JPH1019005A - Output controlling method and system for electro pneumatic converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remarkably improve the control delay of a control valve, generated due to a dead zone which a pilot relay possesses. SOLUTION: A loop gain control part 7 for switching-controlling the loop gain based on the deviation pressure ΔP between the nozzle-back pressure Pn and the driving output pressure Pout is provided, and when a pilot relay 2 entered a dead zone, a large loop gain when compared to other region is selected, and the deviation pressure Δ P is corrected based on the selected loop gain to be outputted to an electro neumatic converter 1 as a deviation signal Id.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a system for controlling the output of an electropneumatic converter, and more particularly, to a pilot relay for generating a driving output pressure for driving a control valve or the like in accordance with a predetermined control signal. The present invention relates to an output control method and system for an electropneumatic converter that outputs pressure.

[0002]

2. Description of the Related Art Generally, when a control valve or the like for adjusting the opening of a valve by air pressure is controlled by a predetermined control signal, an electropneumatic converter (EPM) as shown in FIG. 4 is used. A control signal Iin indicating the opening degree (flow rate) of the control valve 3 is output from a process control device (not shown) or the like, and input to the electropneumatic converter 1. In response, the electropneumatic converter 1 uses the supply pressure Ps to output a nozzle back pressure Pn corresponding to the control signal Iin.
The pilot relay 2 generates a drive output pressure Pout by amplifying the nozzle back pressure Pn using the supply pressure Ps and outputs the drive output pressure Pout to the control valve 3. Thereby, the opening degree of the control valve 3 is controlled, and a predetermined flow rate G is obtained.

The driving output pressure Pout and the nozzle back pressure Pn are detected by pressure sensors 4 and 13, respectively, and output as detection signals Iout and In. The output control unit 12 of the output control device 11 controls the drive output pressure P
From the detection signals Iout and In indicating the out pressure and the nozzle back pressure Pn, a deviation pressure ΔP between them is calculated, and ΔP = n × Pn−Pout (n is the amplification factor of the pilot relay). Thus, the electropneumatic converter 1 finely adjusts the nozzle back pressure Pn so that the deviation pressure ΔP indicated by the deviation signal Id becomes zero, and performs stability control when the deviation pressure ΔP becomes substantially zero. Had become something.

[0004]

However, in such a conventional output control method of the electropneumatic converter, the output from the electropneumatic converter 1 is simply based on the deviation ΔP between the driving output pressure Pout and the nozzle back pressure Pn. Since the nozzle back pressure Pn is controlled, the dead zone of the pilot relay 2 causes a control delay of the control valve 3. A pilot relay such as a non-bleed type which is generally widely used has a dead zone characteristic as shown in FIG.

The nozzle back pressure Pn input to the pilot relay and the drive output pressure Pou output from the pilot relay
When the deviation pressure .DELTA.P calculated from t and the above expression falls within the predetermined pressure range of P1 to P2, the response (slope) of the drive output pressure Pout to the change of the deviation pressure .DELTA.P as compared with other regions. Becomes dull. The area from P1 to P2 is called a dead zone. As shown in FIG. 5B, when the nozzle back pressure Pn increases at the time T0 from the parallel state where the deviation pressure ΔP is almost zero, the deviation pressure ΔP increases accordingly, and the drive output pressure Pout also increases. I do.

As the drive output pressure Pout increases, the deviation pressure Δ
Since P decreases and enters the dead zone when ΔP = P2 (time T1), the operation of the pilot relay becomes dull,
The rising curve of the drive output pressure Pout becomes dull. As a result, the decreasing curve of the deviation pressure ΔP becomes dull, and at time T2,
As P = P1, the state escapes from the dead zone to reach an equilibrium state. As described above, in the conventional output control method of the electropneumatic converter, there is a problem that a control delay of the control valve occurs due to the dead zone of the pilot relay. The present invention has been made to solve such a problem, and provides an output control method and system of an electropneumatic converter that can significantly improve control delay of a control valve due to a dead zone of a pilot relay. It is intended to be.

[0007]

In order to achieve the above object, an output control method and system of an electropneumatic converter according to the present invention calculates a nozzle back pressure from a control signal input to the electropneumatic converter. At the same time, the drive output pressure output from the pilot relay is detected, and the deviation pressure is calculated based on the difference between the drive output pressure and the amplification value of the pilot relay and the integrated value of the nozzle back pressure. Whether the pilot relay is in the dead zone or not is determined, and the loop gain of the feedback control is increased when the pilot relay is in the dead zone as compared to when the pilot relay is not in the dead zone. Therefore, the nozzle back pressure is calculated from the control signal input to the electropneumatic converter, and the deviation pressure is calculated based on the amplification factor of the pilot relay and the difference between the integrated value of the nozzle back pressure and the drive output pressure. It is determined whether the pilot relay is in the dead zone based on the deviation pressure,
When the pilot relay is in the dead zone, the loop gain of the feedback control is larger than when the pilot relay is not in the dead zone.

[0008]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an output control device for a static converter according to an embodiment of the present invention. In FIG. 1, the same or equivalent parts as those described above (FIG. 4) are denoted by the same reference numerals. 1, an output control device 5 calculates a nozzle back pressure Pn output from the electropneumatic converter 1 based on a control signal Iin, and outputs a detection signal In corresponding to the nozzle back pressure Pn. This detection signal In and the pressure sensor 4
Pressure calculator 9 for calculating a difference pressure ΔP between the nozzle back pressure Pn and the drive output pressure Pout from the drive output pressure Pout from
And a loop gain control unit 7 for switching and controlling the loop gain A depending on whether or not the deviation pressure ΔP is in a dead zone.
And the deviation pressure ΔP corrected based on the loop gain A.
And an output control unit for outputting a deviation signal Id indicating the following.

Next, the operation of the present invention will be described with reference to FIG. 2A and 2B are explanatory diagrams showing the operation of the loop gain control unit. FIG. 2A shows the characteristics of the dead zone of the pilot relay,
(B) shows switching control of the loop gain A with respect to the deviation pressure ΔP. In FIG. 2A, when the deviation pressure ΔP is in the dead zone, that is, in the pressures P1 to P2, the rate of change, that is, the gradient of the drive output pressure Pout with respect to the change in the deviation pressure ΔP is
It is slower than other areas.

[0010] The nozzle back pressure calculation unit 8, like the electropneumatic converter 1, controls the control signal I based on a predetermined range and span.
The noise back pressure Pn is calculated from in and the detection signal In is output. The deviation pressure calculation unit 9 calculates a difference between the detection signal In from the nozzle back pressure calculation unit 8 and the detection signal Iout from the pressure sensor 4,
The deviation pressure ΔP between the nozzle back pressure Pn and the drive output pressure Pout is calculated. The loop gain control unit 7 calculates a deviation pressure Δ based on a preset dead zone characteristic of the pilot relay 2.
It is determined whether P is within the dead zone P1 or P2. Here, when it is within the dead zone P1 to P2, the loop gain A
A1 is selected and output as a relatively large value.
If it is in an area other than 2, a relatively small loop gain A0 (A1> A0) is selectively output. The loop gains A1 and A0 may be determined based on the gradient in each area shown in FIG.

Therefore, for example, as shown in FIG. 3A, when the nozzle back pressure Pn output from the electropneumatic converter 1 increases from the equilibrium state at time T0 to a predetermined value according to the control signal Iin. Increases the deviation pressure ΔP accordingly,
The drive output pressure Pout also increases. Subsequently, the drive output pressure Pou
The deviation pressure .DELTA.P decreases as t increases, and enters the dead zone when .DELTA.P = P2 (time T1).

The loop gain control section 7 detects that the pilot relay 2 has entered the dead zone based on the deviation pressure ΔP, and increases the loop gain A from A0 to A1. In response, the output control unit 6 corrects and outputs the deviation signal Id corresponding to the deviation pressure ΔP based on the loop gain A1.
Therefore, the electropneumatic converter 1 is supplied with a deviation signal Id having a sensitivity that is A1 / A2 times higher than that of the area other than the dead zone.
Since the nozzle back pressure Pn increases accordingly, even when the pilot relay 2 is in the dead zone, the drive output pressure Pou
The rising curve of t does not become gentle.

As a result, the drive output pressure Pout continues to increase in the same manner as in other regions even in the dead zone, and the deviation pressure ΔP decreases accordingly. Thereafter, the deviation pressure ΔP becomes equal to the pressure P1
At the time point (time T2), the loop gain controller 7
Detects that the pilot relay 2 has escaped from the dead zone based on the deviation pressure ΔP, and returns the loop gain A to A0. In response, the output control unit 6 corrects and outputs the deviation signal Id corresponding to the deviation pressure ΔP based on the loop gain A1. Accordingly, the deviation signal Id of the original sensitivity is input to the electropneumatic converter 1, and the nozzle back pressure Pn is supplied to the pilot relay 2 in response thereto, and thereafter, the equilibrium state is established.

As described above, the loop gain control unit 7 for switching and controlling the loop gain based on the deviation pressure .DELTA.P between the nozzle back pressure Pn and the drive output pressure Pout is provided, and when the pilot relay 2 enters the dead zone. , A large loop gain is selected as compared with other regions, and a deviation signal Id indicating the deviation pressure ΔP based on the selected loop gain.
Is corrected and output to the electropneumatic converter 1, so that the control delay of the control valve due to the dead zone of the pilot relay can be significantly reduced. Further, since the nozzle back pressure Pn is calculated from the control signal Iin, even when the pilot relay 2 enters the dead zone and the loop gain is switched, the normal nozzle back pressure Pn and the deviation pressure ΔP in the region other than the dead zone are determined. Calculation can be performed easily and stably, and the electropneumatic converter 1 can be controlled stably.

[0015]

As described above, according to the present invention, the nozzle back pressure is calculated from the control signal input to the electropneumatic converter, the amplification factor of the pilot relay, the integrated value of the nozzle back pressure, and the drive output pressure. Calculates the deviation pressure based on the difference between the two and determines whether the pilot relay is in the dead zone based on the deviation pressure. The gain is increased. Therefore, as compared with the conventional method of simply controlling the nozzle back pressure output from the electropneumatic converter based on the drive output pressure and the deviation pressure of the nozzle back pressure, even when the pilot relay has a dead zone, Control delay of the control valve can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of an output control system of an electropneumatic converter according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating an operation of a loop gain control unit.

FIG. 3 is a signal waveform diagram in each section of FIG.

FIG. 4 is a block diagram of a conventional output control system for an electropneumatic converter.

FIG. 5 is a signal waveform diagram in each section of FIG.

[Explanation of symbols]

1: electropneumatic converter, 2: pilot relay, 3: adjusting valve,
4 pressure sensor, 5 output control device, 6 output control unit,
7: loop gain control unit, 8: nozzle back pressure calculation unit, 9 ...
Deviation pressure calculator, Iin: control signal, Pn: nozzle back pressure, P
out: drive output pressure, G: flow rate, In, Iout: detection signal, A: loop gain, Id: deviation signal.

Claims (2)

[Claims] 1. An electropneumatic converter that outputs a nozzle back pressure according to a predetermined control signal to a pilot relay that generates a drive output pressure for driving a control valve and the like. In the output control method of the electropneumatic converter that performs the feedback control of the nozzle back pressure based on the deviation pressure from the nozzle pressure, the nozzle back pressure is calculated from a control signal input to the electropneumatic converter and output from the pilot relay. A drive output pressure is detected, a deviation pressure is calculated based on a difference between the amplification value of the pilot relay and the integrated value of the nozzle back pressure and the drive output pressure, and based on the deviation pressure, whether or not the pilot relay is in a dead zone. When the pilot relay is in the dead zone, the loop gain of the feedback control is increased compared to when the pilot relay is not in the dead zone. Output control method of the electropneumatic converter. 2. An electropneumatic converter that outputs a nozzle back pressure according to a predetermined control signal to a pilot relay that generates a drive output pressure for driving a control valve or the like. An output control system for an electro-pneumatic converter that performs feedback control of the nozzle back pressure based on a deviation pressure between the nozzle back pressure and a pilot back pressure calculating unit that calculates a nozzle back pressure from a control signal input to the electro-pneumatic converter; A pressure sensor for detecting a drive output pressure output from a relay; a deviation pressure calculation unit for calculating a deviation pressure based on a difference between an amplification factor of a pilot relay and an integrated value of the nozzle back pressure and the drive output pressure; Based on the pressure, it is determined whether or not the pilot relay is in the dead zone.When the pilot relay is in the dead zone, the feedback control loop is compared with when the pilot relay is not in the dead zone. A loop gain control unit that instructs to increase the gain, and an output control unit that performs feedback control of the nozzle back pressure based on the deviation pressure and an instruction from the loop gain control unit. Output control system.