Longitudinal control law design for fixed-wing UAV based on multi-model technique

Multi-model technique is studied and adopted for the control design for longitudinal dynamics of fixed-wing unmanned aerial vehicle (UAV) in the paper. A linear model set is built up at a number of operating points which are characterized by the different values of flight velocity and altitude, since the aerodynamics is greatly influenced by the two flight states, and a corresponding controller set for the linearized models is constructed, including discrete-time linear quadratic regulator (DLQR) as the inner loop controller for the velocity and pitch angle control and a PID controller for the altitude tracking and keeping. The switching strategy within the multi-model control scheme is put forward according to the square root of velocity and altitude. Finally, the simulation validates the efficiency of the proposed method, with the F-16 model as the controlled plant.