Simultaneous meeting of robust control specifications in QFT

Simultaneous meeting of different-nature feedback control specifications requires special attention, particularly in the presence of uncertainties. This paper introduces some ideas to obtain a feasible set of QFT bounds, analysing the compatibility of the desired control specifications and the model uncertainty. It studies general robust feedback requirements and their mapping on QFT bounds through quadratic inequalities. Analysing them, it is possible to infer the bound typology with dependence on the model of each particular specification and the uncertainty size. Two bound typologies (amongst three categories: upper, outer and lower bounds) are possible for each type of control objective. On this basis, some general hints are established to guarantee compatible bounds at each frequency, before designing the controller. Copyright © 2003 John Wiley & Sons, Ltd