Terrain and return home and joystick control

Posted by Eben N. Broadbent on May 18, 2017 at 5:36am

As far as I can tell, a copter or plane using UCGS will fly directly into a hill if return home or joystick control is used. I had expected it would follow terrain as it does when creating an initial waypoint or survey. This is a serious risk, especially for flights in complex terrain that UGCS is supposed to be the best in! Basically, in terms of automated failsafes it is the same risk as the DJI return home button on the flight controller. Am I wrong?

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Replies

  • Eben N. Broadbent May 18, 2017 at 2:03pm

    Thanks, Ok I will do that. Yes, very expensive hardware. Another question. Does UGCS trigger RTH itself using the profile battery thresholds, or does it let the Matrice 600 do this itself only? I ask as the A3 Matrice has smart RTH which triggers at different battery volt thresholds based on distance to home, whereas UGCS profile values are static. So I think it would make sense to set the UGCS battery thresholds very low (or turn them off) to avoid having it trigger an RTH before it was necessary?

  • Alexey Dobrovolskiy May 18, 2017 at 12:16pm

    Yes, you can set  "Emergency return altitude"

    3702375217?profile=original

    and next here

    3702375129?profile=original

    In previous version UI will be little bit different, but this option was here.

    Taking in account cost of you equipment I would like to recomment to test this all in safe conditions over flat terrain... And it's good idea to repeat such test after each software/firmware upgrade...

  • Alex May 18, 2017 at 12:11pm

    All this right. I tested and i get something similar. But if you talking about LIDAR on the board! I think you should newer lost it from your sight if you dont want to lost it somehow. $50-150k ...

    3702375195?profile=original

  • Eben N. Broadbent May 18, 2017 at 11:45am

    Yes! That last reply was exactly the situation I was trying to bring up (just didn't do a good job). That was why my copter emulator was flying into the hillside. Am I able to set the 'safe emergency return altitude' separately from the parameter you highlighted of 'safe height over terrain'? This is critical as imagine that to make it over the obstacle in a direct line I would need to fly 200m AGL, but if I set the parameter 'safe height over terrain' to 200m AGL, then I wouldn't be able to fly my mission at only 100m AGL (which is the max that my LiDAR sensor range is). This sounds like it has the same limitation as does the built in Return Home. The only solution I can see is to turn off all automated return home parameters in the software, then set seperately the RTH altitude of the Matrice 600 Pro to 200 m using the DJIGO App (triggered if battery gets too low), and then set the 'safe height over terrain' in the UGCS to 70m (or 50m, something lower than my survey altitude AGL of 100m). Sorry if this got complex, hopefully you can follow! If not, I will try again! Thank you!

  • Alexey Dobrovolskiy May 18, 2017 at 11:05am

    In reality most dangerous situation is BLOS flights when there are obstacle between home and part of route, and obstacle is more high than "Emergency return altitude".

    3702375509?profile=original

    Most horrible here that RTH can be triggered automatically and if really safe emergency return altitude isn't set you will have crash.

    We are considering to add check for each point of route posibility to return home on given "Emergency return altitude", but this will not be implemented in two nearest versions (UgCS 2.11 finished and we have only couple of bugs to fix befory publishing, UgCS 2.12 is almost finished too). May be in 2.13.

  • Alexey Dobrovolskiy May 18, 2017 at 10:56am

    Ok, this situation? First waypoint and home position are on top of Everest (I like this place to test routes in UgCS :), drone will fly down the slope, at some time (when drone is below start point) we will press "return home".

    3702374798?profile=original

    In such case emulator will fly to the home position to the point at altitude specified in route properties in "Emergency return altitude" field. This altitude in most of drones (including UgCS emulator) will be relative home position.

    Modern DJI drones have more safe behavior - they will climb to "Emergency return altitude" (above altitude of home position) and then fly to home.

    I don't remember what will do ArduCopter or PX4 but I hope that they implement quite safe strategy.

  • Eben N. Broadbent May 18, 2017 at 9:02am
    Thank you, but I think your test was not what I meant. Please try this if you have time. Create a home take off location at the top of a hill anywhere, create a waypoint route down the hill about 100 meters descent. Then click the return home button. I think you will see the emulator copter fly straight into the hillside. As this is RTL it is still considered auto mode. Let's ignore any comments I made about joystick for now. Also let's ignore terrain data accuracy as hat applies to the real world collisions, and here we are showing virtual world collisions (which clearly would also happen in the real world, hence the concern). Thanks!
  • Alexey Dobrovolskiy May 18, 2017 at 6:22am

    In manual mode pilot is fully responsible for flight safety. UgCS will correct only planning mistakes and prevent collisions in automatic mode. And yes, only if you have precise enough terrain data..

  • Alex May 18, 2017 at 6:09am

    But the problem is terrain level accuracy. It's 10-50 meters! 

  • Alex May 18, 2017 at 6:04am

    If you set your Landing position in rote it got to work properly and fly above the ground on level "Safe height over terrain"3702375009?profile=original

    3702374773?profile=original

    https://storage.ning.com/topology/rest/1.0/file/get/3702375009?profile=original
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