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Re: [Paparazzi-devel] Magnetometer behavior

From: Felix Ruess
Subject: Re: [Paparazzi-devel] Magnetometer behavior
Date: Mon, 1 Dec 2014 18:19:53 +0100

Hi Sergey,

I think it would be best to implement some sort of "failsafe/fallback" behaviour on the AHRS side if you rely on mag and don't get any new measurements.
IMHO adding fake measurements on the IMU side is not the way to go.

What should actually be done in such a case is not quite straight forward... Simply adding a fake update to keep the last heading will also lead to problems if you either apply some yaw command or have an external disturbance that changes your yaw/heading... but could definitely be one option to choose.

For fixedwings you could fall back to gps course if you have that..

On Sat, Nov 29, 2014 at 10:58 AM, Sergey Krukowski <address@hidden> wrote:
Nice tip!
HMC5xx3 is widely used, and I saw only once or twice, that it was used with real tantalum capacitors.
But anyway, the problem could also be because of the bus stuck. And imo the alternative ahrs/imu behavior would be a better solution in failsafe case.

Maybe this could be helpful for the hardware.

When I find a magnetometer not responding, one possible reason might be
related with the "pump capacitor" (in the case where it is required).
Normally this capacitor is a tantalum one. Depending on the quality of such
capacitor, its series resistor might change dramatically with low
temperatures, leading to a malfunction on the magnetometer.
On Nov 29, 2014 2:15 AM, "Sergey Krukowski" <address@hidden> wrote:

Hi guys!

As I understand, currently if the magnetometer freezes (for any reason),
the on_mag_event function will not be called anymore, which leads to slow
(or even not slow) drift of yaw angle and resulting spinning of the
rotorcraft. Which could be worse for possible failsafe recovery (because
even in attitude mode the rotorcraft will spin around), rather than
updating the ahrs with the last received magnetometer values (in that case
the yaw angle will stay constant and the rotorcraft at least won't spin
If I understand it right, what do you think about possible changing of the
ahrs architecture in that case or should it better be done on particular
boards IMU level?

Best regards,

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