[Paparazzi-devel] Bug found in nav_catapult.c

[Mitchell SLOWER]

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: http://cjoint.com/12sp/BIwrF7EwKoy.htm

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.

Mitchell