Y/X = G/(1+G*H), where H represents negative feedback control block based on a measurement of the output.
I'd like to then use lsim to quantify the noise in the response to a sine wave input. How do I add 5% noise to the feedback signal, such that the noise is greater when there is greater mismatch between actual and desired signal? I.e. if Y is the output signal, I'd want to feedback Y' = Y*(1 + .1*randn(1)) at each point in time during a simulation. Is the only choice to implement the model numerical in discrete time?