Low order controller with regional pole placement

In this paper we propose a method to find a low order controller for a single input single output linear continuous time system which guarantees that the closed loop poles are placed within some pre-specified region in the complex plane. Additionally, the method can also ensure that any subset of the closed loop poles are placed at specific pre-designed locations. Further, it is possible to ensure that the resulting controller is proper. The problem is solved by formulating it as an LMI constrained optimization problem. The proposed method is demonstrated on a power system example.