JPH033007A - Controller - Google Patents

Abstract

PURPOSE:To quickly stabilize a processed variable at the time of switching autotuning to PID control after ending the autotuning by making it possible to change a set value at the time of ending the autotuning. CONSTITUTION:An autotuning end processing part 21 consists of a useless time calculation part 22, a process gain calculation part 23, a tuning end processing part 24, an output holding time control part 25, an integration term changing part 26, and a load ratio output part 27. At the time of receiving a signal from a limit cycle measuring part 10, the useless time calculation part 22 calculates useless time. When a set value is to be changed at the time of ending limit cycle measurement, the tuning end processing part 24 outputs a signal for changing the set value for PID control to a setting part 2. Consequently, the processed variable can be quickly stabilized by the combination between an output holding time and the optimum output corresponding to a load ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a controller having an auto-tuning function using a limit cycle method, and particularly relates to optimal processing at the end of auto-tuning.

<Prior Art> As a conventional controller having an auto-tuning function using the limit cycle method, there is a controller as shown in FIG. 8, for example.

In this controller, ■ is an A/D converter to which control 1t (PV) is input, 2 is a setting section for setting the set value (SV), and 3 is the connection between the control amount (PV) and the set value (SV). 4 is a PID control unit, 5 is an auto-tuning unit, 6 is a switch for switching between auto-tuning/PID control in the auto-tuning unit 5, and 7 is a D/A conversion unit that outputs a manipulation signal (MV). It is a vessel.

The auto-tuning section 5 includes a tuning management section 8
, 0N10FF control section 9, limit cycle measuring section 10, PID constant calculating section 11, and PID constant changing section 1
It consists of 2.

As is well known, in this type of controller, when performing PID control on a controlled object, such as a heating furnace, it is necessary to know the optimum PID constant for the controlled object. , find the optimal PID constant, and use this constant to determine the desired PI
Perform D control.

As one method for this auto-tuning, there is a limit cycle method that performs 0N10FF control on the controlled object and calculates the PID constant from the cycling waveform (limit cycle) of the controlled variable (PV), which is often used. The measurement of this limit cycle is performed over several cycles, and the point in time when the measurement of this limit cycle is completed is defined as the end point of auto-tuning, and at this point, the control is switched to PID control.

At the end of this limit cycle measurement, the set value (SV)
Generally, this is the point when the control amount (PV) and the control amount (PV) become equal.

Also, depending on the controlled object, if the controlled variable (PV) exceeds a certain value, the properties of the controlled object will change. You may dislike it.

However, in auto-tuning using the Mitucycle method, since a limit cycle with a certain amplitude is generated around the set value (SV), it is natural that the control amount (PV
) will inevitably exceed the set value (SV). Conventionally, in such cases, a value smaller than the setting value for actual control (S V s) is set as the setting for auto-tuning (!(SV,), and this setting is Perform auto-tuning with the value (SV,),
At the point when the limit cycle measurement is completed (tx), set value (SV) is changed to PIDIIJ set value (SV).
) and switch to PID control.

<Problems to be Solved by the Invention> However, if the PID control was simply switched from the end of the auto-tuning as described above to the PID control, the following problems would occur.

(1) With conventional controllers, as shown in Figure 8, limit cycle measurement ends at a certain point (tx) and when switching to Pi control, it is either on or off (
For example, MV. 8.MV. (FF state), it is switched as is.

At this switching point, due to delay elements and dead time elements of the controlled object, the operation signal (MV ON
) is the point where the influence of 1jt (PV) is greatest, and as shown in the figure, the slope of control 1jt (PV) is large. On top of that,
The PID control operation signal (MV) is in the off state (MV.
Since the process starts from state F), there are large fluctuations (see fluctuation section A), and there is a drawback that rapid stabilization cannot be expected.

(2) Also, set values for actually performing PID control (S
Even when performing auto-tuning with a set value (SV, ) smaller than Vi, the control amount (PV
) has a large slope, and it is either on or off (
For example, MV. 8, MVOF, state B), the fluctuation is large because it is switched directly (see fluctuation section B1)
However, there was a similar drawback in that rapid stabilization could not be expected.

In other words, when the limit cycle measurement is finished, auto-tuning is immediately terminated and the switch is switched to PID control. (PV) is greatly disturbed and it takes a considerable amount of time to stabilize.

The present invention has been made in view of such conventional circumstances.

One of the features of the present invention is that an auto-tuning end processing section is added to a controller with an auto-tuning function based on the limit cycle method, and this auto-tuning end processing is performed. By keeping either the on or off output state the same as the dead time (L) determined by the limit cycle measurement from the point at which the limit cycle measurement is completed, the delay element or dead time of the controlled object is This makes it possible to switch to PID control when the influence of the 0N10FF control that had been performed until then is reduced, and the load factor (KX) corresponding to the set value (SVX) at that time is used as an operation signal when switching to PID control. )
It is about giving.

Another feature of the present invention is that the auto-tuning end processing section allows the set value (SV) to be changed at the end of the limit cycle measurement, and the actual value after the setting change is changed from the end of the limit cycle measurement. The load factor (KX) corresponding to the set value (SVx) for PID control
) as an operation signal (MVx), and by keeping this output for the same amount of time as the dead time (L) determined by limit cycle measurement, the set value (SVll) caused by delay elements and dead time of the controlled object can be calculated. 0N10FFIIIJ that I went to? It is possible to switch to PID control when the influence of II has decreased, and the setting value (S
The objective is to provide a load factor (KX) corresponding to VX).

Therefore, in the present invention having the above configuration, after the auto-tuning is completed, the PID! When switching to IHI, the control amount (PV
) can be quickly stabilized.

<Embodiment> FIG. 1 shows an embodiment of a controller according to the present invention.

This controller has approximately the same configuration as the controller shown in FIG. 7 described above, except for the three-point changeover switch 16 of the auto-tuning unit 5 and the auto-tuning end processing unit 21, and has the same components as the controller. are given the same reference numerals.

The auto-tuning termination processing section 21 includes a dead time calculation section 22, a process gain calculation section 23, a tuning termination management section 24, an output holding time management section 25, an integral term change section 26, and a load factor output section 27. It consists of

The dead time calculation section 22 is a section that receives a signal from the limit cycle measurement section 1O of the autotuning section 5 and calculates the dead time (L).This dead time (L) is sent to the output holding time management section 25. entered and managed.

The process gain calculation section 2 receives a signal from the limit cycle measurement section 10 of the autotuning section 5, and
This is a part that calculates and stores the process gain (GP) of the controlled object every time the limit cycle measurement ends normally.

The calculation of the dead time and the calculation of the process gain (GP) are performed as follows under the conditions shown in FIG. 2, for example. This figure 2 shows auto-tuning performed using the general limit cycle method, which measures three limit cycles and calculates the PID constant using the relatively stable measured values of two or three limit cycles. 3 shows the relationship between the set value (SV), the operation signal (MV), and the control amount (PV) in the case of FIG.

Depending on how you choose the setting value (SVl) for auto-tuning, the dead time (L3,
Ls ) and sv, > PV and (D dead time ((L4.
L,) may vary considerably.

Therefore, the dead time (L) used for holding the output is calculated as follows using the dead time (L3L,) on the side that actually holds the output.

L=((L3±LS)/2...Formula (1) When calculating the process gain (G,), first, set value (SV
, ) to find the load factor (K1).

K, = (τ08+ +τosz)/(,1 plate +
τ·r)...Equation (2) Then, the process gain (GF) is obtained as follows.

K, (MVON MVOFF) +MVQFF
GP= SVll ......Equation (3) However, in Fig. 2, SV is a set value (sv) for performing auto-tuning, pv is a control amount, and L1 to . The dead time, τ0□, τ, obtained by measuring the beam cycle.

0 is the time when the operation signal (MV) is on (MVos),
τ0FFl+τ0FF11 is the time during which the operation signal (MV) is on (MVo□), and τ1τ2 is one period of the limit cycle.

The tuning completion management section 24 is a section that receives a measurement completion signal from the limit cycle measurement section IO of the autotuning section 5 and sends an operation signal to each section.

The integral term changing section 26 includes the process gain calculating section 2
In response to the first process gain (G,) obtained in step 3, the initial output of the PID control unit 4 when switching from autotuning to PID control is set at that time (1m (
SVX) load factor (KX), and P I D ! is given to the controlled object as the operation signal (MVX). This is the part that calculates and changes the value of the quadrant output (I(II), integral term output at time n) of the II control part type section.For example, it is calculated according to the calculation block diagram of the PID control section shown in Fig. It will be done.

SV (-1=SVx, MV (-1=KX, MV (-1= (100/PB)・(P
(II) From II(11) + D,), 1 (II) = (PB/100)・KX (P
(-)+D+-+)......Formula (4) However, Kx is the load factor corresponding to the set value (SVX), and K
, = G, ・Represented by SVX, SV) is the setting value at time n, P V (n) is the control amount at time n, MV
y, is the operation signal at time n, e(7, is the operation signal at time n.

The deviation at , P(7) is the proportional term output at time n, I (
nl is the integral term output at point n-1, D (fit is the differential term output at point n, PB is the proportional band, T is the integral time, TD is the differential time, and Δ is the sampling time.

The load factor output unit 27 receives the latest process gain (cp) calculated by the process gain calculation unit 23, and
This is the part that calculates the load factor (K,) of the set value (SVX) at that time using K=G, SVX, and sends it to the three-point changeover switch 16 of the auto-tuning section 5.

In this controller configured in this way, during auto-tuning, the tuning management unit 8 connects the movable contact 16a of the changeover switch 16 to the fixed contact 16c side of the 0N10FF control unit 9, and performs 0N10FF control of the controlled object. .

When the limit cycle measurement in the limit cycle measurement section 10 is completed, the end signal is input to the tuning completion management section 24, where the set value (S
It is determined whether or not there is a change in V), and if there is a change, the setting value (SV,) for auto-tuning of the setting unit 2 is set in the setting unit 2 for actual PID control. A signal is output to change the value to (SV, ).

On the other hand, a switching signal for the changeover switch 16 is sent to the tuning management section 8 through the output holding time management section 25 . This switching signal is generated at the end of limit cycle measurement and at the dead time (
L) is the holding time, and the data is sent twice after this time (L) has elapsed.

Then, the specific switching at that time and the operation signal (M
The output value of V) is divided into two cases depending on whether or not the set value (SV) is changed.

(1) At the end of normal auto-tuning without changing the set value (SV).

For example, as shown in FIG. 4 (corresponding to the case of FIG. 9 described above), if the limit cycle measurement ends at time tX, the dead time (L) will elapse and the tuning end management unit will 24 and the tuning management section 8, the movable contact 16a of the changeover switch 16 is kept connected to the fixed contact 16c side of the 0N10FF control section 9, and after continuing to output the off state (MVOFF),
By connecting the movable contact 16a of the changeover switch 16 to the fixed contact 16b side of the PID control section 4, the PID
When switching to the control, the initial output of the PID control section 4 is determined by the latest process gain (G.

) is used to set the load factor (K,'') corresponding to the set value (SVX) at that time, and start by giving it to the controlled object as an operation signal (MVX).

Thereby, it is possible to shift to stable PID control very quickly (see fluctuation section A2).

(2) At the end of auto-tuning that involves changing the set value (SV).

For example, as shown in FIG. 5 (corresponding to the case of FIG. 10 described above), if the limit cycle measurement ends at time tx, at this point, the tuning end management section 24 and the tuning management section 8 , the movable contact 16a of the changeover switch 16 is switched to the fixed contact 16d side of the load factor output section 27, and the load factor (( After continuing the output corresponding to K,), by connecting the movable contact 16a of the changeover switch 16 @ the fixed contact 16b side of the PID control unit 4, this PID
The initial output of the control unit 4 is calculated by using the latest process gain (GP > calculated by the process gain calculation unit 23 described above) to calculate the load factor (K,
) and start by giving it to the controlled object as an operation signal (MVX).

As a result, it is possible to shift to stable ptD control very quickly (see fluctuation section B!).

Next, the operation of this controller will be described according to a flowchart as shown in FIG. This flowchart is actually executed as a program of a microcomputer or the like constituting this controller at every control cycle during auto-tuning execution.

During auto-tuning, step S0 is called from the main program every control cycle, and in step S, it is determined whether or not the auto-tuning is finished.
If YES (in case of auto-tuning end processing),
Proceeding to step S2, it is determined whether or not the output holding time has elapsed (dead time elapsed). If the answer is NO, the process immediately proceeds to step S6, and the auto-tuning program in that control cycle is ended.

If YES, the output holding time has elapsed, the process proceeds to step S3, where the load factor (KX) is calculated, followed by step S4, where the integral term (r+, , ,) is calculated. , the switch to PrD control in step Ss is performed, and its output value is given as the value corresponding to the load factor (Kll >).The auto-tuning ends normally, and the switch to PID control starts from the next control cycle. become.

On the other hand, in the case of No in step SI indicating that auto-tuning is being performed, the process proceeds to step S7, where output calculation of ON10FF control is performed, and step S is reached, where it is determined whether or not auto-tuning is being measured. Here, in the case of YES during measurement, the process advances to step S9, a limit cycle measurement process. In step S, limit cycle measurement processing is performed, and (SVs-sv,) and (sv, -p■) are used for judgment in step srs, which will be described later.
Compare the signs, and if the signs differ, remember that fact. Thereafter, the process proceeds to step S, and the auto-tuning program in that control cycle is ended.

In step S, limit cycle measurement is completed N
In the case of O, each constant of the PID is calculated in step 310, then the dead time is calculated in step Sll, and further step Sl! Then, process gain (cp) is calculated.

Thereafter, in step SI3, it is determined whether or not there is a change in the set value (SV), and if the answer is NO, the process immediately proceeds to the end of step Sh. YE with setting value (SV) change
In the case of S, an actual change is made in step SI, and step srs is reached, where the sign comparison ((SVs S
Compare the signs of V, ) and (SVs PV)] and determine if the signs are not equal even once.
If the answer is NO, the process proceeds to step S6. During limit cycle measurement, if the sign is always equal to YES (-), the load factor (K,) of the set value (sv,)
After that, the process proceeds to step S, which is the end of the process.

<Effects of the Invention> As is clear from the above description, the controller of the present invention provides the following excellent effects.

(1) First, since an auto-tuning end processing section is added to a controller with an auto-tuning function using the limit cycle method, when auto-tuning is finished, the output holding time ( The control amount (PV) can be quickly stabilized by combining the optimum output value corresponding to the dead time (dead time) and the load factor.

(2) Furthermore, the auto-tuning end processing section is comprised of a dead time calculation section, a process gain calculation section, a tuning end management section, an output holding time management section, an integral term change section, and a load factor output section. Because it is configured as Changes etc. can be made.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing an embodiment of the controller according to the present invention, Figure 2 is a graph for determining dead time and process gain, and Figure 3 is a graph for determining changes in integral terms.
A calculation block diagram of the ID control section, Figures 4 and 5 are graphs showing the operating status of this controller, Figure 6 is a flowchart showing the flow of operation of this controller, and Figure 7 is a conventional example. FIG. 8 is a block diagram showing the controller according to the present invention, and FIG. 8 is a graph showing the operating state of the conventional controller. In the figure, 2... Setting section, 3... Deviation calculation section, 4... PID control section, 5... Auto tuning section, 8... Tuning management section, 16...・Switching switch, 21...Auto tuning end processing section, 22...
Dead time calculation section, 23... Process gain calculation section, 24... Tuning end management section, 25... Output holding time management section, 26... Integral term changing section, 27... Load factor output section , Procedural amendment (voluntary) August 31, 1999 Director General of the Japan Patent Office Yoshi 1) Tsuyoshi Moon ■, Indication of the case 1999 Patent Application No. 138522 2, Name of the invention IJ! 4 Section Total 3, Relationship with the case of the person making the amendment Patent applicant Address: 5-16-6 Kugahara, Ota-ku, Tokyo Name: Ri
Chemical Industry Co., Ltd. Representative Teruyuki Hochi 4, Agent 141 603 (440)-67
61 Address: 5-23-1-6 Higashigotanda, Tokyo Parts Ward,
hi Correct Object (1) In the specification, in the Detailed Description of the Invention column and the Brief Description of Drawings column (1), in the specification, ``Figure 8'' on page 2, line 9, is replaced with ``Figure 8''. Figure 7”. (2) "Switching point" on page 4, line 20 in the specification
is corrected as the "switching point". (3) In the specification, "in the state of..." on page 5, line 6 is amended to "in the state of...". (4) In the specification, "dead time" on page 6, line 19 is corrected to "dead time element." (5) In the specification, "actually after the change" in line 9 of page 7 is amended to "(actually) after the change." (6) In the specification, page 7, line 13. "Dead time" in lines 14 to 14 is corrected as "dead time element". ”. (8) In the specification, “Calculation unit 2” on page 9, line 2,
It is corrected as "calculation unit 23". (9), in the specification, page 9, line 19' ((L4
J is corrected as '(L4J. 00), in the specification, page 10, line 4' ((L,
' is corrected as '(L3J. (marked, 'Ka (MV
ONMVOFF) J,'Ka・(MVON-
MVOFF) Correct as J. 02), [On (MV
. rr) J is corrected to "off (MV o□)". θ3), in the specification, "first" on page 11, line 7 is replaced with "
"The latest." a4), “Figure 9” on page 14, lines 1 and 2 in the specification
is corrected as "Fig. 8". aω, "Figure 10" on page 15, lines 2-3 in the specification
is corrected as "Fig. 9". θω, in the specification, “by connecting,” on page 15, line 12, is amended to “when switching to PID control by connecting.” q, in the specification, ``judgment of status'' on page 17, line 7 is corrected to ``judgment of status of status.'' 08), "dead time" ° in lines 19 and 20 on page 17 in the specification is corrected to "dead time L". 09), "Figure 8" on page 20, line 3 in the specification,
[Corrected from FIGS. 8 to 9 J.] CO9 Figures 1, 5 and 6 are corrected as shown in the attached drawings. Written amendment to the above procedure (October 1999, Director General of the Japan Patent Office Yoshi 1) Tsuyoshi Moon 2゜Invention name adjustment meter 3゜4゜Relationship with the case Patent applicant address Ota, Tokyo Kugahara 5-16-6 Name Osamu
Chemical Industry Co., Ltd. Representative Teruyuki Hochi Agent 〒141'! ! ? 03 (440)
-6761 Address: 5-23-1 Higashigotanda, Tokyo Parts Ward
No. 6゜ Target of amendment In the description of contents of amendment in the brief explanation of drawings column, "Figure 8" in the third line of page 20 is amended to "Figures 8 to 9." , the Act was completed by a procedural amendment (voluntary) dated August 31, 1999.

Claims (2)

[Claims] (1) Equipped with a PID control unit and an auto-tuning unit using the limit cycle method, the PID constant for the controlled object is determined by auto-tuning, the controlled variable (PV) is PID-controlled using the constant, and the operation signal (MV) is In a controller that outputs, an auto-tuning end processing section is added, and when the auto-tuning by the auto-tuning section ends, the set value (SV) can be changed, and whether or not the set value (SV) is changed. Regardless of the above, the controller is characterized in that the auto-tuning end processing section quickly stabilizes the controlled variable (PV) after the auto-tuning ends. (2) The auto-tuning termination processing section includes a dead time calculation section, a process gain calculation section, a tuning termination management section, an output holding time management section, an integral term changing section, and a load factor output section. The controller according to claim 1, characterized in that: