JPH0610762B2 - 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.

(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, the manual setting causes temporary or steady process disturbances during process startup, load fluctuations, unexpected disturbances, or systems with nonlinear gain characteristics. In some circumstances, it may have caused economic losses.

Therefore, a controller in which the PI operation constant is self-tuned has been proposed. The self-tuning controllers that have been proposed so far have an auxiliary controller connected in parallel with 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. -Identification of PI constants based on N-limit sensitivity method (1965, Transactions of the Society of Instrument and Control Engineers Vol. 6, No. 6. P55-P60 Adaptive control system using limit sensitivity method, Toshiyuki Kitamori), ON , The off-generator is used to generate a limit cycle, and the optimum PI operation constant is identified from its amplitude (Showa 48
Proceedings of the 12th Academic Lecture Meeting of the Society of Instrument and Control Engineers P617-P624
PID automatic setting type adaptive controller Sumi, Fukuda) etc. In addition, the applicant previously filed Japanese Patent Application No. 60-24845.
No. 1 proposes a self-tuning controller that adjusts the PI operation constant so as to obtain an optimum response by observing changes in the control amount due to disturbances that occur randomly without giving disturbances to the process.

(Problems to be Solved by the Invention) By the way, any of these self-tuning controllers can perform self-tuning under automatic operation. Therefore, for example, in a process such as controlling a pH value, when the pH sensor is regularly cleaned, or when the automatic operation is interrupted in the case of batch off, the process may be temporarily disturbed,
However, there is a problem that self-tuning rather deteriorates controllability.

The present invention has been made in view of these problems,
The purpose is to realize a controller that stops the control operation of self-tuning when the interruption of the automatic operation occurs.

(Means for Solving Problems) According to the present invention for solving the above-mentioned problems, at least PI control means for performing proportional and integral operations and a change in the control amount are checked so that the control amount has an optimum response. Self-tuning control means for adjusting the PI calculation constant in the PI control means and detection means for detecting interruption of automatic operation by the controller are provided, and the self-tuning control means includes a process amount or a process amount and a set value. When the waveform of the deviation signal of is observed and the signal becomes a predetermined value or more, based on the peak information (E1, E2, E3) of the waveform pattern and the time information (t1, t2, t3) at which the peak occurs, Overshoot amount OVS (= -E2 / E1), damping value DMP {= (E3-E2) / (E1-E)
2)} 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 controllability of the process, 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)
Is used to calculate at least proportional and integral constants, and the self-tuning control means is configured to perform self-tuning operation when the detection means detects interruption of automatic operation. It is a controller characterized by stopping.

(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 arithmetic constant is automatically set by a signal from the self-tuning 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 self-tuning block 3, 31 is the set value S
V and process amount PV are input respectively, and the waveform observing means for observing the waveform of the deviation signal ε of SV and PV is used by the waveform observing means OVS of the deviation signal ε, the damping value DMP,
It has a function of obtaining the vibration cycle Tp. Reference numeral 32 is 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. 33
Is a parameter calculation means for calculating a PI calculation constant, and calculates the PI calculation means so that the overshoot amount and the damping value obtained from the waveform observing 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. 4 is a detection means for detecting the interruption of the automatic operation by the controller, for example, a signal instructing the washing of the pH sensor,
It is composed of a digital input circuit for inputting a signal for instructing batch off (contact input of relay, voltage level signal, etc.). The signal from the detecting means 4 is applied to the self-tuning block 3 to instruct the self-tuning operation or stop here.

The operation of the device configured as described above will be described below.

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
The waveform observation is started at a time when is larger than ΔE, 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 Tp are obtained by the following arithmetic expression, and the arithmetic result is given to the parameter arithmetic 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 value information E1, E2, E3 of the waveform.

The Tp = t3−t1 parameter calculation means 33 uses the target setting means 32 to calculate the current proportional constant and integration constant set in the PI control block 2 based on the calculation result obtained by the waveform observing means 31.
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 DM obtained by the waveform observation means 31
It is determined whether P is smaller than "0" (step 1). As a result, it is determined whether the P and I constants currently set in the PI control block 2 are 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 determined that the current controllability by the P and I operation constants is in the A category, and is set in the target setting means 32. A calculation for changing the P and I calculation constants is performed so as to approach the target value (step 2). If the damping value DMP ≧ 0 (if “No” in step 1),
The value R of (cumulative calculation constant T _I ) / (vibration period T _P ) is calculated (step 3), and the magnitude of this value R is judged (step 4), that is, if R <0.2, the current setting is made. It is determined that the PI calculation constants that are stored are 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. In this way, according to the damping value, the vibration period, and the size of R, the four divisions of A, B, C, and D are based on the empirical rule so far. The arithmetic expression in is shown in FIG. In FIG. 4, the horizontal axis is the value of R and the vertical axis is the damping value DMP. In the area where the target values are in the hatched area (near the damping value DMP = 0.2, R = 0.2) in this figure, the predetermined values for obtaining the proportional operation constant PB and the integral operation constant Ti shown for each section are set. By performing the calculation,
The P operation constant and the I operation constant are obtained from any of the sections so that the controllability approaches the target value. Note that 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 the error overshoot, and Edmp is the 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.

The formulas (1A) and (2A) in the category A are the same as the step 2
Applied in, proportional calculation constant PB2, integral calculation constant Ti2
Is required to be a value that increases from the current constant according to the values of the error damping Edmp and the error overshoot Eovr. If Edmp and Eovr are 0, PB2 and Ti
2 is the same value as PB1 and Ti1 this time.

The equations (1B) and (2B) in the section B are the same as those in step 5
Applied in, proportional calculation constant PB2, integral calculation constant Ti2
Are required to be values that decrease from the current constant at a ratio of R / 0.2 (here, R is smaller than 0.2).

Hereinafter, similarly, in the same way, the formula (1C) in the section C, (2
The equation (C) is applied in step 6, and the equations (1D) and (2D) in the section D 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.

Here, when the detecting means 4 detects the interruption of the automatic operation of the controller, it outputs a signal to that effect to the self-tuning block 3. Upon receiving this signal, the self-tuning block 3 stops the self-tuning operation. As a result, even if the process is temporarily disturbed, it does not affect the subsequent self-tuning operation.

FIG. 5 is a functional block diagram showing another example of the device of the present invention. In this embodiment, a switch SW for turning off the control output from the parameter calculation block 3 is provided between the self-tuning block 3 and the PI control block 2.
And the switch SW is driven by a signal from the detecting means 4 and a signal from the external setting switch SWU. As a result, the self-tuning operation can be stopped from the outside by operating the switch SWU in the automatic operation state.

(Effects of the Invention) As described above, according to the present invention, it is possible to realize a self-tuning controller capable of automatically performing a self-tuning operation and a stop according to the status of automatic operation of a process, interruption, and the like.

Further, according to the present invention, as the self-tuning control means, in particular, the process amount or the deviation signal between the process amount and the set value is observed, and when the deviation signal becomes a predetermined value or more, the overshoot amount , The structure is provided with a waveform observing means for obtaining a damping value and a vibration period, and no disturbance is given to the process. Further, since the waveform observing means in the self-tuning control means may perform the calculation for obtaining the overshoot amount, the damping value and the vibration period only when the deviation signal exceeds the predetermined value, the self-tuning control means It is possible to reduce the burden on.

[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 view of a waveform observing method in a waveform observing means, FIG. 3 is a flow chart showing an example of operation of a parameter calculating means, and FIG. Is a conceptual diagram of each section defined by the parameter calculation means, and FIG. 5 is a functional block diagram showing another example of the device of the present invention. 1 ... Process, 2 ... PI control block, 3 ... Parameter calculation block, 4 ... Detection means, 31 ... Waveform observation means, 32 ...
Target setting means, 33 ... Parameter calculating means.

Claims (1)

[Claims] 1. A PI control means for performing at least proportional and integral calculations, and a self-tuning control means for adjusting a PI calculation constant in the PI control means so that the control quantity has an optimum response by observing a change in the control quantity. The controller is provided with detection means for detecting interruption of automatic operation, and the self-tuning control means observes a waveform of a process amount or a deviation signal between the process amount and a set value, and the signal is a predetermined value or more. When it becomes, the overshoot amount OVS (= -E2 / E1) and the damping value DMP {based on the peak information (E1, E2, E3) of the waveform pattern and the time information (t1, t2, t3) when the peak occurs. = (E3-E2) / (E1-E
2)} 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 controllability of the process, 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)
At least proportional and integral constants are applied by applying different arithmetic expressions using at least one of the self-tuning control means and the self-tuning control means, when the detection means detects interruption of automatic operation, self-tuning operation is performed. A controller that is characterized by stopping.