Robust output feedback position control for quadrotor based on disturbance observer

A robust feedback position control scheme is presented for quadrotor helicopter in the presence of model parameter uncertainties and external disturbance. Robust position control is guaranteed by disturbance observers designed to estimate model parameters uncertainties and external disturbance. Nonlinear terms in quadrotor model are also viewed as disturbance in disturbance observer design procedure. By rejecting disturbance, the nonlinear quadrotor helicopter system is compensated to a linear system with nominal parameters. Based on the compensated linear system, fractional controllers are designed to move quadrotor to the desired position. The closed-loop stability is also verified. Robustness and efficiency of the disturbance observer based output feedback control method is demonstrated with a quadrotor model subjected to parameter uncertainties and external disturbance.