JPS629404A - Process controller - Google Patents

Abstract

PURPOSE:To obtain a process controller which is optimum to both the follow-up of the target value and the suppression of disturbance which can be controlled independently with each other, by using an arithmetic means which compensates the control constant set to the target value follow-up optimum characteristics. CONSTITUTION:A control arithmetic part 11 compensates the control constant set in an optimum state for suppression of disturbance by means of parameters alphaand gamma obtains a control constant set in an optimum state for follow-up of target value. However the gain is reduced to the variation of the controlled valuable PV due to the disturbance together with a delayed set time with said control constant set in the optimum state for follow-up of the target value. In this respect, a compensation arithmetic part 10 gives a compensating operation to the control constant in an optimum state for suppression of disturbance and supplies the constant to the part 11. Thus it is possible to obtain a process controller which is optimum to both the follow-up to the target value and the suppression of disturbance which can be controlled independently of each other.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides a control IP that is fed back from a controlled object.
The present invention relates to a process control device that calculates an adjustment calculation output U by performing at least an integral calculation among proportional, integral, and differential calculations for a deviation ε between V and a target value Sv of the controlled variable.

[Technical background of the invention and its problems]

FIG. 10 shows a functional block diagram of a general conventional process control device. In this figure, 1 is a deviation calculating section, 2 is a control calculating section, and 3 is a controlled object. The deviation calculating section 1 calculates the deviation a (=SV-PV) between the control zpv fed back from the controlled object 3 and this target value S■.

The control calculation unit 2 calculates interference type proportionality to the deviation 6 based on the transfer function C(S) of equation (1), for example.

Integral and differential calculations are performed, and the control amount Pv is set to the target value SV.
An adjustment calculation output U that matches the is obtained and output to the controlled object 3. In the controlled object 3, a control operation is executed using this adjustment calculation output U as a manipulated variable, but if a disturbance is applied and the control is disturbed, this is detected as a fluctuation in the controlled variable PV.

Here, KP * TI + TD is the transfer function 0 (S
) are the control constants for proportional gain and integral time, respectively.

It shows differential time. Also, S is a complex variable.

l is a constant of about o, i ~ 0.3.

The response characteristic of this control device is determined by its control constant KP, as can be understood from the transfer function of equation (1).

It is determined by the adjustment state of TI and TD. In a normal process control device, the control constants KP and TI.

The TD is adjusted to a state in which when a disturbance is applied to the controlled object 3, the influence can be quickly suppressed, that is, a disturbance suppression optimum characteristic state.

However, if the control constant is set to this optimum characteristic state for disturbance suppression, the control will be excessive when the target value Sv is changed, and the control amount Pv will not follow the change in the target value Sv, resulting in overshoot. I end up. In addition, if the control constant is set in a state in which the control tPV optimally follows the change in the target value S, that is, in a target value tracking optimal characteristic state, the suppression characteristics against disturbances will become very lenient, and the responsiveness will become longer. Oops.

In this way, the value to be adjusted for the control constant in equation (1) is significantly different between the disturbance suppression optimum characteristic state and the target value tracking optimum characteristic state, and this is explained by the OH method (OH method) shown in Fig. 11.
n, Hrones.

This can be understood using the control constant adjustment formula given by 几eswtck.

However, in the transfer function of the control calculation section 1, only one type of control constant Kpe Tz-Tn L cannot be set for each calculation. For this reason, in conventional devices, the characteristics of the controlled object 3 (for example, the ability to respond to disturbances) and the type of control (for example, the form of changing the target value) are sacrificed, or both are compromised with a certain level of response.

[Purpose of the invention]

The present invention provides a process control device that can independently adjust control constants to optimal characteristic states for both disturbance suppression and target value tracking.

[Summary of the invention]

The present invention provides a process control device that obtains an adjustment output by performing at least one of proportional, integral, and differential calculations on the deviation between a controlled variable and a target value, in which control constants for each of the calculations are set as wf4ffi parameters. The control constant set in the target value tracking optimum characteristic state can be adjusted to the target value tracking optimum characteristic state by using compensation calculation based on the variation of the control quantity in response to fluctuations in the controlled variable due to disturbance. This is equivalent to modifying the state to the optimum characteristic state for disturbance suppression.

Hereinafter, the present invention will be explained using one embodiment with reference to the drawings.

FIGS. 1 and 2 are functional block diagrams showing the configuration of an embodiment of the present invention. In this figure, the same components as in FIG. 10 are designated by the same reference numerals, and their explanation will be omitted.

In the figure, reference numeral 10 denotes a compensation calculation section, which performs a correction calculation on the control amount Pv from the controlled object 3 and supplies the compensation control amount Pv' to the deviation calculation section 1.

The deviation calculation section 1 calculates the deviation between the compensation control amount Pv' and the target value Sv, and outputs it to the control calculation section 11.

The control calculation unit 11 generates a transfer function that compensates and modifies the control constants KPa TI and TD set by the OHR method etc. to the disturbance suppression optimum characteristic state using adjustment parameters α and r, as shown in equation (2). 0Ts) (interference type) is provided. According to this transfer function C(1), the control constants KP and TD in the optimum characteristic state for disturbance suppression are corrected and set to the control constants KP and TD in the optimum characteristic state for tracking the target value in terms of proportionality and differentiation. Based on these control constant numbers KP # TII TD, proportional, integral, and differential calculations are performed with respect to the deviation to obtain the adjustment output μ,
This is output to the controlled object 3.

Here, the adjustment parameter α modifies the proportional gain, and r changes the differential time. These can be calculated as in equations (4) and (5) using the values of adjustment formulas such as the OHR method, and for example, the adjustment mode can be changed. Assuming PID, no overshoot, and minimum settling time, α=0.63. When r = 1.25, the control constant KP is adjusted to the optimal characteristic state for tracking the target value, and 'i''D has a small gain and slow settling time against fluctuations in the control amount Pv due to disturbances. Therefore, the control constant KP of the compensation operation state is
, TD, in order to remove the influence of the correction by the adjustment parameter, control-1-PV is (
A compensation calculation based on the transfer function H(S) shown in equation 6) is executed to obtain the compensation control amount Pv'.

In this way, the control calculation section 11 constantly calculates the optimal follow-up state of target value change, and the compensation calculation section 10 calculates the control constant KP of the control calculation section 11 in advance for fluctuations in the control-jilPV due to disturbances.

TI,< is subjected to a compensation calculation to virtually bring it into an optimal state for disturbance suppression, and then supplied to the control calculation unit 11, thereby tracking the target value.

A two-degree-of-freedom type control device that is optimal for both disturbance suppression and can be adjusted independently of each other can be realized.

Next, the principle of this embodiment will be explained.

The control response of the process shown in FIG. 1 can be expressed as follows.

According to this equation (7), when a disturbance is applied, in order to manipulate the response to this disturbance, 0(S) H(
9) should be corrected.

Therefore, a compensation calculation unit 1° is provided so that 0(S)H(S) is the transfer function C(1) of the disturbance suppression optimum characteristic state. In this case, if C(S This is equivalent to a configuration in which only the response to the target value can be changed using the adjustment parameters α and r in a state where the characteristics are set.

In addition, in order for the process to settle in a steady state,
It is necessary to satisfy the final value theorem, and when the disturbance is constant and the target value SV is changed by a constant value a step, the steady-state deviation aSV=a must become zero. For this purpose, as is clear from FIG. 1, the transfer function H(s) of the compensation calculation unit 10 must satisfy the following equation,
Equation (6) also satisfies this condition.

In this way, the compensation calculation unit 10 virtually sets the control constant adjusted to the target value tracking characteristic to the disturbance suppression characteristic for fluctuations in the control amount PV due to disturbance, and also sets the control constant adjusted to the target value tracking characteristic to the control constant in the steady state. It has been established that it will not have any influence.

Next, we will explain the operation of this embodiment and each control constant.

A method for adjusting adjustment parameters will be explained.

First, as adjustment methods, (1) find the process characteristics (process time constant T, dead time, gain K) and adjust based on this using OHR, method, etc.; and (2) method where the process characteristics are not correct. There is a method of setting one control constant so that the step response of the target value becomes the desired response in a clear state.

In the method (1), the control constants KP, T of the disturbance suppression optimum characteristic state and the target value tracking optimum characteristic state are determined by the 0F(R method etc.).
□Since I'rD, Kp, and Tn can also be calculated,
This result is substituted into equation (4) (51) to calculate the values of the adjustment parameters a and r.

In addition, as for method (2), the adjustment parameters α and r are determined in advance using equations (4) and (5), etc., and then the response to the step change of the target value Sv is the desired (optimal) ) How to adjust so that the characteristics follow the target value, and initially set the adjustment parameter α・r to 1 and set the target value S■
After adjusting the control constant KPI TIITD so that the response PV to a step change in has the optimum disturbance suppression characteristic,
One possible method is to add a step change to the target value Sv again and adjust the response so that it has the optimal target value tracking characteristic.

With the former method, optimum characteristics for both the target value and the disturbance can be obtained with one adjustment, and with the latter method, finer adjustment than the former method is possible.

Figure 3 shows a control target 3 according to the values of adjustment parameters α and r.
The simulation results of the control iPV response when the transfer function G P (s) of is set to -1e-2L1+58 are shown.

Further, since this embodiment has a configuration in which the response can be adjusted by adjustment parameters, various control forms can be realized as shown as N13 in FIG. 3 by changing the values of the parameters α and r. In this case, the comprehensive adjustment mode shows various interference type control forms7, and when α=r=1, the normal one-degree-of-freedom type P(
Proportional), ■ (integral), D (differential) control, α=β=
At 0, only ■control is performed for target value changes, and PID control is executed for control amount fluctuations), 0<α(1,
O(β1, the control constant is set based on the target value change in 1); PD control that can adjust Tπ and the common control constant TI control, P control that can also freely adjust the control amount
A configuration that performs control ①, which is common to D control, is realized. This adjustment parameter α adjusts the proportional gain among the control constants, and by completely changing this value, the rise characteristic of the response and the overshoot state can be corrected. Further, r is used to adjust the differential time, so that the rise characteristic can be modified without significantly affecting the overshoot state.

When a disturbance is applied to a place where the control constants KPITZ, TD and adjustment parameters α, β, r are set in this way, the resulting fluctuation in the control amount Pv is introduced into the compensation calculation unit 10, where the control The control constants of the calculation unit 11 are changed to the compensation control amount PV' that corrects the disturbance suppression optimum characteristic state with equal constraints, and is output to the deviation calculation unit 1, where the deviation from the target value SV is calculated. The control calculation unit 11
It is output to .

Further, when the target value SV is changed, the control calculation unit 11 calculates the adjustment output U of the characteristic state that optimally follows the deviation of the change.

As described above, according to this embodiment, (1) the control constant adjusted to the disturbance suppression state can be virtually corrected to the target value tracking state with respect to the target value, and both the disturbance suppression and target value tracking characteristics are achieved. can be realized at the same time. Furthermore, (2) both the constants for the disturbance suppression state and the target value tracking can be adjusted independently of each other, so it is possible to freely select the optimal state for both. Furthermore, (3) target value Sv
After adjusting the control constants so that the response of the controlled variable PV to
The time can be shortened. Furthermore, configuration (4) can be realized by simply adding the function of the compensation calculation section 10 to the control calculation section 11, and can be easily applied to an existing controller.

In the embodiment described above, the control calculation unit 11 executes proportional, integral, and differential calculations, and the compensation calculation unit 10
0 is explained as executing proportional and differential operations.
However, in the hydrothermal invention, the control calculation unit 11 only needs to be configured to execute at least one calculation, and the compensation calculation unit 10 may also be configured to perform proportional, integral, and differential calculations independently or in accordance with the desired target value tracking response. They can be selectively combined and configured. For example, the control calculation unit 11 is proportional.

If an integral calculation is to be executed and the compensation calculation unit 10 is to compensate for the proportional gain, the configuration will be as shown in FIG. 5, and the control form that can be realized in that case will be as shown in FIG. 4 Nnl. . In addition, when attempting to compensate for integral calculations that were not compensated in one embodiment, it is sufficient to configure the structure as in the second embodiment shown below.In addition, in one embodiment, the control calculation section 10 performs interferometric PID control. Although the explanation has been given using an example of executing the fourth
As shown in Figure 3, even with general PID control, various control forms can be realized by changing the values of adjustment parameters, and as in the embodiment, two degrees of freedom control constants can be realized. can be formed virtually.

Furthermore, in one embodiment, the description has been made using incomplete differentiation, which is commonly used as the differential calculation of the control calculation unit 11.
In the present invention, it goes without saying that the same applies to complete differentiation, and the meaning of differentiation is used to include both.

Next, a first embodiment of the present invention will be described with reference to FIGS. 6 and 8.

Here, the same components as in the first embodiment are given the same reference numerals and the description thereof will be omitted.

This example shows the integral calculation and its compensation calculation, which are the core of optimizing the control response, as shown in Fig. 6.
The control calculation section 11a is configured to be able to adjust the constant of integration Kaoru TI to the target value tracking optimal characteristic state with equal constraints using the adjustment parameter β by the first-order lag element, and the compensation calculation section 10a adjusts the constant of integration TI of the control calculation section 11a. The control amount PV is compensated by a lead/lag element in order to correct the disturbance suppression optimum characteristic state.

This is set as the optimum characteristic state for disturbance suppression.

Now, using these transfer functions, it is possible to satisfy the final value theorem for the integration time T, which has traditionally been difficult to compensate for, and to achieve optimal characteristics (two degrees of freedom) for both disturbance suppression and target value tracking. I will explain the principle.

First, the response of this example is the same as equation (7).In order to satisfy the final value theorem, if equation (9) is modified to satisfy, the denominator and numerator in equation (7) must be the same. It is not a value,
Equation (9) was no longer satisfied. However, in this example,
Equation (9) can be satisfied by changing the integral constant to a first-order delay.

Further, by subtracting this first-order lag element, the integral time with respect to the target value is changed by the fixed value 11.

Show the curves when drawn. According to these curves,
(b) Since El is the integral time of (a) equivalently changed by a first-order lag, according to the -ration, the optimal value of β0 is obtained when 2×β. Since the output of the -order lag function is determined by the value of β, the integration time Tx increases in the order of (A), (B), and (C) as β decreases. Also, in actual control, it is necessary to change the integration time only to the extent of the time it takes for the process to respond (the integration time TI of the integral calculation), and if this is the extent, the integration will be in a #mibolinear state. approximated. In this way, with the curve (A) as a reference, if β is increased in the positive direction, the integral time Ti can be increased, and if β is increased in the negative direction, the integral time T can be decreased.

Next, a method of setting the adjustment parameter 10 in this embodiment will be explained. Note that the adjustment of the control constant TI is the same as that in the above-mentioned embodiment, so a description thereof will be omitted.

stem It is calculated as follows.

'? Kp, Kp, Tz, 'r'ha OHR
Since it is a constant determined by the modulus, the optimum β0 is calculated, and β is calculated based on this.

When the adjustment parameter β is set in this way, the response of the control amount PV to a change in the target value Sv is as shown in FIG.
Overshoot can be improved without affecting the response rise characteristics. For example, when the transfer function GP(s) of the controlled object 3 is: e '' torque and β = oi, if the integration time is not compensated for, there will be a large overshoot as shown in (a), but β = 0. When the equivalent integration time for the target value is changed by setting .15, the target value tracking characteristic is greatly improved as shown in (b).At this time, the control constant TI of the control calculation unit 110 is set to the control constant TI of the disturbance control optimum state. The constant TI is modified by the adjustment parameter β, and has no effect on the disturbance suppression characteristics at all.

In this way, in addition to the effects of the first embodiment, the present embodiment has the following advantages: (5) Integral time T, which was previously thought to be possible
Since I can be equivalently compensated for, controllability can be greatly improved even for an integral process (non-localization process). This is because in the integration process, the integration time in the state of optimal characteristics for disturbance suppression is finite, but it must be infinite in the state of optimal characteristics for target value tracking, and this is necessary to obtain optimal controllability in both states. This is because it is necessary to have a configuration that allows the integration time to be changed. Also, according to the OHR method shown in FIG. 11, only the integral time is determined by different parameters, such as the time constant T of the controlled object for the target value of the dead time L1 of the controlled object for disturbance suppression. , this compensation is absolutely necessary to improve controllability.

If this second embodiment is added as a compensation structure for the integral operation of the first embodiment, a structure can be obtained in which all the proportional, integral, and differential operations of the control calculation section 11 can be compensated for in two degrees of freedom. can be realized.

Next, a third embodiment of the present invention will be described using FIG. 9.

In this embodiment, the control calculation section 11b is proportional and differential.

Each calculation of the integral is executed based on the control constants KP, Tx, TD of the target value tracking optimum characteristic state, and these control constants are set to the disturbance suppression optimum characteristic state KP, TI, for the control amount Pv. This is applied to the adjustment output from the calculation unit 11b that compensates for TD.

That is, in the first and second embodiments, the compensation calculation section
In contrast to the controlled variable filter type in which the controlled variable Pv is compensated so that the control constant KP*"I*TD enters the disturbance suppression state in the control 10 and then supplied to the control calculation section 11, in this embodiment, the control constant KP*"I*TD is Regarding the amount of adjustment output calculated in the target value tracking state by the calculation unit 11b due to fluctuations in the control amount PV, the control amount P
It has a control amount feedback type configuration in which the disturbance suppression state is corrected by the compensation output a(3) calculated based on the compensation value v.

In the figure, the same components as in FIG. 1 are given the same reference numerals. The control calculation unit 11b determines whether the control constant KPeTI+TD, which is set in the optimum characteristic state for disturbance suppression, is in the optimum state following the target value as shown in the equation of α, TLT? Adjust parameters α, β
, r, and the output that has been adjusted and calculated based on this is supplied to the calculation section 12.

Ax 1 β '(s) = Kp (1-α) + (Stone -77) + (1-α
)TD・S) In the computation unit 12, from this adjustment output, the compensation computation unit 10b calculates the proportional
Compensation output a (s) after performing integral and differential compensation operations
This result is output to the controlled object 3 as the manipulated variable U.

β field)=KPca+1+T1. s+r11TDllS) According to this configuration, the controlled object 3 is supplied with the manipulated variable U that is optimal for the change in the target value Sv and the variation in the controlled variable PV due to disturbance.

Next, the control response of this embodiment is as shown in the following equation.

By substituting α2 equation, (OS of equation 13), and Qs+ into equation I, as shown in equation 09, the target value Sv and the denominators of both peaks of disturbance are the control constant KP of the disturbance suppression optimum characteristic state, respectively.
#TI #TD is a general formula for proportional, integral, and differential control, and only the numerator of the term for the target value Sv is changed by the adjustment parameters α, β, and r. As a result, the characteristics against disturbance are optimally fixed,
Only the characteristics with respect to the target value Sv can be freely optimized as desired.

×S 1+(KP(1+5+Tn-8)) ・Gp(s) Also, since this response-like integral term is compensated by a first-order lag element, as mentioned above, the conditions for the process to settle in a steady state, i.e. The final value theorem is also satisfied.

Furthermore, the values of the adjustment parameters α, β, and r are determined by the value of the control constant of the disturbance suppression characteristic KP#T1.TD obtained by the OHR method based on (I) and the value of the control constant of the target value tracking characteristic. Depending on Tt, the lever βG'!1-12Xβ, that is, the vicinity of β=−×βG, is determined by simulation as the optimum value.

Once the values of the adjustment parameters are obtained in this way, the values of the control constants KP, TI, and TD are set so that the response of the control amount Pv when the target value Sv is changed step by step is the desired follow-up characteristic. Accordingly, the disturbance suppression is adjusted to the optimum characteristic state.

As a result, when the control constant is virtually set to be optimal for both disturbance suppression and target value tracking characteristics, when the control amount PV fluctuates due to disturbance, control calculation is performed to compensate for the deviation caused by this. The unit 11b obtains the adjustment output based on the control constant in the target value following state, and adds to this the compensation output a (s) calculated by the calculation unit 12 based only on the control amount Pv independently of the target value Sv, etc. It is outputted as a disturbance suppression state.

This embodiment can also provide the same effects as the first and second embodiments.

In this embodiment, the control calculation unit flb performs proportional, integral,
The explanation has been given using an example in which each differential operation is executed, and the compensation operation unit 10 also executes the corresponding proportional, integral, and differential operations. However, in the present invention, as described above, the control calculation unit 11 only needs to be configured to execute at least one of proportional, integral/minute, and differential calculations, and the control calculation unit Proportional, integral, or differential calculations can be used alone or selectively in combination, as long as the desired target value tracking response can be obtained in correspondence with or independently of the calculations. For example, if only overshoot suppression is required, integral compensation alone may be sufficient, or proportional or differential compensation or a combination of both proportional differential compensation may be sufficient depending on the degree of improvement in the rise characteristics.

Furthermore, in this embodiment, the explanation has been made using a perfect differential as the differential operation of the control calculation unit 11, but it goes without saying that the same applies to the perfect differential, which is commonly used in the present invention. It is used as inclusive.

[Effects of the Invention] As explained above, according to the present invention, the control constant adjusted to the target value pursuit lt1 optimum characteristic state by the adjustment parameter is Since it can be virtually corrected to the suppression optimum characteristic state, disturbances and
The optimum characteristic state for both target values can be easily and freely adjusted and realized.

[Brief explanation of the drawing]

FIGS. 1 and 2 are block diagrams showing the configuration of an embodiment of the present invention, FIGS. 3 and 4 are diagrams for explaining the operation of an embodiment of the present invention, and FIGS. The figure is a block diagram showing the configuration of another embodiment of the present invention, FIGS. 7 and 8 are diagrams for explaining the operation of another embodiment of the present invention, and FIG. 9 is a block diagram showing the configuration of another embodiment of the present invention. A block diagram showing the configuration of an example, and FIGS. 10 and 11 are diagrams for explaining a conventional example. 1... Deviation calculation unit 3... Controlled object 10...
Compensation Calculation Department 11...Control Calculation Department Agent Patent Attorney
Noriyuki Noriyuki Yudo Hirofumi Miho

Claims (6)

[Claims] (1) A deviation calculation means for calculating the deviation between the controlled variable from the controlled object and this target value, and adjustment of the deviation from this deviation calculation means to a characteristic state that optimally follows changes in the target value. control calculation means for performing at least one of proportional integral and differential calculations based on control constants set by parameters and outputting adjustment calculations; A process control device comprising compensation calculation means for equivalently correcting a characteristic state to a characteristic state that optimally suppresses the fluctuation thereof. (2) The process control device according to claim 1, wherein the control calculation means adjusts the control constant of the integral calculation by a delay element. (3) The compensation calculation means adjusts the control constant of the control calculation means to a characteristic state in which the control constant optimally suppresses the fluctuation of the control amount due to the disturbance. 2. The process control device according to claim 1, wherein the control amount is corrected and then supplied to the deviation calculation means. (4) The process control apparatus according to claim 3, wherein the compensation calculation means modifies the control constant of the control calculation means by a lead/lag element. (5) The compensation calculation means calculates a compensation amount for bringing the control constant of the control calculation means into a characteristic state that equivalently suppresses fluctuations due to disturbance optimally based on the fluctuation of the control amount, and performs the compensation. 2. The process control device according to claim 1, wherein the adjustment calculation output from the control calculation means is corrected based on the amount. (6) The process control device according to claim 5, wherein the compensation calculation means equivalently modifies the control constant of the integral calculation of the control calculation means by a delay element.