Position Biased Terminal Guidance Based on Geometric Tangent

Aiming at the close observation of the faulty space crafts, the paper proposes an improved terminal guidance law with biased distance by considering the J2 perturbation and relative motion information. First, considering the J2 perturbation, the motion model of the approaching vehicle and the target is established based on equations of two-body motion. Then, taking into account relative motion information, a method for selecting offset observation points based on geometric tan-gent is raised. The coordinates of the biased point in the line-of-sight coordinate system are given in three-dimensional space, and the conversion relationship between the biased line-of-sight coordinate system and the line-of-sight coordinate system is obtained. Furthermore, the line-of-sight rate and the approach velocity between the approaching vehicle and the biased observation point is achieved. Moreover, the biased line-of-sight rate is introduced into the proportional navigation, and the biased guidance command is obtained, and the switching frequency of the orbit control engine is decreased via introducing the line-of-sight threshold. Last, the simulation experiments are carried out and the results show the accuracy and superiority.