Trajectory tracking of a quadrotor using model predictive and backstepping control with anti-disturbance compensation subjected to variations in the center of gravity

The trajectory tracking control of a quadrotor unmanned aerial vehicle is done in this paper in the presence of changes in the center of gravity due to the variations of a connected load mass and its position, external disturbances, and parametric uncertainties. At first, dynamic equations are obtained using Newton–Euler relations, and then a two-loop control architecture is designed for the trajectory tracking task. Backstepping and model predictive control are used in the inner and outer loops, respectively. An extended disturbance observer is adopted to improve disturbance rejection capabilities in both loops. For the six-degrees-of-freedom unmanned aerial vehicle, the effects of time-varying mass, which leads to the change in the moment of inertia and center of gravity of the system, together with external disturbances and parametric uncertainties are taken into account. It is possible to mount an arbitrary number of different point masses at arbitrary positions on the unmanned aerial vehicle. The proposed control scheme is evaluated using simulation in the presence of uncertainties and external disturbances. According to the simulation results, the developed control scheme can achieve stable flight under different conditions.