Failsafe Landing bug in PX4 1.14?

[hmlow]

Hi

Can i seek some assistance pls to look into this issue?
Its a safety hazard when the aircraft translates in position while descending.

I believe the same behavior is present on the Starlingv2 as well.

Much appreciated.

[Eric Katzfey]

@hmlow We will try to replicate with a Starling

[Eric Katzfey]

@hmlow Do you have any logs that you can share?

[hmlow]

@Eric-Katzfey

Yes pls refer to this ulg log:

horizontal translation while landing

I did a couple of landings in Land flight mode. The first and second landing was from a positive and negative x position (NED) with respect to the Home location, respectively. You will be able to see that during the descend, the aircraft translates in the x-axis toward the home location without any stick inputs from me. There are local position setpoints generated during the descent/translation, which suggests that it is a programmed behavior.

I did a couple of more landings at various positions/orientations with respect to the Home location after that.

[hmlow]

@Eric-Katzfey

Any luck? Does the log make sense to you?

[Eric Katzfey]

@hmlow We did a quick check with HITL simulation but in that case the landing is perfectly straight down every time. So we need to have our flight team recreate this with a real drone to see if it can be replicated but that will take a few days for them to get to it.

[hmlow]

@Eric-Katzfey Thanks keep me posted

[Eric Katzfey]

@hmlow Our flight team was able to recreate the issue today. Now we just need to figure out what is causing that to happen.

[Eric Katzfey]

@hmlow This seems like a fundamental bug in PX4 when dealing with EV modes so we're working with the PX4 developers to figure out who and how this will be addressed.

[hmlow]

@Eric-Katzfey thanks for the update. At least the issue has been identified. Looking forward to some fixes in the near future..

[hmlow]

@Eric-Katzfey hi. Any progress on this?
Thanks

[Eric Katzfey]

@hmlow Not really. I don't think anyone in the px4 community has time to assist on this so it's going to be up to ModalAI to fix it. Unfortunately, I can't offer any estimate on when we will be able to resolve this yet.

[Eric Katzfey]

@hmlow I have been able to recreate the issue in HITL with the Gazebo simulator so that should help with testing and investigation on this issue.

[hmlow]

@Eric-Katzfey that's good. Looking forward to the fix

[Eric Katzfey]

@hmlow This fixes it in HITL:

diff --git a/src/modules/navigator/mission_block.cpp b/src/modules/navigator/mission_block.cpp
index 565b2f2150..ac36732214 100644
--- a/src/modules/navigator/mission_block.cpp
+++ b/src/modules/navigator/mission_block.cpp
@@ -664,8 +664,8 @@ MissionBlock::mission_item_to_position_setpoint(const mission_item_s &item, posi
                return false;
        }
 
-       sp->lat = item.lat;
-       sp->lon = item.lon;
+       sp->lat = static_cast<double>(NAN);
+       sp->lon = static_cast<double>(NAN);
        sp->alt = get_absolute_altitude_for_item(item);
        sp->yaw = item.yaw;
        sp->yaw_valid = PX4_ISFINITE(item.yaw);```

[Eric Katzfey]

@hmlow But that probably only works for VIO mode. Not sure what it would do in GPS mode. So it isn't a fix that will be acceptable for general use. So it still needs more work but that is the heart of the issue.

[swickliff]

@Eric-Katzfey Has any testing been done with this fix in GPS mode?

[Eric Katzfey]

@swickliff No, it hasn't. Supposedly all of this is fixed in latest mainline but we haven't tested it. But we do have a mainline build available to try: http://voxl-packages.modalai.com/dists/qrb5165/dev/binary-arm64/voxl-mainline-px4_1.16.0-1.0.0-202502271326_arm64.deb