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Re: [Paparazzi-devel] Bug found in nav_catapult.c

From: Christophe De Wagter
Subject: Re: [Paparazzi-devel] Bug found in nav_catapult.c
Date: Sat, 22 Sep 2012 20:27:04 +0200

IMU accelerometers are not converted too Body by default, only AHRS is. This probably needs extra code. Maybe the state interface will help here.

And here is how we always have our IMU x pointing forward:

On Sep 22, 2012 5:46 PM, "Mitchell SLOWER" <address@hidden> wrote:
Dear all,

I probably found a bug in sw/airborne/modules/nav/nav_catapult.c

What happened is that motor was not starting automatically on a catapult launch.
I checked the code and found that we are using imu.accel.x for the acceleration threshold detection.
It might work on some cases, but not on others (eg: if we set the IMU in a different orientation - what I did).
I have a BODY_TO_IMU_PSI set to -90°, so x axis becomes y axis and vice versa.

As usual, here is the screenshot of the situation:
As a reference, at 638s, I'm rolling the plane left and right, and bungee start is done at 647s.

Quick and dirty fix (will work only in SOME cases too): I replaced ACCEL_FLOAT_OF_BFP(imu.accel.x) with ACCEL_FLOAT_OF_BFP(imu.accel.y)

It would be better if we could use the body longitudinal acceleration instead of imu.accel.x, but I'm not sure where it is stored.


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