Heavyweight airdrop flight control using backstepping sliding mode with adaptive function approximation

This paper investigates the problem of designing a novel adaptive backstepping sliding mode controller for heavyweight airdrop operations. The design objective is to guarantee tracking performance of the aircraft states in cargo extraction, in the presence of bounded nonlinear uncertainties without the prior knowledge of the bounds. Based on the aircraft-cargo model in strict-feedback form, a backstepping sliding mode controller with adaptive function approximation is developed. The complex nonlinear uncertainty is factorized into a known matrix and an uncertainty function. We use adaptation strategy to approximate the function to achieve robustness, and the knowledge of the bounds on the complex uncertainty is not required. The stability and robustness properties of the control method are proved using Lyapunov theory. Simulations show good performance and robust operation of the controller, and the airdrop mission performance indexes are satisfied in the presence of ±15% aerodynamic data uncertainty and ±0.01 rad/s pitch rate disturbance.