Quantitative feedback theory technique and applications

Quantitative feedback theory (QFT) technique has emerged as a powerful multivariable control system design method. This design method addresses real-world problems with structured plant parameter uncertainties. The paper provides the control community with an overview and the basic mathematical concepts of the QFT technique. The solutions to some real-world flight control problems and a very powerful design tool (QFT CAD package) are presented. One of these solutions was successfully implemented and flight tested.