JPH0439701A - Controller - Google Patents

Abstract

PURPOSE:To prevent the overshoot of the process quantity by providing an auxiliary control part to which a target set value and the process quantity are inputted, monitoring the settling state of the process quantity to the target set value by this auxiliary control part, deriving an auxiliary set value by a prescribed operation and applying it to a control arithmetic part. CONSTITUTION:The controller is provided with a control arithmetic part 1 to which a target set value and the process quantity are inputted, and which outputs a manipulated variable to a process by a prescribed operation, and an auxiliary control part 3 to which the target set value and the process quantity are inputted. Also, the auxiliary control part 3 is constituted so that a state that the process quantity is set to the target set value is monitored, an auxiliary set value for changing temporarily the target set value in accordance with its result is generated, and also, when this auxiliary set value is eliminated, an auxiliary manipulated value for maintaining the manipulated variable is outputted to the control arithmetic pat 1. In such a way, when a temporary auxiliary set value is applied, and eliminated thereafter, a position relation between a deviation of the process quantity and the target set value, and the control manipulated variable is corrected temporarily and automatically, the overshoot is suppressed, and also, the settling time can be shortened.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a controller suitable for controlling the temperature of an electric furnace, etc., and more specifically, to a controller suitable for controlling the temperature of an electric furnace, etc. This is related to the controller.

<Prior Art> FIG. 9 shows the IIN configuration of a conventionally known controller.

TSP and process amount P, which are target setting values for process amount
(2) is input to the PID control calculation section 1.

The PID control calculation unit 1 calculates the target set value TSP and the process amount P.
Proportional, integral, and differential calculations are performed on the deviation from v to calculate the control operation amount, and this is output to the process 2, such as an electric furnace, so that the process amount finally matches the target set value TSP. controlled by.

Note that there is also a configuration in which the target set value TSP is input to the change rate regulation section to obtain a set value that increases (or decreases) at a constant rate, and this set value is input to the PID control calculation section 1.

In a controller having such a configuration, it is important to prevent overshoot of the process amount Pv.

In other words, the process amount asymptotically approaches the target set value TSP,
This TSP must not be exceeded.

FIGS. 10(A) to (D> are waveform diagrams representing an example of control, in which Pv represents the process amount, OUT represents the change in the manipulated variable, and it is assumed that the target set value TSP is applied at time to. As soon as the target set value TSP is applied, the control manipulated variable 01JT is output, and the process variable PV approaches the target set value TSP asymptotically.By gaining experience, the operator can adjust the state of change in the process variable PV. , it is possible to determine the presence or absence of overshoot.

For example, in the case of (A), there is a risk of overshoot (
In the case of (B), it can be determined that there is no overshoot (represented by G). Similarly, at times (C) and (D) different from (A) and (B), (C) reduces the risk of overshooting (NG
), it can be determined that (D) should not be done (G).

FIG. 11 is a waveform diagram showing an example of faster response than FIG. In this case as well, the operator can use (A) and (C) based on experience.
) indicates the risk of overshoot (NG), (B), (
D) can be determined not to do (G). When the operator detects a risk of overshoot,
Take measures such as lowering the voltage of the electric furnace's starter power supply.
Try to prevent overshoot.

<Problems to be Solved by the Invention> However, in such controllers, the operator must be able to detect the risk of overshooting the process amount through experience, so the operator must be present at all times, making it difficult to save labor. The problem was that it was not possible.

In addition, since experience is required to detect the danger of overshoot, we devised a controller that is difficult for beginners to use (Japanese Patent Application No. 1-262531).

This controller is provided with an auxiliary control section into which the target set value and the process amount are input, the auxiliary control section monitors the situation in which the process amount settles to the target set value, and calculates the auxiliary set value by a predetermined calculation. By applying this to the control calculation unit, overshoot of the process amount is prevented.

<Objective of the Invention> The object of the invention is to further improve a controller with a new configuration in which such an auxiliary control section is provided, and to prevent overshoot of the process amount and at the same time shorten the settling time. Our goal is to provide controllers.

Means for Solving the Problems> In order to solve the above problems, the present invention includes: a control v4 calculation unit into which a target set value and a process amount are input, and outputs a manipulated variable to the process by a predetermined calculation; and an auxiliary control unit into which the process quantity is input, and the auxiliary control unit monitors the situation in which the process quantity settles to the target set value, and temporarily changes the target set value according to the result. The controller is configured to generate an auxiliary set value for the operation, and to output an auxiliary operation amount for maintaining the operation amount when the auxiliary set value is removed to the control calculation section.

Effect> The auxiliary control section sequentially calculates the amount of change in the process amount P■, and temporarily outputs the auxiliary setting value based on this. Further, when this auxiliary setting value is removed, an auxiliary operation amount is outputted to maintain the control operation amount that has been output up to that point.

As a result, when a temporary auxiliary set value is applied and then removed, the deviation between the process variable and the target set value and the positional relationship between the control manipulated variable are temporarily automatically corrected to prevent overshoot. It becomes possible to suppress this and shorten the settling time.

<Embodiment> FIG. 1 is a configuration block diagram showing an embodiment of a controller according to the present invention.

In Figure 1, 1 is goal setting ITSP and process 2
The process amount Pv from is input, for example, proportional (P),
This is a control calculation unit that performs predetermined control calculations such as integration (I) and differentiation (D) and outputs the control operation amount OUT to the process 2.

Reference numeral 3 denotes an auxiliary control section to which the target set value TSP and the process amount Pv are input. In this auxiliary control section 3, an auxiliary set value 31 monitors the situation in which the process amount Pv settles to the target set value TSP, and generates an auxiliary set value SSP for temporarily changing the target set value TSP according to the result. The output means 32 is an auxiliary operation amount output means that outputs an auxiliary operation amount 5O1JT for maintaining the control operation amount OUT to the control calculation unit 1 when this auxiliary set value SSP is removed.

The operation of the controller configured in this way will be explained next.

The PID IIJ control calculation unit 1 inputs the difference between the target set value TSP and the auxiliary set value ssp (TSP-3SP) and the process amount P■ from the process 2, and performs normal PID calculation on the deviation DV. .

The auxiliary control unit 3 controls the target set value TSP (or the set value S
P) and process amount Pv, and perform the following (1) and (2).
Based on the formula, it is determined whether an overshoot of the process amount Pv is likely to occur (NG) or not (G).

When DV≧, G when DPV (1
)DVK -DPVV) When it is NG......(
2) DV2 Deviation between target set value TSP (or set value SP) and process amount Pv DPV: Change in process amount Pv per predetermined time tL: Constant Figure 2 shows an example of control, and PV is the process amount, OUT is the manipulated variable, TSP is the target set value, and LAG is the equivalent waste time of the process, which is the time from when the manipulated variable is input to the process until the process variable changes.
= 2, in the case of (A), DV<K - DPV at the tip, so the judgment is NG from the above equation (2), and overshoot may occur. (B) satisfies DV>K-DPV at its tip, and from the above equation (1), the determination is G, and it is determined that overshoot does not occur. Note that the predetermined time tL
As, 1/2 of the process equivalent dead time LAG is used.

The determination of the above expressions <1) and (2) was derived based on empirical rules. When the process amount Pv has not risen sufficiently, that is, when DV is large, the determination is always G, and there is no risk of overshoot.

In the auxiliary control section 3, when the determination is NG, the auxiliary set value output means 31 temporarily outputs the auxiliary set value ssP for correcting the set value to the PID control calculation section 1 so as to be separated from the eye WA set value TSP. When determining G, a value corrected to approach the target set value TSP is temporarily output.

Such an operation can prevent overshoot of the process amount P■.

The auxiliary operation amount output means 32 controls the operation in which the control fxJ operation amount OUT of the PID control calculation unit 1 suddenly changes when the auxiliary setting tIissP is removed during the operation of the auxiliary set value output means 31. An operation is performed to continue to maintain the manipulated variable OUT and to generate an auxiliary manipulated variable 5OUT to shorten the settling time.

Auxiliary operation amount 5OUT from which the auxiliary operation amount output means 32 appears
may be a bias amount that is simply added to the control operation amount OUT. This value 5OUT depends on the auxiliary set value ssP, for example, as expressed by equation 3).

5OLIT= (0-3SP)*PB... (3) However, PB is the proportional gain of the PID control calculation section 1. Figures 3 to 5 are the auxiliary settings temporarily output by the auxiliary set value output means 31. It is a figure for explaining the value of a value. Auxiliary setting value SSP
Although the value of may be determined experimentally by various processes, in this example, the auxiliary setpoint SSP is set to two setpoints SS
The case is shown in which it is given as the sum of P1 and 5SP2 (SSP1+5SP2).

In these figures, Ko is the ratio (
Ko=DPV/DPVmax>.

Figure 3 shows the state of 5SPI, and the 5SP when the initial value when giving SSP is 5SPI (F).
The function of I is expressed by equation (4), and is a function that gradually decreases with respect to time t and eventually reaches "0".

S S P 1 = 5SPI (F) - 3SP1 (
F) It/2 tables [... (4) Here, it is given by 5SP1 (F)=2-Ko-DPViax.

FIG. 4 shows 5SP2, the number of which is expressed by equation (5) and is a function proportional to the amount of change DPV in the process from time to time.

S S P 2 = 2 * K * D P V
---(5) FIG. 5 is a diagram showing the added value (SSP1+5SP2) of the two setting values 5spi and 5SP2.

Here, each characteristic of ■ and ■ is the DPV with time t.
This is the case when .

In Fig. 5, auxiliary setting value ssp (=ssp1-)
-3SP2) is removed from the target setpoint TSP when the relationship SSP<5SPI (F)* is established.

FIG. 6 is a diagram showing the relationship between the deviation when removing the auxiliary set value SSP and the operation output OUT. Here,■
.about.■ correspond to those in FIG. 5, respectively. ■,
It can be seen that the case (2) is more strongly influenced by the decrease in the manipulated output OUT than the cases (2) and (2), and the change in SSP is faster.

FIG. 7 is a time chart showing the operation when using 5SP2 with the characteristics of ■ and ■ in FIG.

At what point the auxiliary set value SSP should be applied to the target set value TSP is another issue, but in this case, the process amount PV is approaching the target set value TSP, and TSP
The voltage is temporarily applied when the difference between P and P becomes 8 times or less the magnitude of DPV. That is, the fifth
In the figure, the amount of SSP with Ko=1 is chosen to be 1/2 of the difference between TSP and pv. Then, at the time when such auxiliary set value SSP is removed, auxiliary operation amount 5OUT is applied to control operation amount OUT.

In this way, by applying the temporal auxiliary set value and the auxiliary operation amount, overshooting of the process amount Pv can be prevented and the settling time to the target set value can be shortened. Here, in the comparison of the characteristics of ■■, it can be seen that the characteristic of ■ has a weak movement toward stabilization in the process amount Pv.

FIG. 8 shows that when the present invention is applied, after determining the auxiliary setting value SSP, that value is multiplied by 1.5.

FIG. 7 is a diagram showing a settling curve of the process amount P■ when it is intentionally changed to 1.0 times, 0.5 times, etc.

From these figures, it can be seen that even if the value of the auxiliary setting value SSP is slightly varied, there is no influence on the effect of setting the process amount Pv.

In the embodiment described above, the correlation between DV and DPV is determined in two states, G and NG, but when used for operating the auxiliary setting value SSP, the states may be evaluated in more detailed manner.

Furthermore, at the time when the auxiliary set value SSP is removed from the target set value TSP, the auxiliary operation amount 5OUT to be applied is not only added to the control operation amount OUT but also applied to the integral term of the PID control calculation unit 1, for example. Good too.

In addition, the value of the auxiliary setting value SSP is 2 as shown in FIG.
For example, the value of SSP may be determined with reference to the proportional constant (P) used in the PID control calculation section 1. ) with the same value as the auxiliary setting value SSP,
When the difference between TSP and Pv enters a range that is twice the proportional band or less, the target setting value TSP may be temporarily applied.

<Effects of the Invention> As described above in detail based on the embodiments, according to the present invention, the auxiliary control section obtains the auxiliary set value, corrects the target set value TSP using the auxiliary set value, and also corrects the target set value TSP. By applying the auxiliary manipulated variable 5OUT at the time when is removed, overshoot of the process amount can be effectively prevented, and the settling time can be shortened.

[Brief explanation of drawings]

Fig. 1 is a configuration block diagram showing one embodiment of the controller according to the present invention, Fig. 2 is a characteristic curve diagram for explaining its operation, and Figs. 3 to 5 show that the auxiliary setting value output means is temporarily Figure 6 is a diagram for explaining the value of the auxiliary set value that is output when the auxiliary set value (SSP) is removed. 5 is a time chart showing the operation when using 5SP2 with the characteristics of ■. FIG. 8 is a time chart showing the operation when using the 5SP2 with the characteristics of ■. After determining the auxiliary setting value SSP, the value is changed to 1. 5 times, 1.0
Process amount Pv when intentionally changed to double, 0.5 times, etc.
Fig. 9 is a block diagram showing the configuration of a conventionally known controller, Fig. 10 is a waveform diagram showing an example of control, and Fig. 11 shows an example with a faster response than Fig. 10. FIG. 1... PID control calculation unit, 2... Process, 3...
・Auxiliary control unit, 31...Auxiliary set value output means 32...Auxiliary operation amount output means'<e2Figure 3Figure 4Figure 2Figure 5■C Figure■Figure (A) (B) (C) m-time (D) th (A) CB) (C) (I)) t. t. t. t. □Time

Claims (3)

[Claims] (1) A control calculation section into which target set values and process quantities are input and which outputs manipulated variables to the process through predetermined calculations, and an auxiliary control section into which the target set values and process quantities are input; The control unit monitors the situation in which the process amount settles to the target set value, generates an auxiliary set value to temporarily change the target set value according to the result, and performs an operation when the auxiliary set value is removed. A controller characterized in that an auxiliary operation amount for maintaining the process amount is output to the control calculation section to prevent overshoot of the process amount. (2) The auxiliary control unit provides the auxiliary set value in relation to the amount of change in the process amount, and temporarily provides the auxiliary manipulated value before the deviation between the target set value and the process amount reaches zero. The controller according to claim 1, characterized in that: (3) The controller according to claim 1, wherein the auxiliary control section determines the magnitude of the auxiliary set value by referring to the equivalent dead time of the process.