仿真
我們考慮了4個具有不同Impulse Factors（脈沖因子）的仿真情景。該過程的操作條件如下：
? 容器液位初始值在其設定值50（Setrange High設定高限 = Setrange Low設定低限= 50)。
? MV初始值也為50，最大值為100，最小值為0，最大動作幅度為2。
? Inlet Flow 進料流量(DV)起始于操作點0。
? 為了生成可重復測量噪聲，我們設定“Measurement_Noise” DV的“Noise Seed = 1”和“Noise std dev = 1.0”。為了由SMOCPro將這一測量量實現為真實不可見噪聲，我們需要將“Measurement_Noise” DV的“Disconnected（斷開連接）”標簽設定為“True”。
控制器在Standby （掛起）模式下開始，并在第5步時切換到control（控制）。在第30步時我們給inlet flow（進料流量）引入一10個單位的斜坡干擾，在第80步時我們將inlet flow（進料流量）設定回初始值。在第140步時我們將液位設定值由50下調到40（Setrange Low設定低限 = Setrange High 設定高限= 40)。
我們運行199步仿真，并觀察SMOCPro計算的將儲罐液位帶回設定點的動作計劃。所考慮的4個仿真場景除了液位POV的Impulse Factors（脈沖因子）不同，其余條件都相同。其值分別為0,0.5,0.9和0.99。
上圖顯示了具有4個不同液位POV Impulse Factors（脈沖因子）的仿真情景運行結果。可以明顯地看出不同的Impulse Factors（脈沖因子）將影響控制器性能。在所有附圖中，我們可以看到頂部是傳感器噪聲（綠色），往下是可測量干擾（紫色），再往下是藍色的MV，最下面是紅色的CV。需要強調的三個重要方面是：
? 左上象限為脈沖因子設定為0時的仿真結果。如指南文件中所討論的一樣，這種情況將導致SMOCPro突出所有的不可測干擾，因此斜坡CV將把所有的不可測干擾整合進未來。最終的結果是，由于移動目標計算的緣故，SMOCPro層面將過度計算MV動作。這可以通過藍色虛線所示的MV目標值的快速變化看出。
? 提高脈沖因子將使得MV動作更為平滑，但可能導致對一個“真正的”擾動存在響應遲緩。
? 最后，由于脈沖因子的“指數”性質，從圖的下半部分可以看出，IP=0.9和IP=0.99有明顯的不同。請注意藍色的MV目標值在IP=0.99時是穩定的，但在IP=0.9時依然有略微鋸齒狀。
原文：
***Simulation ***
We consider four simulation scenarios with different Impulse Factors. The operating conditions for the process are the following:
? Initially the level in the vessel is at its setpoint of 50 (Setrange High = Setrange Low = 50).
? The MV also starts at 50 with a Maximum value of 100, Minimum value of 0 and Maximum Move Size of 2.
? The Inlet Flow (DV) starts at an operating point of 0.
? To generate repeatable measurement noise we set “Noise Seed = 1” and “Noise std dev = 1.0” for the “Measurement_Noise” DV. To implement this measurement as a true unseen noise by SMOCPro we must set the “Disconnected” flag for the “Measurement_Noise” DV to “True.”
The controller starts off in Standby mode and is switched to control at step 5. At step 30 we introduce a ramp disturbance of 10 units into the inlet flow and at step 80 we bring back the Inlet Flow to its starting point. At step 140 we lower the setpoint in the level from 50 to 40 (Setrange Low = Setrange High = 40).
We run the simulation for 199 steps and observe the planned moves that SMOCPro calculates to bring the vessel level back to setpoint. The four simulation scenarios under consideration are all identical with the only difference being the different Impulse Factors on the Level POV. These values are: 0, 0.5, 0.9 and 0.99.
The figure above shows the results of running the simulation scenario with the four different Impulse Factors for the Level POV. It is clearly seen that having different Impulse Factors affects the performance of the controller. On all figures, we see the sensor noise (green) at the top, followed by the measured disturbance (purple), the MV is shown next in blue and the CV is shown at the bottom in red. Three important aspects that should be highlighted are:
? The top left quadrant shows the simulation results of setting the impulse factor of 0. As discussed in the guidelines document, this case results in SMOCPro projecting any unmeasured disturbance so that the ramp CV will assume that the unmeasured disturbance must be integrated wholly into the future. The end result is that for the case with levels SMOCPro calculates excessive MV movement due to moving target calculations. This can be seen by the quickly changing MV targets depicted by the dashed blue lines.
? Increasing impulse factor smoothes out MV movement but may result in sluggish response in the presence of a “real” disturbance.
? Lastly, due to the “exponential” nature of the impulse factor, there is a non-trivial difference between IP=0.9 and IP=0.99 as can be seen in the bottom half of the figure. Notice how the target values for the MV in blue are steady in the 0.99 case but still are slightly jagged for the 0.9 case.
2016.5.21
