Specifications

5 Designing and Testing Controllers in Simulink
5-6
In the MPC open loop plant 1 node of the tree, click Operating Point.
The software found a steady-state operating point (derivatives are close to zero).
However, the reactor temperature (CSTR_ClosedLoop/CSTR/T_K) is very low, yielding
a low reaction rate. Compare the values of the residual concentration state (9.9919 kmol/
m
3
) and the feed concentration (10 kmol/m
3
) to confirm the low reaction rate.
Because this operating point does not result in a significant reaction, calculate another
operating point with a higher reaction rate.
Calculate Desired Operating Point for Plant Model
Suppose the desired operating point is:
•
Residual concentration is 2 kmol/m
3
• Reactor temperature is 370 K
Specify output constraints on all the OV/MV/MD signals connected to the MPC
Controller. This step is required because the software uses the steady-state values of
these signals as the nominal values for the controller. In the Simulink model, right-click
the MO signal entering the controller. Select Linear Analysis Points> Trim Output
Constraint. Repeat for the MV signal of the MPC Controller block. All constrained
signals are marked with T.