PID控制器在抗干擾模式下由PID回路產(chǎn)生不可測(cè)干擾。FOT (PV)對(duì)FOT(Error)的階躍響應(yīng)如下圖所示：
值得一提的是，PID抗干擾通過動(dòng)態(tài)鏈接的方法傳遞到溫度和質(zhì)量。我們現(xiàn)在開始搭建基于這些響應(yīng)的控制器。進(jìn)行的仿真具有下列特征：
1、 在第5步時(shí)質(zhì)量的設(shè)定點(diǎn)從80改到85；
2、 系統(tǒng)中引入了兩種類型的干擾。首先是爐溫（在第70步時(shí)使用FOT(Error)注入的5攝氏度斜坡），其次是反應(yīng)器溫度（在第120步時(shí)使用溫度(Error)注入的10攝氏度斜坡）。
3、 反應(yīng)器溫度被保持在最高溫度615℃以下。爐的PV不控制，但僅把它當(dāng)做一個(gè)中間變量。
4、 溫度上限比質(zhì)量的設(shè)定點(diǎn)具有更高的優(yōu)先級(jí)（溫度的優(yōu)先級(jí)是1，質(zhì)量的是10）。
該方案（信息）表視圖如下：
? General選項(xiàng)：
? Sub-controller選項(xiàng):
下圖顯示了該例子的仿真結(jié)果。
對(duì)質(zhì)量的設(shè)定點(diǎn)變化是不可行的（黃色的質(zhì)量最小值單元格），因?yàn)闇囟鹊搅松舷蓿ňG色的溫度最大值單元格）。
很顯然在第70步，SMOCPro很難通過操作FOT SP（和Quench）補(bǔ)償FOT的擾動(dòng)。這是因?yàn)楦鶕?jù)PID控制器，其預(yù)測(cè)的質(zhì)量依然處于穩(wěn)定的狀態(tài)。
在第120步，SMOCPro預(yù)測(cè)到質(zhì)量將偏離標(biāo)準(zhǔn)，于是開始操作FOT SP和Quench（激冷氣）以消除干擾。
方案2
控制器模型中不包括PID配置；但為PID控制器閉環(huán)動(dòng)態(tài)選擇了一個(gè)PID/串級(jí)回路設(shè)定。
添加了不可測(cè)擾動(dòng)的模型如下所示：
Figure -6 Reactor model with unmeasured disturbances
圖6：添加了不可測(cè)擾動(dòng)的反應(yīng)器模型
和選項(xiàng)1一樣，PID控制器在抗干擾模式下由PID/串級(jí)回路產(chǎn)生不可測(cè)干擾動(dòng)態(tài)。如下圖所示為模型對(duì)不可測(cè)干擾的階躍響應(yīng)。
和前面一樣，PID抗干擾通過動(dòng)態(tài)鏈接的方法傳遞到溫度和質(zhì)量。此建模方法搭建控制器的性能與第一個(gè)案例是類似的。
原文：
The unmeasured disturbance generated for the PID loop models the disturbance rejection pattern of the PID controller. The response of the FOT (PV) to a step response in the FOT (Error) is:
It is worth noting that the PID disturbance rejection spreads to the Temperature and the Quality by means of the dynamic links. We now proceed to build a controller based on these responses. The simulation is performed with the following characteristics:
- A setpoint change for the quality is forced at step 5 from 80 to 85.
- Two types of disturbances are introduced into the system. First on the temperature of the furnace (5-degree ramp injected using FOT (Error) at step 70) and then on the reactor temperature (10-degree ramp injected using Temperature (Error) at step 120)
- The reactor Temperature is kept under a maximum of 615 degrees C. The furnace PV is not controlled but used only as an intermediate variable.
- The Temperature upper limit has a higher ranking than the Quality setpoint. (Priority 1 for Temperature and, 10 for Quality).
The scenario (information) table views are:
? General tab:
? Sub-controller tab:
The figure below shows the simulation results for this study.
The setpoint change on the Quality is infeasible (Minimum cell of Quality in yellow) because the Temperature reaches its upper limit (Maximum cell of Temperature in Green).
It is clear that SMOCPro hardly manipulates the FOT SP (and Quench) to compensate the disturbance on FOT at step 70. This is because it can predict the quality remains on specification at steady state due to the PID controller.
At step 120, SMOCPro predicts the quality off specification and manipulates the FOT SP and Quench to reject the disturbance.
Option 2
The PID configuration is not included in controller model; but a PID/Cascade loop setting is chosen for the closed loop dynamic of the PID controller.
The model with the unmeasured disturbances looks like:
As with Option 1, the unmeasured disturbance dynamics generated for the PID/Cascade loop model the disturbance rejection pattern of the PID controller. This is illustrated in the model responses to steps in the unmeasured disturbances as shown below.
As before, the PID disturbance rejection spreads to the Temperature and the Quality using the dynamic links. The performance of the controller built with this modeling approach is similar to that seen with the first option.
2016.5.17
