Litchi Waypoints smart RTH or Not

[Scomich]

Hi, Sorry if this has been asked before , I have searched. Today I flew 3 missions each one well outwith radio control and video , And each time when the bird was on return it had initiated go home. In admission one of them was almost 10k. But upon watching the video it initiated the go home when it was on a straight flightpath on the return leg. It made it home safe.
Would this be the smart return to home initiating this and should I disable it on these kind of missions?

P.s. PS3 Standard 100% battery on takeoff, 3 mph wind approx. at 150m I never went above 85m and most the flight was about 36m above water.

This was the mission.

Mission Hub - Litchi

 

[tevek]

Sounds like it returned on low battery RTH as the quad calculated the remaining battery life and decided it's safer to return home (my experience has been that the settings for low battery rth is very conservative). You can disable that function in the app but I leave it on as at a reasonable distance from home, I don't know what sort of effect the wind etc will have on the return trip.

 

[Scomich]

Thanks for the quick reply. What seems stupid to me is that the go home altitude was set to 120m which in my mind would have actually used more battery when it stopped ascended to the 120m then returned slower than what I had my mission set at. That's my thoughts anyway. But still learning.

 

[smiller]

There's another current thread where the operator reported that upon low battery RTH his aircraft didn't ascend to RTH altitude, and returned at the mission speed. We need some more testing to confirm just what does and doesn't happen during low battery RTH while on a Litchi waypoint mission.

 

[Meat]

...We need some more testing to confirm just what does and doesn't happen during low battery RTH while on a Litchi waypoint mission.

I have a 42 minute @5mph mission set up for this purpose. Just waiting for the weather to co-operate. High winds and rain at my location until at least Thursday.

 

[smiller]

Thanks for your efforts!

 

[Scomich]

When I did 3 separate missions yesterday I can confirm each time when rth initiated for whatever reason the bird did ascend to the preset height. But did return at a slower speed, on all occasions.
It also returned with plenty of power that could have completed the missions. So the question again should smart rth be turned off on such missions?

 

[tevek]

When I did 3 separate missions yesterday I can confirm each time when rth initiated for whatever reason the bird did ascend to the preset height. But did return at a slower speed, on all occasions.
It also returned with plenty of power that could have completed the missions. So the question again should smart rth be turned off on such missions?

I have had a couple of low battery warnings and the quad returned home. I could have overridden it due to the amount of battery life remaining but let it be due to to whatever conditions were out there at the time. From what I can see in the app, there is no option to turn that function off unless it is tied into the smart RTH mode. If I turn that off, that would be a problem if I can't bring it back during a flight where I want to finish a trip under manual operation.

 

[smiller]

Is it possible that for low-battery RTH Litchi uses the retained setting from DJI GO? (which I believe is stored onboard the aircraft.) I suspect that if you set low battery RTH level to a low number in DJI GO then that would carry over to Litchi.

With respect to RTH speed, that is an interesting subject in itself. It would make the most sense if RTH occurred at the best endurance speed, not necessarily the fastest speed. That may be what is happening.

 

[Scomich]

Is it possible that for low-battery RTH Litchi uses the retained setting from DJI GO? (which I believe is stored onboard the aircraft.) I suspect that if you set low battery RTH level to a low number in DJI GO then that would carry over to Litchi.

With respect to RTH speed, that is an interesting subject in itself. It would make the most sense if RTH occurred at the best endurance speed, not necessarily the fastest speed. That may be what is happening.

I totally agree that the fastest speed might not be the most efficient, but surely the bird coming to a stop and ascending to whatever height you have set, if that is a higher altitude, then continuing is most definitely inefficient.

 

[smiller]

I totally agree that the fastest speed might not be the most efficient, but surely the bird coming to a stop and ascending to whatever height you have set, if that is a higher altitude, then continuing is most definitely inefficient.

But that's the way RTH has to work, to ensure that the aircraft is above any obstacles on its return. I suppose once object avoidance improves to near perfection a fixed RTH altitude may no longer be necessary, but that's a ways off.

 

[Scomich]

Yeah I understand that's how RTH works , and I'm glad it does , or my repairs to date would probably be more than the bird is worth.
But what my point is, if the smart return to home has worked out and has taken quite a few variables into account that it requires x amount of power to Stop, Ascend, then return to home. Which must take quite a bit processor power. which I'm thinking is the smart bit. Why cant it be smart enough to know it had enough power to complete the pre planned mission?

That says to me not so smart. Am I expecting to much from the entry level bird? Maybe! I am still a Newb so still learning , but that's my way of thinking . Which could be entirely wrong.

Also on the mission I posted it was on its return leg , had ample power left and I have my low power warning set at the standard 30% . I was still not getting a low battery warning when bird was back connected to the controller.

 

[Meat]

Hi everybody,

Just squeezed in the test mission mentioned in post #5 yesterday. Results were very different from my mission a couple of weeks ago. Also very different results from the 3 missions that Scomich referred to in post #7.

This time, the bird initiated SmartRTH, climbed to RTH altitude and raced back to the home point. The controller was off, simulating a loss-of-signal situation, so I don't know what speed it attained on its way back but it was clearly much faster than the 5mph cruising speed set in the mission.

So, now I'm puzzled at all of the obviously inconsistent results.

EDIT: The bird landed with 10% battery remaining.

 

[smiller]

Yeah I understand that's how RTH works , and I'm glad it does , or my repairs to date would probably be more than the bird is worth.
But what my point is, if the smart return to home has worked out and has taken quite a few variables into account that it requires x amount of power to Stop, Ascend, then return to home. Which must take quite a bit processor power. which I'm thinking is the smart bit. Why cant it be smart enough to know it had enough power to complete the pre planned mission?

That says to me not so smart. Am I expecting to much from the entry level bird? Maybe! I am still a Newb so still learning , but that's my way of thinking . Which could be entirely wrong.

Also on the mission I posted it was on its return leg , had ample power left and I have my low power warning set at the standard 30% . I was still not getting a low battery warning when bird was back connected to the controller.

Low-battery RTH does tend to be conservative, probably because the aircraft cannot know critical factors such as headwinds on the return route and such. It seems that DJI has chosen to err on the side of starting back too soon instead of too late, and if faced with the choice that is what we would want. Always being exactly correct is better of course, but technology does not permit that quite yet.

 

[smiller]

Hi everybody,

Just squeezed in the test mission mentioned in post #5 yesterday. Results were very different from my mission a couple of weeks ago. Also very different results from the 3 missions that Scomich referred to in post #7.

This time, the bird initiated SmartRTH, climbed to RTH altitude and raced back to the home point. The controller was off, simulating a loss-of-signal situation, so I don't know what speed it attained on its way back but it was clearly much faster than the 5mph cruising speed set in the mission.

So, now I'm puzzled at all of the obviously inconsistent results.

EDIT: The bird landed with 10% battery remaining.

That is much more like the behavior one would expect (climbing to RTH altitude, and returning home at a decent clip.) However it would be nice to know what caused your variation. The .DAT files on board the aircraft may hold the answer, but it would take some expertise to read them and sort it all out.

 

[Meat]

That is much more like the behavior one would expect (climbing to RTH altitude, and returning home at a decent clip.) However it would be nice to know what caused your variation...

Exactly.

I would have slapped another battery into the bird and run the same test with controller on for the entire flight but it's threatening rain here. Also, sitting in the car watching the quad circle a sports field at 5mph for 23 minutes isn't terribly thrilling. Perhaps on the weekend when the weather is a little less wet and winds are calmer.

 

[smiller]

Also, sitting in the car watching the quad circle a sports field at 5mph for 23 minutes isn't terribly thrilling.

Lol, I bet not. Thanks for your time in doing the test.

 

[Meat]

Thanks for your time in doing the test.

Thanks not necessary but appreciated.

I'm rather concerned at the inconsistent results. Means that I simply don't know what to expect now. I usually run long Litchi missions and I normally have SmartRTH turned off anyway (never had a problem this way) but still...

 

[Scomich]

The results are definitely inconsistent, I'm sorry for starting all this, but just like to try and get things straight in my head. Thanks for testing Meat. If I get time on the weekend , ill try some testing as well weather permitting.

If you don't mind me asking what sort of distance on the Litchi Missions with smart return home off are you running?

 

[Meat]

@Scomich - Don't apologize for starting something like this and especially for something that you actually didn't start. This subject was being discussed in another current thread and we simply hijacked your thread . It kinda started as a result of these anomalies occurring during a waypoint mission I did a couple of weeks ago.

I enjoy running longer one-way missions...from one town to the next as an example. It generally involves starting a mission, then driving to the next town to cancel the mission and land the bird. Five or six miles one-way is typical for me.

Obviously, it would never get to the next location if SmartRTH was enabled.