A Novel Sliding Mode Attitude Control for Hypersonic Vehicle with Mismatched Uncertainties

A novel sliding mode control method is proposed for the reentry phase of hypersonic vehicle with mismatched uncertainties composed of strong coupling and disturbances based on a nonlinear disturbance observer (DOB). Firstly, an extended DOB is established to estimate the disturbances including internal perturbation and unknown disturbance in the attitude dynamics model of hypersonic vehicle. Secondly, the error dynamic model is built by introducing reference model, and a new sliding mode surface with the uncertainties estimation is designed, the sliding mode control is derived from the erorr dynamic model. Comparing the traditional sliding mode control, the feature of the proposed method has the better performance in the robustness to the mismatched uncertainty. Meanwhile, the problem of differential expansion in the back-stepping method is avoided. Finally, simulation results show that the proposed attitude control could be stably tracked with expected commands in the case of there exists the parameters deviation and unknown disturbances, and the performance of tracking accuracy and robustness is better than the traditional sliding mode controller.