Flight control law using nonlinear dynamic inversion combined with quantitative feedback theory

A method of designing control laws for uncertain nonlinear systems is presented Dynamic inversion is used to partially linearize the dynamics and then a nonlinear version of quantitative feedback theory (QFT) is applied to the resulting system which assures robustness to plant uncertainty. The design yields good performance with low bandwidth. An application to the design of flight control laws for a high performance aircraft is presented. The control laws demonstrate good performance by accurately following large angle of attack commands at flight speeds ranging from 53 to 150 m/s. Robustness is verified by including +/-20 percent variations in pitching moment derivatives. The reduced bandwidth compared to a fixed-gain, linear design, lends to greatly reduced actuator transients, which should give improved reliability and longer life for the actuators and associated structure.