RIMU Misalignment Vector Decomposition

A general misalignment parameter vector for a redundant inertial measurement unit (RIMU) comprises two misalignment angles for each of n sense axes (n > 3). A transformation is derived to separate 3 rotational misalignments and 2n i 3 nonorthogonal misalignments in the parameter vector. The model order can be reduced by explicitly eliminating the three rotational misalignments. It is shown that the model order can also be implicitly reduced by appropriately initializing the covariance with the aid of the transformation. The equivalence of rotational misalignments modeled at either the RIMU or at the attitude sensors is shown empirically via simulation. Results apply also to nonredundant IMUs (n = 3).