Optimal adaptive integral sliding mode control for reentry vehicle attitude

In this paper, an optimal adaptive integral sliding mode control (OAISMC) strategy is proposed for the reentry vehicle with a strong coupling, nonlinearity and uncertainty. Firstly, the State Dependent Riccati Equation (SDRE) is used to design the attitude controller for the nonlinear reentry vehicle without uncertainties. Then the integral sliding mode control theory is applied to reentry vehicle with parameter variations or external disturbances. By combining the integral sliding mode control theory with SDRE, the optimal performance index is achieved and the uncertainties can be rejected. Moreover, by using an adaptively adjusted switching gain, the upper bound of the lumped uncertainty is not required to be known. A sliding mode disturbance observer is introduced to improve the control performance. Finally, simulation is made in the presence of external disturbance and as well as perturbation by aerodynamic coefficients and atmospheric density. The validity and robustness of the proposed strategies are verified by simulation results.