JPS629405A - Process controller - Google Patents

Abstract

PURPOSE:To attain the control of the integration time to the change of the target value without giving any change to the disturbance control state, by using an advance/delay arithmetic means which changes equivalently the integration time to the change of the target value. CONSTITUTION:The target value SV is calculated by an advance/delay arithmetic part 5 and a subtraction part 7 subtracts the measured value PV from the output signal of the part 5. Thus a deviation epsilon2 is obtained. An integration arithmetic part 9 performs the integration operation to the deviation epsilon2. Then the output signal of the part 9 is added with a deviation epsilon1 at an addition part 11. Then the output signal is multiplied by a proportion gain Kp through a proportion gain part 13. Here the coefficient beta of the part 5 is changed to fix the integration term against disturbance. Under such conditions, the integration time can be changed equivalently.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a process control device, and in particular to an excellent process control device that can equivalently change the integration time.
1 device.

[Technical backstory of the invention and its problems] In a process control device, the proportional gain Kp, the integral time Ti
, the response characteristic is determined by the state of each control constant of the differential time Td. Usually these control constants Kp, Ti
, Td is i! iQ III A state in which this IEW can be quickly suppressed when a disturbance O is applied to the target, that is,
Generally, it is adjusted to the optimum characteristic state for disturbance suppression. However, in this case, if the target value is changed, the control goes too far and the control amount cannot follow the change in the target value, resulting in overshoot. On the contrary, there is no control over changes in the target value.
If the control constant is set to a state in which I1m optimally follows, that is, a target value tracking optimal characteristic state, the suppression characteristics against disturbances will become very weak, and the responsiveness will become long.

As described above, the values to be adjusted for the control constants Kp, Ti, and Td are significantly different between the disturbance suppression optimum characteristic state and the target value tracking optimum characteristic state, and this is explained by the control constants Kp, Ti, and Td shown in FIG.
HR (Chern, Hrones, Re5w1c
k) can be understood using the control constant adjustment formula using the method.

For this reason, a two-degree-of-freedom PID 1tI11 that allows adjustment of both the disturbance suppression characteristic and the target value tracking characteristic is used.
A control device has been developed.

In this conventional two-degree-of-freedom PID control device, as shown in FIG. 8, a target value S■ is input to a coefficient section 101, and its output signal αSV is led to an addition section 103, where it is subtracted from a measured value PV. This gives the deviation ε, and this deviation ε1
is input to addition section 105.

On the other hand, the target value SV is input to a first-order lag filter 107 and subjected to a first-order lag calculation. The output is the subtractor 109
Here, the measured value P■ is subtracted to obtain the deviation ε2. This deviation ε2 is input to the integral calculation section 111,
An integral calculation is performed.

The output signal from this integral calculation section 111 is
5 and are added together with the previous deviation ε1. Then, the output signal is applied to the controlled object 115 as an operation signal MV via the proportional calculation section 113, and the measured value PV is adjusted so as to match the target value Sv.

As is clear from FIG. 8, in the conventional control device described above, 1 +++ (sunir(" +v
Calculation adjustments are being made for T,,s,〒cho).

Here, the disturbance suppression optimum parameters are set for the proportional gain Kp and the integral time Ti, and the coefficient α and the first-order lag filter 0
By varying the time constant To of 7, the target value tracking characteristic is R-optimized without affecting the disturbance suppression characteristic.

That is, by changing the time constant TO of the filter 07, the integration time is adjusted in response to a change in the target value.

However, there is a problem in that adjustment of the integration time by varying the time constant TO is very delicate and difficult to adjust, as will be explained below.

When the integral term is transformed from equation (2), it becomes as follows.

= Yan-()・(F7-Pa・ peek In the above equation (3), the first term is an integral term for the integral time T1.

The second term is an adjustment term by the time constant TO. In the second term of the above equation (3), the adjustment term by the time constant TO, (2) When the time constant TO is changed, the gain of the adjustment term also changes at the same time. ■If the integration time T1 is changed, the gain of the adjustment term will change. ■If you change the integration time Ti, there is a problem that the relationship with the equivalent integration time (equivalent integration time for a change in target value) will change, and it will become an interference system where parameters influence each other, making adjustment very difficult. becomes complicated. This conventional characteristic is shown in FIG. This characteristic is a graphical representation of the output for a unit change in the target value Sv for two cases where the time constant TO is To=Ti and To=Ti/2. It can be seen that when the time constant To is changed, the gain changes, and in particular, the characteristics from time 0 to Ti change.

Further, even if the time constant To=Ti is changed to To=Ti/2, the gain change will not be doubled, but will become very complicated. Therefore, the above-mentioned conventional apparatus has a problem in that it is completely impractical in plants and the like that use a large number of apparatuses.

[Object of the Invention] An object of the present invention is to provide a process control device that makes it possible to adjust the integration time in response to a change in a target value without making any changes to the disturbance suppression state.

[Summary of the Invention] In order to achieve the above object, the present invention comprises: a deviation calculation means for calculating the deviation between a control target and a target value; a control calculation means for performing at least proportional and integral calculations on the deviation; The gist of the present invention is to have a lead/lag calculation means that equivalently varies the integration time with respect to a change in mff1.

Embodiment of the Invention FIG. 1 is a functional block diagram showing the configuration of an embodiment of an apparatus according to the present invention.

In the coefficient unit 1, the target value SV is multiplied by a coefficient α, and the measured value PV is subtracted from the output signal αS2 in the adder 3 to obtain the deviation ε1 (=α5V−PV).

On the other hand, the target value SV is calculated by leading/11 in the lead/lag calculating section 5, and the measured value PV is subtracted from the output signal in the subtracting section 7 to obtain the deviation ε2.

The integral calculation unit 9 performs an integral calculation on the deviation ε2, and the output signal thereof is added together with the previous deviation ε1 in the addition unit 11. The output signal is then input to the proportional gain section 13 and multiplied by the proportional gain Kp.

The output signal of the proportional gain unit 13 is applied to the controlled object 15 as the operation signal MV, and thereby the measured value PV is adjusted and controlled to match the target value S■.

In this embodiment, the following equation (4>) is used as the equation for the lead/lag calculation 8II5.

However, T1 is the integration time and β is a variable parameter.

S is a complex variable.

As is clear from the figure, for changes in the measured value PV, I don't like it) Yu (!;) T1・S Also, regarding target value changes, calculation adjustments are made. Here, the proportional gain Kp.

The disturbance suppression optimum parameter, -, is set as ffflTi at the time of integration.

In addition, in response to a change in the target value SV, by changing the coefficient α in the equation (6) and the coefficient β of the calculation unit 5, which is the advance of the target value Sv by 7M, the integral term for the disturbance is kept fixed. Only the integration time can be changed equivalently.

Therefore, when the integral term is modified from equation (6), in equation (7) above, the first term is an integral term of the integration time Ti, and the second term is an integral adjustment term by the lead/lag calculating section 5. Therefore, the above (7
By changing the coefficient β of the integral adjustment term in the equation ), it is possible to change the equivalent integration time Te (equivalent integration time) with respect to the target value change.

In equation (7) above, when β = 0, the equivalent integration time Te - integration time Ti is obtained without adjusting the integration time, and β〉
When it is 0, equivalent integration time Te>integration time Ti.

Furthermore, it is easily understood that when β is 0, the equivalent integration time Te<integration time Ti. Therefore, once the disturbance suppression optimum integration time Ti is determined, the equivalent integration time Te can be easily changed by varying the coefficient β.

FIG. 2 shows the output for a unit change in the target value Sv for two cases with coefficients β-1 and 1/2.

In the figure, (a) is the curve where the integral term is 1/TiS, and (b) is the curve from (a) to the integral adjustment term (first-order lag, β/1+TiS) (
(c) shows the curve obtained by subtracting the integral adjustment term β/'(1+Ti S) (when β=1) from (a). The integration time Ti is (
It becomes larger as B)→(B)→(C). In other words, if it is below curve (a), the equivalent integration time To is Te
> Ti and becomes large, and if it is above the curve (a), the integral time Te becomes equal to e < Ti,
It becomes smaller. Therefore, by setting the magnitude of the coefficient β, it is possible to change the equivalent integration time Te.

Next, +), ■+ for each control constant in this example.

The method of adjusting Td and coefficients (variable parameters) α and β and the operation of this embodiment will be explained.

First, the adjustment methods are (1) finding the process characteristics (time constant TO, dead time, and gain K of the process) and adjusting based on this using the CHR method, etc., and (2) when the process characteristics are unclear. There is a method of adjusting each control constant so that the step response of the target value becomes the desired response.

(In the method 1>, both the control constants for the disturbance suppression optimum characteristic state and the target value tracking optimum characteristic state can be calculated by the CHR method etc., so the values of the coefficients α and β can be calculated based on these results.

Moreover, method (2) is a method used in many cases. In this method, the target value SV is changed in steps,
As a result, the control constant Kp is set so that the response of rnmPv reaches the desired disturbance suppression optimum characteristic state to suppress the control amount.
After adjusting Ti and Td, the coefficients α and β are modified so that the response becomes the desired target value tracking optimum characteristic state. For example, transfer function of controlled object 15 G r) (S) *
/-? -55e, the response changes depending on the values of the coefficients α and β, as shown in FIGS. 3 and 4.

The coefficient α is used to adjust the proportional gain Kp among the control constants, and by changing this value in the range 0≦α≦1, as shown in Figure 3, the rise characteristics of the response and the overshoot state can be selected. I can do it. Further, the coefficient β changes the integration time T1, and as shown in FIG. 4, this value can improve overshoot without affecting the rise of the response. In the actual simulation, α=0.4. Optimal characteristics are obtained when β=0.15.

When the control constants Kp, Ti, Td and coefficients α, β are set as described above, when a disturbance is applied to the controlled object 15, the deviation between the fluctuation of the control m1pv and the target value S■ is The control constant K is set to the optimum characteristic state for disturbance suppression.
p, Ti, Td 1. : Wzuki, operation message @M■
is calculated, and by supplying this operation signal MV to the till-lit target 15, fluctuations due to disturbances are quickly suppressed. When the target value SV changes, by changing the coefficient β of the integral adjustment term as shown in equation (7) above, the change in the target value SV can be adjusted while keeping the disturbance suppression characteristics fixed. control to optimally respond to

As explained above, according to this embodiment, the lead/N difference calculating section 5 is provided for the target value SV, and the deviation ε2 between the target value and the measured fiPV via the lead/lag calculating section 5 is calculated by integral calculation. Since the equilateral edge time Te is adjusted, the gain of the adjustment term is determined only by the coefficient β, and even if the integration time Ti is changed, there is no effect on the adjustment term gain. There is no need to affect it. Furthermore, since it is normalized, even if the integration time Ti is changed, the relationship between the integration time Ti and the equilateral edge time Te remains unchanged.
Adjustment of the integration time becomes extremely easy. Therefore, even if a large number of devices of this embodiment are used in plant control, the controllability of each control device can be improved to the limit, and the plant operating characteristics of the entire system can be dramatically improved.

Furthermore, it can be easily realized by simply adding the advance/delay calculation section 5 to the existing process control device.

FIG. 5 shows another embodiment of the device according to the invention, and FIG.
The figure shows a further embodiment of the device according to the invention. In each figure, the same components as those in the embodiment shown in FIG.

The embodiment shown in FIG. 3 is a so-called PV differential leading type PI.
D adjustment device, the differential calculation unit 17 performs a differential calculation on the measured value PV, and the output signal is the deviation ε1. ε
2 and is added and synthesized by the adder 11. Note that the other structural parts are the same as those of the embodiment shown in FIG. 1 above.

The embodiment shown in FIG. 4 is an incomplete differential operation type PID.
In the adjustment device, the target value SV is multiplied by a coefficient γ in the coefficient unit 19, and the measured value PV is subtracted from the output signal γSv in the subtraction unit 21 to obtain the deviation ε3 (=γ5V−PV). . The differential calculation unit 17 performs a differential calculation on this deviation ε3, and the output signal is the deviation ε1. ε2
The addition section 11 performs addition and synthesis with the addition section 11.

Also in these embodiments shown in FIGS. 5 and 6, the lead/lag computing section 5 performs integration adjustment, so that the integration time can be easily changed by varying the coefficient β.

FIG. 7 shows another embodiment of the process control device according to the present invention. In this figure, the same components as those in the embodiment shown in FIG.

In this process control device, the target value SV is input to the coefficient unit 1, and is also input to the delay calculation unit 25, and is subtracted by the measured value PV in the subtraction unit 7, and is input to the integral calculation unit 9. The output signal subjected to the delay calculation in the delay calculation section 25 and the output signal subjected to the integral calculation in the integral calculation section 9 are subjected to subtraction processing in the subtraction section 27, and are output to the addition section 11.

Specifically, the delay calculation unit 25 is set with a first-order lag element represented by β/1+T+S, and the output signal from the subtraction unit 27 to the addition unit 11 is as shown in the following equation.

Therefore, the subtraction units 7, 27 . The integral calculation section 9 and the delay calculation section 25 constitute advance/delay calculation means, and the operation signal MV is expressed by the following equation.

As a result, in the process control device of this embodiment, the ill! III is performed, and by changing the coefficients α and β with respect to the change in the target value S, it is possible to change only the integral time with respect to the change in the target value to the same side while keeping the integral term with respect to the disturbance fixed. In addition, in FIG. 1, advance /i is used to change the integration time.
However, this embodiment has the advantage of not requiring such a complicated calculating section and can be configured with a simple first-order delay element.

Although the so-called position type calculation method has been described above, the present invention is not limited to this.
Of course, it is also applicable to the speed-type calculation method that is frequently used in TA+ Control).

[Effects of the Invention] As described above in detail, according to the present invention, the integration time can be easily adjusted by using the target value advance/delay means. As a result, the controllability of the process control device can be improved to the limit, and the controllability is dramatically improved in the case of plant operation using a large number of process control devices.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram showing the configuration of one embodiment of the apparatus according to the present invention, FIGS. 2 to 4 are diagrams for explaining the operation of one embodiment of the present invention, and FIGS. The figure is a functional block diagram showing the configuration of another embodiment of the device according to the present invention,
FIG. 7 is a configuration block diagram showing the configuration of another embodiment of the device according to the present invention, FIG. 8 is a functional block diagram showing the configuration of a conventional example, and FIGS. 9 and 10 explain the same conventional example. This is a diagram for 5...Advance/lag calculation unit 7.27...Reduction unit 9...Integral calculation unit 13...Proportional gain unit 15...Control pair ↑ 2゛5...Delay calculation unit 1st Fig.2 Fig.3 Fig.4

Claims (1)

[Scope of Claims] Deviation calculation means for calculating the deviation between the controlled variable and the target value; control calculation means for performing at least proportional and integral calculations on the deviation; and equivalent integration time for the change in the target value. 1. A process control device comprising: advance/delay calculating means that is variable.