JPH06274202A - Imc controller - Google Patents

Abstract

(57) [Summary] [Object] To provide an IMC controller that does not require readjustment even if there is an identification error in the dead time or time constant of an internal model that expresses the controlled process as a mathematical expression. A feedback amount e is subtracted by a first subtraction processing unit 3 from an output of a target value filter unit 2 to which a target value r is input. The manipulated variable u is calculated from the subtracted output by the manipulated variable calculator 4.
Is calculated and output to the controlled process. 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 of the control target process to obtain the feedback amount e. The dead time error detection unit 10 analyzes the control amount y stored in the control amount storage unit 9, and when the dead time of the internal model has a model identification error, a correction signal is output. The dead time corrected by the correction signal is output from the dead time correction processing unit 11 to the internal model storage unit 6a, and the dead time of the internal model is corrected.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an IMC (Internal Model)
The present invention relates to a controller using a control algorithm having a control structure, and particularly to a controller capable of correcting an identification error of an internal model.

[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. 6 is a block diagram of a control system using this IMC controller. Reference numeral 33 denotes a first subtraction processing unit that subtracts a feedback amount, which will be described later, from a target value, 32 denotes a filter unit that prevents a change in the output of the first subtraction processing unit 33 from being transmitted abruptly, and 34 denotes a filter unit 32. An operation unit that calculates an operation amount based on the output of the control target, an internal model 36 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, and 38 from the control amount A second subtraction processing unit 40 that subtracts the reference control amount from the internal model 36 and outputs a feedback amount is a control target process. Further, F, Gc, Gm, and Gp are the filter unit 32, the operation unit 34, the internal model 36,
The transfer function of the control target process 40, 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 33 subtracts the feedback amount e from the target value r, and the result is output to the filter unit 32 for preventing a rapid change in the target value r from being transmitted. Next, the operation amount u is calculated by the operation unit 34 from the output of the filter unit 32, and is output to the control target process 40 and the internal model 36 of the controller. Then, the second subtraction processing unit 38 subtracts the reference control amount ym from the internal model 36 that approximates the control target process 40 from the control amount y of the control target process 40, and the result is the feedback amount e. A feedback control system that is fed back to the first subtraction processing unit 33 is configured as.

Ideally, the internal model 36 of such an IMC controller is mathematically expressed so as to be exactly the same as the controlled object process 40, and the operating section 34 is also used.
Is ideally the inverse characteristic (1 / Gm) of the transfer function of the internal model 36, but since the elements of the dead time in the internal model 36 cannot be reciprocal, normally the elements of the dead time are 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 36 is equal to the transfer function Gp of the control target process 40, and the transfer function Gc of the operating unit 34 is the reciprocal of the transfer function of the internal model 36 (1 / Gm =
Assuming an ideal state equal to 1 / Gp), equation (1) becomes y = F × r + (1-F) × d (2)

Furthermore, under ideal conditions where the target value r does not change suddenly, the filter unit 32 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, when focusing on the disturbance d in the control system of FIG. 6, even if the controlled object process 40 and the internal model 36 have a large dead time, both exhibit the same characteristics with respect to the manipulated variable u, so the second subtraction is performed. It can be seen that the feedback amount e that is the output of the processing unit 38 is only the disturbance d, and the disturbance d can be suppressed.

Such an IMC controller is usually
It is designed based on a design condition for robust stability indicating stability when the error between the controlled process 40 and the internal model 36 becomes large, and similarly robust performance indicating performance when the error becomes large. Further, when the internal model 36 is determined by such a model identification technique, a model identification error of the internal model 36 with respect to the control target process 40 is unavoidable to some extent, but the control when the estimation of the model identification error is erroneous is performed. Since it does not operate as expected, countermeasures in that case are performed by an expert having knowledge of control.

[0008]

Since the conventional IMC controller is configured as described above, if there is an error in the internal model identification and the estimation is inappropriate, the controller does not operate as expected, There has been a problem that an operator other than an expert having control knowledge has to give up the use of the IMC controller. Also, when this identification error occurs in the dead time or time constant of the internal model and it is corrected, there is no specific index for detecting the error in the dead time or time constant, and it is necessary to use trial and error. There was a point. In order to solve the above problems, it is an object of the present invention to provide a highly accurate IMC controller that does not need to be corrected even if there is an identification error in the dead time or time constant of the internal model.

[0009]

According to the present invention, there is provided a first subtraction processing unit for subtracting a feedback amount from a signal based on a target value, and an operation amount from an output of the first subtraction processing unit based on a parameter of an internal model. The operation amount calculation unit for calculating and the parameters of the internal model are stored, and when the dead time of the internal model in this parameter is input to the error-corrected dead time, it is updated to this error-corrected dead time. The model storage unit, the internal model output operation unit that calculates the reference control amount from the operation amount output from the operation amount operation unit based on the parameters of the internal model, and the internal model output operation unit based on the control amount of the controlled process A second subtraction processing unit that subtracts the reference control amount and outputs a feedback amount, a control amount storage unit that stores the control amount of the control target process, and a control amount storage unit Based on the stored control amount, the error detection unit that outputs a correction signal when there is an error in the dead time of the internal model with the process to be controlled, and the error correction when the correction signal is output from the error detection unit A correction processing unit that calculates the dead time and outputs it to the internal model storage unit. Also, instead of the dead time, the time constant is targeted.

[0010]

According to the present invention, the first subtraction processing unit subtracts the feedback amount from the signal based on the target value, and the operation amount calculation unit calculates the operation amount from the output of the first subtraction processing unit. And output to the controlled process and the internal model output operation unit. Next, 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. Is configured. Then, based on the control amount stored in the control amount storage unit, when the error detection unit has a model identification error with the process to be controlled in the dead time or time constant of the internal model, a correction signal is output, and then this correction signal is output. The dead time or time constant corrected by the error is output from the correction processing unit to the internal model storage unit by the output of the correction signal, so that the dead time or time constant of the internal model is corrected.

[0011]

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 unit for inputting a target value r set by an operator (not shown) to this controller, and 2 is a target value filter unit for outputting the target value r from the target value input unit 1 with a characteristic that the transfer function has a first-order lag. Reference numeral 3 is a first subtraction processing unit that subtracts the feedback amount e from the output of the target value filter unit 4, and 4 is an operation amount from the output of the first subtraction processing unit 3 based on a parameter from an internal model storage unit described later. A manipulated variable calculator 5 that calculates u is a signal output unit that outputs the manipulated variable u output from the manipulated variable calculator 4 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. Reference numeral 9 is a target value input unit 1 to which a target value r that is a step input is input and control is started. The control amount storage unit 10 stores the control amount y from the beginning, and the error amount that outputs the correction signal when the control amount y stored in the control amount storage unit 9 is analyzed to detect the error of the dead time of the internal model. A dead time error detection unit, which is a detection unit, 11 is a dead time error detection unit 1
When a correction signal is output from 0, the dead time correction processing unit is a correction processing unit that calculates a new dead time and corrects the dead time of the internal model stored in the internal model storage unit 6a.

In FIG. 2, reference numeral 4a indicates the inside of the manipulated variable calculating unit 4, and the transfer function of the output of the first subtraction processing unit 3 is 1
Target value / disturbance filter unit that outputs with the characteristics of the next delay, 4b
Is also inside the target value / disturbance filter unit 4a.
An operation unit for calculating the manipulated variable u from the output of F, an internal model 6 including an internal model storage unit 6a and an internal model output operation unit 6b, F1 a transfer function of the target value filter unit 2, and F2 a target value / disturbance filter unit. 4a is a transfer function. In addition,
FIG. 2 shows the IMC controller of FIG.
The control system including 0 and the disturbance d is rewritten as a control system except for the control amount storage unit 9, the dead time error detection unit 10, and the dead time correction processing unit 11.

Next, the operation of such an IMC controller will be described. The target value r is set by the operator or the like of this IMC controller, and is 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 characteristic of the transfer function F1 as shown in the following equation, the time constant of which is T1. F1 = 1 / (1 + T1 × s) (3) 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 with the characteristic of the transfer function F2 such that the time constant is T2. . F2 = 1 / (1 + T2 × s) (4) Similarly, the internal operation unit 4b 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 (5) Here, 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)} (6) 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 40 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 unit 6a as the parameters to control the process 40 to be controlled by the first-order delay and the dead time. 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) (7) Next, the second subtraction processing unit 8 receives the control target process 40 input via the control amount input unit 7. The reference control amount ym from the internal model output calculation unit 6b is subtracted from the control amount y from the above, and 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.

In such a control system, the internal model 6
When there is a model identification error that the dead time Lm is larger than the dead time of the controlled process 40, the control amount storage unit 9, the dead time error detection unit 10, and the dead time correction processing unit 11 perform the following algorithm. The dead time Lm of the internal model 6 can be corrected with. To explain this algorithm, FIG. 3 is a diagram showing the target value followability when there is a model identification error in the dead time Lm of the internal model 6 in the IMC controller of this embodiment,
The vertical axis represents the liquid level height (control amount y), and the horizontal axis represents time.

FIG. 3 shows a case where the IMC controller of this embodiment is used to control the height of the liquid level in the tank.
It is a simulation result in which a target value r (broken line) is input as a step input of 4 cm in liquid level in seconds, and a control amount y (solid line) which is the liquid level height of the control result is obtained. Here, the gain Km of the internal model 6 is 4.0, the dead time Lm is 50 seconds, the time constant Tm is 10 seconds, and the gain and time constant of the liquid 40 in the tank to be controlled 40 are the same as those of the internal model 6. The dead time of the controlled process 40 is set to 40 seconds assuming that the model identification error is 20%. Further, the time constant T of the target value filter unit 2
1. The time constant T2 of the target value / disturbance filter unit 4a is set to 15 seconds.

As shown in FIG. 3, when the dead time Lm of the internal model 6 is larger than the dead time of the controlled process 40, the control amount y changes in the opposite direction before it becomes equal to the target value r. At the time (90 to 100 seconds in FIG. 3,
160-180 seconds, around 230-250 seconds). That is, if the existence of such a change can be confirmed, it can be determined that there is a model identification error that the dead time Lm of the internal model 6 is larger than the dead time of the controlled process 40.

Therefore, the control amount storage unit 9 first stores the control amount y after the target value r, which is a step input, is input to the target value input unit 1 and the control is started for each sampling time of the control system. To do. Next, the dead time error detection unit 10
When it is determined that the target value r and the control amount y are equal and the control is settled, the control amount y stored in the control amount storage unit 9 before the settling as shown in FIG. Whether or not there is a change is determined by the following equation, and if there is such a change, a correction signal is output. dy × (r−y0) <0 (8) where dy is a change amount of one sampling of the control amount y, y
0 is the initial value of the controlled variable y (0 cm in FIG. 3). Figure 3
, The target value r is 4 cm, and the initial value y0 of the controlled variable y is 0.
In cm, if the determination of the equation (8) is repeated for each sampling, there is a time point at which the equation (8) is satisfied, that is, the change amount dy of the control amount y becomes negative, and therefore a correction signal is output.

Next, when the dead time error detection unit 10 outputs a correction signal, the dead time correction processing unit 11 stores the internal model 6 stored in the internal model storage unit 6a according to the following equation.
A new dead time Lm2 is calculated from the dead time Lm and output to the internal model storage unit 6a. Lm2 = A × Lm (9) Here, A is a constant, and in this embodiment, for example, 0.
95. Therefore, the dead time Lm of the internal model 6 stored in the internal model storage unit 6a is updated to this Lm2 and is smaller than the present time (0.95 × 50 = 47.5 seconds).
Will be corrected to.

When the above-described control is performed again and the dead time error detection section 10 makes a determination, the dead time Lm of the internal model 6 is still the controlled process 40.
Since it is greater than, the above modification is repeated. When such correction is repeated four times, the error of the dead time Lm of the internal model 6 is about 40.7 seconds, which is small, and the above-mentioned change in the control amount y is no longer recognized. Complete. Therefore, the identification error of the dead time Lm of the internal model 6 can be corrected without relying on an expert having control knowledge. In the present embodiment, such correction of the dead time Lm of the internal model 6 is performed by the IMC having the configuration as shown in FIG. 1 except for the control amount storage unit 9, the dead time error detection unit 10, and the dead time correction processing unit 11. Although it is applied to the controller, it can be applied to a controller having another IMC structure.

The control system by the IMC controller of this embodiment is similar to 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. Therefore, the control amount y is given by the following expression from Expression (1). 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 IMC controller has a transfer function F2 having a first-order delay characteristic with respect to the disturbance d, and a transfer function F1 × F2 having a second-order delay characteristic with respect to the target value r.

In the example of FIG. 1, the case where the model identification error occurs in the dead time of the internal model has been described. However, the model identification error may occur in the time constant of the internal model. In this case, the present invention is also applied. Can be applied. FIG. 4 is a block diagram of an IMC controller showing another embodiment of the present invention, and the same parts as those in FIG. 1 are designated by the same reference numerals. Two
Reference numeral 0 denotes a time constant error detection unit which is an error detection unit that outputs a correction signal when the control amount y stored in the control amount storage unit 9 is analyzed and an error of the time constant Tm of the internal model 6 is detected.
When the correction signal is output from the time constant error detection unit 20,
The time constant correction processing unit is a correction processing unit that calculates a new time constant and corrects the time constant Tm of the internal model 6 stored in the internal model storage unit 6a.

Next, the operation of such an IMC controller will be described. The IMC structure is exactly the same as the example of FIG.
Therefore, the operation of the control system is exactly the same. Therefore, the simulation result of the target value tracking is obtained as in the case of FIG. FIG. 5 is a diagram showing the target value followability when the time constant Tm of the internal model 6 has a model identification error in the IMC controller of the present embodiment. In FIG. 5, the internal model 6
The dead time Lm and the dead time of the controlled process 40 are 50 seconds, the time constant Tm of the internal model 6 is 10 seconds,
The time constant of the controlled process 40 is set to 5 seconds assuming that a model identification error of 50% exists. The other parameters are the same as in the example of FIG.

Similar to FIG. 3, in FIG. 5 as well, when the time constant Tm of the internal model 6 is larger than the time constant of the controlled process 40, the change in the controlled variable y is reversed (at 110 in FIG. 5). (Around 120 seconds) is present. Therefore, the time constant Tm of the internal model 6 can be corrected by the same algorithm as in the example of FIG.

That is, when the time constant error detection unit 20 determines that the target value r and the control amount y are equal and the control is settled, it is stored in the control amount storage unit 9 before the settling as shown in FIG. The control amount y is analyzed to determine whether or not there is such a change by the formula (8), and if there is such a change, a correction signal is output. Next, the time constant correction processing unit 2
When the correction signal is output from the time constant error detection unit 20, 1 is a new time constant Tm2 calculated from the time constant Tm of the internal model 6 stored in the internal model storage unit 6a as shown in the following equation. It is output to the model storage unit 6a. Tm2 = B × Tm (11) Here, B is a constant, and in this embodiment, for example, 0.
Set to 9.

That is, as in the example of FIG. 1, the internal model 6
When the correction of the time constant Tm of 6 is repeated 6 times, the above-mentioned change of the control amount y is not recognized and the correction of the time constant Tm is completed. Therefore, the identification error of the time constant Tm of the internal model 6 can be corrected without relying on an expert having control knowledge. Further, this embodiment can be applied to a controller having another IMC structure as in the example of FIG.

[0031]

According to the present invention, by providing the control amount storage unit, the error detection unit, and the correction processing unit, even if there is a model identification error in the dead time or time constant of the internal model, this model identification error Since the IMC controller is detected and corrected, an IMC controller with high accuracy and reliability can be realized, and even an operator who does not have knowledge of control can perform control by making use of the advantages of the IMC 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 when there is a model identification error in the dead time of the internal model in the IMC controller of FIG.

FIG. 4 is a block diagram of an IMC controller showing another embodiment of the present invention.

FIG. 5 is a diagram showing target value followability when there is a model identification error in a time constant of an internal model in the IMC controller of FIG.

FIG. 6 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 Manipulation amount calculation unit 6a Internal model storage unit 6b Internal model output calculation unit 8 Second subtraction processing unit 9 Control amount storage unit 10 Dead time error detection unit 11 Dead time correction Processing unit 20 Time constant error detection unit 21 Time constant correction processing unit Lm Time delay of internal model Tm Time constant of internal model r Target value u Manipulation amount y Control amount ym Reference control amount

Claims (2)

[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 first subtraction processing unit that subtracts a feedback amount from a signal based on a target value, and an operation amount calculation unit that calculates an operation amount from an output of the first subtraction processing unit based on a parameter of an internal model. An internal model storage unit that stores the parameters of the internal model and updates the dead time of the internal model in the parameters to the error-corrected dead time when the error-corrected dead time is input; An internal model output operation unit that calculates a reference control amount from the operation amount output from the operation amount operation unit based on a model parameter, and a reference control output from the internal model output operation unit based on the control amount of the control target process. A second subtraction processing unit that subtracts the amount and outputs the feedback amount; and a control amount record that stores the control amount of the control target process. And an error detection unit that outputs a correction signal when there is an error between the control target process and the dead time of the internal model based on the control amount stored in the control amount storage unit, and corrects from the error detection unit. And a correction processing unit for calculating the error-corrected dead time and outputting it to the internal model storage unit when a signal is output.
C controller. 2. A reference control amount corresponding to the control amount of the control target process, which is a control result, is calculated by calculating an operation amount to be output to the 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 first subtraction processing unit that subtracts a feedback amount from a signal based on a target value, and an operation amount calculation unit that calculates an operation amount from an output of the first subtraction processing unit based on a parameter of an internal model. An internal model storage unit that stores a parameter of the internal model and updates the time constant of the internal model in the parameter to the error-corrected time constant when an error-corrected time constant is input; An internal model output operation unit that calculates a reference control amount from the operation amount output from the operation amount operation unit based on a model parameter, and a reference control output from the internal model output operation unit based on the control amount of the control target process. A second subtraction processing unit that subtracts an amount and outputs the feedback amount; and a control amount storage unit that stores the control amount of the control target process. An error detection unit that outputs a correction signal when the time constant of the internal model has an error with the control target process based on the control amount stored in the control amount storage unit; and a correction signal is output from the error detection unit. IMC, a correction processing unit that calculates the error-corrected time constant and outputs the calculated time constant to the internal model storage unit.
controller.