I going to select the disturbance models $C_f$ and $H$. I know my plant $P$ and the controller $C_b$. I also know that the disturbance $d$ is step formed. The noise $v$ is $v = 0$.
Question:
How should I select $C_f$ and $H$?
I have a theory. If $r = 0$, and the only input to the system is $d$. Then I can write this transfer function:
$$y = PC_fd + Hd$$
And if I want full disturbance rejection, e.g $y = 0$ when $d > 0$.
$$y = (PC_f + H)d = 0$$
That means $PC_f + H = 0$ where $P$ is a known transfer function and $C_f$ and $H$ is unknown transfer functions.
One idea from my self is to set $C_f = \frac{-H}{P}$, but still ... what should $H$ be for transfer function if $d$ is a step-shaped disturbance?
Could I set $H = \frac{1}{s}$ as a disturbance model?