Re: [Paparazzi-devel] Measured info from sensors in ahrs_int_cmpl_euler filter

[Felix Ruess]

You might want to take a look at the floating point implementations first, since they are easier to understand without all the shifts used for different fixedpoint representations.

F_UPDATE is the update frequency.

On Fri, Nov 6, 2015 at 7:43 PM, flavio_just <address@hidden> wrote:

Hi guys!
I would like to know exactly what expressions are used to calculate the
direct angles from accel and mag by this filter, since bitshifts is often
used and confuses me.

Currently, I am using the following expressions in matlab to reproduce what
pprz does:

roll=atan2(-accel(k,2),-accel(k,3));
pitch=atan2(accel(k,1),-accel(k,3));
yaw=atan2((-mag(k,2)*cos(roll)+mag(k,3)*sin(roll)),(mag(k,1)*cos(pitch)+sin(pitch)*(mag(k,2)*sin(roll)+mag(k,3)*cos(roll))));

for the roll and pitch angles the dynamics is the same but with an error of
about 4 or 5º everytime. For the mag is completely different the result.

By the way, can someone also tell me why F_UPDATE exists and what it does?

Thank you so much guys,
Flávio




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