False obstruction detection?

[dennyc39]

Normal flight at 300 ft., drone in sight, GSP waypoint mission ended and cancelled. I flew manually and normally for a while, but commanded RTH when battery got down below 50% and as a very light drizzle began. The drone commenced RTH at 300 ft altitude, but stopped about 200 ft. from home point after flying about 1000 ft. horizontally. Message: Obstruction Detected, fly with caution."

The highest obstructions within a half mile were about 200 ft. above home point.

I cancelled RTH with the pause button, but it ignored commands to go further, hovering as battery slowly went down. The drone was pointed away from the sun, but sky was solid overcast anyway. video feed and signal strength looked normal. At this point, my memory is sketchy on how I regained control. I think l yawed it around about 180 degrees and backed it up to about 200 ft the other side of home point. When I then pressed the RTH button, it returned home normally, landing within half a foot of takeoff point. The drone body showed a few drops of moisture, but the lenses seemed clear.

1. Anyone have idea on what caused the obstruction warning and avoidance behavior?

2. What could I expect if I did not interrupt with the pause button and let things continue? The way things were going, it looked as though the next event might be a low battery emergency (<10% charge remaining).

 

[dbyantis]

Perhaps a drop of the drizzle, or fogging of the sensor in high humidity with no sun to dry? My guess as to next event would be forced landing whenever critical battery was achieved. If I am bring the bird home and I can see it, I cancel RTH any way and take over, you can switch to sport mode, off and on, to cancel any current flight mode, that may have granted you control, again.

 

[Mossiback]

I have had it happen but while flying toward an evening sun. It is a quick and simple matter to turn off OA if it is causing problems. Switching into Sport mode also would have freed you since it turns off OA in the process. Your solution of flying backwards also works since OA does not work in reverse in normal flight. The M2 series might be different as firmware updates change how the rear and side sensors are used. As to your questions:

1. Since this normally happens while flying towards a low or reflected sun, I can only speculate that the moisture and perhaps bright-featureless overcast sky had something to do with it.
2. Normally these false detections are short-term so it might have corrected itself and continued, at least until it faulted again. Changing angle from flying to hovering will sometimes correct the false detection. If not, it should follow whatever RTH instructions you have selected; rise above, move horizontally, or hover. If it continues to fault then it will eventually hit the low batter forced landing level.

These false positive situations can happen at any time in normal fight so you should be prepared to deal with it. Since I fly VLOS and high enough to clear obstacles, I fly with OA turned off. It gives me better performance without the more sensitive stick response of sport mode.

 

[dennyc39]

My recollection is that it stopped, gave the message, then rose to the set altitude ceiling, 398 feet. After that, it seemed to hover, but I may have gotten impatient and intervened. My assumption was that when it sensed obstacle, then hit altitude ceiling, that it didn't know what to do.

 

[Mossiback]

My recollection is that it stopped, gave the message, then rose to the set altitude ceiling, 398 feet. After that, it seemed to hover,...

It makes sense that it stopped at max height and hovered, since it was detecting an obstacle.

 

[FlyGuy8675309]

OA sensor anomalies are fairly common. Sunlight or reflection are the usual causes, but I agree a drop of water could have messed up the sensor.

 

[AMann]

I had the same thing happen flying over a large rock outcrop, was in P mode and it wouldnt go sideways over the rock even though I was 30-feet above it. S-Mode override worked just fine. When I returned to the same spot later in P-Mode, it worked just fine.

 

[gnirtS]

I've had it quite a bit with a low sun angle NOT directly towards the sun but numerous reflections from a smooth river and large low tide, wet beach.
What i found is far more detections at above 9m/sec speed and none lower than that so i assume the attitude gets large enough that the front sensors point down more and get confused.
I had one flight with it showing a permanent "object" 8.5m again in some directions on the front sensors only.

You can try cleaning the sensors and also calibrating them.

Its worse than my M1 currently for them and ruining some videos. Im going to do a sensor calibration when i finish travelling and go through the insecure nightmare of getting the DJI drivers installed.

 

[Mossiback]

...Its worse than my M1 currently for them and ruining some videos. Im going to do a sensor calibration when i finish travelling and go through the insecure nightmare of getting the DJI drivers installed.

You could just turn off OA. It is not needed if flying above obstacles. I turn it on only if needed.

 

[Cheech Wizard]

I was testing some carbon fiber props and just went through a firmware update and new phone. I couldn't figure out what was going on until I started filming. First just thought it was the shade, I couldn't see the rays with my bare eyes.