Robust control of quadrotor system in the presence of disturbances and uncertainties: using a virtual control approach

The aim of the paper is to design a controller for a quadrotor robot in the presence of external disturbances and uncertainties in the system parameters in such a way that the robot tracks a commanded trajectory accurately. In our approach, the system model is divided into two subsystems, i.e. the under-actuated translational dynamics and the fully-actuated rotational dynamics. At the first step, to control the translational dynamics, we take advantage of a virtual controller, from which the commanded attitude and the thrust input is calculated. In the design of the virtual controller, we exploit an auxiliary system to deal with the under-actuation of the translational dynamics. A prior-bounded estimator is also exploited to counteract the effect of the translational disturbances. After that, a sliding mode controller is developed for the rotational dynamics to tackle the parametric uncertainty and external disturbances in the rotational dynamics. Using Lyapunov function theory, the overall stability of the proposed control scheme is assured. Finally, simulation results are presented to show the effectiveness of the proposed controller.