Robust Attitude Stabilization for Nonlinear Quadrotor Systems With Uncertainties and Delays

Robust attitude stabilization problem is dealt with for quadrotor systems subject to nonlinear and coupling dynamics, uncertainties including parametric uncertainties, unmodeled uncertainties, and external disturbances, and time-varying state and input delays. A robust attitude stabilization controller is proposed consisting of a nominal state-feedback controller and a robust compensator. The nominal controller is designed for the uncertain and delay free model to achieve the desired control performances, while the robust compensator is added to restrain the effects of uncertainties and delays on the closed-loop control system. The design method leads to a linear time-invariant feedback controller and the resulted closed-loop control system has a feature of two-loop type. The robust uniform asymptotical stability and bounded-input bounded-state stability are proven. Experimental results on the quadrotor system are given to validate the effectiveness of the designed robust control method.