Indirect adaptive flight control based on nonlinear inversion

There are two difficulties in flight control system design, i.e., aircraft model is nonlinear and model parameters are time-varying with flight status. Nonlinear dynamic inversion is a powerful technique, which enables designers to effectively cope with nonlinear systems. And adaptive method is used to deal with time-varying model parameters. In this paper, an indirect adaptive flight controller based on dynamic inversion and recursive least-square (RLS) identification algorithm is presented. Aircraft system states are separated into fast and slow time-scale variables, and then dynamic inversion control laws are designed respectively for the two corresponding control loops. The standard form of the dynamic inversion is transformed to fit the least-square identification algorithm, so that the time-varying parameters needed in the dynamic inversion control law can be identified online. The performance of the designed indirect adaptive controller is demonstrated via simulation of a six-degree-of-freedom (DOF) nonlinear aircraft model.