Compound Control Methodology for Small-Scaled Unmanned Helicopters

This work studies the trajectory tracking problem of small-scale helicopters with model uncertainties and external disturbances. Applying a compound strategy, a robust nonlinear controller is designed based on high-order sliding mode disturbance observer and backstepping control. Backstepping enables to provide the basic framework of controller and the stability guarantee of closed-loop system. The lumped force and moment disturbances including unmodeled uncertainties, parameter variations and external gust disturbances can be estimated via high-order sliding mode disturbance observer. Additionally, derivatives of virtual control signals in backstepping process are calculated through high-order sliding mode differentiator to avoid differential explosion. Finally, numerical simulations highlight the capabilities of the proposed controller.