JPH08241102A - Pid control unit - Google Patents

Abstract

PURPOSE: To provide the PID controller which can have both a PID value and a control mode adjusted at the same time so as to perform excellent control over variation in desired value. CONSTITUTION: This PID controller consists of a coefficient element 1 which outputs an externally set coefficient value, a PID value computing element 2 which outputs a PID value for basic PID control mode and a PID value for I-PD control mode on the basis of the coefficient value outputted from the coefficient element 1, and a PID controller 3 which outputs a basic type PID control mode output, an I-PD control mode output, or the compromised control mode output of the basic type PID control mode output and I-PD control mode output as a manipulated variable to a controlled system on the basis of the basic type PID control mode PID value outputted from the PID value computing element 2 and the basic type PID control mode PID value and I-PD control mode PID value outputted from the PID value computing element 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PID controller for feedback control of flow rate, pressure, temperature, liquid level, composition, etc. in various equipment industries such as petroleum, chemical, iron and steel, electric power and paper manufacturing.

[0002]

2. Description of the Related Art A dependent compensation type basic PID controller is known as a device for performing proportional / integral / derivative operations on a control deviation and outputting a manipulated variable. FIG. 4A is a diagram showing a configuration of a dependent compensation type basic PID controller. When controlling various process amounts using the basic compensation type basic PID controller as shown in the same figure, if the PID value that can follow the target value change well is set and set, FIG. A good control response as shown in a) can be realized.

However, for example, in a system in which a valve is opened / closed as shown in FIG. 6 and a flow rate is used as an operation amount, when a step disturbance enters the controlled object inlet (operation amount) like a change in the original pressure of the fluid, As shown in FIG. 5B, a phenomenon occurs in which the control amount does not quickly return to the original target value.

On the other hand, if the PID value is determined and set so that even if a step disturbance is introduced into the inlet of the controlled object, a good control response can be obtained as shown in FIG. 5 (c). it can.

However, when the PID value is determined and set so that the step disturbance can be satisfactorily suppressed even when the step disturbance enters the inlet of the controlled object, when the target value is changed stepwise as shown in FIG. 5 (d). Inconveniences such as a large overshoot occurring in the control response of 1.

In order to avoid such a trade-off,
As shown in FIG. 4B, the PID controller in the I-PD control mode, that is, I, performs only the integration operation for the control deviation E and performs the proportional / derivative operation for the control amount PV.
-The PD controller is used.

Further, as shown in FIG. 4 (c), the target value S
Two types of freedom, such as using a lead / lag target value filter in the input section of V, or a target value field forward method of adding the target value SV to the manipulated variable MV via a transfer characteristic element as shown in FIG. Degree PID controllers are also used.

Control responses when such an I-PD controller is used are shown in FIGS. 7 (a) to 7 (c). FIG. 7A shows
The figure which shows the control response at the time of change of target value step, Figure 7 (b)
FIG. 7 is a diagram showing a control response when a step disturbance enters the controlled object inlet, and FIG. 7C is a diagram showing a control response when a step disturbance enters the controlled object outlet.

Further, there is also known a PID controller capable of realizing an eclectic control mode of a basic type PID control mode and an I-PD control mode by adjusting a coefficient value (Japanese Patent Publication No. 54242/1992).

[0010]

The step disturbance applied to the controlled object is not always applied to the controlled object inlet (manipulation amount). When the PID controller in the I-PD control mode or the two-degree-of-freedom PID controller described above is used, for example, like the steam control valve opening change in the boiler main steam pressure control system, the control target outlet (control amount ) May be disturbed.

In this case, as in the control response characteristic shown in FIG. 7 (c), the control amount is large and the overshoot response becomes vibrational. Therefore, in such a case, it is understood that a better control response can be obtained by using the basic type PID controller as shown in FIG.

That is, in order to properly suppress the disturbance of the control amount due to the step disturbance while maintaining the good control response to the change of the target value, it is necessary to consider which part of the controlled object the disturbance is added to. Good controllability cannot be realized unless the control mode and the PID value are determined by using. In addition,
Disturbances may be added in the middle in addition to the inlet / outlet of the controlled object, or may be added with a certain transfer characteristic, and these are in the normal state. Therefore, the PID controller in the conventional I-PD control mode or The degree-of-freedom PID controller has a problem in this respect that it can realize a good control response only in a very limited case.

In addition, it is often unclear at the designing stage where the step disturbance is added to the controlled object. Therefore, the PID control can be easily adjusted at the same time as the PID value so that the PID control device is installed in the actual plant and is actually operated, and then the step disturbance peculiar to the control loop can be well controlled. Equipment is needed. However, heretofore, a PID control device having such a function has not been provided.

Further, a method such as H infinity control is known in which attention is paid to a main frequency component of the step disturbance, and the step disturbance of the frequency component is suppressed, and the step disturbance is also added to this control method. It does not provide a control method considering the location.

The present invention has been made in view of the above situation, and it is possible to adjust the PID value and the control mode from the outside at the same time, so that it is not affected by the input point of the step disturbance and various. PID that can realize good control even when the target value changes
An object is to provide a control device.

[0016]

Therefore, first, in order to achieve the above object, the present invention is based on a coefficient element for outputting a coefficient value set from the outside and a coefficient value output from the coefficient element. Calculated P for basic PID control mode
P that outputs the ID value and the PID value for the I-PD control mode
ID value calculation element and PI for the basic type PID control mode
A basic type PID control mode output, an I-PD control mode output, and the basic type PID based on the D value, the PID value for the I-PD control mode, the control amount for the controlled object, and the target value thereof.
Control mode output calculating means for calculating an eclectic control mode output of the control mode output and the I-PD control mode output, and calculation by the control mode output calculating means based on the coefficient value output from the coefficient element Basic type PID
Operation on the controlled object by selecting any one of the control mode output, the I-PD control mode output, and the eclectic control mode output of the basic PID control mode output and the I-PD control mode output. It is a PID control device provided with a control mode selection means for outputting as a quantity.

[0017]

In the invention according to claim 1, the control mode selecting means outputs the basic type PID control mode output calculated by the control mode output calculating means on the basis of the coefficient value output from the coefficient element, and the I-PD control. Mode output and basic type PID
Since either one of the eclectic control mode output of the control mode output and the I-PD control mode output is selected and output as the manipulated variable for the control target, by setting the coefficient value appropriately, the control target specific It is possible to provide a versatile two-degree-of-freedom PID control device capable of effectively suppressing various types of step disturbances and having excellent target followability.

[0018]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a PID according to an embodiment of the present invention.
It is a figure which shows schematic structure of a control apparatus. As shown in the figure, the PID control device according to the present embodiment has a coefficient element 1 and a PI.
It is composed of a D value calculation element 2 and a PID controller 3. Here, the coefficient element 1 is set to a value from 0 to 1 from the outside. Then, the coefficient element 1 outputs this coefficient value a to the PID value calculation element 2 and the PID controller 3.

The coefficient value a output from the coefficient element 1
Is set so as to suppress various step disturbances peculiar to the controlled object based on the manipulated variable (MV), and follow the target satisfactorily.

That is, when it is considered that the step disturbance enters the controlled object inlet (manipulated amount), the coefficient value is "0", and when it is considered that it enters the controlled object outlet (controlled amount), the coefficient value is "0". 1 ”is set.

When the step disturbance enters the controlled object, that is, when there is a transfer characteristic between the manipulated variable and the step disturbance input point, there is also a transfer characteristic between the step disturbance input point and the controlled variable. In this case, the coefficient value output from the coefficient element 1 is set to a value between "0" and "1".

The PID value calculation element 2 is a PID value for the basic type PID control mode suitable for target value tracking control (proportional gain KP (PID), integration time TI (PID), differential time T).
D (PID) and PID value for I-PD control mode [KP (I-PD), TI (I-P) suitable for suppressing inlet disturbance
D), TD (I-PD), and these basic type PIs
PID value for D control mode and PI for I-PD control mode
Using the D value and the coefficient value a output from the coefficient element 1, the PID value is calculated according to the following equations (1) to (3) and output to the PID controller 3.

KP = a.KP (PID) + (1-a) .KP (I-PD) (1) TI = a.TI (PID) + (1-a) .TI (I-PD) ... (2) TD = a.TD (PID) + (1-a) .TD (I-PD) (3) The PID value for the basic PID control mode and the I-PD value for the I-PD control mode are , Identify the characteristics of the controlled object,
For example, the partial model matching method (Kitamori "Design method of control system based on partial knowledge of controlled object", Institute of Instrument and Control Engineers, Vol.15, No.4) and the improved limit sensitivity method (Kuwata "Improved type" Limiting Sensitivity Method and PID; Characteristics of I-PD Control "Transactions of the Society of Instrument and Control Engineers Vol.23, No.3)
Based on.

Further, the coefficient value a output from the coefficient element 1
Is set to "1" and the target value can be changed or disturbance can be applied to the controlled outlet to achieve the best control.
PI value for basic PID control mode
D value, then, the coefficient value a is set to “0”, disturbance is applied to the controlled inlet, and a PID value that can suppress the inlet disturbance best is obtained by trial and error, and the PID value for the I-PD control mode is obtained. It may be a PID value.

The PID controller 3 receives the target value (SV) and the controlled variable PV as inputs, and is designated by using the taken in PID value, the proportional gain KP, the integration time TI, the differential time TD, and the coefficient value a. The control mode control calculation is performed and the manipulated variable MV is output to the controlled object.

Specifically, the basic type PID control mode P
From the ID value, the PID value for the I-PD control mode, the control amount PV for the control target, and the target value SV, the basic type PID
The control mode output, the I-PD control mode output, and the eclectic control mode output of the basic type PID control mode output and the I-PD control mode output are calculated.

Also, based on the coefficient value output from the coefficient element, the basic type PID control mode output, I-
One of the PD control mode output, the eclectic control mode output of the basic type PID control mode output, and the I-PD control mode output is selected and output as an operation amount for the control target.

The manipulated variable MV is specifically calculated based on the following equation (4). MV = KP {(1 / TIS) (SV-PV) + (1 + TDS) (aSV-PV)} (4) where S: Laplace operator, SV: target value, PV: control amount, KP: Proportional gain, TI: integration time, TD: derivative time.

That is, when the coefficient value a is "1",
The basic type PID control mode suitable for the target value tracking control and the step disturbance suppression entering the control target outlet is set, and the coefficient value a
Is 0, the I-PD control mode is suitable for the target value tracking control and the step disturbance suppression entering the control target inlet. Further, when the coefficient value a is a value between "0" and "1", the eclectic control mode of the basic type PID control mode and the I-PD control mode corresponding to the value is set.

FIG. 2 shows the PID of the PID control device shown in FIG.
It is a figure which shows the concrete structure of the ID value calculation element 2 and the PID controller 3 of multiple modes. The PID value calculation element 2 is a PID value for the basic PID control mode (proportional gain KP (PI
D), integration time TI (PID), differential time TD (PI
D) set storage element 21 and the PID values for the I-PD control mode (KP (I-PD), TI (I-PD), TD
(I-PD) set storage element 22 and subtraction element 23
a to 23c and multiplication elements 24a to 24c and 25a to 25
c and addition elements 26a to 26c.

The subtraction element 23a outputs a signal (1-a) obtained by subtracting the coefficient value a from "1" to the multiplication element 25a. The multiplication element 24a receives the signal KP from the storage element 21.
(PID) is multiplied by the coefficient value a input from the coefficient element 1, and the signal a · KP (PID) is output to the addition element 26a.

The multiplication element 25a receives the signal K P (I-PD) from the storage element 22 and the signal (1-
The signal (1-a) .multidot.KP (I-PD) multiplied by a) is output to the addition element 26a.

The addition element 26a adds the signal aKP (PID) from the multiplication element 24a and the signal (1-a) KP (I-PD) from the multiplication element 25a to obtain PID as the proportional gain KP. It outputs to the coefficient element 36 of the controller 3.

The subtraction element 23b outputs a signal (1-a) obtained by subtracting the coefficient value a from "1" to the multiplication element 25b. The multiplication element 24b receives the signal TI from the storage element 21.
(PID) multiplied by the signal a from coefficient element 1
The TI (PID) is output to the addition element 26b.

The multiplication element 25b has a signal TI (I-PD) from the storage element 22 and a signal (1- (1) from the subtraction element 23b).
The signal (1-a) .TI (I-PD) multiplied by a) is output to the addition element 26b.

The addition element 26b adds the signal aTI (PID) from the multiplication element 24b and the signal (1-a) TI (I-PD) from the multiplication element 25b to obtain an integration time T.
It is sent as I to the integral element 33 of the PID controller 3.

The subtraction element 23c outputs a signal (1-a) obtained by subtracting the coefficient value a from "1" to the multiplication element 25c. The multiplication element 24c is the signal TD from the storage element 21.
(PID) is multiplied by the coefficient value a input from the coefficient element 1, and the signal aTD (PID) is output to the addition element 26c.

The multiplication element 25c receives the signal TD (I-PD) from the storage element 22 and the signal (1-
a) and is multiplied by and the signal (1-a) .TD (I-PD) is output to the addition element 26c.

The addition element 26c adds the signal aTD (PID) from the multiplication element 24c and the signal (1-a) TD (I-PD) from the multiplication element 25c to obtain the differential time TD.
To the differential element 34 of the PID controller 3.

Next, the configuration of the PID controller 3 for a plurality of modes will be described. This multi-mode PID controller 3
Is a multiplication element 30, a sign inversion element 31, and an addition element 3
2, 35, 37, an integration element 33, a differentiation element 34,
And a coefficient element 36.

The multiplication element 30 multiplies the target value SV and the coefficient value a and outputs the signal aSV to the addition element 37. The sign reversal element 31 inverts the sign of the controlled variable PV to control-P.
It is output as V to the addition element 32 and the addition element 37.

The addition element 32 adds the target value SV and the control amount −PV whose sign is inverted by the sign inversion element 31 and outputs it as a control deviation E to the integration element 33. Integral element 33
Is the integration time T output from the addition element 26b of the PID value calculation element 2 based on the control deviation E output from the addition element 32.
It integrates based on D and outputs to the addition element 35.

The addition element 37 multiplies the target value SV output from the multiplication element 30 by the coefficient value a, and the sign-inverted control amount -P output from the sign inversion element 31.
V is added and output to the addition element 35 and the differentiation element 34.

The differentiation element 34 differentiates the signal output from the addition element 37 with the differentiation time TD output from the addition element 26c of the PID value calculation element 2 and outputs it to the addition element 35. As shown in FIG. 2, the differential element 33 is, for example, a signal filtered TD.S /, instead of the one having a perfect differential characteristic whose transfer function is TD.S.
An element having an incomplete differential characteristic having a transfer function of (1 + η · TD · S) may be used.

The addition element 35 adds the output from the integration element 33, the output from the addition element 37, and the output from the differentiation element 34, and the added output signal is added to the coefficient element 36.
Is output to.

The coefficient element 36 multiplies the output signal from the addition element 35 by the proportional gain Kp output from the addition element 26a of the PID value calculation element 2 to output the manipulated variable MV to the control target, and the control target Feedback control.

Next, the operation of the PID controller constructed as described above will be described. First, the target value SV and the control amount −PV whose sign is inverted by the sign inversion element 31 are added by the addition element 3
2 is added and output as the control deviation E to the integration element 33. The integration element 33 integrates the control deviation E output from the addition element 32 on the basis of the integration time TD output from the addition element 26b of the PID value calculation element 2 to obtain the addition element 3
Output to 5

The target value SV is multiplied by the coefficient value a in the multiplication element 30 and output as the signal aSV to the addition element 37. This signal aSV is a sign-inverted control amount −P output from the sign inversion element 31 in the addition element 37.
V is added and output to the addition element 35 and the differentiation element 34.

The signal output to the differentiating element 34 is the PID
After being differentiated by the differentiation time TD outputted from the addition element 26c of the value calculation element 2, it is outputted to the addition element 35. The addition element 35 includes the output from the integration element 33 and the addition element 3
The output from 7 and the output from the differentiating element 34 are added,
The added output signal is output to the coefficient element 36.

The coefficient element 36 multiplies the output signal from the addition element 35 by the proportional gain Kp output from the addition element 26a of the PID value calculation element 2, and manipulates the manipulated variable M.
V is output to the controlled object, and the controlled object is feedback-controlled.

Therefore, according to this embodiment, the PID value for the basic type PID control suitable for the target value follow-up control determined by the characteristics of the control target and the I-PD control suitable for the step disturbance suppression entering the control target inlet. PID value of PID value calculation element 2
By setting and operating the PID controller, as shown in FIG. 3A, it is possible to provide a PID control device having excellent target value followability.

By adjusting the value set in the coefficient element 1, for example, when step disturbance enters the controlled object inlet, as shown in FIG. 2B, when step disturbance enters the controlled object outlet. As shown in FIG. 2 (c),
It is possible to provide a feedback PID control device that can effectively suppress various disturbances and realize more versatile two-degree-of-freedom control.

The PID controller 3 is not limited to this embodiment, but is disclosed in Japanese Patent Publication No. 4-542.
Basic type PI of those shown in No. 42 and other configurations
PID that can implement D control mode and I-PD control mode
It may be a controller. Also, although an analog embodiment has been described, this may be implemented by a digital controller.

[0054]

As described above in detail, according to the present invention,
Even during the control of the actual plant, the control mode and the PI are controlled by the coefficient values that can suppress various disturbances unique to the controlled object set from the outside and follow the target satisfactorily.
A versatile two-degree-of-freedom PID that automatically switches the D value, can effectively suppress various types of step disturbances unique to the controlled object, and has excellent target followability.
A control device can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a PID control device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a specific configuration of a PID control device in the embodiment.

FIG. 3 is a diagram showing a control response when feedback control is performed on a control target using the PID control device in the embodiment.

FIG. 4 is a diagram showing a configuration of a conventional PID controller.

FIG. 5 is a diagram showing a control response when feedback control is performed on a control target using a conventional PID controller.

FIG. 6 is a feedback PI indicating an inlet disturbance and an outlet disturbance.
Explanatory drawing of a D control system.

FIG. 7 is a diagram showing a control response when a conventional two-degree-of-freedom PID (I-PD) controller is used.

Description of Codes 1 ... Coefficient element, 2 ... PID value calculation element, 3 ... PID controller, 21, 22 ... Storage element, 23a-23c ... Subtraction element, 24a-24c, 25a-25c ... Multiplication element, 26
a to 26c ... Addition element, 30 ... Multiplication element, 31 ... Sign inversion element, 32, 35, 37 ... Addition element, 33 ... Integral element, 34 ... Differentiation element, 36 ... Coefficient element.

Claims (1)

[Claims] 1. A coefficient element for outputting a coefficient value set from the outside, a PID value for a basic type PID control mode and a PID for an I-PD control mode calculated based on the coefficient value output from the coefficient element. A PID value calculation element that outputs a value, a PID value for the basic PID control mode, a PID value for the I-PD control mode, a control amount for a control target, and a target value from the basic PID control mode output, the I-PD A control mode output, and a control mode output calculating means for calculating an eclectic control mode output of the basic type PID control mode output and the I-PD control mode output, and a coefficient value output from the coefficient element, The basic type PID control mode output calculated by the control mode output calculating means, the I-PD control mode output, and the basic type PID control mode output, A PID control device comprising: a control mode selection unit that selects any one of the eclectic control mode outputs of the I-PD control mode outputs and outputs the selected operation amount as an operation amount for the control target. .