JPH06266411A - IMC controller - Google Patents

Abstract

PURPOSE:To dispense with adjustment of a filter part being different with a control object process. CONSTITUTION:In an internal model storage part 6a, a parameter of an internal model formed by expressing a control object process by a mathematical expression is stored. Based on a dead time of the internal model outputted from the internal model storage part 6a by a time constant change processing part 9, a first time constant and a second time constant are operated. By a first time constant, a characteristic of a target value filter part 2 is determined, and by a second time constant, a target value of the inside of a manipulated variable arithmetic part 4, and a characteristic of a disturbance filter part are determined, therefore, adjustment of the filter part becomes unnecessary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a general-purpose controller, and more particularly to a controller using a control algorithm having an IMC (Internal Model Control) structure.

[0002]

2. Description of the Related Art Conventionally, a PID has been used as a general-purpose controller.
The one using control is generally used. The PID controller uses an operation unit that performs a combined operation of the proportional action P, the integral action I, and the derivative action D to obtain a target value (e.g., if the controller is an indoor air conditioner, the indoor temperature set value) and the feedback amount. The operation amount (the temperature of hot air or cold air from the indoor air conditioner) that is the output of this controller is calculated from the difference between the output and this operation amount, and this operation amount is output to the control target process (indoor environment), which is the control result. This is a feedback control system that returns the amount (indoor temperature) as a feedback amount. However, the PID controller
If the dead time that is the time from the output of the manipulated variable until the change in the controlled variable in the controlled process appears (for example, the time from the hot air being blown until the indoor temperature rises in an indoor air conditioner) is large, There is a problem that it is difficult to deal with the dead time because an operation amount that is larger than the original operation is output and the control amount overshoots or vibrates.

Therefore, there has been proposed a controller using an IMC structure control algorithm for performing control by incorporating an internal model in which a process to be controlled is expressed by a mathematical expression. FIG. 4 is a block diagram of a control system using this IMC controller. Reference numeral 13 denotes a first subtraction processing unit that subtracts a feedback amount, which will be described later, from a target value, 12 denotes a filter unit for preventing a change in the output of the first subtraction processing unit 13 from being rapidly transmitted, and 14 denotes a filter unit 12 An operation unit that calculates an operation amount based on the output of 16 is an internal model that outputs a reference control amount corresponding to the control amount of the control target process by approximating the control target process by a mathematical expression. A second subtraction processing unit 20 that subtracts the reference control amount from the internal model 16 and outputs a feedback amount is a control target process. Further, F, Gc, Gm, and Gp are the filter unit 12, the operation unit 14, the internal model 16, and
The transfer function of the process 20 to be controlled, r is a target value, u is an operation amount, d is a disturbance corresponding to an outdoor environment with respect to an indoor environment, y is a control amount, ym is a reference control amount, and e is a feedback amount.

Next, the operation of such an IMC controller will be described. First, the first subtraction processing unit 13 subtracts the feedback amount e from the target value r, and the result is output to the filter unit 12 for preventing a rapid change in the target value r from being transmitted. Next, the operation amount u is calculated by the operation unit 14 from the output of the filter unit 12, and is output to the control target process 20 and the internal model 16 of the controller. Then, the second subtraction processing unit 18 subtracts the reference control amount ym from the internal model 16 that approximates the control target process 20 from the control amount y of the control target process 20, and the result is the feedback amount e. A feedback control system that is fed back to the first subtraction processing unit 13 is configured as.

Ideally, the internal model 16 of such an IMC controller is expressed by a mathematical expression so as to be exactly the same as the controlled process 20, and the operating unit 14 is also used.
Is ideally the inverse characteristic (1 / Gm) of the transfer function of the internal model 16, but since the elements of the dead time in the internal model 16 cannot be reciprocated, the elements of the dead time are normally used. Ignore.

Therefore, the control amount y can be obtained by the following equation from the target value r and the disturbance d with such a configuration. y = F * Gp * Gc * r / {1 + F * Gc * (Gp-Gm)} + (1-F * Gm * Gc) * d / {1 + F * Gc * (Gp-Gm)} ... (1 Here, the transfer function Gm of the internal model 16 is equal to the transfer function Gp of the controlled process 20, and the transfer function Gc of the operating unit 14 is the reciprocal of the transfer function of the internal model 16 (1 / Gm =
Assuming an ideal state equal to 1 / Gp), equation (1) becomes y = F × r + (1-F) × d (2)

Further, under ideal conditions where the target value r does not change suddenly, the filter unit 12 is unnecessary and F = 1 can be set, so that the control amount y becomes equal to the target value r (y =
r), it is possible to realize the control without any influence of the disturbance d. Further, focusing on the disturbance d in the control system of FIG. 4, even if there is a large dead time in the controlled object process 20 and the internal model 16, both exhibit the same characteristics with respect to the manipulated variable u, so the second subtraction It can be seen that the feedback amount e, which is the output of the processing unit 18, is only the disturbance d, and the disturbance d can be suppressed.

[0008] Such an IMC controller is usually
Design based on the robust stability indicating the stability against the disturbance d when the error between the controlled process 20 and the internal model 16 becomes large, and the robust performance indicating the performance when the error becomes large similarly. To be done.
In addition, the filter unit 12 determines the internal model 1 after the internal model 16 is determined by such a model identification technique.
6 needs to be adjusted by an expert having knowledge of control based on the model identification accuracy with the controlled process 20.

[0009]

Since the conventional IMC controller is configured as described above, an expert having knowledge of control of the characteristics of the filter portion for stabilizing the control according to the control target process. Needs to be adjusted,
There is a problem that it is unsuitable as a controller used for general purpose. In order to solve the above problems, the present invention is a highly versatile IM that does not require adjustment of the characteristics of the filter unit when model identification of a process to be controlled is performed.
The purpose is to provide a C controller.

[0010]

According to the present invention, a target value filter section for outputting an input target value with a characteristic determined by a first time constant, and a feedback amount is subtracted from the output of the target value filter section. A first subtraction processing unit, a target value / disturbance filter unit that outputs the output of the first subtraction processing unit with a characteristic determined by a second time constant, and a target value / disturbance filter based on the parameters of the internal model. An operation amount calculation unit including an operation unit that calculates an operation amount from the output of the unit, an internal model storage unit that stores parameters of the internal model,
An internal model output calculation unit that calculates a reference control amount from the operation amount output from the operation amount calculation unit based on the parameters of the internal model, and a reference control amount output from the internal model output calculation unit from the control amount of the controlled process And a second subtraction processing unit that subtracts and outputs a feedback amount, and calculates and outputs a first time constant and a second time constant based on the dead time of the internal model output from the internal model storage unit. And a time constant change processing unit.

[0011]

According to the present invention, the time constant change processing unit calculates the first time constant and the second time constant based on the dead time of the internal model output from the internal model storage unit.
Then, the target value is input to the target value filter unit whose characteristics are determined by the first time constant, and the first subtraction processing unit subtracts the feedback amount from the output of the target value filter unit. Next, this result is output to the target value / disturbance filter unit in the manipulated variable calculation unit whose characteristics are determined by the second time constant, and the manipulated variable is calculated from this result in the manipulated unit, and the controlled object process and internal model output calculation Output to the department. Then, the second subtraction processing unit subtracts the reference control amount from the internal model output calculation unit from the control amount of the control target process, and the result is fed back to the first subtraction processing unit as a feedback amount. Becomes

[0012]

1 is a block diagram of an IMC controller showing an embodiment of the present invention, and FIG. 2 is a block diagram of a control system using this IMC controller. In FIG. 1, 1
Is a target value input section for inputting a target value r set by an operator (not shown) to this controller, 2 is a first time when the target value r from the target value input section 1 is output from a time constant changing processing section described later. The target value filter unit 3 that outputs with a characteristic determined by a constant is a first subtraction processing unit that subtracts the feedback amount e from the output of the target value filter unit 2, and 4 is the output from a time constant change processing unit that will be described later. Second
Is calculated from the output of the first subtraction processing unit 3 on the basis of the time constant and the parameter output from the internal model storage unit, which will be described later, and the operation amount calculation units 5 and 5 output from the operation amount calculation unit 4. It is a signal output unit that outputs the manipulated variable u to a control target process (not shown in FIG. 1).

Further, 6a is an internal model storage unit for storing the parameters of the internal model of this IMC controller, 6a
b is a reference control amount ym that is calculated as an internal model based on the parameters output from the internal model storage unit 6a.
, An internal model output operation unit for outputting the control amount y from the controlled object process to the IMC controller, and an internal model output operation for the control amount y output from the control amount input unit 7. A second subtraction processing unit that subtracts the reference control amount ym output from the unit 6b and outputs a feedback amount e, and 9 is based on the dead time of the internal model output from the internal model storage unit 6a. It is a time constant change processing unit that determines a constant and a second time constant.

In FIG. 2, reference numeral 4a is inside the manipulated variable calculating unit 4, and the characteristic of the output of the first subtraction processing unit 3 is determined by the second time constant output from the time constant changing processing unit 9. Output from the target value / disturbance filter unit 4b is also inside thereof, and is an operation unit for calculating the manipulated variable u from the output of the target value / disturbance filter unit 4a. 6 is an internal model storage unit 6
a and an internal model composed of the internal model output operation unit 6b,
F1 is the transfer function of the target value filter unit 2, and F2 is the target value
It is a transfer function of the disturbance filter unit 4a. Note that FIG. 2 is a rewrite of the IMC controller of FIG. 1 as a control system including the process 20 to be controlled and the disturbance d and excluding the time constant change processing unit 9.

Next, as the operation of such an IMC controller, the operation of the time constant change processing unit 9 for determining the time constants of the target value filter unit 2 and the target value / disturbance filter unit 4a will be described. When the first time constant that determines the characteristic of the target value filter unit 2 is T1 and the second time constant that determines the characteristic of the target value / disturbance filter unit 4a is T2, the time constant change processing unit 9 uses the internal model The first time constant T1 and the second time constant T2 are calculated by the following equations from the dead time of the internal model 6 output from the internal model storage unit 6a storing the parameters of No. T1 = A × Lm (3) T2 = B × Lm (4) Here, Lm is a dead time of the internal model 6, and A and B are certain constants. With this, the target value filter unit 2 and the target value
The characteristics of the disturbance filter unit 4a, that is, the transfer functions F1 and F2 are determined.

Next, the target value r is set by the operator or the like of this IMC controller and input to the target value filter unit 2 via the target value input unit 1. The target value filter unit 2 outputs the target value r with the characteristics of the transfer function F1 determined by the first time constant T1 output from the time constant change processing unit 9 as the following equation. F1 = 1 / (1 + T1 × s) (5) Next, the first subtraction processing unit 3 uses the target value filter unit 2
The feedback amount e output from the second subtraction processing unit 8 is subtracted from the output of.

Then, the target value / disturbance filter unit 4a in the manipulated variable calculation unit 4 outputs the output of the first subtraction processing unit 3 by the second time constant T2 output from the time constant change processing unit 9 as follows: The characteristic of the transfer function F2 determined as follows is output. F2 = 1 / (1 + T2 × s) (6) Similarly, the operation unit 4b therein also calculates the operation amount u from the output of the target value / disturbance filter unit 4a, but its transfer function Gc is The gain and time constant of the internal model 6 output from the model storage unit 6a give the following expression, which is the reciprocal of the transfer function Gm of the internal model 6 excluding the elements of the dead time Lm as in the example of FIG. Gc = (1 + Tm × s) / Km (7) where Km and Tm are gains of the internal model 6, respectively.
It is a time constant.

Therefore, the transfer function of the operation amount computing section 4 as a whole is given by the following equation. F2 × Gc = (1 + Tm × s) / {Km × (1 + T2 × s)} (8) In this way, the manipulated variable u is calculated from the output of the first subtraction processing unit 3 and the signal output unit It is output to the control target process 20 via 5 and is also output to the internal model output calculation unit 6b.

Next, the internal model 6 uses the gain Km, the dead time Lm, and the time constant Tm stored in the internal model storage section 6a as the parameters, which are the first-order lag and the dead time of the controlled process 20. This is a mathematical expression expressed as having elements, and the reference control amount ym is calculated from the operation amount u output from the operation amount operation unit 4 in the internal model output operation unit 6b. The transfer function Gm is given by the following equation. Gm = Km × exp (−Lm × s) / (1 + Tm × s) (9)

Next, the second subtraction processing unit 8 subtracts the reference control amount ym from the internal model output calculation unit 6b from the control amount y from the control target process 20 input via the control amount input unit 7. Then, the feedback amount e is output. Then, this feedback amount e is input to the first subtraction processing unit 3 as described above. This completes the feedback control system consisting of this IMC controller.

If there is a change in the process 20 to be controlled, it is necessary to adjust the characteristics of the filter section 12 after changing the internal model 16 in the IMC controller of the example shown in FIG. In the IMC controller of the internal model storage unit 6 in order to change the internal model 6,
This can be dealt with only by changing the parameter stored in a in accordance with the control target process 20.

That is, by changing the dead time Lm of the internal model 6, the time constant change processing unit 9 outputs new first time constant T1 and second time constant T2, and the target value filter unit 2 Since the transfer functions F1 and F2 of the target value / disturbance filter unit 4a are changed, an expert having knowledge of control does not need to readjust. Therefore, it is possible to realize a general-purpose IMC controller that requires less adjustment operation by the operator even if the control target process 20 is changed.

The control system by the IMC controller of this embodiment is the same as the control system of the example of FIG.
2 corresponds to the control system in which the target value / disturbance filter unit 4a is set and the target value filter unit 2 is added to the target value r. y = F1 * F2 * Gp * Gc * r / {1 + F2 * Gc * (Gp-Gm)} + (1-F2 * Gm * Gc) * d / {1 + F2 * Gc * (Gp-Gm)} ... (10)

That is, as shown in the equation (10), the disturbance d
The second term on the right side [(1-F2 × Gm × Gc) × d /
Since only the transfer function F2 of the target value / disturbance filter unit 4a is related to {1 + F2 × Gc × (Gp−Gm)}], the target value / disturbance filter unit 4a adjusts the disturbance d during design. To do. Also, the first term on the right side [F1 × F2 × G
p * Gc * r / {1 + F2 * Gc * (Gp-Gm)}]
Therefore, regarding the target value r, the target value / disturbance filter unit 4a
The target value filter unit 2 is adjusted after the adjustment of. That is, the transfer function F2 has a first-order delay characteristic with respect to the disturbance d, and the transfer function F1 × F2 has a second-order delay characteristic with respect to the target value r.

FIG. 3 is a diagram showing the target value followability when the IMC controller of this embodiment is used for controlling the height of the liquid level in the tank. The vertical axis represents the liquid level height (control amount y), the horizontal axis represents time, and yf represents the control when the first time constant T1 and the second time constant T2 are fixed and controlled in the IMC controller of this embodiment. Is the amount. In FIG. 3A, the target value r (dashed line) is input as the liquid level height of 4 cm at 0 seconds,
It is the simulation result which calculated | required the control amount y (solid line) which is the height of the liquid level of the control result.

Here, the gain of the control target process 20 which is the liquid in the tank is 4.0, the dead time is 55 seconds and the time constant is 10 seconds, and the gain K of the internal model 6 of this embodiment is set.
It is assumed that m and the time constant Tm are the same as those of the control target process 20, and the dead time Lm is 50 seconds assuming that the model identification error is 10%. Further, the constants A and B of the time constant change processing unit 9 for determining the first time constant T1 and the second time constant T2 are set to 0.3. Therefore, according to the equations (3) and (4), the first time constant T1 and the second time constant T2 are 15 seconds, and
1 when the time constant T1 and the second time constant T2 are fixed
5 seconds. In FIG. 3A, since the first time constant T1 and the second time constant T2 are both the same, the IMC of this embodiment is the same.
The control amount y by the controller and the control amount yf by the controller fixing them have naturally the same result.

On the other hand, in FIG. 3B, the dead time of the controlled process 20 is set to 11 under the same conditions as in FIG. 3A.
This is the result when 0 seconds is set and the dead time Lm of the internal model 6 is set to 100 seconds. Therefore, the first time constant T1 and the second time constant T2 of the IMC controller of this embodiment are 30 seconds. In FIG. 3B, the IMC controller of the present embodiment maintains a stable control with a good control result as compared with the case where the first time constant T1 and the second time constant T2 are fixed (15 seconds). I see what I can do.

[0028]

According to the present invention, when the characteristics of the target value filter unit and the target value / disturbance filter unit are changed in association with the dead time of the internal model, the model identification of the process to be controlled is performed. It is possible to realize a highly versatile IMC controller that does not need to adjust the characteristics of the filter section, so that even an operator who does not have knowledge of control can use the IMC controller.
It is possible to perform control that takes advantage of the controller.

[Brief description of drawings]

FIG. 1 is a block diagram of an IMC controller showing an embodiment of the present invention.

FIG. 2 is a block diagram of a control system using the IMC controller of FIG.

FIG. 3 is a diagram showing target value followability of the IMC controller of FIG. 1.

FIG. 4 is a block diagram of a control system using a conventional IMC controller.

[Explanation of symbols]

 2 target value filter unit 3 first subtraction processing unit 4 manipulated variable calculation unit 4a target value / disturbance filter unit 4b operation unit 6a internal model storage unit 6b internal model output calculation unit 8 second subtraction processing unit 9 time constant change processing Part T1 First time constant T2 Second time constant e Feedback amount r Target value u Manipulation amount y Control amount ym Reference control amount

Claims (1)

[Claims] 1. A reference control amount corresponding to a control amount of a control target process, which is a control result, is calculated by calculating an operation amount to be output to a control target process from a control target value, and using an internal model expressing the control target process by a mathematical expression. Control is performed by calculating and feeding back the difference between the control amount and the reference control amount I
In the MC controller, a target value filter unit that outputs the input target value with a characteristic determined by a first time constant, a first subtraction processing unit that subtracts a feedback amount from the output of the target value filter unit, A target value / disturbance filter unit that outputs the output of the first subtraction processing unit with a characteristic determined by a second time constant, and an operation amount from the output of the target value / disturbance filter unit based on the parameters of the internal model. An operation amount calculation unit including an operation unit that calculates a value, an internal model storage unit that stores parameters of the internal model, and a reference control based on an operation amount output from the operation amount calculation unit based on the parameters of the internal model. The internal model output calculation unit that calculates the quantity and the reference control amount output from the internal model output calculation unit from the control quantity of the controlled object process A second subtraction processing unit that outputs a feedback amount; and a time constant that calculates and outputs the first time constant and the second time constant based on the dead time of the internal model output from the internal model storage unit. An IMC controller having a change processing unit.