A robust filtering algorithm for integrated navigation system of aerospace vehicle in launch inertial coordinate

In ordinary aircrafts, the geographic coordinate is usually taken as reference coordinate to build navigation systems. Changes of gravity field and radius caused by the non-perfect sphere and uneven mass distribution of the earth are ignored or simplified in navigation algorithm, which have little effect on the accuracy of the navigation system in a short-time and short-distance flight. As the Aerospace Vehicles (ASVs) have to complete long-term on-orbit maneuver over wide flight enveloping, ignoring changes of gravity field and radius will bring about cumulative navigation errors and result in the declined accuracy of the navigation system. Hence, this paper first proposes an inertial navigation algorithm in launch inertial coordinate for ASVs aimed at reducing the effects caused by the inaccurate earth model on the navigation system. Then, the model of INS/CNS/GPS integrated navigation system in launch inertial coordinate is built. Considering the uncertain noise in space, the performance of Kalman filter may be poor, a robust filtering algorithm based on extended H∞ filter is designed to realize multi-sensors information fusion; The state model and measurement model in launch inertial coordinate are built. The simulation results show that the proposed method and algorithm can improve the accuracy and reliability of the integrated navigation system for ASVs.