Disturbance estimation backstepping flight control based on the discrete Fourier transform

This paper presents the design of an adaptive backstepping (BS) nonlinear controller for time-varying disturbances in flight control. The discrete Fourier transform (DFT) is used to design an adaptive law to suppress the influence of time-varying disturbances. The traditional adaptive BS method ignores the derivatives of disturbances in the deduction process and cannot address certain fast, time-varying disturbances well. Therefore, an improved adaptive BS method based on the DFT is proposed. Instead of estimating the disturbance directly, the proposed method obtains the time-domain expression of the disturbance indirectly by estimating the disturbance spectrum and performing inverse DFT. The proposed method effectively overcomes the inability of the traditional adaptive BS method to estimate fast, time-varying disturbances accurately. Finally, the proposed method is compared with traditional adaptive BS and radial basis function (RBF) neural network control methods. Simulation results confirm that the proposed method outperforms other methods under Gaussian disturbance and turbulence.