SDRE and LQR Controls Comparison Applied in High-Performance Aircraft in a Longitudinal Flight

Abstract

This paper presents the design of the LQR (Linear Quadratic Regulator) and SDRE (State-Dependent Riccati Equation) controllers for the flight control of the F-8 Crusader aircraft considering the nonlinear model of longitudinal movement of the aircraft. Numerical results and analysis demonstrate that the designed controllers can lead to significant improvements in the aircraft's performance, ensuring stability in a large range of attack angle situations. When applied in flight conditions with an angle of attack above the stall situation and influenced by the gust model, it was demonstrated that the LQR and SDRE controllers were able to smooth the flight response maintaining conditions in balance for an angle of attack up to 56% above stall angle. However, for even more difficult situations, with angles of attack up to 76% above the stall angle, only the SDRE controller proved to be efficient and reliable in recovering the aircraft to its stable flight configuration.

Validation of Quad Tail-sitter VTOL UAV Model in Fixed Wing Mode

“…The UX-7V VTOL UAV operator can easily control the aircraft in a position-assisted flight mode [84] [85]. The altitude and position are locked in this mode by the computed trajectory of the flight controller [86][87] [88]. Therefore, the input to the empirical model of this research is not the remote-control input from the operator but the command given to the actuator from the flight controller.…”