8.10. Improved Disturbance Rejection Design
We can achieve improved disturbance rejection by specifying a different IMC filter design procedure. We perform the same factorization of the process model as before. The difference is in the selection of the IMC filter transfer function. Here, rather than using a filter of the form
we use a filter with the form
where γ is selected to achieve good disturbance rejection. In practice, γ will be selected to cancel a slow disturbance time constant. Consider the closed-loop transfer function ...