Le 19/12/2012 17:54, James Turner a écrit :
> On 19 Dec 2012, at 16:22, Curtis Olson wrote:
>
>> Gyros: /orientation/{p,q,r}-body
>> Accelerometers: /accelerations/pilot/{x,y,z}-accel-fps_sec
>>
>> Both of these are expressed in the pilot/body frame of reference. The
>> accelerometer values include gravity. I've used these to drive a 15 state
>> kalman filter and observe good attitude estimate convergence for both yasim
>> and jsbsim aircraft.
>>
> Right - but I think exposing the values without gravity added in is useful,
> and the for the internal (C++) value, the Yasim one doesn't include gravity,
> so neither should then JSBsim value (both FDMs compute both variants
> already!). Then we could start exposing linear accelerations over MP (or a
> future MP system) and make the prediction better. (And obviously that
> prediction won't want to include gravitational terms)
>
>
> James
>
>
hi, my two cents, as someone interested in better formation flight.
First, about using FGAccelerations::GetUVWdot as acceleration, i'm not
sure you will have what you want. i'm trying to do (slowly) something
about the lag ( http://wiki.flightgear.org/Mp-patch ), and i tried to
use UVWdot, but seems to me it give the dérivative of the speed in the
aircraft reference, not "the acceleration in ECEF, expressed in body
coordinate".
if the speed vector is stable/aircraft, UVWdot will be 0, but the the
body acceleration can be huge in inertial referential. (that's how i
understand the effect i see, and the UVWdot props variation in constant
g turns, i didn't went to understand the jsbsim code ;)
second, could it be possible to have a look at other fdm properties wich
are inconsistent between yasim and jsbsim ?
i think of velocity_wind_body (maybe a "velocity_body" is needed) (bug 202)
and bug 901 (orientation/side-slip-deg)
chears
jano
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