案例4：三個儲罐串聯(lián)的液位控制
(\Program Files\ShellGlobalSolutions\PCTP\Tutorial\SMOCPro\Tutorial4_TanksInSeries..wsp)
本例中所考慮的應(yīng)用是此前研究中發(fā)現(xiàn)情況的延伸∮岸ぃ考慮3個相等尺寸容器串聯(lián)的一個流程伶椿。控制目標(biāo)是保證3個容器的液位（CVs）對規(guī)定的用戶指定設(shè)定點(diǎn)保持敏感。為此，可將三個流量速率閥門的OP（MVs）作為操作變量。第一個容器的進(jìn)料流量速率是一個測量干擾匀钧，不適用于操作的（DV）。下圖為流程原理圖谬返。
流程模型
下圖為用于該系統(tǒng)的流程模型之斯。注意模型中的彩色塊與仿真曲線具有相同的顏色編碼，紫色的是DV遣铝，紅色的是CV1佑刷，綠色的是CV2莉擒，最后的藍(lán)色是CV3∠钇梗控制模型編譯后控制周期為1.0分鐘啰劲。
控制器設(shè)計(jì)
正在研究的控制器應(yīng)用將所有的液位（CVs）定義在一個子控制器下。
我們?yōu)樗械腗Vs和CVs指定共同的權(quán)重：
最后檀何，如下圖所示，與前面的單容器例子一樣廷支，我們將這個控制器的MV時域由其默認(rèn)值100 × dT修改為5 × dT频鉴。同時記住要使用Calculator功能，這樣CV預(yù)測時域就會相應(yīng)的自動調(diào)整恋拍。
該控制器既沒有經(jīng)濟(jì)函數(shù)也沒有靜態(tài)約束垛孔。
仿真
在這個例子中，我們研究了一系列的實(shí)驗(yàn)以建立在多個競爭斜坡CVs存在的情況下正確地指定CV優(yōu)先次序的重要性施敢。當(dāng)控制器在殘缺模式下運(yùn)行時周荐，正確地執(zhí)行說明顯得尤其重要。
本例中所要介紹的所有仿真的運(yùn)行初始條件指定如下僵娃。POV的起始條件為：
|步驟| 部分 |變量| 屬性| 新值|
| ------------- |:-------------:| -----:|
|1 |POV |All CVs |脈沖因子| 0.9|
|1 |POV |All CVs |操作點(diǎn) |50.00|
基本上我們所有的液位CVs初始值都為50概作，并且都具有較高的Impulse Factor。然后默怨，CV的起始條件為：
|步驟 |部分| 變量 |屬性 |新值|
| ------------- |:-------------:| -----:|
|1 |CV |CV_1| Setrange High |60.00|
|1 |CV| CV_1| Setrange Low |60.00|
|1 |CV| CV_2| Setrange High |60.00|
|1| CV |CV_2| Setrange Low |50.00|
|1 |CV| CV_3 |Setrange High |40.00|
|1| CV |CV_4| Setrange Low |40.00|
液位所需設(shè)定值有60讯榕、50和40，分別表示為Level 1匙睹，Level 2和Level 3愚屁。最后，MV的起始條件和操作約束為：
|步驟 |部分 |變量 |屬性 |新值|
| ------------- |:-------------:| -----:|
|1| MV |All MVs |Control Status（控制狀態(tài)）| Remote|
|1| MV| All MVs| Maximum（最大值） |100.00|
|1| MV |All MVs| Maximum Move Size（最大動作幅度）| 10.00|
|1| MV |All MVs| Minimum（最小值）| 0.00|
|1| MV| All MVs |Operating Point（操作點(diǎn)）| 50.00|
原文：
Case 4: Level Control for Three Tanks in Series
The application under consideration in this example is an extension of the case seen in the previous case study. Consider a process containing three equally-sized vessels in series. The control objective is to maintain the three vessel levels (CVs) of interest at prescribed user-specified set points. To that end, three flow rates valve OPs (MVs) are available for manipulation. The inlet flow rate into the first vessel is a measured disturbance not available for manipulation (DV). The figure below shows the process schematic.
**Process Model **
The figure below shows the process model used for the system. Note the colored blocks in the model as the simulation plots will have the same color coding, purple for DV, red for CV1, green for CV2 and lastly blue for CV3. The control model is compiled with a Control Period of 1.0 minute.
Controller Design
The controller application under consideration has all the levels defined as CVs in a single sub-controller.
We specify unity weights for all the MVs as well as CVs:
Lastly, as in the previous single vessel example we modify the MV horizon for this controller from its default value of 100 × dT to 5 × dT as seen below. Again, remember to use the Calculator feature so that the CV prediction horizon gets automatically adjusted accordingly.
The controller has neither economic functions nor static constraints.
**Simulation **
In this example we consider a series of experiments to establish the importance of correctly specifying the CV priorities in the presence of multiple competing ramp CVs. Performing this specification properly is especially important when the controller runs in crippled mode.
All of the simulation runs to be presented in this example have the starting conditions specified below. The POV starting conditions are:
|Step| Section| Variable |Attribute| New Value|
| ------------- |:-------------:| -----:|
|1 |POV |All CVs| Impulse factor| 0.9|
|1 |POV |All CVs |Operating Point| 50.00|
Essentially we start all the level CVs at 50 and they all have a high Impulse Factor. Next, the CV starting conditions are:
|Step |Section |Variable |Attribute| New Value|
| ------------- |:-------------:| -----:|
|1 |CV| CV_1 |Setrange High |60.00|
|1 |CV| CV_1 |Setrange Low |60.00|
|1| CV| CV_2 |Setrange High |60.00|
|1| CV| CV_2| Setrange Low| 50.00|
|1| CV| CV_3| Setrange High| 40.00|
|1| CV |CV_4| Setrange Low| 40.00|
The desired setpoints for the levels are 60, 50 and 40 respectively for Level 1, Level 2 and Level 3. Lastly, the MV starting conditions as well as operating constraints are:
|Step| Section |Variable| Attribute |New Value|
| ------------- |:-------------:| -----:|
|1| MV| All MVs |Control Status| Remote|
|1| MV| All MVs| Maximum |100.00|
|1| MV| All MVs| Maximum Move Size |10.00|
|1| MV| All MVs| Minimum| 0.00|
|1| MV| All MVs| Operating Point| 50.00|
2016.5.26
