Issue with LGR_DEPLOY and/or rangefinder

I am using the automatic landing gear retraction to switch on anti-collision lights automatically at a certain height. Today I tested this in 4.0 and I found the following issue:
LGR_DEPLOY_ALT is set to 3
LGR_RETRACT_ALT is set to 5

The TFmini rangefinder is set to:

The “landing gear” retracts automatically at 5 meters height. And it deploys again at 3 meters height. However, it also deploys again at 20 meters height. This is when the rangefinder is at its limit and gives some spurious data.

The log is here:

What can be done about this…? Thanks!!

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Thanks for this report. I can also see in the logs that the landing gear is deploying because the lidar altitude is suddenly falling from about 19m to 0.3m. From the main vehicle code it currently has no way to know this is incorrect.

The issue seems to be very repeatable and always happens when the lidar is reporting between 19m and 20m. I suspect that we either have an issue in our driver or the sensor has an issue.

I’ll bring this up with Benewake and see if they have any ideas and also I’ll add it to the Copter-4.0 issues list.

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Thanks for your feedback! I gave it another try, and this time the lidar didn’t have these jumps…
I was flying at the same spot, everything was the same except for the weather conditions and 1kg additional weight on the copter, updated pids and with notch filters (dynamic and static) enabled.

It is good that the gear deploys when the lidar reports ground proximity. But it should also retract again if the lidar && altitude estimate report a height larger than LGR_RETRACT_ALT.

I got some feedback from the Benewake people who said:

I have checked the data. The TFmini give some wrong data at 15m-16m height.
If the reflectivity of the ground is relatively strong, TFmini still get a strong signal above 15m, and it is possible to give a short-range output. This is caused by the principle of TFmini’s phase ranging.
For this problem, the signal strength threshold of TFmini can be increased to eliminate these abnormal data; the default signal strength threshold is 20; the customer can change the signal strength threshold of TFmini to 30 through instructions.

Hope that helps…