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Re: [Paparazzi-devel] IMU's

From: Hector Garcia de Marina
Subject: Re: [Paparazzi-devel] IMU's
Date: Tue, 9 Aug 2011 08:19:01 +0200

Hello 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 velocities.

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 Sandercock <address@hidden> wrote:
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.


From: Prof. Dr.-Ing. Heinrich Warmers <address@hidden>
To: address@hidden
Sent: Tuesday, 9 August 2011 1:31 AM
Subject: Re: [Paparazzi-devel] IMU's

Hi Oli,
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 electronic

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 rates
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 modules (  ADXRS613-Breakout  )

 to a box (total cost < 80 Euro). This is software compatible to the paparazzi DCM implementation.  You can find them  in the repository of Christian Niemann.
I think this will also solve you problem with IC-motors.


Ensslin Oliver (enso) schrieb:
Hi All
I beleive the ArduIMU+ V2 has been discontinued. As we fly our UMARS (with Tiny 2.11) with this IMU and several “student planes” I am thinking of changing to another IMU.
What would be your recommendation?
How do the other IMU’s compare with the ArduIMU? (for fixed wing)
Would the Aspirin IMU be appropriate for the replacement?
How is the vibration tolerance for Aspirin?
I would be thankful if you would tell me your experience.

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