Research on terminal guidance for re-entry vehicle based on second-order sliding mode control

A new robust terminal guidance law based on second-order sliding mode control is proposed for the problems existing in vehicle re-entry phase after starting of terminal guidance system, such as model uncertainty, complex aerodynamic conditions and constraint conditions for falling angle. Based on second-order variable structure control theory, a terminal guidance law with finite convergence time is designed; meanwhile, in order to weakening the influence of disturbance and chattering, a super-spiral algorithm is introduced for designing the second-order sliding mode terminal guidance law with finite convergence time and continuous control effect. Controlled by this guidance law, the angular rate of line-of-sight (LOS) and constraint conditions for falling angle can converge quickly, thus ensuring higher guidance accuracy. Theoretic proof of stability based on Lyapunov theorem and simulation results show that the proposed guidance law is effective.