Partial Internal Model Control For Unstable Plants

In this paper, two design methods of controller for plants with stable and unstable poles at the same time are proposed based on partial internal model control(PIMC) structure. First, a plant model is expressed as the sum of stable and unstable parts and only the stable part of the process model is used as the internal model. So, the plant stable part is canceled by the internal model and the controller is designed only for the remaining unstable part.The fist method adopts the coprime factorization to design the controller and improves the shortage of the conventional internal model control and feedback control. The first part uses the one-degree-of-freedom controllers to stabilize the unstable part and enable the system tracking the set-point and reject the disturbance when the system reaches the steady state. To improve the tracking performance, the second part uses two-degree-of-freedom controllers. In this paper, the system is optimized for the tracking error ,disturbance rejection or robust performance ,respectively.When the system has the unstable process of the low order, we can consider a simple controller with two tuning parameters to stabilize the system. First, we compute the characteristic polynomial of the system. Secondly, we can use the stability criterion to decide the region of parameter to enable the system stable. Finally, we can search the...