Optimal robust control for attitude of quad-rotor aircraft based on SDRE

The attitude control is the key of the automatic flight for a quad-rotor aircraft. In order to guarantee the robustness of the quad-rotor aircraft for various uncertainties, a new design method of the robust optimal control that integrates the sliding mode control theory with state-dependent Riccati equation (SDRE) is proposed in this paper. First, the whole attitude kinematical model is obtained. By using the SDRE approach, an optimal control law of the attitude for quad-rotor aircraft without uncertainties is obtained. Then, the sliding mode control theory combing with SDRE is applied to improve the robustness of the quad-rotor aircraft. As a result, the system is robust optimal to the parameters variations or extraneous disturbances and the stability is proved. Finally, the validity and robustness of the proposed algorithm are verified by simulation results.