JPH0749703A - Controller - Google Patents

Abstract

PURPOSE:To provide a controller having IMC construction and capable of correcting the gain of an internal model and stabilizing control even if an error is included in the identification of the internal model. CONSTITUTION:An objective value (r) is inputted to an objective value filtering part 2 and the 1st subtracting processing part 3 subtracts a feedback value (e) from the output of the filtering part 2. A manipulated variable operation part 4 operates a manipulated variable (u) based upon the subtracted value and outputs the variable (u) to a process and an internal model output operation part 6b. The 2nd subtracting processing part 8 subtracts a reference controlled variable (ym) from a controlled variable (y) to find out the feedback value (e). A step width calculating part 9 calculates the step width of the controlled variable (y) and the reference controlled variable (ym). A response start area detecting part 10 detects the response start areas of those variables (y), (ym) based upon the step width. A model gain calculating part 11 calculates correction gain from the variation of those variables (y), (ym) and outputs the correction gain to an internal model storing part 6a to correct the gain of the internal model.

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 destabilization of control due to an identification error of an internal model.

[0002]

2. Description of the Related Art Conventionally, there has been proposed a controller using an IMC structure control algorithm for performing control by incorporating an internal model in which a control target process is expressed by a mathematical expression.
If this IMC controller is used, a large dead time (time from when hot air comes out of the air conditioner to when the indoor temperature rises) in the process to be controlled (e.g., if this controller is an indoor air conditioner corresponds to the indoor environment) It has an excellent advantage that it can be dealt with even if it exists.

FIG. 14 is a block diagram of a control system using a conventional 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 (indoor temperature setting value), and 32 denotes a filter unit that prevents a change in the output of the first subtraction processing unit 33 from being rapidly transmitted. ,
Reference numeral 34 is an operation unit for calculating an operation amount (temperature of hot air or cold air coming out of the indoor air conditioner) which is the output of the controller based on the output of the filter unit 32, and 36 is a mathematical expression approximating the control target process. And a second subtraction process for outputting a feedback amount by subtracting the reference control amount from the internal model 36 from the control amount, and outputting a reference control amount corresponding to the control amount (indoor temperature) as a control result. Part 40 is a process to be controlled.

Further, F, Gc, Gm, and Gp are the transfer function of the filter unit 32, the operating unit 34, the internal model 36, and the process 40 to be controlled, r is the target value, u is the manipulated variable, and d is the d.
Is, for example, a disturbance corresponding to the outdoor environment with respect to the 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. 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 control target process 40, and the operating unit 34 is also used.
Is ideally the inverse characteristic (1 / Gm) of the transfer function of the internal model 36, but the inverse of the dead time element of the internal model 36 is not possible, so normally the dead time element is 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 section 34 is the reciprocal of the transfer function of the internal model 36 (1 / Gm = 1 / Gp). Assuming an ideal state equal to, 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 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. Focusing on the disturbance d, the controlled process 4
0 and the internal model 36 have the same dead time with respect to the manipulated variable u even if there is a large dead time, the feedback amount e output from the second subtraction processing unit 38 is equal to the disturbance d.
It is understood that the disturbance d can be suppressed.

Such an IMC controller is usually
Robust stability showing stability when the model identification error between the controlled object process 40 and the internal model 36 becomes large,
And similarly, the design is performed based on the design condition for the robust performance indicating the performance when the error becomes large. In addition, the internal model 36
When determining, the model identification error of the internal model 36 with respect to the control target process 40 is unavoidable to some extent, but control is not performed as expected when the estimation of the model identification error is incorrect. Is done by experts with control knowledge.

[0010]

Since the conventional IMC controller is configured as described above, if there is an error in the internal model identification and the estimation is improper, the controller does not operate as expected and fails. There is a problem in that the operator becomes stable and an operator other than an expert having control knowledge has to give up the use of the IMC controller. In addition, it is particularly effective to correct the gain of the internal model when there is an error in the identification of the internal model, but there is no specific index for correcting the gain and there is the problem that trial and error must be used. It was In order to solve the above problems, the present invention provides a controller having an IMC structure capable of automatically correcting the gain of the internal model to stabilize the control even when the internal model identification includes an error. With the goal.

[0011]

According to the present invention, there is provided a target value filter section for outputting an input target value for control with a characteristic of a time delay of a transfer function, and subtracting a feedback amount from the output of the target value filter section. 1 subtraction processing unit, a target value / disturbance filter unit that outputs the output of the first subtraction processing unit with a time delay characteristic of the transfer function, and an output of the target value / disturbance filter unit based on the parameters of the internal model. When the internal model parameters are stored and the internal model parameters are stored and the internal model parameters are stored, the internal model gain in the parameters is set to this modified gain. An internal model storage unit to be updated, an internal model output calculation unit that calculates a reference control amount from an operation amount based on the parameters of the internal model, and an internal model from the control amount of the control target process A second subtraction processing unit that subtracts the reference control amount output from the force calculation unit and outputs a feedback amount, and an initial value and settling of the control amount and the reference control amount based on the target value, the control amount, and the reference control amount. A step width calculation unit that calculates a step width that is a difference from the value, and a response start area in which the control amount and the reference control amount start to change based on the step widths of the control amount and the reference control amount is detected, and the response start region is detected. Response start area detection unit that outputs the control amount and the reference control amount, and the model gain calculation that calculates the correction gain of the internal model from the control amount based on the response start region and the reference control amount and the change amount of the reference control amount And a part.

Further, when the correction gain output from the model gain calculation unit is out of the predetermined range, the model gain limiter unit is arranged to change the correction gain so as to be within the predetermined range and output the change to the internal model storage unit. I have.

Further, when the change amount of the operation amount output from the operation amount calculation unit exceeds a predetermined upper limit value, the operation amount limiter unit for suppressing this change amount by the predetermined upper limit value is provided.

Further, instead of the model gain calculation unit, a safety factor is multiplied when calculating the modified gain of the internal model from the control amount based on the control amount in the response start region and the reference control amount and the change amount of the reference control amount. It has a non-linear correspondence model gain calculation unit that calculates this modified gain.

[0015]

According to the present invention, the target value is input to the target value filter unit, the feedback amount is subtracted from the output of the target value filter unit in the first subtraction processing unit, and the operation amount calculation unit outputs the first feedback value. The operation amount is calculated from the output of the subtraction processing unit and output to the control target process and the internal model output calculation 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 output as the feedback amount to the first subtraction processing unit. Is configured. Then, the step width calculation unit calculates the step width of the control amount and the reference control amount, and the response start area detection unit detects the response start area of the control amount and the reference control amount based on the step width, and calculates the model gain. The gain of the internal model is corrected by calculating the correction gain of the internal model from the control amount of the response start region and the change amount of the reference control amount and outputting the correction gain to the internal model storage unit.

Further, the correction gain output from the model gain calculation unit is suppressed by the model gain limiter unit so as to fall within a predetermined range. Further, the change amount of the operation amount output from the operation amount calculation unit is suppressed by the operation amount limiter unit so as not to exceed a predetermined upper limit value. The correction gain is calculated by multiplying the safety factor when the correction gain of the internal model is calculated from the change amount of the control amount in the response start region and the change amount of the reference control amount by the non-linear corresponding model gain calculation unit.

[0017]

1 is a block diagram of an IMC structure controller showing an embodiment of the present invention, and FIG. 2 is a block diagram of a control system using the IMC structure controller. Figure 1
1 is a target value input section for inputting a target value r set by an operator (not shown) to this controller, and 2 is a transfer function for the target value r from the target value input section 1.
The target value filter unit 3 that outputs with the characteristic of the next delay 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 a first subtraction processing unit based on a parameter from an internal model storage unit that will be described later. The operation amount calculation unit 5 for calculating the operation amount u from the output of the subtraction processing unit 3 of 1 is an operation amount calculation unit 4
This is a signal output unit for outputting the manipulated variable u output from the control target process 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 the controller, and 6b is an operation as an internal model based on the parameters output from the internal model storage unit 6a and outputs a reference control amount ym. An internal model output operation unit, 7 is a control amount input unit for inputting a control amount y from a control target process to this controller, and 8 is an internal model output operation unit 6b based on the control amount y output from the control amount input unit 7. Output reference control amount ym
The second subtraction processing unit 9 which subtracts from the output value e to output the feedback amount e. The control value y and the reference control amount ym are based on the target value r, the control amount y, and the reference control amount ym. It is a step width calculation unit that calculates a step width that is a difference up to a settling value.

Numeral 10 is a response start area detector,
Based on the step widths of the controlled variable y and the reference controlled variable ym, the manipulated variable computing unit 4 outputs the manipulated variable u in response to the respective response start regions, that is, the input of the target value r. A region where the amount ym starts to change from the initial value is detected. Reference numeral 11 denotes a modified gain of the internal model based on the control amount y and the reference control amount ym of the response start region output from the response start region detection unit 10 to obtain the gain of the internal model stored in the internal model storage unit 6a. It is a model gain calculation unit for correction.

In FIG. 2, reference numeral 4a is inside 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. Also,
du is a manipulated variable disturbance, and can be treated as equivalent to the controlled variable disturbance d by setting the disturbance d = Gp × du.

FIG. 2 shows the target value filter unit 2 of FIG.
The basic configuration of the controller of this IMC structure including the first subtraction processing unit 3, the manipulated variable calculation unit 4, the internal model storage unit 6a, the internal model output calculation unit 6b, and the second subtraction processing unit 8 has a control target process. 40, the disturbance d, and the manipulated variable disturbance du are rewritten as a control system.

Next, the operation of the basic structure of such a controller will be described. The target value r is set by the operator of this controller or the like, 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)

The time constant T1 is the dead time L of the internal model 6 which will be described later, excluding the preset initial value.
With the change of m, it is set as the following equation. T1 = 4 × α × Lm (4) Here, α is a proportional constant, for example, α = 0.3.

Next, the first subtraction processing unit 3 subtracts the feedback amount e output from the second subtraction processing unit 8 from the output of the target value filter unit 2. The target value / disturbance filter unit 4a in the manipulated variable calculation unit 4 includes the first subtraction processing unit 3
Of the transfer function F2 with the time constant T2. F2 = 1 / (1 + T2 × s) (5)

The time constant T2 is also set by the target value filter unit 2
Similar to the time constant T1 of (1), it is changed as shown in the following equation with the change of the dead time Lm excluding the initial value. T2 = α × Lm (6) That is, the time constant T1 is set to four times the time constant T2 as a standard setting.

Similarly, the operation unit 4 in the operation amount calculation unit 4
b is the manipulated variable u from the output of the target value / disturbance filter unit 4a.
Of the internal model storage unit 6
The following expression is obtained by the gain and time constant of the internal model 6 output from a, and 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 40 via 5 and is also output to the internal model output calculation unit 6b.

Next, the control target process 40 assumes that the transfer function Gp has the elements of the first-order delay and the dead time.
Can be expressed by the approximate transfer function as follows. Gp = Kp × exp (−Lp × s) / (1 + Tp × s) (9) where Kp, Lp, and Tp are the gain, dead time, and time constant of the controlled process 40, respectively.

The internal model 6 is a mathematical expression of the control target process 40 as described above by these parameters including the gain Km, the time constant Tm, and the dead time Lm stored in the internal model storage unit 6a. Then, the internal model output operation unit 6b calculates the reference control amount ym from the operation amount u output from the operation amount operation unit 4. The transfer function Gm is given by the following equation. Gm = Km × exp (−Lm × s) / (1 + Tm × s) (10)

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 controlled object process 40 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, which is the basic configuration of the controller with this IMC structure.

In such a control system, the step size calculator 9, the response start area detector 10, and the model gain calculator 11 are as follows in the first half of the response to the input target value r. Correct the gain Km of.
FIG. 3A is a diagram showing the target value followability of the control amount y for explaining the operation of the step width calculation unit 9, and FIG. 3B is a diagram showing the target value followability of the reference control amount ym. is there.

Y0 is an initial value of the control amount y, ym0 is an initial value of the reference control amount ym, rm is a set value of the reference control amount ym corresponding to the target value r, and ST is a target value r and an initial value of the control amount y. The step width STm, which is the difference from y0, is the step width that is the difference between the settling value rm and the initial value ym0 in the reference control amount ym.

In FIG. 3A, at time 0 (initial state), the target value r, which is a step input, is input, and the operation amount u is output from the controller to the controlled process 40. As a result, the control amount y is initialized to y0. It is shown that the state changes from and finally matches the target value r and shifts to the settling state.
Further, FIG. 3B also shows a state in which the reference control amount ym output from the internal model output operation unit 6b is similarly settled to the settling value rm.

Then, the step width calculation unit 9 calculates the step width ST of such a control amount y as in the following equation. ST = | r−y0 | (11) Similarly, the step width STm of the reference control amount ym is calculated by the following equation. STm = | rm-ym0 | (12)

Here, the control amount y of the controlled process 40 and the reference control amount ym output from the internal model 6 can be obtained from the target value r and the disturbance d by the following equation. y = F1 * F2 * Gp * Gc * r / {1 + F2 * Gc * (Gp-Gm)} + (1-F2 * Gm * Gc) * d / {1 + F2 * Gc * (Gp-Gm)} ... (13) ym = F1 * F2 * Gm * Gc * r / {1 + F2 * Gc * (Gm-Gp)} + (-F2 * Gm * Gc) * d / {1 + F2 * Gc * (Gm-Gp)}.・ ・ (14)

Then, assuming that the initial value of the gain Km of the internal model 6 is Km0, the initial value ym0 of the reference control amount ym is given by the following equations (13) and (14). ym0 = (y0-d) × Km0 / Kp (15) From the equation (15), if the disturbance d = 0, the control amount initial value y0
And the reference control amount initial value ym0 match the ratio between the gain Kp (here, the estimated value) of the controlled process 40 and the initial gain value Km0 of the internal model 6 as in the following equation. Kp / Km0 = y0 / ym0 (y0 ≠ 0, ym0 ≠ 0) (16)

Therefore, the gain K of the controlled process 40
p can be estimated as in the following equation. Kp = Km0 × y0 / ym0 (17) Further, similarly, the set value r of the target value r and the reference control amount ym is similarly set.
The ratio with m matches the ratio between the gain Kp and the initial gain value Km0. Kp / Km0 = r / rm (18)

Therefore, the equation (12) is expressed by the equations (16)-
From (18), it can be transformed into the following equation. STm = | rm-ym0 | = | r × Km0 / Kp-y0 × Km0 / Kp | = | r-y0 | × Km0 / Kp = | (r × ym0 / y0) -ym0 | (19) Thus The step width calculation unit 9 calculates the step width ST of the control amount y and the step width STm of the reference control amount ym from the formula (1
1) and (19), and outputs them to the response start area detection unit 10.

Next, the response start area detector 10 determines the control amount y and the reference control amount y based on the step widths ST and STm.
A response start region of m, that is, a region in which the control amount y and the reference control amount ym start to change from the initial values y0 and ym0, respectively, by outputting the manipulation amount u from the manipulation amount calculation unit 4 in response to the input of the target value r To detect.

FIG. 4A is a diagram showing the response start area of the control amount y for explaining the operation of the response start area detecting section 10,
FIG. 4B is also a diagram showing a response start region of the reference control amount ym, where y1 and y2 are control amounts at the start time and end time of the response start region, and ym1 and ym2 are at the start time and end time. It is a reference control amount. Further, each number of 1, 2, ... Ny, Ny + 1 ... N, n + 1 is a sampling time point of this control system, and the start time point of the response start area is 1. FIGS. 4A and 4B correspond to enlarged views of the change start portion in FIGS. 3A and 3B, respectively.

First, the response start area detector 10 sets the sampling time point detected by the following equation as the start time point of the response start area of the controlled variable y. | Y−y0 |> β × ST (20) Here, β is a proportional constant, for example, β = 0.05. That is, at the start time of the response start region of the controlled variable y, the difference between the current controlled variable y and the initial value y0 exceeds this threshold with β × ST as the threshold as shown in FIG. 4A. This is the first sampling point. Thus, the control amount y at the start
1 is required.

Then, the start time of the response start area of the reference control amount ym is similarly detected. | Ym−ym0 |> β × STm (21) That is, at the start time of the response start region of the reference control amount ym, the current reference control is performed with β × STm as a threshold as shown in FIG. 4B. It is the first sampling time when the difference between the quantity ym and its initial value ym0 exceeds this threshold. In this way, the reference control amount ym1 at the start point is obtained.

Next, the end time point of the response start area of the controlled variable y is n sampling points after the start time point of the response start area of the controlled variable y (for example, n = 9), or the first sampling satisfying the following equation. Whichever of the time points is detected first. | Y−y0 |> δ × ST (22) Here, δ is a proportional constant, for example, δ = 0.20. Then, when the sampling time point by the equation (22) is set as the end time point, the number of samplings from the start time point to the end time point is set as Ny.

That is, in the present embodiment, the end point of the response start area of the controlled variable y is the point after 9 samplings (see FIG. 4).
(N + 1 time point in (a)), or the earlier of the first sampling time points (Ny + 1 time point in FIG. 4A) when the difference between the current control amount y and its initial value y0 exceeds 20% of the step width ST. Therefore, in FIG. 4A, the point Ny + 1 is set as the end point of the response start area. In this way, the control amount y2 at the end point is obtained.

The end point of the response start area of the reference control amount ym is n sampling points after the start point of the response start area of the reference control amount ym, or the same start point by the sampling number Ny obtained above. To the time after Ny sampling, whichever is earlier. In this way, the reference control amount ym2 at the end point is obtained.

Therefore, the number of samplings from the start point to the end point of the response start area of the control amount y and the reference control amount ym.
The number of samplings from the start time point to the end time point of the response start area is matched. Also, as described above, the detection of the end point is the earlier of the two points,
This is because if only the fixed sampling number n is detected, the control amount y may approach the settling state earlier and the correction of the gain Km described later may not be in time.

The response start area detecting unit 10 outputs the control amounts y1 and y2 and the reference control amounts ym1 and ym2 in the response start area thus detected to the model gain calculating unit 11. Next, the model gain calculation unit 11 calculates the correction gain Km1 of the internal model 6 from these values output from the response start area detection unit 10 according to the following equation. Km1 = Km0 × (y2-y1) / (ym2-ym1) (23)

The corrected gain Km1 is output to the internal model storage unit 6a, so that the gain initial value Km0 stored in the internal model storage unit 6a is updated to the corrected gain Km1. Such gain Km (K
The correction of m0) is performed once when the response start region ends for both the control amount y and the reference control amount ym. Therefore, the correction of the gain Km by the step size calculator 9, the response start area detector 10, and the model gain calculator 11 is performed in the first half of the response to the input of the target value r.

Here, the reason why the gain Km of the internal model 6 is modified as described above is as follows. The target value r, which is a step input, is input to the operation unit 4b through a transfer function filter unit having a delay of about 1st to 2nd order (in the embodiment, the target value filter unit 2 and the target value / disturbance filter unit 4a cause a 2nd order delay) In this case, the first half, which is the response to the input high frequency included in the target value r, is the most unstable state in the overall response.

Therefore, in the IMC controller, it is important for its stability that the error between the internal model 6 and the controlled process 40 is small in the first half of the response including the response start region. Therefore, the gain Km of the internal model 6 is corrected so that the rate of change of the control amount y of the controlled object process 40 and the rate of change of the reference control amount ym of the internal model 6 in the first half of the response are close to each other as shown in equation (23). . Then, the effect of the gain Km can be sufficiently obtained if the correction of the gain Km is performed in the first half of the response according to the detection result of the response start area.

By the correction of the gain Km, the rate of change of the control amount y and the reference control amount ym may not match from the latter half of the response to the final settling, but in the latter half of the response approaching the settling state. Target value r to the operation unit 4b
Since the input of is at a sufficiently low frequency compared to the first half of the response, it has little effect on the stability of control. Therefore, the gain Km of the internal model 6 is corrected only once. Therefore, a stable response can be obtained even when the model identification of the controlled process 40 includes an error.

FIG. 5 is a diagram showing the target value followability when the controller of the present embodiment is used for controlling the height of the liquid level in the tank, and FIG. 6 is a diagram similarly showing the target value followability of the PID controller. FIG. 7 is a diagram showing the target value followability of the conventional IMC controller. In FIGS. 5 to 7, the target value r (dashed line) is input as a step input of 4 cm in liquid level at 0 seconds, and the control amount y (solid line), which is the liquid level height as a result of the control, is obtained. It is a simulation result. The conventional IMC controller used here is the controller of this embodiment in which the gain Km of the internal model 6 is not corrected.

Here, the gain Kp of the controlled object process 40, which is the liquid in the tank, is 18, the time constant Tp is 6 seconds, and the dead time Lp is 10 seconds, and the gain of this embodiment and the internal model 6 of the conventional IMC controller is set. Km = 12, time constant T
It is assumed that m is 12 seconds, dead time Lm is 10 seconds, and model parameters for adjusting the PID controller are the same as those of the internal model 6. Therefore, there is a model identification error in the gain Km and the time constant Tm. Further, the time constant T1 of the target value filter unit 2 of this embodiment and the conventional IMC controller is 24 seconds, and the time constant T2 of the target value / disturbance filter unit 4a is 6 seconds.

Then, the response start area detecting section 1 of this embodiment
The end time of the response start area detected by 0 is n from the start time.
It is the time after sampling. Further, the gain of the PID controller is 0.06, the integration time is 12 seconds, the differentiation time is 5 seconds, and the sampling cycle of all the controllers is 1 second. As is clear from the comparison of FIGS. 5 to 7, it can be seen that the controller of the present embodiment can obtain a stable response compared to the PID controller and the conventional IMC controller even when the model identification includes an error.

FIG. 8 is a block diagram of a controller having an IMC structure showing another embodiment of the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals. When the correction gain Km1 output from the model gain calculation unit 11 is smaller than a minimum value within a predetermined range, the correction gain Km1 is changed so as to fall within the predetermined range, and the internal model storage unit 6 is provided.
It is a model gain limiter unit for outputting to a.

The configuration of the controller of this embodiment is exactly the same as the example of FIG. 1 except for the model gain limiter section 12. The basic operation is exactly the same as in the example of FIG. 1, and the correction gain Km1 of the internal model 6 is calculated by the model gain calculation unit 11 in the first half of the control response. However, the correction gain Km1 in the example of FIG. 1 may be calculated to be an excessively small value, and in such a case, control safety is impaired.

Therefore, the model gain limiter section 12
Modified gain Km output from the model gain calculation unit 11
When 1 is smaller than the minimum value as in the following equation, it is judged that the safety limit has been exceeded, and the correction gain K is set so that it falls within the limit.
Limit m1. Km1 <R × Km0 (24) Here, R is a proportional constant, for example, R = 0.1.

That is, the corrected gain Km1 is the initial gain value K of the internal model 6 stored in the internal model storage unit 6a.
If it is less than 10% of m0, it is judged to be out of the limit. Then, at this time, the correction gain Km1 is set to Km1 = R
× Km0, and the correction gain Km contained within this limit
1 is output to the internal model storage unit 6a.

Therefore, the modified gain K shown in the example of FIG.
Even if the correction gain Km1 that is too small is calculated when m1 is calculated, the safety can be ensured. Although only the lower limit is set as the predetermined range for the correction gain Km1 in the present embodiment, if the upper limit limiter is provided in addition to the lower limit in consideration of the fluctuation of the controlled process 40, safer control can be performed. .

In the example of FIGS. 1 and 8, the gain Km of the internal model 6 is corrected in the first half of the response. At this time, however, the control transition becomes discontinuous due to the sudden change of the gain Km.
If the correction amount of the gain Km is large, an excessive change occurs in the operation amount u. At this time, if an excessively large operation amount u of this change amount is output to a control device, for example, a valve when controlling the liquid level, the valve may be damaged. Therefore, a limiter that limits the amount of change in the manipulated variable u is required.

FIG. 9 is a block diagram of a controller having an IMC structure showing another embodiment of the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals. 13 is a manipulated variable calculation unit 4
When the variation amount of the manipulated variable u output from exceeds a predetermined upper limit value, the variation amount is suppressed to be smaller than the predetermined upper limit value, and the manipulated variable u is suppressed to the signal output unit 5 and the internal model output calculation unit 6b. It is a manipulated variable limiter unit for outputting to. The configuration of the controller of this embodiment is exactly the same as the example of FIG. 1 except for the operation amount limiter unit 13.

The basic operation is the same as in the example of FIG. 1, but the operation amount limiter unit 13 first changes the amount Δu of the operation amount u, which is a predetermined upper limit value, during one sampling as shown in the following equation. The upper limit value ΔUL of is calculated. ΔUL = ε × ΔU1 × T2 ² (25)

Here, ε is a proportional constant, and for example, ε = 0.05 when the sampling period is 1 second. Further, ΔU1 is the difference between the initial manipulated variable u and the initial value of the manipulated variable u, which is the response to the target value r input to this controller, that is, the initial change amount of the manipulated variable u, and T2 is the above-mentioned target value. It is a time constant of the disturbance filter unit 4a.

Next, the operation amount limiter unit 13 checks the change amount Δu of the operation amount u during the control operation, and Δu> ΔUL.
In this case, the change amount Δu is set to Δu = ΔUL, and Δu <−ΔU
When L, Δu = -ΔUL. Then, the manipulated variable u obtained as a result of suppressing the change amount Δu in this way is output to the signal output unit 5 and the internal model output calculation unit 6b. Therefore, it is possible to avoid destruction of the control device and waste of energy due to an excessive change in the operation amount u.

As described above, the amount of change Δu is suppressed based on the first amount of change ΔU1 so that the manipulated variable u is different from the target value filter unit 2 and the target value r as shown in FIG. The value / disturbance filter unit 4a is used for 2
This is because it has the characteristic of the next delay, and as a result, the first change in the manipulated variable u is within an appropriate amount for setting the upper limit value when viewed from the control device.

FIG. 10 is a diagram showing the target value followability when the controller of this embodiment is used for controlling the height of the liquid level in the tank, as in the example of FIG. 5, and FIG. 11 is a diagram of the example of FIG. It is a figure which shows the target value followability of a controller. Here, the gain Kp of the controlled process 40 is 8, the time constant Tp is 20 seconds,
The dead time Lp is 10 seconds, the gain Km of the internal model 6 of the controller of this embodiment and FIG. 1 is 20, the time constant Tm is 8 seconds, and the dead time Lm is 10 seconds. Therefore, the gain K
There is a model identification error in m and the time constant Tm.

The other parameters are shown in FIG.
The same as the example above. Although a steep change in the manipulated variable u due to the correction of the gain Km is recognized in FIG. 11, it can be seen in FIG. 10 that the change is suppressed.

In the example of FIGS. 1, 8 and 9, the control target process 4
When the gain Kp of 0 changes greatly during the response,
That is, if the gain Kp has nonlinearity that changes according to the control amount y or time-varying that changes according to time, the control may become unstable. This is because the correction of the gain Km of the internal model 6 is performed by detecting the response start region in the first half of the response, and therefore the change in the response start region and the consistency of the characteristics of the controlled process 40 in the latter half of the response. This is because the effect of correcting the gain Km cannot be maintained if the value is bad.

Therefore, by providing a non-linear corresponding model gain calculating section corresponding to the non-linear controlled object process 40 in place of the model gain calculating section 11 of FIG. 1, it is possible to stabilize the control. The configuration of the controller in the present embodiment is exactly the same as the example of FIG. 1 except for the non-linear corresponding model gain calculating unit instead of the model gain calculating unit 11, so this is referred to as the non-linear corresponding model gain calculating unit 11a, and the other reference numerals are the same as in FIG. The same reference numerals are used to describe the operation.

This non-linear correspondence model gain calculation section 11a
Is the same as in the example of FIG. 1, the correction gain Km1 of the internal model 6 is calculated from the control amounts y1 and y2 and the reference control amounts ym1 and ym2 in the response start area output from the response start area detecting unit as calculate. Km1 = ρ × Km0 × (y2-y1) / (ym2-ym1) (26) Here, ρ is a safety factor, for example, ρ = 2.0.

The corrected gain Km1 is output to the internal model storage section 6a, and the subsequent operation is exactly the same as in the example of FIG. Therefore, by using the safety factor ρ that secures the safety of the controller, a gain correction with a margin for the variation of the gain Kp of the control target process 40 in the latter half of the response is executed, and the nonlinear control target process 40 is corrected. However, good control can be performed.

At this time, when the gain Kp of the process 40 to be controlled does not change or decreases with the passage of time, it may have an adverse effect. However, in practice, when the safety factor ρ = 2.0. In addition, the deterioration of the control characteristic due to the above-described adverse effect does not appear so significantly. Therefore, even when it is considered that the controlled process 40 is almost linear and the fluctuation of the gain Kp is small, ρ =
There is no problem even if a safety factor ρ of about 1.5 to 2.0 is used.

FIG. 12 is a diagram showing the target value followability when the controller of this embodiment is used for controlling the height of the liquid level in the tank as in the example of FIG. 5, and FIG. 13 is a diagram of the example of FIG. It is a figure which shows the target value followability of a controller. Here, the gain Kp of the control target process 40 is Kp = 0.8 × y + 6.
4, that is, it changes in association with the control amount y.

Further, the time constant Tp of the controlled process 40
Is 20 seconds and the dead time Lp is 10 seconds.
The gain Km of the internal model 6 of the controller is set to 20, the time constant Tm is set to 8 seconds, and the dead time Lm is set to 10 seconds. Also,
Other parameters are the same as in the example of FIG.
As is clear from the comparison between FIGS. 12 and 13, it can be seen that the controller of the present embodiment can obtain better characteristics than the controller of FIG.

[0075]

According to the present invention, by providing the step width calculating section, the response start area detecting section, and the model gain calculating section, the target value tracking control operation can be performed even if the model identification of the controlled object process includes an error. Since the gain of the internal model is automatically corrected, it is possible to perform highly accurate and reliable control, and it is also possible to deal with characteristic changes of the controlled process. Further, since it is possible to prevent the occurrence of troubles due to the identification error of the process to be controlled, it is possible to reduce the work load on the operator who does not have specialized control knowledge.

Further, by providing the model gain limiter unit so that the correction gain calculated by the model gain calculation unit falls within a predetermined range which is the limit range of safe operation, safer control can be performed. it can.

Further, since the operation amount limiter section is provided, it is possible to prevent an excessive change in the operation amount due to the gain correction of the internal model, so that it is possible to avoid destruction of the control device and waste of energy.

A non-linear control model gain calculation unit is provided in place of the model gain calculation unit, and the correction gain is calculated using the safety coefficient for ensuring control safety to correct the gain of the internal model. It is possible to avoid the deterioration of the control characteristics for the target process.

[Brief description of drawings]

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

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

FIG. 3 is a diagram showing target value followability of a control amount and a reference control amount.

FIG. 4 is a diagram showing a response start region of a control amount and a reference control amount.

FIG. 5 is a diagram showing a target value followability of a controller having the IMC structure of FIG. 1.

FIG. 6 is a diagram showing a target value followability of a PID controller.

FIG. 7 is a diagram showing a target value followability of a conventional IMC controller.

FIG. 8 is a block diagram of an IMC structure controller according to another embodiment of the present invention.

FIG. 9 is a block diagram of an IMC structure controller according to another embodiment of the present invention.

FIG. 10 is a diagram showing target value followability of the controller having the IMC structure of FIG. 9.

FIG. 11 is a diagram showing target value followability of the controller having the IMC structure of FIG. 1.

FIG. 12 is an IM using a non-linear model gain calculator.
It is a figure which shows the target value following property of the controller of C structure.

FIG. 13 is a diagram showing target value followability of the controller having the IMC structure of FIG. 1;

FIG. 14 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 4a Target value / disturbance filter unit 4b Operation unit 6 Internal model 6a Internal model storage unit 6b Internal model output calculation unit 8 Second subtraction processing unit 9 Steps Width calculation unit 10 Response start area detection unit 11 Model gain calculation unit 12 Model gain limiter unit 13 Manipulation amount limiter unit

Claims (4)

[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 a controller having an MC structure, a target value filter unit that outputs a target value of input control with a characteristic that a transfer function has a time delay, and 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 time delay characteristic of the transfer function, and an operation amount is calculated 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 outputs the internal model, and a parameter for the internal model is stored. When a correction gain of the internal model is input, the gain of the internal model in the parameter is updated to the correction gain. A model storage unit, an internal model output computing unit that computes a reference controlled variable from the manipulated variable based on the parameters of the internal model, and a controlled process A second subtraction processing unit that subtracts the reference control amount output from the internal model output calculation unit from the control amount and outputs the feedback amount; and a control amount and a control amount based on the target value, the control amount, and the reference control amount. A step width calculation unit that calculates a step width that is a difference between an initial value and a set value of the reference control amount, and a response start that the control amount and the reference control amount start to change based on the step width of the control amount and the reference control amount. A response start area detection unit that detects a region and outputs a control amount and a reference control amount of the response start region, and a control amount based on the control amount and the reference control amount of the response start region and a change amount of the reference control amount from the change amount. A controller having a model gain calculation unit that calculates a modified gain of the internal model. 2. The controller according to claim 1, wherein when the correction gain output from the model gain calculation unit is out of a predetermined range, the correction gain is changed to fall within the predetermined range and the internal model storage unit is changed. A controller having a model gain limiter unit for outputting to a controller. 3. The controller according to claim 1, wherein when the amount of change in the operation amount output from the operation amount calculation unit exceeds a predetermined upper limit value, the operation amount limiter unit suppresses this change amount by the predetermined upper limit value. A controller characterized by having. 4. The controller according to claim 1, wherein the modified gain of the internal model is calculated from the control amount of the response start region and the control amount based on the reference control amount and the change amount of the reference control amount, instead of the model gain calculation unit. A controller having a non-linear corresponding model gain calculation unit for calculating the modified gain by multiplying the safety factor when the controller is operated.