So far we have used two example processes: (i) first-order and (ii) second-order with a RHP zero. Now is the time to generalize our results to any process system.
First of all, we have been using the inverse of the process transfer function, gp(s), in our control law. We must realize that the actual process transfer function is never known exactly. We now use two transfer function representations of the process. One is considered the process (sometimes we use the term plant), which is never known exactly. The other is considered the process model, which we do know exactly.
Recall that when the process had a RHP zero, we performed a factorization, so that ...