The guidance, navigation and control (GNC) system of hypersonic boost-glide (HBG) vehicle employs the launch centered inertial (LCI) frame as the reference frame during the vertical boost phase, while it uses the local-level (LL) frame as the reference frame during the gliding phase. The HBG vehicle needs not only the navigation solutions relative to LCI frame for controlling and guiding, but also the expanding of its navigation solutions relative to LL frame. In the current study, the algorithm of SINS in LCI frame has been introduced, and how to obtain the position and velocity vector relative to LL frame from the navigation solutions relative to LCI frame has been presented. Additionally, the theory of coordinate transformation (CT) has been described, and the relationship of the direction cosine matrix (DCM) between the LCI frame and LL frame has been deduced. Thus, Euler angles relative to LL frame can be obtained from the DCM relative to LCI frame. The obtained results show that the proposed algorithm is correct, and it can meet the navigation solutions requirement of GNC of HBG vehicle during all the phases such as boost, reentry and gliding phase.
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