Multi‐input, multi‐output flight control system design for the YF‐16 using nonlinear QFT and pilot compensation

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Abstract
Nonlinear quantitative feedback theory (QFT) and pilot compensation techniques are used to design a 2 × 2 flight control system for the YF‐16 aircraft over a large range of plant uncertainty. The design is based on numerical input‐output time histories generated with a FORTRAN implemented nonlinear simulation of the YF‐16. The first step of the design process is the generation of a set of equivalent linear time‐invariant (LTI) plant models to represent the actual nonlinear plant. It has been proven that the solution to the equivalent plant problem is guaranteed to solve the original nonlinear problem. Standard QFT techniques are then used in the design synthesis based on the equivalent plant models. A detailed mathematical development of the method used to develop these equivalent LTI plant models is provided. After this inner‐loop design, pilot compensation is developed to reduce the pilot's workload. This outer‐loop design is also based on a set of equivalent LTI plant models. This is accomplished by modelling the pilot with parameters that result in good handling qualities ratings, and developing the necessary compensation to force the desired system responses.