General pole restriction controller design

Pole-assignment controller design suffers from the disadvantage that the prescribed pole locations may not be a suitable choice when the dynamics of the process are changing. A general design method that restricts the closed-loop poles to be within a certain desired region specified by engineering judgement, instead of fixing the poles in a prescribed location, is presented. The method can be used for regulating a process with time delay, non-minimum zero-phase behaviour, and open-loop unstable characteristics.