Control of wing rock based on high order sliding mode disturbance observer

Wing rock is a highly nonlinear phenomenon, which is a main limit-cycle oscillation for an aircraft operating at subsonic speeds and high angles of attack. It is a challenge to design a valid controller under the condition that there exists model error and external disturbance. In this paper, a sliding mode disturbance observer based on homogeneity is proposed to improve the disturbance estimate performance. Then, the robust tracking control scheme is developed for the wing-rock using the output of the designed sliding mode disturbance observer. The disturbance observer can provide the corresponding compensation for the model error and external disturbance, and the developed tracking controller can guarantee tracking error converge to zero. Simulation results demonstrate that the proposed control system can achieve satisfactory tracking control performance for the wing rock motion.