Development of a State Dependent Ricatti Equation Based Tracking Flight Controller for an Unmanned Aircraft

A dual loop nonlinear State Dependent Riccati Equation (SDRE) control method is developed for the ight control of an unmanned aircraft. The outer loop addresses the attitude and altitude kinematics, while the inner loop handles the translational and rotational equations of motion. The control strategy utilizes a tracking control problem. The mismatch due to the SDC factorization of the inner loop is handled with a nonlinear compensator again derived from the tracking control formulation. The quadratic optimal control problems of the inner and outer loops are solved at discrete intervals in time. A nonlinear simulation model of the UAV is used to examine the performance of the SDRE controller. Two ight scenarios are considered: a coordinated turn maneuver and a high angle of attack ight. These simulation results show the eectiveness of the proposed nonlinear controller.