Abstract:

With focus on the “entry state deviation” problem of the mars entry phase guidance a desensitized trajectory design method is used to enhance guidance robustness and improve terminal state accuracy. Firstly, the influence of bank angle inverse logic on the guidance accuracy of a spacecraft with weak maneuver capability is analyzed. Analysis result shows that the inverse logic will cause terminal state error and make system more sensitive to entry state error if bank angle adjust performance is limited, and even worse when guidance principle is chosen to be longitudinal desensitization method, and serious failure will arise. Secondly, on the basis of solution to the sensitivity propagation singular problem, a three degree of freedom desensitization design is proposed. Its main idea is to adopt three degree of freedom dynamics equations in trajectory optimization while the longitudinal sensitivity propagation equation is still used to obtain the sensitivity penalty term. Monte-Carlo simulation results have shown its remarkable robustness improvement in dealing with entry state deviation.

Key words: Mars entry phase accurate guidance, Robust guidance, Trajectory desensitize optimization, Gauss pseudospectral method optimization, Desensitized optimal control