针对导弹拦截机动目标有限时间约束问题，在末端制导阶段，考虑自动驾驶仪动态延迟特性建立弹目拦截系统数学模型，对于传统终端滑模导引律存在的奇异问题导致的导弹制导稳定性差等问题，提出了基于改进的扩张状态观测器的新型非奇异终端滑模导引律。该方法能够确保视线(LOS)角速率在有限时间内收敛到零，且在平衡点处快速收敛; 为了避免传统的扩张状态观测器(ESO)导致的曲线非光滑情况，通过改进扩张状态观测器准确估计外部扰动，并对系统进行状态补偿。设计地空导弹模型进行仿真验证，结果表明，该方法不但缩短了系统收敛时间，还提高了地空导弹制导精度。

To solve the problem of finite-time constraints when the missile intercepts a maneuvering target in the terminal guidance stage, the mathematical model of the target interception system is established considering the dynamic delay of the autopilot.To solve the problem of poor guidance stability caused by the singularity of the traditional terminal sliding mode guidance law, a new non-singular terminal sliding mode guidance law based on the improved Extended State Observer (ESO) is proposed.This method ensures that the Line-of-Sight (LOS) angular rate converges to zero in a finite time and converges quickly at the equilibrium point.In order to avoid curve chatter caused by the traditional ESO, an improved ESO is adopted to accurately estimate external disturbances and compensate for the systems state.A model of the surface-to-air missile is designed for simulation verification.The simulation results show that this method not only shortens the systems convergence, but also improves the guidance precision of the surface-to-air missile.