I am running into a conceptual problem with how to use IMU data in my kalman modeling.

For the acceleration given by the IMU, I have assumed that the raw acceleration data must be manipulated to eliminate centripital/gravitational effects, using

$\displaystyle \Delta v / \Delta t = \begin{pmatrix} a_x \\ a_y \\ a_z \end{pmatrix} - \begin{pmatrix} p \\ q \\ r \end{pmatrix} \times \begin{pmatrix} u \\ v \\ w \end{pmatrix} - RotationMatrix*\begin{pmatrix} 0 \\ 0 \\ g \end{pmatrix}$

But I also read that the $\displaystyle a_x,a_y,a_z$ terms come from prior (buffered) position or velocity data... ie

$\displaystyle a_n = ((v_n)-v_{n-1})/\Delta t$

So am I guessing correctly that $\displaystyle a_x,a_y,a_z$ represents the raw IMU output? Thanks