ALT HOLD -> going down and landing

Dear All,

I am using PX V1.8.1 on a pixhawk 2.1
I have installed a lidar lite V3 for Z measurement
Fusion is achieved with LPE. LPE_FUSION set to “Flow gyro compensation” and “Land detector” (I assumed that Land detector is related to the sensor which is providing Z measurement ):

I do not have GPS in this setup but it should not matter for Altitude hold (I guess).

However when I try ALT HOLD I observed the following behavior:

(1) the quad is goind done let say 10 to 20cm
(2) stay there for a while

Repeat (1) and (2) until it touches the ground.

I have a short video showing the behavior of the drone but unfortunately I cannot download it here …

The logs are available here

Can you please tell me what can be the cause of such behavior and what I missed here?

In the logs you will see that I have also need to tune the ROLL/PITCH_RATE because they are really noisy (my current values are MC_ROLLRATE_D = 0.0030/MC_ROLLRATE_P=0.2/MC_PITCHRATE_D=0.003/MC_PITCHRATE_P=0.2)
I probably need ro reduce the D value.

Thank you very much


Add-on: I checked on the table Local NED Z (which should be computed by LPE after fusing the baro and the lidar) and it looks like this:

Really bad, because if I look at the distance measured by the lidar (at a point I let up the drone and put it on the table again), it is pretty correct:

But if I unmarker barometer in LPE fusion (so just the lidar for the z measurement), in the widget Analyze, I cannot see Local NED X, Y and Z anymore! Is it meaning that LPE is not able to compute local NED without the baro?

If someone can give me some hints, it will be very helpfull :slight_smile:

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