Research On Control Strategy Of Close-range Rendezvous Based On Trajectory Safety

To analyze the trajectory safety of spacecraft is very significant for setting down trajectory strategy. To set down proper trajectory safety criteria, we must make judgments for trajectory safety correctly and properly, which can be adapted to different errors in measurement. In this thesis, we focus on the research on trajectory safety theory, which is later used to solve trajectory safety problems of spacecraft, and also used in guidance of autonomous rendezvous. The method and conclusions in this thesis would be available in theory and practice for the rendezvous mission. The main results achieved in this dissertation are summarized as follows.Several new concepts on trajectory safety problems are imported while expressions concerned are deduced. (1) A common theory model of trajectory safety problem is proposed, in which we define safe-set and unsafe-set of the problem. (2) The subjectivity verification criterion is proposed, associating subjective randomicity in measure with trajectory safety criteria. The criterion is used to judge whether a trajectory safety criterion is correct and proper. (3) The concept of Same-Probability Surface is imported, which is used to research the rule of safe-set and unsafe-set under probability criterion spreading in the space.A conception named False-Judgement Probability (FJP) is proposed. (1) FJP is imported in this thesis by Probability-Dilution Problem. The False-Judgement problem of trajectory safety criteria is researched, with measurement and judgement, over the whole impersonal motion. (2) The FJP under Probability Criterion is researched, and the explicit expression between FJP and Collision Warning Probability (CWP) is deduced. (3) A common flow is proposed in correcting trajectory safety criteria with FJP. Research on the avoidance strategy of space objects. (1) The trajectory safety of orbits with different height is analyzed, by comparing the statistical encounter times per year within a safety distant. Moreover, a method of defining safety distant is proposed by FJP. (2) The trajectory safety of a single encountering event is analyzed, of which the avoidance maneuver strategy is given by the Probability Criterion corrected with FJP.Research on the control strategy of autonomous rendezvous considering trajectory safety based on FJP. (1) The explicit expression of avoidance maneuver impulse under the condition of low relative velocity is deduced, considering the characteristics of autonomous rendezvous, which is almost as accurate as high precision method but much more efficient. (2) A method of designing safe trajectory is proposed, base on multi-impulse maneuver and the explicit expression. Homing and approaching trajectory during the close range rendezvous is designed by this method.