JPH0610761B2 - Controller - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a controller that automatically adjusts at least proportional (P) and integral (I) operation constants to optimum values. More specifically, the present invention provides
Looking at the change in the control amount due to randomly generated disturbances,
The present invention relates to an auto tuning controller that adjusts a PI calculation constant so as to obtain an optimum response.

(Prior Art) In the process PI controller used for feedback control, the PI calculation constant is currently set manually based on the long-term knowledge and experience of the process driver or instrumentation engineer. is there. However,
With manual configuration, the process startup,
Under load fluctuation, unexpected disturbance, or under the condition of a system having non-linear gain characteristics, the process operation may be disturbed temporarily or steadily, and economic loss may be caused depending on the condition.

Therefore, a controller in which the PI calculation constant is automatically tuned has been proposed. The auto-tuning controllers that have been proposed so far have an auxiliary controller connected in parallel to the main controller, increase the gain of the auxiliary controller, cause vibration, and from the amplitude and frequency, the so-called Z by Ziegler, Nichols. , N Determine the PI constant based on the limit sensitivity method (Showa 45, The Society of Instrument and Control Engineers Vol.6 No.6 P55-P60 Adaptive control system using the limit sensitivity method, Toshiyuki Kitamori), On, Off Generate a limit cycle using a generator and select the optimum PI from its amplitude
There is one that decides the operation constant (Proceedings of the 12th Academic Lecture Meeting of the Society of Instrument and Control Engineers 1973, P617-P624 PID automatic setting adaptive controller Sumi, Fukuda).

(Problems to be Solved by the Invention) However, in the auto-tuning controller having such a configuration, it is necessary to put the process in an oscillating state or forcibly give a disturbance (identification signal) to the control system when the PI constant is determined. However, there is a problem that this has a considerable influence on the process.

The present invention has been made in view of such problems,
Its purpose is to optimize P without affecting the process.
It is intended to realize a controller having an auto-tuning function capable of setting an I operation constant.

Another object of the present invention is to optimize the optimum P with a small number of calculations.
It is to realize a controller that can be quickly tuned to the I operation constant.

(Means for Solving Problems) The present invention for achieving the above-mentioned object is to perform an integral operation at least in proportion to a deviation signal between a process amount from a process and a set value, and obtain the manipulated variable in the process. The PI control means for outputting and the waveform of the deviation signal between the process amount or the process amount and the set value are observed, and when the signal becomes a predetermined value or more, peak information (E1, E2, E3) of the waveform pattern and Overshoot amount OVS (= -E2 / E) based on time information (t1, t2, t3) at which the peak occurs.
1), damping value DMP {= (E3-E2) / (E1
-E2)} and a vibration period Tp (= t3-t1), a waveform observing unit, a target setting unit that sets at least an overshoot amount and a damping value that are targets of the process controllability, and the waveform observing unit. The amount of overshoot (O
VS), damping value (DMP) and vibration period (TP)
And a target value set by the target setting means, respectively, and a parameter calculating means for calculating a parameter to be set in the PI control means, wherein the parameter calculating means is obtained by the waveform observing means. According to whether the damping value (DMP) is larger than a predetermined value or not, it is divided into two sections, and one of the sections is further obtained by the integration constant (TI) set in the PI control means and the waveform observing means. It is divided into a plurality of calculation sections according to the magnitude of the ratio R (= TI / TP) to the vibration period (TP), and the target value of the overshoot given from the target setting section and the waveform observing section for each section. The error overshoot amount (Eovr) indicated by the difference between the overshoot amount obtained in step 1, the target value of the damping value given from the target setting means, and the waveform view. Error damping value indicated by the difference between the damping values obtained by means (EDMP),
Ratio (R) of the integration time (TI) and the vibration period (TP)
It is a controller characterized in that at least proportional and integral constants are calculated by applying different arithmetic expressions using at least one of the above.

(Example) FIG. 1 is a functional block diagram showing an example of an apparatus according to the present invention. In the figure, reference numeral 1 is a block showing a process target, and its dynamic characteristics are assumed to change depending on the driving target. 2 is set value SV and process amount PV from process 1
In the PI control block whose input signal is the deviation ε from
The calculation constant is automatically set by a signal from the parameter calculation block 3 surrounded by a broken line. The output signal MV from the PI control block 2 is applied to the process 1.

In the parameter calculation block 3, 31 is the set value SV,
A waveform observing means for observing the waveform of the deviation signal ε between the SV and PV by inputting the process amount PV respectively, and the overshoot amount OVS of the deviation signal ε, the damping value DMP, the vibration period T _P
Has the function of seeking. Reference numeral 32 denotes a target setting means for setting a target value which is a target of controllability, and at least an ideal overshoot amount OVS in the process 1 and a damping value DMP are set therein. Reference numeral 33 is a parameter calculation means for calculating the PI constant by calculation, and calculates the PI calculation constant so that the overshoot amount and the damping value obtained from the waveform observation means 31 approach the target value set by the target setting means 32. Each of these means 31, 32, 33 is realized by a program by a microcomputer installed in the controller, for example.

FIG. 2 is an explanatory diagram of a waveform observation method in the waveform observation means 31. The waveform observing means 31 first obtains a deviation ε between the set value SV and the process amount PV, and when the deviation ε becomes larger than a predetermined value ΔE set in the preliminary target setting means 32, the waveform observation is started. To do. Assuming that this deviation ε changes with time as shown in the figure, this deviation ε
When the waveform becomes larger than ΔE, the waveform observation is started, the peak values E1, E2, E3 of the waveform are detected, and the times t1, t2, t3 until the peak values are reached are measured. Using these values, the overshoot amount OVS, the damping value DMP, and the vibration period T _P are calculated by the following calculation formula, and the calculation result is given to the parameter calculation means 33.

In the example of FIG. 2, the pattern of the waveform observed by the waveform observing means 31 oscillates around the 0 level, but it may fluctuate around a certain value (for example, a set value). , Observation waveform peak information E1 to E
3 will use the absolute value in the following calculation.
Further, the waveform observing means 31 detects each peak value of the observed waveform, but if no peak is detected even after a predetermined time has elapsed after starting the observation of the waveform (for example, in the case of a non-oscillating system), The value at the time when a predetermined time has elapsed is taken in as the peak value E1, and the peak values E2 and E3 corresponding to the second and third peaks are treated as 0. And

Here, the overshoot amount OVS and the damping value DM
The significance of defining P by the following arithmetic expression is that those values can be obtained only by the peak information E1, E2, E3 of the waveform.

T _p = t3-t1 parameter calculation unit 33, based on the calculation result obtained by the waveform observing means 31, the current proportional constant set in the PI control block 2, is the integration constant, the target setting means 32
Recognize the relationship between the proportional constant and the integral constant, which are the targets for realizing the overshoot amount and damping value set in, and according to some categories determined by each relationship. , And apply different arithmetic expressions to calculate at least a new proportional constant and integral constant (change amount from the current value). The new proportional constant and integral constant thus obtained are reset in the PI control block 2, and the PI control block 2 then performs PI calculation based on the newly set constant and outputs the operation signal. Output to process 1.

FIG. 3 is a flowchart showing an example of the operation of the parameter calculation means 33. Here, an example in which four divisions are determined is illustrated.

First, the damping value DMP obtained by the waveform observation means 31.
Is smaller than "0" (step 1). As a result, P, which is currently set in the PI control block 2,
It is determined whether or not the I constant is in the A section described later. That is, when the damping value DMP is smaller than "0", it shows a non-oscillating response characteristic, and it is judged that the present controllability by the P and I operation constants is in the A category, and the target setting means
A calculation for changing the P and I calculation constants is performed so as to approach the target value set to 32 (step 2). Damping value DMP
When ≧ 0 (“No” in step 1), the value R of (integral calculation constant T _I ) / (vibration period T _P ) is calculated (step 3) and the magnitude of this value R is determined ( Step 4), that is, if R <0.2, it is determined that the PI operation constant currently set is in the B category, and the process proceeds to step 5. If 0.2 ≦ R ≦ 0.4, it is determined to be in the C category, and if R> 0.4, it is determined to be in the D category, and the process proceeds to step 7. Thus, depending on the damping value, the vibration period, and the magnitude of R,
FIG. 4 shows the concept of each division and the arithmetic expressions in each division, which are divided into four divisions A, B, C, and D, and are based on the empirical rule up to now. In FIG. 4, the horizontal axis is the value of R and the vertical axis is the damping value DMP. The hatched area (damping value DMP = 0.2, R =
In the area where the target value is around (0.2), the controllability goes to the target value from any section by performing the predetermined calculation for obtaining the proportional calculation constant PB and the integral calculation constant Ti shown for each section. Such P operation constant and I operation constant are obtained. The present invention can be similarly applied to a controller including a differential (D) operation, and FIG. 4 also shows, for reference, an arithmetic expression for obtaining a differential operation constant Td. is there.

In each equation shown in FIG. 4, PB1 and PB2 are the current and next proportional computation constants, Ti1 and Ti2 are the current and next integral computation constants (integration time), Eovr is error overshoot, and Edmp is error damping. .

Here, the error overshoot Eovr is the difference between the overshoot amount OVS given from the waveform observing means 31 and the ideal overshoot amount OVS set in the target setting means 32, and the error damping Edmp is the waveform. It is the difference between the damping value DMP given from the observing means 31 and the ideal damping value DMP set in the target setting means 32. If the observed waveform pattern shows an ideal response, these are the differences. Each error value Eov
Both r and Edmp are zero.

Equations (1A) and (2A) in category A are applied in step 2, and the proportional calculation constant PB2 and the integral calculation constant Ti2 are
Depending on the values of the error damping Edmp and the error overshoot Eovr, values that both increase from the current constant are obtained. If Edmp and Eovr are 0, PB2 and Ti2
Is the same value as PB1 and Ti1 this time.

Equations (1B) and (2B) in category B are applied in step 5, and the proportional calculation constant PB2 and the integral calculation constant Ti2 are
Values that decrease from the current constant at a ratio of R / 0.2 (here, R is smaller than 0.2) are obtained.

In the same manner, equations (1C) and (2C) in section C are applied in step 6 to (1C) and (2C) in section D.
Equations (D) and (2D) are applied in step 7.

In step 8, the proportional operation constant and the integral operation constant obtained in any of steps 2, 5, 6, and 7 are reset in the PI control block.

By the above operation, the PI control block 2
Whatever value the proportional calculation constant and integral calculation constant are set to, the controllability will be automatically adjusted so as to finally reach the optimum target value.

In the above description, the waveform observing means 31 is configured to observe the waveform of the deviation signal between the process amount and the set value, but if the set value is constant, the waveform of the process amount is May be observed. Further, in the above description, the controller having the PI control block is described as an example, but the controller may be applied to the controller having the PID control block.

FIG. 5 is a diagram showing how the controlled variable PV, the proportional constant P and the integral constant I change when the set value SV is changed stepwise in the controller according to the present invention. is there. In the controller, the target of controllability is the damping amount.
DMP = 0.300 and overshoot amount OVS = 0.200.

FIG. 6 is a block diagram of the simulation used to obtain the diagram of FIG. 5, where L = 6 seconds, T = 6 seconds, and K = 1.0.

As can be seen from the results of this experiment, according to the controller of the present invention, the PI constant that provides the optimum response is automatically set by executing the parameter calculation several times.

(Effects of the Invention) As described above, the present invention observes the waveform of the process amount or the deviation signal due to the change of the set value or the load change in the process, and based on the observation result, the P and I operation constants are calculated. I am trying to change to the optimum value. Therefore, according to the present invention, it is possible to realize a controller having an auto-tuning function capable of setting an optimum PI calculation constant without adversely affecting the process.

Further, in the present invention, the parameter calculation means includes a calculation classification which is classified according to whether or not the damping value (DMP) obtained by the waveform observation means is larger than a predetermined value,
If it does not fall within this calculation section, there are a plurality of calculation sections divided according to the ratio R (= TI / TP) between the integration constant (TI) and the vibration period (TP) set in the PI control calculation means. And the error overshoot amount (Eov with respect to the target value given from the target setting means for each section).
r), an error damping value (Edmp), and a different calculation formula using at least one of the ratio (R) of the integration time (TI) and the vibration period (TP) is applied to calculate at least a proportionality and an integration constant. To do. Therefore, according to the present invention, it is not necessary to identify the dynamic characteristics of the process, and the method of operation division and the operation formula set for each operation are
It is possible to apply know-how based on many years of knowledge and experience, and it is possible to quickly tune to an optimum PI calculation constant with a small number of calculations.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing an example of an apparatus according to the present invention, FIG. 2 is an explanatory diagram of a waveform observing method in a waveform observing means, and FIG. 3 is a flowchart showing an example of the operation of the parameter calculating means 33. FIG. 4 is an explanatory view showing the concept of each section defined by the parameter calculating means and an arithmetic expression in each section, FIG. 5 is a diagram showing how the PI constant changes in the controller of the present invention, and FIG. 6 is FIG. 5 is a block diagram of the simulation used to obtain the diagram of FIG. 1 ... Process, 2 ... PI control block, 3 ... Parameter calculation block, 31 ... Waveform observation means, 32 ... Target setting means,
33 ... Parameter calculation means.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 54-116580 (JP, A) JP 50-12491 (JP, A) JP 60-63601 (JP, A)

Claims (1)

[Claims] 1. PI control means for performing at least proportional and integral calculations on a deviation signal between a process amount and a set value from a process and outputting the obtained manipulated variable to the process, the process amount or the process amount and the setting. When the waveform of the deviation signal from the value is observed and the signal becomes a predetermined value or more, the peak information (E1, E2, E3) of the waveform pattern and the time information (t1, t2, t3) at which the peak occurs are used. Based on the overshoot amount OVS (= -E2 / E
1), damping value DMP {= (E3-E2) / (E1
-E2)} and a vibration period Tp (= t3-t1), a waveform observing unit, a target setting unit that sets at least an overshoot amount and a damping value that are targets of the process controllability, and the waveform observing unit. The amount of overshoot (O
VS), damping value (DMP) and vibration period (TP)
And a target value set by the target setting means, respectively, and a parameter calculating means for calculating a parameter to be set in the PI control means, wherein the parameter calculating means is obtained by the waveform observing means. According to whether the damping value (DMP) is larger than a predetermined value or not, it is divided into two sections, and one of the sections is further obtained by the integral constant (TI) set in the PI control means and the waveform observing means. It is divided into a plurality of calculation sections according to the magnitude of the ratio R (= TI / TP) to the vibration period (TP), and the target value of the overshoot given from the target setting section and the waveform observing section for each section. The error overshoot amount (Eovr) indicated by the difference between the overshoot amount obtained in step 1, the target value of the damping value given from the target setting means, and the waveform view. Error damping value indicated by the difference between the damping values obtained by means (EDMP),
Ratio (R) of the integration time (TI) and the vibration period (TP)
A controller that calculates at least proportional and integral constants by applying different arithmetic expressions using at least one of the above.