Design of nonlinear terminal SMGL (sliding-mode guidance law) for KKV (kinetic kill vehicle)

SMGL has drawn great attention for its superior performance; during the design of SMGL, the key is how to choose a sliding-mode. Traditionally we choose a linear sliding-mode, with which the tracking error of system will asymptotically converge to zero. But the shortcoming of linear-mode is that we cannot control the convergence time and that sometimes this cannot meet the requirement of rapid response. To avoid this problem, we can use terminal sliding-mode control law(TSMCL), in which a nonlinear function is introduced in the sliding-mode, and this can satisfy that tracking error converges to zero in finite time. In this paper, we analysed the problems of a kind of nonlinear terminal sliding-mode surface that emerged in its utilization. Then, aiming at the above problem, we put forward a novel improved nonlinear terminal sliding-mode(NTSM) and derived the expression of convergence time that is needed by the system to arrive at balance state from an initial state. Finally, for KKV, we designed a new nonlinear terminal sliding-mode guidance law using the improved NTSM. Representative simulation results and their analysis show preliminarily that the new guidance law not only meets the requirement of kinetic kill assignment, but also converges quickly; furthermore the miss distance is smaller than that of traditional sliding-mode guidance law.