Nonlinear dynamic modeling and hybrid control design with dynamic compensator for a small-scale UAV quadrotor

This paper presents a detailed nonlinear dynamic model and the development of a flight control scheme for an unmanned aerial vehicle (UAV) quadrotor. In the dynamic modeling, significant aerodynamic effects arising from the blade deformation of the rotor and the induced momentum are taken into account. The model is capable of representing the quadrotor behavior for more flight regimes, including not only hover but also high-speed and translational flights. Such a model can benefit the controller design from the improvement of the stability as well as the reduction of development period. Furthermore, a hybrid control scheme incorporating optimal linear quadratic regulator (LQR) and robust sliding mode control (SMC) techniques is designed in a hierarchical multiple-layer structure. In actual practice, only partial states of the quadrotor are readily measurable. A reduced-order observer is hence developed and integrated into the compensator to estimate the unmeasured states. The simulation results show that the designed controller can achieve outstanding performance which is greatly superior than conventional control techniques can do.