Evaluation of hypersonic vehicle SINS navigation solution in the hardware-in-the-loop simulation

In order to evaluate hypersonic vehicle flight control system in the hardware-in-the-loop simulation (HILS), the comparison and analysis method between strapdown inertial navigation system (SINS) navigation solution (position, velocity, attitude, angle of attack, and sideslip angle) and solution of six-degree-of-freedom (6DoF) model in the hypersonic vehicle HILS is studied. The coordinate systems that used in the space field and aeronautics field are listed, and the relationships between coordinate systems in the two fields are analyzed. The theory of coordinate transformation among the coordinate frames is introduced. The relationships of direction cosine matrix (DCM) or Euler angles from the reference frames to body frames are studied. A mathematical model comparing the SINS position of local-level east-north-up (ENU) frame in aeronautics with the position of launch centered earth-fixed (LCEF) frame in space, and also a mathematical model comparing the velocity vector in ENU frame with the vector in LCEF frame is introduced. According to the theory of coordinate transformation, the comparison model is derived, and also the method for comparing the Euler angles of SINS with Euler angles in LCEF frame is analyzed. The digital simulation reveals that the proposed evaluation method is correct and feasible. The HILS result indicates that the accuracy of SINS navigation solution satisfies the requirements of flight control system.