Robust optimal attitude control of hexarotor robotic vehicles

Multirotor aerial robotic vehicles attract much attention due to their increased load capacity and high maneuverability. In this paper, a robust optimal attitude controller is proposed for a kind of multirotor helicopters - hexarotors. It consists of a nominal optimal controller and a robust compensator. The nominal controller is designed based on the linear quadratic regulation (LQR) method to achieve desired tracking of the nominal system, and the robust compensator is added to restrain the influence of uncertainties. The key contributions of this work are twofold: firstly, the closed-loop control system is robust against coupling and nonlinear dynamics, parametric uncertainties, and external disturbances; secondly, a decoupled and linear time-invariant control architecture making it ideal for real-time implementation. The attitude tracking errors are proven to be ultimately bounded with specified boundaries. Simulation and experimental results on the hexarotor demonstrate the effectiveness of the proposed attitude control method.