Poor land detection

[LorenzMeier]

@MaEtUgR @bkueng Could you have a look? This is blocking v1.8

A new flight report just got uploaded:
https://review.px4.io/plot_app?log=22cb36a7-2ac1-4cd8-b42c-cea152c7a141

Description: beta18_mc03_pxr(05)
Feedback: take-off in position mode; steady hold; nice tracking; good nav; poor land detection
Rating: Unsatisfactory
Wind Speed: Breeze
Uploader: santiago@3dr.com

Vehicle type: Quadrotor
Airframe: DJI Flame Wheel F450, Quadrotor x
Hardware: PX4FMU_V4
Vehicle UUID: 003200333435510837363434
Software git hash: aa625d9

[bkueng]

@santiago3dr Can you describe what you mean with poor land detection?

[MaEtUgR]

The first suspect for any problems with land detection is in my experience the hover thrust configuration.
In the log MPC_THR_HOVER, 0.5 the hover thrust is 50% while the vehicle uses ~38% to hover in the equilibrium. Not sure from the problem description but it might be that setting the parameter MPC_THR_HOVER to 0.38 already solves the problem or at least helps to improve it.

This setting should be part of the initial setup procedure and could in the future even be detected automatically (not for 1.8).

[santiago3dr]

@bkueng
The issue I encounter is that when the copter touches the ground, sometimes the copter jumps back up about 1 meter and lands again or the other thing that happens is the copter upon touching the ground, lifts two legs and sort of jumps a few times before disarming.

I was not able to reproduce this in today's flights but as soon as I see it again, I'll send you a video clip of said behavior.

[santiago3dr]

I was able to reproduce the issue with the new stable release 1.8.0

great land detection:
https://review.px4.io/plot_app?log=9e3e76c7-7ac5-4e17-a624-069706e0d654

poor land detection:
https://logs.px4.io/plot_app?log=406113d2-d981-4794-958f-5fb6b295a2ec

video:
https://drive.google.com/open?id=1ad_aCtLa5KU97Y7FDC6LLEK0hgDC8m2v

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[MaEtUgR]

@stale_bot There is recent activity, see #11172 in which I referenced this issue.