A Study of Pole Placement in Linear Control Design

The design of linear control by pole placement in continuous time domain formulation has been investigated by many researchers. Numerous techniques have been proposed for the design of a proportional feedback law so that closed loop poles can be specified a priori. However, because many industrial processes are large dimensional systems with many states but very few measurements and controls, the number of poles that can be specified is severely limited. In practice, exact placement of the poles is not important but that all the poles must be placed to the left of the complex plane. This paper desribes a simple technique which generates a series of feedback laws that progressively shift the closed loop poles into ´faster response´ region of the complex plane. The designer simply chooses one of these laws based on other considerations. It is demonstrated that the method is simple and effective in arriving at a suitable feedback control of a distillation column.