Robust attitude control design for a low-cost hexarotor micro aerial vehicle

This article proposes a new practical robust attitude state feedback controller of a low-cost hexarotor micro aerial vehicle under the effects of noise in angular velocity measurements and multiple uncertainties (called the equivalent disturbance), which consist of external time-varying wind disturbance, nonlinear dynamics, coupling and parametric uncertainties. The proposed method is designed in two simple steps. Firstly, a nominal cascade controller is designed to reduce noise in angular velocity measurements and to achieve good attitude tracking performance in nominal conditions. Then, a second-order robust compensator is integrated into the closed-loop system to reduce the effects of the equivalent disturbance. The proposed control design is a linear time-invariant controller which is easily implemented in practical applications. Compared to other advanced attitude controllers, the proposed controller incurs lower computational costs and can easily be implemented in a low-cost embedded microcontroller system. In addition, a practical computational design procedure and an intuitive online tuning method for the proposed controller are presented in this article in order to provide a complete reference to micro aerial vehicle developers. The simulation and experimental results are presented to demonstrate the robustness of the proposed controller in operation in outdoor environments, to show good steady-state and dynamic tracking performance of the closed-loop system and to prove that the tracking errors are ultimately bounded within desired limits.