? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?圖7：制定一控制計劃驅動誤差為零
上圖所示為1個MV削樊，1個CV系統(tǒng)詳細控制動作開發(fā)∷岣伲控制作用所需效果應由與CV穩(wěn)態(tài)目標（CV.SP）相關的CV預測值鏡像限定捣鲸。
如果控制作用與期望效果完全相同，錯誤將被精確地抵消闽坡。CV將立即進入穩(wěn)態(tài)目標值并在未來時域內得到保持栽惶。
因為我們知道需要從控制操作中得到所需的效果，以及過程模型描述了自變量的移動對因變量變化影響疾嗅，可以合理假設模型可用于規(guī)劃MV未來動作外厂。
上圖還顯示了MV計劃的控制作用。需要注意的是CV曲線顯示了“在控制作用下的CV預測圖”代承。曲線是加入了計算控制作用影響的CV預測值汁蝶。（僅基于自變量過去的動作）。
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 圖8：復雜精餾塔被控變量動作
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 圖9：復雜精餾塔操作變量動作計劃
上面兩圖顯示了復雜精餾塔控制器解決方案的簡介论悴。這些圖將被用于展示DMCplus控制器的主要特點掖棉。
每一欄包含了一個CV或MV的信息。Y軸是CV或MV的工程單位意荤，x軸是時間啊片。每欄最左側表示的是當前時間。需要注意的是計算出的未來動作將使其大約經過時間軸一半時間到達穩(wěn)態(tài)玖像。
還需要注意每一欄右側超出穩(wěn)態(tài)時間的部分紫谷，稱為“控制器時域”。這一擴展時間用來觀察大部分未來動作的影響捐寥。因此“控制器時域”等同于穩(wěn)態(tài)時間加未來大部分動作時間笤昨。
每個CV的預測值曲線用虛線表示。這些預測值是基于5個自變量歷史值及本節(jié)前述所示模型得到的（圖4）握恳。
這些預測值代表沒有任何控制動作下對3個CVs的預測瞒窒。
還需要注意到所有MVs和CVs都有上下操作限。這些限制定義可接受操作區(qū)乡洼。CVs預測穩(wěn)態(tài)值和MVs當前值定義了當前穩(wěn)態(tài)操作點崇裁。
通過這一個點、經濟信息束昵，和操作限制定義的可接受操作區(qū)拔稳，穩(wěn)態(tài)求解器計算出最優(yōu)穩(wěn)態(tài)操作點。這表現(xiàn)為每一欄右側的穩(wěn)態(tài)目標锹雏“捅龋控制器中每一MV和CV都有一個穩(wěn)態(tài)目標值。
下一步是制定詳細的控制作用計劃。如圖9所示轻绞，每一MV未來一系列動作都被計算出來采记。這些動作經歷大約一半的穩(wěn)態(tài)時間，并達到MV穩(wěn)態(tài)目標值政勃。
這些動作通過使所有3個CVs的預測值與穩(wěn)態(tài)目標錯誤值最小化計算得到唧龄。圖8所示為每一CV的“預測控制動作”。該曲線表示基于圖9?MV控制動作的未來預測CV響應值稼病。
需要注意的是根據(jù)穩(wěn)態(tài)求解器計算得到的所有MVs和CVs預測值最終都在它們各自的穩(wěn)態(tài)目標值选侨。這并不是偶然的；如果MVs最終停在各自所需的穩(wěn)態(tài)目標值然走，CVs也會停在穩(wěn)態(tài)目標值。
最后需要提一點戏挡，圖8和圖9僅表示一個控制器在一個控制周期內的計算值芍瑞。每一MV計算出的14步中第一步將被送入監(jiān)督控制系統(tǒng)，剩下的部分將被舍棄褐墅。
如果下一控制周期中拆檬，沒有干擾進入系統(tǒng)并且模型失配是可以忽略的，其解決方案將與上一周期解決方案的剩余部分非常相似妥凳。
然而竟贯，如果系統(tǒng)進入一主要干擾，正如預測本身一樣逝钥，最佳穩(wěn)態(tài)操作點將會改變（干擾反應）屑那。這將需要對控制方案作出立即改變，因此這一情況下控制方案將不會像前一控制周期的方案一樣艘款。
正是因為這個原因持际，除了第一步動作以外，其它所有動作都將被舍棄哗咆。鑒于第一步控制動作將受到預測未來違反MV約束的影響蜘欲，這些未來動作的計算依舊是必不可少的。換句話說晌柬，一個特殊的MV可能需要較現(xiàn)在移動地更多以避免未來違反限制姥份。如果未來整個動作軌跡未被計算，操作限制問題將無法得到答案年碘。
附原文：
? The figure above shows the development of a detailed control action for a one MV,one CV system.The desired effect of the control action is defined by the mirror image of the CV Prediction about the CV Steady-State Target (CV Set Point).
If control action could be found that had exactly the desired effect, the error would be exactly canceled out. The CV would go immediately to the steady-state target and remain there across the future time horizon.
Since we know the effect needed from the control action, and since the model of the process describes the effect on a dependent variable of a move in an independent variable, it is reasonable to assume that the model can be used in planning the future MV control moves.
The figure above also shows the control action planned for the MV. Note that the CVplot displays a "CV Prediction with Control Moves". This curve is theresult of adding the effect of the calculated control action to the CV Prediction (based only on past moves in the independent variables).
The two figures above show a snap shot of a controller solution for the Complex Fractionator. These figures will be used to demonstrate the key features of the DMCplus controller.
Each box contains information on one CV or MV. The y-axis is in engineering units ofthe CV or MV, while the x-axis is time. The left side of each box represents current time. Notice that the future moves are calculated approximately halfway across the time to reach steady state.
Also notice that the right hand side of each box is beyond the steady-state time,referred to as the "controller time horizon".This extension of time is required to allow the entire effect of the future most move to be seen. So the"controller time horizon" is equal to the steady-state time plus the time of the future most move.
Each of the three CVs has a prediction denoted by the dotted line. These predictions are based on the past history of the five independent variables and the model shown previously in this section (Figure 4).
Thesepredictions represent where the three controlled variables are predicted to goin the absence of any control action.
Also note that all of the MVs and CVs have upper and lower operating limits. These limits define an acceptable operating region. The predicted steady-state values of the CVs and the current values of the MVs define the current steady-state operating point.
Using this point, economic information, and the acceptable operating region defined by the operating limits, the Steady-State solver calculates the optimal steady-state operating point. This appears as the steady-state target on the right side of each box. There is a steady-state target for every MV and CV inthe controller.
The next step is to develop a detailed plan of control action. This plan can beseen in Figure 9, where a series of future moves has been calculated for each MV. These moves extend about half way across the steady-state time, and are required to reach the MV steady-state target.
These moves are calculated by minimizing the errors for all three CVs between the Predictions and the CV steady-state targets. Figure 8 shows a "Prediction with Control Moves" for each CV. This curve represents how that CV is predicted to respond in the future,based on the control action?shown in Figure 9.
Notice that all MVs and CVs are predicted to end up at their respective steady-state targets, calculated by the Steady-State solver. This is no accident; if the MVs are required to end up at their steady-state target, the CVs?must?end up at their targets also.
A final point to make is that Figures 8 and 9 represent a single calculation of the controller at one control interval only. The first move of the 14 calculated in each MV is sent to the regulatory control system, and the rest of the moves are thrown away.
If,at the next control cycle, no disturbances have entered the system and model mismatch is negligible, the solution will be very similar to the remainder of the solution from the previous cycle.
However,if a major disturbance has entered the system, the optimal steady-state operating point will change, as will the predictions themselves (reflecting the disturbance). This will require an immediate change in control strategy, so the control action in this scenario will not resemble the solution from the previous control cycle.
It is for this reason that all the moves except for the first one are thrown away.It is still essential that these future moves be calculated, since the size ofthe first control move will be affected by projected MV constraint violations in the future.In other words, a particular MV might have to be moved more now in order to prevent a future limit violation. This would not be known if the entire trajectory of future moves was not calculated,subject to the operating limits.
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?2015.9.11
