Abstract
This paper proposes a robust optimal attitude control design for hexarotor unmanned aerial vehicles (UAVs) under the effects of uncertainties which consist of external disturbances, nonlinear dynamics, coupling, and parametric uncertainties. The proposed optimal control is designed for pitch, roll, and yaw subsystems and it consists of a nominal optimal controller and a plug-in gain scheduling robust compensator. The nominal optimal controller is based on linear quadratic regulator (LQR) control approach to ensure a stable closed-loop nominal system, whilst a plug-in gain scheduling robust compensator is added in order to improve the attitude tracking performance due to the presence of uncertainties where the amount of uncertainties are changing dynamically. The simulation results prove the attitude tracking errors are bounded in specified boundaries and demonstrate the robustness of the proposed control scheme and thus suitable for real flight condition.
