Re: [Paparazzi-devel] ACC_AMP value derivation in booz2_filter_attitude_cmpl_euler.c

[antoine drouin]

2^10 and 2^12 are fixed point scaling factors

Nevertheless, I'd advise to use the latest AHRS
(sw/airborne/subsystems/ahrs/ahrs_int_cmpl.c) and not the one you're
referring too which is  4 years old.

Regards

Poine

On Thu, Feb 9, 2012 at 8:36 PM, Avinash Rao <address@hidden> wrote:
> Hi all,
>
> I'm new to the mailing list and just wondering if anyone can help me with
> understanding how ACC_AMP is calculated in
> booz2_filter_attitude_cmpl_euler.c?
>
> In the code, the following formula is used:
>
> /*
>  * ACC_AMP
>  * 9.81 * 2^10 * sin(pi/4) * ACC_AMP = pi/4 * 2^12 * F_UPDATE
>  *
>  */
>
> and I understand from a previous thread
> (http://lists.gnu.org/archive/html/paparazzi-devel/2010-06/msg00014.html)
> that this is a linearization for the euler angle formulae:
>
> phi = -atan(ay/az)
> theta = asin(ax/|a|)
>
> which is where the pi/4 / sin(pi/4) part would come from, however I'm unsure
> of where the other terms (2^10, 2^12, 9.81 (obviously gravity in some way!))
> come from. Can anyone show me how this is derived?
>
> Thanks very much in advance to anyone who can help.
>
> Regards,
>
> Avinash.
>
>
> --
> Avinash Rao
>
>
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