Analysis of attitude error models of strapdown inertial navigation system

In strapdown inertial navigation system(SINS),the digital platform is the coordinate transformation matrix stored in the navigation computer,whose functions are the same as that of mechanical platform in the gimbaled navigation system.The quaternions and the rotation vector are two commom methods to describe the attitude of SINS.The conventional linearized error models,such as psi-angle model and the equivalent tilt(ET) model,are effective only for the systems with infinitesimal attitude errors.In this paper,the rotation vector error(RVE) model was introduced as a nonlinear error model for the systems with large attitude error.The attitude error models in terms of additive quaternion,multiplicative quaternion and rotation vector were presented respectively,and they were found to be equivalent among them.Besides,the multiplicative quaternion error model and the rotation vector error model can be reduced to ET model in case the system’s attitude errors are very small.