Adaptive Backstepping Sliding Mode Control of Morphing Aircraft with Unknown Disturbances

In this paper, a nonlinear control scheme is proposed for the altitude tracking of morphing aircraft with unknown aerodynamic disturbances under the condition of high maneuver. Considering the characteristics of high order and strong nonlinearity of the system, the scheme divides the system into inner loop (pitch angle tracking) and outer loop (height tracking). An adaptive sliding mode controller is designed for the inner loop subsystem to avoid the influence of unknown aerodynamic disturbances on tracking performance. The upper bound of disturbances is estimated in real time by adaptive update rules to compensate for the unknown disturbances. To prevent the problem of ‘differential explosion’ induced by the high order, a backstepping tracking controller with dynamic surface is designed for the outer loop subsystem. The stability of the closed-loop system is analyzed utilizing Lyapunov theory. Finally, the effectiveness of the proposed scheme is validated by comparative simulations.