Re: Re: [Paparazzi-devel] Paparazzi EKF- and compelmentary- filter

[Felix Ruess]

Hi Andrew,

some (unpublished) filters are used on an external more powerful
hardware (gumstix and atom). There is also the error state space KF I
wrote in float for testing in simulation under
sw/airborne/booz/ahrs/booz_ahrs_float_lkf. But you can't fly with that
one at the moment (too long to compute in float and probably still has
some bugs I guess).

Cheers, Felix

2010/4/13 Andrew S <address@hidden>:
> Hi Felix,
> Where is the paparazzi KF?
> Andrew
>
>
> 13.04.10, 08:35, "Felix Ruess" <address@hidden>:
>
>> Hi Andrew,
>>
>>  Whether you represent your angles in a way that they have
>>  singularities (like euler angles) or not (like quaternions or dcm) has
>>  nothing to do with the choice of your estimator (e.g. EKF or
>>  complementary filter or your PI controller). In any case you have to
>>  transform your IMU measurements from the IMU frame into the navigation
>>  frame (assumed to be the same as the inertial frame considering the
>>  quality of the sensors).
>>  The paparazzi KF uses quaternions as angle representations (you really
>>  don't want to use dcm here) but also converts the latest quaternion
>>  attitude estimate to euler angle and dcm representations for ease of
>>  use.
>>
>>  Cheers, Felix
>>
>>  2010/4/6 Andrew S :
>>  > Hi
>>  > For my view, EKF is unnecessary as it loads microcontroller. You can use 
>> even simple PI controller. It works worse than EKF, but quite well. For good 
>> results PI regulator should be adjusted for 10 seconds of correction after 
>> 180 degrees error. Also I can say cheap two axis gyros by ST are unusable 
>> because of cross axis interference and whey do not have tolerancy against 
>> vibration. Complementary one axis Z-gyros are better.
>>  > For correct angles EKF is not a solution, you need for example 
>> Directional cosine matrices for calculations between body and earth frames. 
>> The problem is that gyros works in the body frame, but accelerometers works 
>> in the earth frame. In fact when pitch is near 90 degrees, the roll gyro 
>> indicates jaw :)  EKF will not helps for this.
>>  > Andrew
>>  >
>>  > 02.04.10, 17:41, "Prof. Dr.-Ing. Heinrich Warmers" :
>>  >
>>  >> Hello,
>>  >>  we made same experiments with a EKF based  on the rotomotion solution in
>>  >>  combination with the tiny13 and a low cost analogue IMU from sparkefun.
>>  >>  By the test i saw that the software is not  possible to  deal with
>>  >>  pitch  angeles over  90°. So  to fly a looping is impossible.
>>  >>  If  90° arrives it is  impossible to get the correct angeles by the g
>>  >>  force since static  z acceleration is zero.
>>  >>  If the pitch angels is more than  120°  the roll angeles rotate fast.
>>  >>  What is about the  paparazzi  booz ekf and complementary filter. Can
>>  >>  they deal  all angeles ?
>>  >>  In the video from 2006  i saw only small  angeles.
>>  >>
>>  >>  Cheers
>>  >>
>>  >>  Heinrich
>>  >>
>>  >>
>>  >>
>>  >>
>>  >>
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