Nonlinear output feedback tracking control of a quadrotor UAV in the presence of uncertainty

A nonlinear output feedback control method is presented, which achieves asymptotic altitude and attitude trajectory tracking of a quadrotor system in the presence of model uncertainty and unknown external disturbances. To address a practical scenario where velocity measurements are not available, a bank of dynamic filters is utilized, which acts as a velocity observer in the closed-loop system. A primary focus of the proposed control method is detailed development that shows how a computationally minimal strategy can be utilized to compensate for multiple sources of uncertainty without the use of adaptive parameter estimation or function approximators. A rigorous Lyapunov-based stability analysis is utilized to prove semi-global asymptotic trajectory tracking in the presence of parametric uncertainty and unmodelled external disturbances. Numerical simulation results are also provided to demonstrate the performance of the proposed control law.