圆弧预测变系数显式拦截中制导

为了满足临近空间机动目标拦截中制导预测和多约束要求，设计了一种基于圆弧预测的变系数显式拦截中制导方法。首先针对临近空间目标滑翔段飞行特性，提出了基于圆弧的几何目标预测方法，将目标机动轨迹近似为圆弧，通过多个间隔时刻的目标位置确定圆弧参数，依据圆弧预测轨迹估计剩余飞行时间，并以当前速度递推预测拦截点状态，进而推导了三维角约束显式制导律。在此基础上，通过在性能指标中构建动压权重函数，以飞行动压近似可用过载变化，设计了变系数显式制导律，实现了制导增益的自适应更新，从而可以使得需用过载在飞行全程中合理分配，满足可用过载约束。最后结合圆弧预测和变系数显式制导，实现了对机动目标的预测拦截。仿真结果表明所提方法具有较好的目标预测精度，而且可以满足终端交会角以及可用过载约束。

Explicit guidance law with varying gain and circular prediction for mid-course interception

In order to improve the estimation accuracy of target's state and to satisfy multi-constraints of intercepting process in the near space, an explicit mid-course guidance law with varying gain against high maneuverable target is designed. Firstly, the dynamic characteristics of the target in the near space was analyzed. Based on it, a geometric prediction method of the target's trajectory is proposed, which approximates the target trajectory to circular arc. Subsequently, the state of target and the interception time-to-go can be more accurately predicted along the arc. Secondly, the explicit guidance law with three-dimensional angular constraints are derived. In order to restrict commanded acceleration within feasible boundaries, a weight function is constructed with respect to dynamic pressure, and is enforced to the performance index function to modulate the guidance gain. Accordingly, the acceleration command can be adjusted to avoid over demanded by the adaptive update of guidance gain as flight altitude increasing. Finally, by combining circle prediction and the explicit guidance law with varying gain, high terminal interception accuracy against high speed maneuverable target is achieved. The simulation results show the proposed method can significantly improve the accuracy of target prediction as well as satisfy the constraints of the terminal impact angle and the available accelerations.