Frequency Response Specifications and Sensitivity Functions in Quantitative Feedback Theory

Quantitative Feedback Theory (QFT), a robust control methodology for frequency response design, has been found to have favorable properties in many applications, particularly those in which performance robustness is a primary objective. In this paper preliminary results are developed in terms of sensitivity functions, giving definitive conditions under which the QFT closed loop specifications are achievable. As a benefit of the sensitivity formulation, distinct comparisons may be made between the design constraints of the H^¿ and the QFT methodologies.