Abstract: An adaptive backstepping controller was designed for quadrotor UAV with non-linear and couplings.In order to obtain the virtual control item derivatives,low-pass first order filter was introduced.A sufficiently smooth projection operator was employed to estimate and compensate the model unmatched uncertainties for the sake of the inhibition of the parametrical drift and broaden the request of traditional projection operator which is conscious of the upper and the lower bounds of the uncertainties.Simulation results show that the designed controller possesses productive control effect and robustness.

Key words: Quadrotor UAV,Adaptive backstepping controller,Low-pass first order filte,Sufficiently smooth projection operator