8.5. Development of the IMC Structure
Consider the open-loop control structure shown in Figure 8-3.
We now consider a process model that receives the same manipulated variable signal as the actual process (Figure 8-8). We can now subtract the difference between the process output (actually measured) and the process model output (model predicted) to determine the model error. This is shown in Figure 8-9. We must also realize that disturbances can enter the system, as shown in Figure 8-10.
Figure 8-8. Process model in parallel with the actual process.
Figure 8-9. Calculating model error.
Figure 8-10. Incorporating the process disturbance.