2.將dSPdVLo/Hi增益的量綱設置為等于MV范圍：
這樣做最重要的是要保證在界限時增益具有正確的符號。
4.監(jiān)測并比較計算的MV限和用戶指定的SPLo和SPHi限。如果這些值是不同的，必須特別注意采取措施處理差異。
注意事項：以這種方式設置的限制保證了閥位永遠不會在DCS閥位高低限之外。然而，SMOCPro擁有的防止飽和和控制器飽和度的任何功能都將被禁用。
?最后，當我們控制一個OP且防止控制器飽和被視為關鍵時， OP可以明確地作為CV被添加到SMOCPro控制器的過程模型中。這一步可以通過使用圖形化模型構建器（GMB）內(nèi)的“變換”功能來表示非線性閥特性而大大受益。
SMOCPro dSPdV計算示例
我們現(xiàn)在通過例子來說明dSPdV計算。第一個例子突出了 “正常”操作狀態(tài)的場景。第二個例子顯示了當用了飽和PV時dSPdV計算的行為。最后，第三個例子顯示了相對于dSPdV計算，為MV指定適當Max Move Size值的重要性。最終，我們提出了在處理OP所需的抗物理限時，兩種仿真在計算SP限時行為的不同。
例1：正常操作
考慮圖1（上文）描繪的具有以下特征的系統(tǒng)：
|低限 |高限|
| ------------- |:-------------:| :-----:|
|OPLo = 10| OPHi = 90|
|SPLo = 500 |SPHi = 1000|
|dSPdVLo = 20| dSPdVHi = 5|
當前的運行情況是在OP=60時，SP（回讀）= PV = 800。
我們首先需要計算的是OP對SP的增益。根據(jù)用戶指定的參數(shù)，在當前OP時增益為：
接下來我們通過計算等式（1a-b）獲得內(nèi)部限制：
最后，求解方程（2a-b）獲得所計算的限制：
在這個例子中我們注意到，當OP = 60時控制器依然可以訪問整個MV范圍。傳遞到內(nèi)核的計算值等于用戶指定的這些值。
例2：飽和PV
現(xiàn)在我們來考慮當OP值在低于SPHi時飽和的情況。因此我們需要將控制器的SPHi帶回PV以使其能做出任何相關動作。該系統(tǒng)的條件是：
|低限 |高限|
| ------------- |:-------------:| :-----:|
|OPLo = 10 |OPHi = 90|
|SPLo = 500| SPHi = 1000|
|dSPdVLo = 10 |dSPdVHi = 15|
原文：
- Set the magnitude of the dSPdVLo/Hi gains equal to the MV range:
In doing this, it is critical that the gains at both limits have the correct sign. - Monitor and compare the calculated MV limits vs the user-specified SPLo and SPHi limits. Should these values be different, special attention must be taken to address the discrepancy.
Word of Caution: Setting the limits in this manner ensures that the valve position is never outside the DCS valve low and valve high limits. However, any capabilities that SMOCPro possesses to prevent wind-up and controller saturation will be disabled.
? Lastly, when controlling an OP and preventing controller wind-up is deemed critical, the OP can be explicitly added to the process model in the SMOCPro controller as a CV. This step can greatly benefit by using the “Transforms” feature within the Graphical Model Builder (GMB) to represent nonlinear valve characteristics.
**SMOCPro dSPdV Sample Calculations **
We now present examples illustrating the dSPdV calculations. The first example highlights a “normal” operating regime scenario. The second example shows what the dSPdV calculation does when presented with a saturated PV. Lastly, the third example shows the importance of specifying an appropriate MV Max Move Size value with respect to the dSPdV calculation. Lastly, we present two simulations highlighting difference in behavior for the calculated SP limits when dealing with desired versus physical limitations on the OP.
**Example 1: Normal operation. **
Consider the system depicted in Figure 1 (above) with the following characteristics:
| Low Limits | High Limits|
| ------------- |:-------------:| :-----:|
| OPLo = 10| OPHi = 90|
| SPLo = 500| SPHi = 1000|
| dSPdVLo = 20 | dSPdVHi = 5|
The current operating conditions are SP(readback) = PV = 800 at OP = 60.
The first thing we need to calculate is the OP to SP gain. With the user-specified parameters, the gain at the current OP is:
Lastly, evaluate equations (2a-b) to get the calculated limits:
Next, we calculate the internal limits using equations (1a-b) to obtain:
In this example we notice that at OP = 60 the controller still has access to the full MV range. The calculated values passed to the kernel are equal to those specified by the user.
Example 2. Saturated PV.
Now consider the case when the OP is saturated at a value lower than SPHi. Thus we need to bring the SPHi to the PV for the controller to be able to do any relevant controller moves. The system conditions are:
| Low Limits| High Limits|
| ------------- |:-------------:| :-----:|
| OPLo = 10| OPHi = 90|
| SPLo = 500| SPHi = 1000|
| dSPdVLo = 10 | dSPdVHi = 15|
2016.7.5
