An autopilot inner loop that combines backstepping control with adaptive function approximation is developed for airdrop\noperations. The complex nonlinear uncertainty of the aircraft-cargo model is factorized into a known matrix and an uncertainty\nfunction, and a projection-based adaptive approach is proposed to estimate this function. Using projection in the adaptation law\nbounds the estimated function and guarantees the robustness of the controller against time-varying external disturbances and\nuncertainties. The convergence properties and robustness of the control method are proved via Lyapunov theory. Simulations are\nconducted under the condition that one transport aircraft performs a maximum load airdrop task at a height of 82 ft, using single\nrow single platform mode. The results show good performance and robust operation of the controller, and the airdrop mission\nperformance indexes are satisfied, even in the presence of �±15% uncertainty in the aerodynamic coefficients, �±0.01 rad/s pitch rate\ndisturbance, and 20% actuators faults.
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