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Re: [Paparazzi-devel] IMU's
Christophe De Wagter
Re: [Paparazzi-devel] IMU's
Thu, 1 Sep 2011 20:17:55 +0200
the DCM_float implementation in paparazzi indeed only estimates attitude (called AHRS in paparazzi) but it does use GPS velocity to compensate centripetal forces and to estimate heading (magnetometer could be used)
-assumes all velocity is in body X direction (= aircraft model)
-does not compensate longitudinal acceleration (change is velocity)
-does not improve GPS measurements using accelerometers (called INS in paparazzi)
On Thursday, September 1, 2011, Hector Garcia de Marina wrote:
I have writen about the DCM algorithm (mahony papers) only estimates the attitude, not the 3D position as it does not take into account any position observation, as GPS, vision, or whatever :P. But of course, the DCM algorithm estimates the attitude, althougt as it only relies in accelerometer for measuring the gravity, the algotihm can not estimate the yaw angle.
On Tue, Aug 9, 2011 at 11:17 AM, Prof. Dr.-Ing. Heinrich Warmers <address@hidden>
you're are right that in the current implementation only compensate
the centrifugal force for circles around the z axis.
It it not a problem to solve vector f = vector omega (vector
multiplication ) vector V.
By adding this simple equation also to the AHS of paparazzi it would
be possible to fly acrobatic with normal planes for a long time period.
I think you're are wrong, that the current implementation oft the
DCM do not estimate the 3D attitude.
We have flown circles for 20 minutes (angel up to 70° radius down to
We have also flown in clouds and circles up to to 1700m ground level
The paparazzi estimator (estimator.c) calculate position and speed and
fill the gap between the 250ms until the next gps information.
It would be a nice work to implement acrobatic flight components like
F3A in Paparazzi.
Hector Garcia de Marina schrieb:
Todd, as the DCM algorithm does not estimate the 3D position/velocity,
it can not compensante the centripetal acceleration. You can still
using the DCM algorithm but with poor performance, specially when you
have mid/large wz (gyro in z axis) for instance in a turn, even at low
Note that even if you have a GPS, the ground speed will have a delay
(depending on your GPS could be even more than 1 sec). So if you do not
take account this, for non-stationary flight (under
linear-accelerations) the performance of the DCM algorithm stills poor.
As always, the quality performance depends on your mission requirements.
On Tue, Aug 9, 2011 at 2:30 AM, Todd
From just my reading into the Paparazzi's DCM code, it
also does centripetal acceleration compensation via GPS... as long as
"USE_GPS" is defined.
Prof. Dr.-Ing. Heinrich Warmers <address@hidden>
Sent: Tuesday, 9
August 2011 1:31 AM
I think the rating of the IMU`s depend of there vibration resistance
and the bias of the rate sensors.
I think there is the following rating:
1. Bosch (SMG074)
2. Analog device (ADXRS620..) 3.Melexsis 4. Invensense 5. ST
The Bosch and the Analoag device are made for automotive applications
and therefore they deliver a maximum of vibration tolerance.
For normal planes the best algorithm in my opinion is the dydrohnes
DCM, since this can correct the attitude given by integration of the
even when continuos circles are flown.
You have to consider the centripetal forces. Every IMU without
measuring the speed over ground can't do this.
If you want to test the Analog device types you can fit sparkefun
to a box (total cost < 80 Euro). This is software compatible to the
paparazzi DCM implementation. You can find them in the repository of
I think this will also solve you problem with IC-motors.