Comparison of SDINS in-flight alignment using equivalent error models

The psi-angle model and the equivalent tilt(ET) model have been widely used for in-flight alignment (IFA) to align and to calibrate a strapdown inerti al navigation system (SDINS) on a moving base However, these models are not effective for a system with large attitude errors because the neglected er ror terms in the models degrade the performance of a designed filter, In th is paper, with an odometer as an external aid, a velocity-aided SDINS is de signed for IFA, And equivalent error models applicable to IFA with large at titude errors are derived in terms of relation vector error and additive an d multiplicative quaternion errors. It is fouled that error models in terms of additive quaternion error (AQE) become linear. Thus the proposed error models reduce unmodeled error terms for a linear biter, From a number of va n tests, it is shown that the proposed error models effectively improve the performance of IFA.