Controller robustification using equivalent observer based structure

Deals with equivalent observer based structure and controller robustification. The purpose of the method is to find an observer based controller equivalent to an initial controller (designed using H/sub /spl infin// or /spl mu/ techniques for example). Matrices of the equivalent "observer plus feedback" are synthesized to guarantee the same closed loop eigenstructure and input/output behaviors than the initial controller. Contrary to other methods there is no restrictions on the initial controller order. The relations coming from this equivalence permits us to point out the fundamental matrices of observer and static feedback which are used to initialize a parametric robustification design procedure. The observer structure, this permits one to improve the parametric robustness of the initial controller without paying attention to the controller closed loop dynamic. Finally the global method (equivalent observer plus robustification) is applied to the robust control of the Space Shuttle described in a /spl mu/-analysis and synthesis toolbox.