Saturated Backstepping-Based Tracking Control of a Quadrotor With Uncertain Vehicle Parameters and External Disturbances

Knowing the vehicle's parameters (e.g., mass, moment of inertia) in advance is not always possible in quadrotor control applications, especially if we use the quadrotor for cargo transportation. Uncertain cargo weight and size together with external disturbances may result in closed-loop performance degradation or even instability. In light of this problem, this letter proposes a saturated robust adaptive tracking controller for a quadrotor based on nonlinear Lyapunov-theory, where a set of estimation laws are designed to compensate for uncertain parameters and disturbances, achieving global uniformly ultimately boundedness (GUUB). Additionally, through the use of saturation functions, the designed thrust force is ensured to be bounded by a predefined value. Numerical simulation examples are presented and discussed to validate the effectiveness of the proposed solution. To further highlight the enhancements of the presented method, comparison results with an existing control strategy are provided and analyzed.