Robust Adaptive Control for a Quadrotor UAV with Uncertain Aerodynamic Parameters

In controller design for quadrotors, the drag coefficients, thrust coefficients, and aerodynamic damping coefficients are usually unmeasurable, and they have to be regarded as uncertain parameters. Meanwhile, the position information provided by the GPS receiver is easy to get disturbed by environmental noise. A backstepping-based robust adaptive control scheme is proposed in this article to address uncertain parameters, bounded external disturbances, and the noise in measurement. The proposed approach overcomes singularities resulted from using inverse trigonometric functions of Euler angles. A continuous function is introduced to replace signum functions, such that the closed-loop system satisfies Lipschitz condition. Boundedness of estimation errors and tracking errors are guaranteed by the proposed approach and their boundary can be modified. The advantages of the proposed controller are supported by numerical examples and experimental results, where comparisons with proportional-integral-derivative (PID), backstepping, geometric control, and the other existing robust adaptive controller are provided.