基于非线性Terminal滑模的动能拦截器末制导律设计

Design of Nonlinear Terminal SMGL (Sliding-Mode Guidance Law) for KKV(Kinetic Kill Vehicle)

滑模制导律由于具有优越的性能而得到广泛关注,其设计的关键是滑模面的选取。传统的滑模变结构制导律通常都选择线性滑动平面,并保证系统到达该平面后跟踪误差渐近地收敛到零,在此过程中对收敛时间没有约束,因此不能满足快速性要求。针对这一问题,可以采用Terminal滑模控制策略,即在滑模面设计中引入非线性函数,使跟踪误差在有限时间内收敛到零。分析了一类非线性Terminal滑模面在应用中存在的问题,针对该问题设计了一种改进形式的非线性Terminal滑模面,并推导了系统从任意初始状态到达平衡状态所需时间的表达式。之后,针对动能拦截器末制导,基于改进方法设计了一种非线性Terminal滑模制导律,仿真结果表明,相对于传统的滑模制导律,所设计的制导律可以满足动能拦截的要求,不仅能够使系统状态在有限时间内收敛,而且脱靶量更小。

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 ter- minal 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.