Robust Nonlinear Output Feedback Control of a 6-DOF Quadrotor UAV

A robust nonlinear output feedback control method is presented, which achieves asymptotic position and attitude regulation for a six degrees of freedom (6-DOF) quadrotor unmanned aerial vehicle (UAV). The control law is designed to compensate for uncertainty in the quadrotor system dynamic model, including input-multiplicative parametric uncertainty. To reduce the computational requirement in the closed-loop system, constant feedforward estimates of the input-multiplicative uncertainty are utilized in lieu of adaptive parameter estimates. In order to avoid the high-gain feedback requirement that is characteristic of standard sliding mode observer methods, the proposed control method utilizes a bank of dynamic filters, which operates as a velocity estimator in the closed-loop system. Simulation results are provided to demonstrate the performance of the attitude control method using the Quanser 6-DOF QBall 2 system test bed.