Estimation error of INS transfer alignment through observability analysis

Estimation errors of the transfer alignment of the inertial navigation system (INS) are presented in two cases, which are stationary state and constant velocity maneuver. The analyzed state variables include misalignment and inertial sensor errors. The INS transfer alignment model uses the velocity matching algorithm in this paper. In order to simplify the deduction process, the velocity matching model is obtained by utilizing the virtual variables to replace the parameters of the master inertial navigation system (MINS) except for the corrected velocity information from the MINS. So it is similar to the common in-motion alignment model. Then, the observability of the transfer alignment is analyzed. There are at least 3 unobservable states at rest or during the constant velocity motion. The conclusion is obtained, that the estimation errors are not fixed, but changed with the sensed specific force and angular rate during the constant velocity motion