Process Control: Modeling, Design, and Simulation

8.8. The IMC Design Procedure

The IMC design procedure for SISO systems is identical to the design procedure that we developed for open-loop controller design earlier. The assumption we are making is that the model is perfect, so the relationship between the output, y, and the setpoint, r, is given by Equation (8.1). Model uncertainty is handled by adjusting the “filter factor” for robustness (tolerance of model uncertainty) and speed of response. The IMC design procedure consists of the following four steps.

1.	Factor the process model into invertible (“good stuff”) and noninvertible (“bad stuff”—time delays and RHP zeros) elements (generally, an all-pass factorization will be used). Equation 8.39 This factorization is performed so that the ...