 in series. Line.

The electropneumatic positioner 3 (3-1, 3-2)
It includes a communication line drive unit 3A, a data processing control unit 3B, an electropneumatic conversion unit 3C, and an angle sensor (VTD) 3D. The communication line driving unit 3A has an interface 3A1 for communicating data with the controller 1.

The data processing control unit 3B has a CPU 3B1 and a memory 3B2, receives set value data from the controller 1 via the communication line driving unit 3A , processes the set value data, and performs electro-pneumatic conversion through an electro-pneumatic conversion unit 3C. Signal control valve 2
(2-1, 2-2). The angle sensor 3D is a sensor that detects the opening degree of the control valve 2 as the rotation angle position (lever angle position) of the feedback lever (4 shown in FIG. 1), and sends the detected lever angle position to the data processing control unit 3B. send. The data processing control unit 3B includes an angle sensor 3D
The feedback control of the valve opening of the control valve 2 is performed on the basis of the lever angle position from.

[Embodiment 1] Next, functions unique to the present embodiment provided in the data processing control section 3B will be described with reference to FIGS. FIG. 1 is a diagram showing an arrangement relationship between the angle sensor 3D of the electropneumatic positioner 3 and the control valve 2. The control valve 2 includes a drive unit 2A, a valve shaft 2B, and a valve 2C. The drive unit 2A has a diaphragm, and adjusts the opening of the valve 2C by moving the valve shaft 2B up and down according to the air pressure introduced from the electropneumatic conversion unit 3C.

The lift position of the valve shaft 2B, that is, the valve 2
A feedback lever 4 is connected between the angle sensor 3D and the valve shaft 2B to detect the opening of C. The feedback lever 4 rotates about the center O of the angle sensor 3D as an axis according to the lift position of the valve shaft 2B. The opening degree of the valve 2C can be known from the rotation angle position (lever angle position) of the feedback lever 4.

The data processing control unit 3B includes a controller 1
When a zero / span automatic adjustment command is sent from the
Step 301), a closing pressure is applied to the control valve 2 (Step 302). As a result, the valve opening of the control valve 2 is closed, and the control valve 2 is fully closed. Data processing control unit 3
B detects the fully closed state of the valve opening of the control valve 2 as a point in time when the change in the lever angle from the angle sensor 3D is stopped (step 303). When the data processing control unit 3B detects the fully closed state of the valve opening of the control valve 2, the data processing control unit 3B determines the angle α from the horizontal position of the feedback lever 4 at that time.
Is obtained as a zero point position LRV (α) (step 304), and the obtained zero point position LRV is obtained.
(Α) is stored (step 305).

Next, the data processing control unit 3B calculates θs = α + tan ⁻¹ (S / l−ta) from the horizontal distance 1 from the center O of the angle sensor 3D to the valve shaft 2B and the nominal stroke S.
nα) to determine the span angle θs (step 30).
6), the valve opening position indicated by the span angle θs is stored as the span point position URV (θs) (step 30).
7).

In this embodiment, θs = α +
The expression tan ^-1 (S / l-tan α) is derived as follows. That is, in FIG.
It is shown as S1 + S2 and is expressed as S2 = S-S1.
Θs = α + β, and tanβ = S2 / l
= (S-S1) / l = S / l-S1 / l = S / l-ta
It is expressed as nα = K. Therefore, β = tan ⁻¹ K
= Tan ^-1 (S / l-tan α), and θs = α + t
expressed as an ^-1 (S / l-tan α).

In this embodiment, the automatic zero / span adjustment command from the controller 1 to the electropneumatic positioner 3 is given as a special pattern of line current. For example, as shown in FIG.
The pattern is such that the repetition of A every two seconds continues three times. This zero / span automatic adjustment command may be any pattern as long as it is a pattern that never occurs in normal times.

Second Embodiment In the first embodiment, in step 306 in FIG. 3, the span angle θs is obtained as θs = α + tan ⁻¹ (S / l-tanα). On the other hand, in the present embodiment, the span angle θs is determined as θs = 2 · α. However, in this case, it is assumed that the valve opening of the control valve 2 is adjusted to 50% at the horizontal position of the feedback lever 4 . That is, in the present embodiment,
The angle sensor 3D and the valve shaft 2 are adjusted so that the valve opening of the control valve 2 is 50% at the horizontal position of the feedback lever 4.
By adjusting the relationship between B and the feedback lever 4 in advance, the span angle θs is obtained by a simpler expression than in the first embodiment.

Third Embodiment In the second embodiment, it is assumed that the valve opening of the control valve 2 is adjusted to 50% at the horizontal position of the feedback lever 4, but it has been used for a long time. It is conceivable that a deviation occurs in this relationship. In the present embodiment, assuming such a deviation, when the first zero / span automatic adjustment command is received, the flowchart shown in FIG. 3 is followed. According to the flowchart shown in FIG.

That is, when a zero / span automatic adjustment command is sent from the controller 1 (step 501), the data processing control unit 3B applies a closing pressure to the control valve 2 (step 502). As a result, the valve opening of the control valve 2 is closed, and the control valve 2 is fully closed. Data processing control unit 3
B detects the fully closed state of the valve opening of the control valve 2 as the point in time when the change in the lever angle from the angle sensor 3D is stopped (step 503). When the data processing control unit 3B detects the fully closed state of the valve opening of the control valve 2, the data processing control unit 3B determines the angle α from the horizontal position of the feedback lever 4 at that time.
2 is determined as the zero point position LRV (α2) (step 504), and the determined zero point position L
RV (α2) is stored (step 505).

Next, the data processing control unit 3B calculates the angle α from the horizontal position of the feedback lever 4 obtained this time.
2 is compared with the previous angle α1 (step 506).
If 2 ≦ α1, then set the span angle θ _s2 as θ _s2 = 2 · α2.
(Step 507), if α2> α1, θ _s2 = tan ⁻¹ ｛2tanα1 / (1 + tan ² α2-
2tanα1 · tanα2)｝ to determine the span angle θ _s2 (step 508), and store the valve opening position indicated by the obtained span angle θ _s2 as the span point position URV (θ _s2 ) (step 509).

In this embodiment, θ _s2 = ta
n ^-1 ｛2tanα1 / (1 + tan ² α2-2tanα
The expression 1 · tanα2)｝ is derived as follows. That is, in FIG. 6, S = 2ltan
α1, S1 = ltanα2, S2 = ltan (α2-θ
_s2 ).

[0024] Since at S = S1-S2, S = l {tanα2-tan (α2-θ s2)} = l {tanα2- (tanα2-tanθ s2) / (1 + tanα2 · ta nθ s2)} = l {( tan ² α2 · tan θ _s2 + tan α ² ) / (1 + tan α 2 · tan θ _s2 )｝.

Therefore, ² tan α1 = l tan θ _s2 · ｛(1 + tan ² α
2) / (1 + tan α2 · tan θ _s2 )｝.

Here, tan α1 = a, tan α2 =
b, tan θ _s2 = x, 2a = x · (1 + b2) / (1 + bx) 2a · (1 + bx) = x (1 + b2) 2a + 2abx = x (1 + b2) x (1 + b2-2ab) = 2ax = 2a / (1 + b2) −2ab) = tan θ _s2 θ _s2 = tan ⁻¹ x, and θ _s2 = tan ⁻¹ ｛2tan α1 / (1 + tan
Expressed as ^{2 α2-2tanα1} · ^tanα2)}.

[0027]

As is apparent from the above description,
According to the present invention, when a zero / span automatic adjustment command is given to the electropneumatic positioner, the zero point position LRV (α) and the span point position URV (θs) are automatically changed to the zero point position LRV.
Regarding (α), the flow when closing pressure is applied to the control valve
From the angle α of the feedback lever from the horizontal position
And the span point position URV (θs)
The angle θs is to substitute the above angle α into a predetermined arithmetic expression.
And zero / span adjustment can be performed automatically and remotely. This eliminates the need for a mechanism such as a zero / span adjustment knob.
Cost reduction can be promoted. Further, zero / span adjustment can be performed in a short time, and zero / span adjustment can be performed in a dangerous place such as an explosion-proof area. In addition, by performing a zero / span automatic adjustment command common to each electropneumatic positioner and transmitting it in a predetermined pattern of line current, zero / span adjustment of a plurality of electropneumatic positioners connected in series can be performed at once. Will be able to

[Brief description of the drawings]

FIG. 1 is a diagram showing an arrangement relationship between an angle sensor of an electropneumatic positioner and a control valve.

FIG. 2 is a system configuration diagram of a control valve control system to which the present invention is applied.

FIG. 3 is a flowchart illustrating a characteristic operation performed by a data processing control unit of the electropneumatic positioner when a zero / span automatic adjustment command is received in the first embodiment.

FIG. 4 is a diagram illustrating a special pattern of line current as a zero / span automatic adjustment command.

FIG. 5 is a flowchart illustrating a characteristic operation performed by a data processing control unit of an electropneumatic positioner when a next zero / span automatic adjustment command is received in a third embodiment.

FIG. 6 shows Embodiment 3 where θ _s2 = tan ⁻¹ ｛2t
anα1 / (1 + tan ² α2-2tanα1 · tan
It is a figure for explaining the derivation process of the formula of α2)｝.

[Explanation of symbols]

1 ... controller, 2 (2-1, 2-2) ... control valve, 3
(3-1, 3-2) ... electro-pneumatic positioner, L1, L2, L
3 communication line, 3A communication line driving unit, 3B data processing control unit, 3C electropneumatic conversion unit, 3D angle sensor, 2A
... Drive unit, 2B ... Valve shaft, 2C ... Valve, 4 ... Feedback lever, LRV (α) ... Zero point position, URV (θs) ...
Span point position.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G05D 3/00-3/20 G05D ⁷ /00-7/06 G05D 16/00-16/20

Claims (4)

(57) [Claims] 1. A zero point position LR serving as a reference when controlling a valve opening of a control valve in response to a zero / span automatic adjustment command.
V (alpha) and span point position URV a ([theta] s), the zero point
For the position LRV (α), close the shutoff pressure to the control valve.
Angle from the horizontal position of the feedback lever when applying
The span point position URV (θs) is obtained from the degree α.
The span angle θs is measured from the center of the angle sensor to the valve shaft.
Θs = α + ta from horizontal distance l and nominal stroke S
A zero / span adjustment method for an electropneumatic positioner, wherein the method is determined as n ^-1 (S / l-tan α) . 2. A zero point position LR serving as a reference when controlling a valve opening of a control valve in response to a zero / span automatic adjustment command.
V (α) and the span point position URV (θs) are obtained for the zero point position LRV (α) from the angle α from the horizontal position of the feedback lever when the closing pressure is applied to the control valve, and the span point position URV A method for adjusting the zero / span of an electropneumatic positioner, wherein the span angle θs is determined as θs = 2 · α for (θs). 3. The method according to claim 2, wherein
The zero point position LRV (α2) was obtained in response to the dynamic adjustment command.
When the angle α2 of the zero point position LRV (α2) is
Zero point obtained in response to the zero / span automatic adjustment command
When the position LRV (α1) is larger than the angle α1,
For span point position URV (θ _s2 ), its span angle
Let θ _s2 be θ _s2 = tan ^-1 ｛2tan α1 / (1 + tan ²
α / 2-tanα1 · tanα2)｝ . A method for adjusting the zero / span of an electropneumatic positioner, wherein 4. The method according to claim 1, wherein
Number of electro-pneumatic positioners connected in series, zero / span automatic adjustment
Command is common to each electropneumatic positioner, and
A zero / span adjustment method for an electropneumatic positioner, characterized in that transmission is performed in a predetermined pattern .