New non-linear QFT technique

A robust feedback synthesis problem around single-input single-output nonlinear uncertain plant is considered. A new design methodology have been developed that do not use the Schauder fixed point theorem, which is a major limitation of existing nonlinear Quantitative Feedback Theory (QFT) methodology. The new method presents necessary conditions on prefilter F and linear-time-invariant controller G to satisfy closed loop tracking performance specifications. A domain of choice for G is found, translated into the frequency domain, and is presented in the form of QFT bounds for the solution controller. The result is a synthesis technique that requires shaping both of a controller and a pre-filter to satisfy QFT bounds. The new technique produces solutions with lower control efforts than the existing ones, and can be successfully applied to a much larger class of nonlinear plants as well as of specifications sets.