JPH06103445B2 - Process control method - Google Patents
Process control methodInfo
- Publication number
- JPH06103445B2 JPH06103445B2 JP60078433A JP7843385A JPH06103445B2 JP H06103445 B2 JPH06103445 B2 JP H06103445B2 JP 60078433 A JP60078433 A JP 60078433A JP 7843385 A JP7843385 A JP 7843385A JP H06103445 B2 JPH06103445 B2 JP H06103445B2
- Authority
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- Japan
- Prior art keywords
- value
- dead zone
- control
- deviation
- set value
- Prior art date
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Classifications
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B13/00—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion
- G05B13/02—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric
- G05B13/0205—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric not using a model or a simulator of the controlled system
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- Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Artificial Intelligence (AREA)
- Computer Vision & Pattern Recognition (AREA)
- Evolutionary Computation (AREA)
- Medical Informatics (AREA)
- Software Systems (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Automation & Control Theory (AREA)
- Feedback Control In General (AREA)
Description
【発明の詳細な説明】 〔発明の技術分野〕 本発明はたとえば、プラント内に配置されるタンクの水
位を一定に保つ場合等に用いられるプロセス制御方法に
関するものである。Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a process control method used, for example, when a water level of a tank arranged in a plant is kept constant.
第３図に示すようなタンク１の水位を一定制御する場
合、タンク１の水位Ｌを水位設定値LSVに保つべく、水
位計２からの入力と設設値３とから、水位調節器４に設
定された所定の制御アルゴリズムにより流出流量設定値
を求め、これを流量調節器５に通知する。流量調節器５
は流量計６からの流量現在値と上記流量設定値とを比較
し、その結果流量調節弁７の開度を操作する。ここで、
流量調節器５における時間遅れ要素はほぼ無視できるの
で、本系をPI（比例積分）制御にてフイードバツク制御
を行なう場合のブロツク線図は第４図に示すようにな
る。ここでLSVは水位設定値、Ｌは水位現在値、Ｑは流
量現在値enは水位偏差、KP,TI制御定数、Ｋはプロセス
の比例定数を示す。When the water level of the tank 1 as shown in FIG. 3 is constantly controlled, in order to keep the water level L of the tank 1 at the water level set value L SV , the water level adjuster 4 is operated from the input from the water level meter 2 and the set value 3. The outflow flow rate setting value is obtained by the predetermined control algorithm set in (1) and is notified to the flow rate controller 5. Flow controller 5
Compares the current value of the flow rate from the flow meter 6 with the above-mentioned flow rate setting value, and as a result, operates the opening degree of the flow rate control valve 7. here,
Since the time delay element in the flow rate controller 5 can be almost ignored, the block diagram when the feedback control of this system is performed by PI (proportional integral) control is as shown in FIG. Here, L SV is the water level set value, L is the current water level value, Q is the current flow rate value en, the water level deviation, K P , T I control constant, and K is the proportional constant of the process.
従来の制御装置の動作フローを第５図に示す。FIG. 5 shows an operation flow of the conventional control device.
制御周期のタイミングで、プロセス値が不感帯W1の範囲
内に入つているかを判定する（ステツプ）。不感帯の
範囲外にある場合は、例えばＰ−Ｉ制御アルゴリズム等
に従い、制御信号（操作量）を出力する（ステツプ
）。不感帯の範囲内にあれば、プロセス値は設定値に
充分接近しているとみなし、制御信号は出力しないで、
次の制御周期を待つ（ステツプ）。At the timing of the control cycle, it is determined whether the process value is within the dead zone W 1 (step). If it is outside the dead zone, a control signal (manipulation amount) is output (step) according to, for example, the PI control algorithm. If it is within the dead zone, it is considered that the process value is sufficiently close to the set value and the control signal is not output.
Wait for the next control cycle (step).
従来の方法による制御を行なつた場合の動作を第６図の
タイムチヤートにより説明する。第６図（ａ）中直線10
は設定値の付近に設けられる不感帯の値の変化を示して
いる。この従来例では、不感帯の値は常に一定としてい
る。The operation when control is performed by the conventional method will be described with reference to the time chart of FIG. Straight line 10 in Fig. 6 (a)
Indicates the change in the value of the dead zone provided near the set value. In this conventional example, the value of the dead zone is always constant.
通常、不感帯は、設定値に幅をもたせることで、プロセ
ス値（現在値）の微小変動（センサノイズ等の外乱）に
対し不要な制御を行なわない様するために設けられる。
さらに、本系のような積分系プロセス（第４図のプロセ
ス伝達関数がK/S）の場合、制御出力を切つた後も、時
間遅れを伴つてプロセス値が変動するため、その対策と
して不感帯を設けている。Normally, the dead zone is provided so that the set value has a width so that unnecessary control is not performed for a minute fluctuation (disturbance such as sensor noise) of the process value (current value).
Furthermore, in the case of an integral system process (the process transfer function in Fig. 4 is K / S) like this system, the process value fluctuates with a time delay even after the control output is cut off. Is provided.
第６図（ｂ），（ｃ）でこの動作を説明する。（ｂ）は
水位設定値LSV（図中11）に対し、一定の不感帯W1を設
けて制御を行なつた場合のプロセス値の変動12,13,14を
示す。（ｃ）は流量変更のための制御出力を行なつてい
るか否かのタイムチヤートを示す。This operation will be described with reference to FIGS. 6 (b) and 6 (c). (B) shows fluctuations 12, 13, 14 of the process value when the control is performed by setting a constant dead zone W 1 with respect to the water level set value L SV (11 in the figure). (C) shows a time chart of whether or not the control output for changing the flow rate is being performed.
（ｂ）で、プロセス値が不感帯W1内に入るt1時刻以降
（ｃ）に示すように、制御出力は停止する。しかし、上
述したように、積分系プロセスに於ては、時間遅れが伴
なうため、その後もプロセス値はしばらく上昇を続け、
（ｂ）図中曲線13のように設定値LSV付近に落ち着くも
のと期待される。しかしながら、プロセス値が最終的に
不感帯内のどの位置に落ち着くかは、系の状態によつて
変化するため、（ｂ）図中曲線12,14で示すように、不
感帯W1の範囲いつぱいのところで落ち着くこともある。
この場合、プロセス値は不感帯の中に含まれているとい
えども所期の目標値からずれた値のまま保持されること
になる。またプロセス値の外乱に関しても、プロセスの
状態が変化している時などは、プロセス値そのものも流
動的である。通常、外乱等が大きく発生しやすい制御系
でも系が安定しているような状態では、比較的外乱は発
生しにくい性質がある。In (b), the control output is stopped as shown in (c) after time t 1 when the process value falls within the dead zone W 1 . However, as mentioned above, in the integral system process, there is a time delay, so the process value continues to rise for a while,
(B) It is expected that it will settle near the set value L SV as shown by the curve 13 in the figure. However, the final position of the process value within the dead zone varies depending on the system state. Therefore, as shown by the curves 12 and 14 in the figure (b), the dead zone W 1 range It may calm down.
In this case, even if the process value is included in the dead zone, the process value is held as a value deviating from the desired value. Regarding the disturbance of the process value, the process value itself is also fluid when the state of the process is changing. Normally, even in a control system in which a large disturbance or the like is likely to occur, the system has a property that the disturbance is relatively unlikely to occur in a state where the system is stable.
つまり、外乱や時間遅れを考慮すると、制御の操作端
（本例では流量調節弁７）の動作回数をなるべく少なく
するため、安全サイドをとり、通常の不感帯を大きくせ
ざるを得ない。しかし不感帯が大きいと、その時の系の
状態によつては、前述の如く大きな不感帯の中で、プロ
セス値が設定値から大きくシフトした値のままとどま
り、比較的安定した状態を保つているという状況が発生
する。即ち、従来の装置では、時として不必要に不感帯
が大きいために、制御の精度が悪くなるという欠点があ
る。That is, in consideration of disturbance and time delay, the number of operations of the control operation end (the flow rate adjusting valve 7 in this example) is reduced as much as possible, so that the safety side must be taken and the normal dead zone must be increased. However, if the dead zone is large, depending on the state of the system at that time, in the large dead zone as described above, the process value remains largely shifted from the set value and remains relatively stable. Occurs. That is, the conventional apparatus has a disadvantage that the precision of control deteriorates because the dead zone is unnecessarily large.
本発明の目的は、プロセス値が不感帯に入つた後、プロ
セス値と設定値の偏差の大小を判定し、偏差が大きい場
合につき、一時的に不感帯を縮小することで、プロセス
値をより設定値に近ずけるよう修正を加えるプロセス制
御方法を提供することにある。An object of the present invention is to determine the magnitude of the deviation between the process value and the set value after the process value enters the dead zone, and when the deviation is large, temporarily reduce the dead zone so that the process value becomes a set value. It is to provide a process control method for making a correction so as to approach the above.
本発明によるプロセス制御方法は、プロセス値をある定
められた設定値になるように制御するに当り、上記設定
値に対する不感帯に対し、上記制御によりプロセス値が
この不感帯内に入った場合、この不感帯に入った時点か
ら一定時間T1経過後にプロセス値と設定値との偏差を一
定時間T2にわたって求め、この求められた偏差が許容偏
差より大なる場合は、設定値に対する不感帯の大きさを
一時的に小さくし、前記プロセス値がこの小さくなった
不感帯に入るように制御するものである。In the process control method according to the present invention, when the process value is controlled so as to reach a predetermined set value, when the process value falls within the dead band due to the above control, the dead band is set in the dead band. After a lapse of a fixed time T1 from the time of entering, the deviation between the process value and the set value is calculated over a fixed time T2.If the calculated deviation is larger than the allowable deviation, the size of the dead zone for the set value is temporarily changed. The process value is controlled to be small so that the process value falls within the dead zone.
以下本発明の実施例を図面を参照しながら詳細に説明す
る。Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
この実施例における被制御装置の構成は、例えば第３図
に示すような構成とする。このような被制御装置に対す
る制御方法の動作フローチヤートを第１図に示す。本フ
ローチヤートと第２図のタイムチヤートにて本発明を説
明する。The controlled device in this embodiment has a structure as shown in FIG. 3, for example. FIG. 1 shows an operation flow chart of a control method for such a controlled device. The present invention will be described with reference to this flow chart and the time chart of FIG.
制御タイミングで、まず、プロセス値が通常の不感帯W1
の範囲内にあるかを判定する（ステツプ）。範囲内に
あれば何もせず次の制御周期を待つ（ステツプ）。W1
の範囲外であれば、例えばＰ−Ｉ制御アルゴリズム等に
従い、制御信号（操作量）を出力（ステツプ）した
後、次の制御周期を待つ（ステツプ）。そして次の制
御周期において不感帯W1の範囲内にプロセス値が入つて
いるかを判定し（ステツプ）、入つていれば、ある時
間T1待つ（ステツプ）、その後、時間T2の間、プロセ
ス値の設定値LSVに対する偏差△Ｌを計算する。偏差の
計算は例えば時間T2の間、プロセス現在値を短周期にて
サンプリングし、平均をとるなどする。あわせて偏差の
標準偏差σ△Ｌを求める（ステツプ）。ここで、前記
時間T1はプロセス系の時間遅れを考慮し、プロセス値が
十分に落ち着くまでの時間として設定しておく。At the control timing, first, the process value is the normal dead zone W 1
It is judged whether or not it is within the range of (step). If it is within the range, do nothing and wait for the next control cycle (step). W 1
If it is out of the range, the control signal (manipulation amount) is output (step) according to, for example, the PI control algorithm, and then the next control cycle is waited (step). Then, in the next control cycle, it is determined whether the process value is within the dead zone W 1 (step), and if it is, the process waits for a certain time T 1 (step), and then during the time T 2 , the process Calculate the deviation ΔL from the set value L SV . The deviation is calculated, for example, by sampling the process current value in a short cycle and averaging it during the time T 2 . In addition, the standard deviation σΔL of the deviation is calculated (step). Here, the time T 1 is set as a time until the process value is sufficiently settled in consideration of the time delay of the process system.
求めた偏差△Ｌと、予め設定した許容偏差△Lmaxを比較
する（ステツプ）。偏差が小さいと判定された場合、
即ち、△Ｌ≦△Lmaxの場合には、制御良好と判断し、次
の制御周期を待つ（ステツプ）。偏差が大きい場合、
即ち△Ｌ＞△Lmaxの時は、不感帯の幅を小さくし、W
2（＜W1）とする（ステツプ）。W2の値は、例えば偏
差△Ｌと△Ｌの標準偏差σ△Ｌから０＜W2＜△Ｌ−σ△
Ｌと設定する。このようにして不感帯を小さくした後、
プロセス値が不感帯W2の範囲外になるよう設定する。た
だし、標準偏差σ△Ｌが大きい場合、即ちプロセス値の
変動がノイズ等外乱によつて大きい場合には、不感帯の
縮小を行なわない。The calculated deviation ΔL is compared with a preset allowable deviation ΔLmax (step). If it is determined that the deviation is small,
That is, when ΔL ≦ ΔLmax, it is determined that the control is good, and the next control cycle is waited (step). If the deviation is large,
That is, when ΔL> ΔLmax, the dead zone width is reduced and W
Set to 2 (<W 1 ) (step). The value of W 2 is, for example, 0 <W 2 <ΔL−σΔ from the deviation ΔL and the standard deviation σΔL of ΔL.
Set to L. After reducing the dead zone in this way,
Set the process value so that it is outside the dead zone W 2 . However, when the standard deviation σΔL is large, that is, when the fluctuation of the process value is large due to a disturbance such as noise, the dead zone is not reduced.
不感帯をW2にした後プロセス値がW2の範囲内に入るまで
制御周期ごとに制御信号を出力する（ステツプ
）。その後、不感帯はもとの値W1に戻し（ステツプ
）、次の制御周期を待つ（ステツプ）。After setting the dead zone to W 2 , the control signal is output every control cycle until the process value falls within the range of W 2 (step). After that, the dead zone is returned to the original value W 1 (step) and waits for the next control cycle (step).
以上の動作をタイムチヤートにて第２図（ａ），
（ｂ），（ｃ）に示す。（ａ）は不感帯の変化、（ｂ）
はプロセス値の変動、（ｃ）は制御信号出力の有／無を
表わしている。不感帯15がW1からW2に変更される時刻t2
からプロセス値16はより設定値に近づく方向へ修正が加
えられる。The above operation is shown in FIG. 2 (a) in a time chart.
Shown in (b) and (c). (A) is a change in dead zone, (b)
Represents the fluctuation of the process value, and (c) represents the presence / absence of the control signal output. Time t 2 when the dead zone 15 is changed from W 1 to W 2
Therefore, the process value 16 is corrected so as to be closer to the set value.
本例の場合、第２図（ｂ）に示すように、最初不感帯W1
の境界付近に落ち着いていたプロセス値が、途中で一時
的に不感帯をW2（＜W1）とすることで修正され、より設
定値に近づくことがわかる。In this example, as shown in FIG. 2 (b), the first dead zone W 1
It can be seen that the process value settled near the boundary of is corrected by temporarily setting the dead zone to W 2 (<W 1 ) on the way, and comes closer to the set value.
ここで、プロセス値が設定値から大きくシフトしている
かどうかの判定は、前記の例で示したあるT2時間内に平
均をとる方法の他、プロセス値が不感帯に入つている
間、常に定期的にプロセス値を監視し一定時間毎に平均
を計算し、その平均の変動が少なくなつた時点での平均
と設定値を比較する方法でもよい。この場合、不感帯内
でプロセス値の変動が激しい場合などに一時的にT2時間
の平均のみで判断するよりも安全である。また、小さな
不感帯W2から大きな不感帯W1に戻つた後も、プロセス値
と設定値のシフトを監視しつづけることができる。Here, in order to determine whether the process value is largely deviating from the set value, other than the method of averaging within a certain T 2 time shown in the above example, while the process value is in the dead zone, it is always periodical. Alternatively, a method may be used in which the process value is monitored, an average is calculated at regular time intervals, and the average and the set value are compared when the fluctuation of the average is reduced. In this case, it is safer to make a judgment based only on the average of T 2 hours temporarily when the process value fluctuates greatly within the dead zone. Moreover, even after the small dead zone W 2 is returned to the large dead zone W 1 , the shift between the process value and the set value can be continuously monitored.
以上述べたように、概してプロセス値の変動（ノイズ等
の外乱）が時として比較的大きいとか、系の時間遅れ要
素が大きい、などの制御系に対して、プロセス値が所期
の設定値になるよう制御する場合、頭初の不感帯幅を大
きくとらざるを得ないことがある。しかし、このような
場合にでも、本発明によるプロセス制御装置では、プロ
セス値が不感帯に入つたあと、設定値から大きくシフト
した値で留まつていないかどうかを判定し、シフトが大
きく、しかも系が安定していると判断した場合に、不感
帯を一時的に小さくして修正をかけるため、プロセス値
をより精度よく設定値に接近させることができる。ま
た、不感帯を一時的に縮小し、その後また元の不感帯に
戻すため、将来起こりうる系の不安定化による外乱の発
生に対しても、大きな不感帯により対処することができ
るものである。As described above, the process value is generally set to a desired set value for a control system in which fluctuations in the process value (disturbances such as noise) are sometimes relatively large or the time delay element of the system is large. In some cases, the dead band width at the beginning of the head must be increased when controlling so that However, even in such a case, in the process control device according to the present invention, after the process value has entered the dead zone, it is determined whether or not the value remains largely shifted from the set value, and the shift is large, and the system When it is determined that is stable, the dead zone is temporarily reduced and correction is performed, so that the process value can approach the set value with higher accuracy. Further, since the dead zone is temporarily reduced and then returned to the original dead zone, it is possible to deal with the occurrence of disturbance due to destabilization of the system in the future with the large dead zone.
第１図は、本発明によるプロセス制御方法の一実施例を
示す動作フローチヤート、第２図は同じく動作タイムチ
ヤート、第３図は本発明の適用例分野として水位一定制
御を実現するプロセス制御装置の構成例を示す図、第４
図は第３図の制御系のブロツク線図、第５図は従来のプ
ロセス制御装置の動作フローチヤート、第６図は従来の
プロセス制御装置の動作タイムチヤートである。 W1,W2……不感帯の大きさ、LSV……設定値FIG. 1 is an operation flow chart showing an embodiment of a process control method according to the present invention, FIG. 2 is an operation time chart of the same, and FIG. 3 is a process control apparatus for realizing constant water level control as an application field of the present invention. Showing an example of the configuration of No. 4,
FIG. 5 is a block diagram of the control system of FIG. 3, FIG. 5 is an operation flow chart of the conventional process control device, and FIG. 6 is an operation time chart of the conventional process control device. W 1 , W 2 …… Dead zone size, L SV …… Set value
Claims (1)
ように制御するに当り、上記設定値に対する不感帯に対
し、上記制御によりプロセス値がこの不感帯内に入った
場合、この不感帯に入った時点から一定時間T1経過後に
プロセス値と設定値との偏差を一定時間T2にわたって求
め、この求められた偏差が許容偏差より大なる場合は、
設定値に対する不感帯の大きさを一時的に小さくし、前
記プロセス値がこの小さくなった不感帯に入るように制
御することを特徴としたプロセス制御方法。1. When a process value is controlled to reach a predetermined set value, when the process value falls within the dead zone due to the control, the dead zone is entered due to the control. After a lapse of a fixed time T1 from the time point, the deviation between the process value and the set value is obtained over a fixed time T2, and when the obtained deviation is larger than the allowable deviation,
A process control method characterized in that the size of a dead zone with respect to a set value is temporarily reduced and the process value is controlled to fall within the reduced dead zone.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60078433A JPH06103445B2 (en) | 1985-04-15 | 1985-04-15 | Process control method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60078433A JPH06103445B2 (en) | 1985-04-15 | 1985-04-15 | Process control method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS61237104A JPS61237104A (en) | 1986-10-22 |
| JPH06103445B2 true JPH06103445B2 (en) | 1994-12-14 |
Family
ID=13661905
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP60078433A Expired - Lifetime JPH06103445B2 (en) | 1985-04-15 | 1985-04-15 | Process control method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH06103445B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63310001A (en) * | 1987-06-11 | 1988-12-19 | Hitachi Ltd | Control device |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5625041Y2 (en) * | 1974-06-06 | 1981-06-12 |
-
1985
- 1985-04-15 JP JP60078433A patent/JPH06103445B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPS61237104A (en) | 1986-10-22 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EXPY | Cancellation because of completion of term |