Exact observer-based structures for arbitrary compensators

In this paper, some new techniques for determining the observer-based or LQG form of any compensator with arbitrary order are discussed. The practical appeal of such techniques is that they allow for a simplified implementation and reduced memory storage of general controllers and offer additional flexibility for handling gain-scheduling and input saturation constraints as compensateor states become meaningful variables. The derived observers-based controllers are input-output equivalent to the original controller but with an explicit separated estimation/control structure. Such structures involve both static control and estimation gains with an extra Youla parameter that can be either static or dynamic. The proposed techniques are applicable both in continuous-and discrete-time, to full-order controllers, that is, controllers whose order controllers whose orders are greater or smaller, respectively. Necessary conditions to apply this general controller equivalence principle are derived. The interest and practicality of such techniques are then investigated with regards to the LQG implementation of Hinfinty and u controllers, classes of controllers that does not generally enjoy ease of implementation.