Nonsingular finite-time second order sliding mode attitude control for reentry vehicle

This paper presents nonlinear robust flight control strategies for the reentry vehicle which is nonlinear, coupling, and includes parameter uncertainties and external disturbances. Firstly, a finite-time second order sliding mode attitude control strategy is pointed out with the introduction of a nonsingular finite-time sliding mode manifold. By the proposed controller, the attitude tracking errors are mathematically proved to converge to zero within finite time and the chattering of sliding mode controller is alleviated without any deterioration of robustness and accuracy. For further alleviation of chattering, a smooth second order sliding mode attitude control strategy is then designed based on an improved nonsingular finite-time sliding mode manifold. Finally, the proposed strategies are applied to the attitude control of X-33 RLV in the reentry phase to verify the validity and robustness of the proposed strategies.