A PI controller with disturbance estimation

Many chemical processes can be modeled for the purpose of feedback controller tuning by a first-order process. In this case, PI feedback controllers are mostly used to regulate the process. Due to the capabilities of the integral action to estimate load disturbance, a certain stability margin in the closed-loop system is obtained. That is, the integral variable provides an estimate of the load disturbance, which is counteracted in the feedback loop. The aim of the work is to derive a model-based PI feedback controller with extended capabilities to estimate dynamic disturbances (PII2 feedback controller). It is shown that, under certain gain choices, the proposed controller reduces to a classical PI one. The performance of the controller is illustrated via numerical simulations of two chemical processes.