Integral backstepping based hovering control of an unmanned coaxial helicopter

Due to the aerodynamic disturbance between two rotors of coaxial helicopters, serious coupling exists among control channels which makes the flight controller design for this kind of helicopter more difficult. This paper proposed a hovering control strategy based on integral backstepping method for our coaxial helicopter under research. At first, the nonlinear dynamic model considering interaction between two rotors is established by use of the basic principle of rotor aerodynamics. The height-attitude subsystem is extracted, and then expressed in strict feedback form under several necessary simplifications. The stabilizing controller is designed based on integral backstepping method step by step for the subsystem and the stability of the closed-loop system is guaranteed by analysis using Lyapunov stability theory. After that, a PD controller is designed for the closed-loop subsystem to achieve position control. The effectiveness of the proposed controller is demonstrated by numerical simulation.