Second-order sliding-mode guidance law with impact angle constraint

A new second-order sliding-mode guidance law with finite time stability is proposed for the design of the guidance law for the air-surface missile with impact angle constraint. Based on the relative motion model of the missile and the target, the terminal trajectory inclination angle constraint is transformed to the terminal line of sight (LOS) angle constraint, which is taken as the terminal control goal of the guidance system. In order to satisfy the annihilation of LOS rate and the terminal angle constraint, a second-order sliding mode guidance law is designed by using a new second-order sliding mode surface with twisting control algorithm, which is used to suppress the uncertainty of guiding system. Based on the Lyapunov stability theory, a new Lyapunov function is adopted to verify the strict stability of the guidance system in finite time. The air-surface missile guidance system is simulated numerically. A comparison with the conventional sliding mode guidance law and a second-order sliding mode guidance law using super twisting algorithm shows that the method proposed in this paper can improve the accuracy of terminal angle constraint in finite time and avoid the problem of too many parameters in the super twisting algorithm, and can guarantee the guidance accuracy at the same time.