JPH0816204A - Method for cutting integration operation of pid controller - Google Patents

Abstract

PURPOSE:To provide a cutting method for the integration operation of a PID controller which can execute control having high control responseness when a controlled system is disturbed or execute sharply changed. CONSTITUTION:The PID control has proportional operation and integration operation based upon a control deviation XW consisting of a difference between a set value SV and a controlled variable PV, a multiplier 6 having an window function for multiplying the control deviation XW by a coefficient is connected to the input side of an integrator 7, the window of the multiplier 6 has positive and negative control deviation width (-XPB to +XPB) equivalent to a proportional band, and an output coefficient has '1' when the control deviation XW is '0' or '0' when the absolute value of the deviation XW is more than a control deviation value XPB equivalent to the proportional band. Thus the coefficient is smoothly changed from '0' to '1' in accordance with the control deviation XW when the deviation XW is within the range of the width (-XPB to +XPB) equivalent to the proportional band.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is in the field of control using a PID controller, and suppresses an excessive amount of control amount (hereinafter, abbreviated as overshoot) when a target value is largely changed. Regarding the method.

[0002]

2. Description of the Related Art In a continuous control method using a PID controller, for example, when a target value is largely changed,
Also, when a strong disturbance is added to the controlled object,
Overshoot occurs in the control result. This is because
When such a large setting change of the target value is made,
The operating end operated by the PID controller goes through a transient phenomenon of a fully open or fully closed state, and the actual operation amount is restricted to a finite value. During this period, the integral operation of the PID controller is performed. Is overintegrated, and as a result, overshoot occurs in the control result.

As a means for suppressing such an overshoot, in the prior art, for example, as described above, the control operation is the PD operation during the transient phenomenon period corresponding to the saturation state when the operating end is fully open or fully closed. As a controller, the integral operation is cut, and when the control amount falls within a predetermined range, the control operation is a PID operation controller, and the offset correction operation is performed by the integral operation, and control without an offset amount is performed. .

In the prior art, the condition for switching the control operation mode of the controller between the PD operation and the PID operation is the control deviation amount or the operation output value as an index, and the control operation mode can be switched by this value. Has been done.

[0005]

In the control mode switching between the PD operation and the PID operation of the prior art, particularly in the start-up control such as the batch control process, the control with a small overshoot amount or almost no overshoot is performed. In addition, the disturbance of the controlled object is controlled by the control parameter having the best response controllability, and an effective control result is obtained.

In order to reduce the overshoot amount as much as possible by such control, for example, when the control operation mode is switched by the control deviation, it is desired to switch the control mode by the control deviation amount as small as possible. However, the smaller the control deviation amount for switching the control mode, the more
It becomes easy to be influenced by the characteristic change of the controlled object over time.
That is, when the PD operation control does not fall within the range of the control deviation amount of the control mode switching due to the characteristic change of the controlled object, there is no offset correction operation by the integration operation,
The offset is permanently generated.

Similarly, when the control mode is switched by the operation output value, the normal PID is controlled by the PD operation.
When it does not fall within the operation output range of the operation, there is no offset correction operation by the integration operation, and the offset is permanently generated. That is, in the method according to the conventional technique, it is necessary to set these control mode switching ranges with a certain margin in consideration of the influence of the characteristic change of the controlled object over time.

The present invention has been made in view of the above points, and an object thereof is to solve the above-mentioned problems and to perform control with good control responsiveness to a disturbance of a controlled object and to significantly increase a target value. For setting changes, control is performed with a small overshoot amount, and control is performed so that a steady offset does not occur even if there is a characteristic change over time in the controlled object.
It is to provide a method of cutting the integral operation of an ID controller.

[0009]

In order to achieve the above object, in the invention according to claim 1 of the present application, a setter for setting a target value, an input circuit for receiving a controlled variable input from a controlled object, And a PID controller at least
It has a proportional action and an integral action based on a control deviation consisting of a difference between a target value and a controlled variable, and has a multiplier having a window function on the input side of an integrator that performs the integral action. The signal multiplied by the coefficient is input to the integrator, and the multiplier outputs
The window on the input side has a positive / negative control deviation value width corresponding to the proportional band, the output coefficient has a control deviation of 0 and a coefficient of 1, and the absolute value of the control deviation is equal to or larger than the control deviation value corresponding to the proportional band. In the range of the control deviation value in which the control deviation corresponds to the proportional band, the coefficient varies smoothly between 0 and 1 according to the control deviation.

Further, in the invention according to claim 2 of the present application, it is assumed that the window on the input side of the multiplier can set the cut width with a window setting parameter coefficient.

[0011]

With the above construction, by providing a multiplier having a window function with a coefficient of 1 to 0 on the input side of the integrator performing the integration operation, the integration time of the PID controller is changed in inverse proportion to the coefficient on the input side. be able to. That is, in the area of the coefficient 1 in the vicinity of the control deviation 0, the integration time becomes the integration time itself set in the controller, and becomes 0 when the absolute value of the control deviation is equal to or larger than the control deviation value corresponding to the proportional band. Therefore, there is no input to the integrator here. That is, in the range where the absolute value of the control deviation is equal to or larger than the control deviation value corresponding to the proportional band, P
The integration operation of the ID controller is cut off. Further, within the range of the control deviation value corresponding to the proportional band or less, the coefficient smoothly changes between 0 and 1 according to the control deviation, so that the integration time of the PID controller can be continuously and largely changed.

Further, according to the present invention, since the control deviation for cutting the integral operation of the PID controller is selected as the control deviation value corresponding to the proportional band, within this control deviation value corresponding to the proportional band,
Any PD controller output from 0 to 100% can be obtained. That is, according to the method of the present invention, for example, even when the PD operation is controlled during the startup control, the control deviation value controlled by the PD operation always falls within the control deviation value corresponding to the proportional band. Can be switched to the PID operation. As a result, it is possible to solve the conventional problem that "the offset may remain permanently depending on the change in characteristics of the controlled object over time". That is, control with good control responsiveness to the disturbance of the controlled object, small overshoot amount to the large setting change of the target value, and the influence of the characteristic change of the controlled object over time. It is possible to perform control not to receive.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram for explaining a method of cutting an integral operation of a PID controller as an embodiment of the present invention, and FIG. 2 is a method of cutting an integral operation of another embodiment of the present invention. It is a block diagram. In FIG. 1, a PID controller includes a setter 1 for setting a target value SV and an input circuit 2 for receiving a controlled variable PV input from a control target (not shown).
And a P calculator 3 that performs a proportional operation, an I calculator 4 that performs an integral operation, a multiplier 6 and an integrator 7 based on a control deviation XW that is a difference between the target value SV and the control amount PV. , A D computing unit 5 that performs a differential operation of the control amount PV, and an output circuit 8 that adds the outputs of these P computing unit 3, integrator 7, and D computing unit 5 and converts it into an operation output signal. To be done.

In the above structure, a multiplier 6 having a window function is provided on the input side of the integrator 7 for performing the integration operation, and the control deviation XW is multiplied by the multiplier 6 in the range of 0 to 1. It is input to the integrator 7. Therefore, when the coefficient of the multiplier 6 is 1, it has the same integration time as the integration time set by the PID parameter setting of the PID controller, and when the coefficient of the multiplier 6 is 1 or less, it is multiplied by that coefficient. A small control deviation is input to the integrator 7, and as a result, the integration time becomes longer in inverse proportion to this coefficient times the integration time set by the PID parameter setting. When the coefficient of the multiplier 6 is 0, the control deviation XW is not input to the integrator 7. That is, the integration time corresponds to infinity, and the integration operation is cut.

PID when this integration operation is cut
Regarding the operation of the controller, the integrated output value of the integrator 7 immediately before the integration operation is cut becomes the bias value of the PD operation controller after the integration operation is cut, and the output of the PD operation controller is the control deviation XW = When the bias value is 0, the bias value is output, and with this value as the center, the PD calculation operation based on the control deviation XW is output.

In the multiplier 6 shown in FIG. 1, the abscissa represents the control deviation XW, and the ordinate represents the coefficient of the multiplier 6 from 0 to 1. The multiplier 6 has a window characteristic that allows the control deviation XW within the positive and negative control deviation width (-XPB to + XPB) corresponding to the proportional band to pass, and the output coefficient at this time is 0 for the control deviation and 1 for the coefficient.
The control deviation is equivalent to the proportional band of control deviation (-XPB to + XPB)
Within the range, the coefficient 0 to 1 changes smoothly according to the control deviation, and the control deviation corresponds to the proportional band (-XPB to + X).
It has a coefficient of 0 in the range other than PB).

The proportional band of the controller is 0 to the operation output of the controller.
Since it is defined by the input (control deviation) width required to change 100%, the integral operation is cut in the control deviation width (-XPB to + XPB) range corresponding to the proportional band which is the window characteristic of the multiplier 6. When the bias output of the integrator 7 of the PD controller at the time is arbitrary operation output (0 to 100%), the operation output of the PD controller can be controlled in the range of 0 to 100% by the control deviation XW. Means a range.

Therefore, when the target value is largely changed, the controlled object is first controlled by the PD operation so that the overshoot is small, and the control amount is stabilized near the target value. In this state, the control deviation XW of the PD controller always falls within the range of the control deviation width (-XPB to + XPB) corresponding to the proportional band described above.
It is possible to switch to the control by the ID operation, and it is possible to prevent the occurrence of the offset amount due to the lack of the I operation.

FIG. 2 shows another embodiment of the present invention. The difference from FIG. 1 is that the multiplier 6A has a setting device 9 for the integral cut strength (Ar). That is, the window on the input side of the multiplier 6A is set to the control deviation value (-XPB, + XPB) corresponding to the proportional band, which is the cut width, by the setter 9 for the integrated cut strength (Ar) that is the window setting parameter coefficient. On the other hand, the magnification can be changed by the setting device 9, and the switching range of the PD operation and the PID operation can be expanded / contracted by Ar times with respect to the above range.
The integral cut strength (Ar) can be adjusted in size of the integral cut amount according to the process characteristics, and fine adjustment can be made to suit the control purpose.

[0020]

As described above, according to the present invention, the cut of the integral operation can prevent the overshoot, and as a side effect of the cut of the integral operation, the permanent change is caused by the characteristic change of the controlled object over time. It is possible to solve the concern that the offset remains. In the first embodiment, since the integration time smoothly changes within the window range of the multiplier, a good control result can be obtained without finely adjusting and setting the cut point of the integration operation as in the prior art. .
Further, in the second embodiment, since the window range of the multiplier can be set according to the process characteristics, the overshoot amount can be adjusted quite freely.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a method of cutting an integral operation of a PID controller according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a method of cutting an integral operation according to another embodiment of the present invention.

[Explanation of symbols]

 1 Setting device 2 Input circuit 3 P computing device 4 I computing device 5 D computing device 6, 6A Multiplier 7 Integrator 8 Output circuit 9 Integral cut strength setting device SV Target value PV control amount MV operation output

Claims (2)

[Claims] 1. A setter for setting a target value, and an input circuit for receiving a controlled variable input from a controlled object,
The PID controller has at least a proportional action based on a control deviation consisting of a difference between the target value and the control amount, and an integral action, and a window is provided at an input side of an integrator that performs the integral action. A signal having a coefficient multiplied by the multiplier is input to the integrator, and the multiplier has a positive and negative control deviation in which an input side window corresponds to the proportional band. A control having a value range, an output coefficient having a control deviation of 0, a coefficient of 1, an absolute value of the control deviation having a coefficient of 0 or more when the absolute value of the control deviation is greater than or equal to a proportional band, and the control deviation having a proportional band. A method for cutting an integral operation of a PID controller, wherein the coefficient smoothly changes between 0 and 1 within a range of a deviation value according to a control deviation. 2. The PID controller according to claim 1, wherein the window on the input side of the multiplier has a window setting parameter coefficient to set the cut width. How to cut the integral action of the meter.