提出了三维真比例导引律的降维分析方法。首先研究视线的运动规律，提出了视线的两种旋转角速度及其计算方法，建立了视线运动方程与新的弹目相对运动方程。其次通过对弹目相对运动的分析，发现在三维空间中存在视线瞬时旋转平面，可以在该平面内构造二维制导律，以应用于三维拦截问题的制导控制。然后将空间真比例导引律不加任何近似与线性化直接引入视线瞬时旋转平面，使其维度从三维降为二维，并对其制导特性进行了分析。最后通过仿真对比分析，验证了真比例导引律降维分析方法的有效性。

The dimension reduction method of the true proportional navigation (TPN) guidance law is proposed. Firstly, the rotation principle of the line of sight (LOS) was investigated, two kinds of angular velocities of LOS were presented, and so were their calculation methods. Then, the LOS kinematic equation was advanced, and the new relative dynamic equation between interceptor and target was proposed. It was found that there is an instantaneous rotation plane of LOS (IRPL) in the three dimensional (3D) space, in which two dimensional (2D) guidance laws can be constructed to serve for 3D interception guidance. The spatial 3D true proportional navigation (TPN) guidance law was directly introduced into IRPL without any approximation and linearization to transform into dimension reduced 2D TPN, and the characteristics were studied. Finally, an exoatmospheric interception was taken for simulation to demonstrate the effectiveness of the theory presented in this paper.