Feedback and assistance with new takeoff behaviour

Leonardthall · March 15, 2023, 10:46pm

Anybody want to test some code?

github.com/ArduPilot/ardupilot

Copter: Add TKOFF_TH_MAX

ArduPilot:master ← lthall:20230315_Takeoff_Throttle_Max

opened 01:29PM - 15 Mar 23 UTC

lthall

+10 -2

This PR follows the discussion here: https://discuss.ardupilot.org/t/feedback-a…nd-assistance-with-new-takeoff-behaviour/ This PR provides the ability for the user to specify the throttle point where the vertical position controller will initialise and take over from the linear throttle ramp. If the takeoff detection is activated before this then there will be no change in behaviour. Aircraft setup with high vertical climb rates and acceleration settings will detect takeoff at a higher threshold as these parameters are used to define the detection point. These thresholds are hard coded to 50% acceleration and 10% velocity. By setting this parameter below hover throttle a user could get a fast thrust slew to that point then let the vertical position controller lift the aircraft off the ground. Further if the user has high vertical acceleration this parameter can be set just above hover throttle to prevent too much power being applied when using a fast ramp time.

Yuri_Rage · March 15, 2023, 11:31pm

I’m happy to give it a try if the wind and rain give it a rest for a bit this week. I have a 2kg quadcopter that should be a decent testbed and performed well with the previous takeoff params. Will keep an eye on the thread in case someone hopefully beats me to it.

Leonardthall · March 16, 2023, 1:14am

Can you roll your own firmware or do you need some help?

Yuri_Rage · March 16, 2023, 1:22am

I can compile as needed, but today was very windy, and it’s supposed to rain all day tomorrow. Will report back if I can get er done!

Yuri_Rage · March 16, 2023, 1:59am

Actually, @Leonardthall, I’ll go you one better. Wind died just a touch (still pretty breezy as you might see in the log), so I went for it.

Hover throttle is ~0.16, so I set TKOFF_TH_MAX to 0.14 for the first takeoff. I then did two more takeoffs with TKOFF_TH_MAX at 0.9. The last one was back to 0.14. All Loiter mode.

I saw little difference, but I THINK I prefer the 0.14 value.

Log file here

Leonardthall · March 16, 2023, 4:49am

Thanks @Yuri_Rage, for such a quick response.

Your test is exactly what I expect to see:

With the low value of TKOFF_TH_MAX = 0.14 we see slightly smoother transition to flight as the aircraft comes almost to takeoff then takes off with some additional build up from the position controller as it takes over. It gets to 20% throttle maximum before coming down again.

When using TKOFF_TH_MAX = 0.9 the aircraft is using the takeoff detection code and the throttle ramps to 21% before detecting takeoff.

For your settings this makes very little difference to the takeoff. If you were using variable payload’s then you would probably leave it at 0.9.

Yuri_Rage · March 16, 2023, 2:14pm

Excellent. I saw the slight “knee” in the 0.14 takeoff graphs and figured that was the expected behavior. I have some lighter, supposedly high energy density batteries on the way and will remember to adjust the params if I fly them with this firmware still installed.

If anyone else with a Cube Orange would like to try it out, here’s the bdshot firmware from this branch.

DroneUnit · April 9, 2023, 3:16pm

@Leonardthall Been using this for the last few weeks now. Thanks for creating this. It’s works exactly as I expected and super happy with it. Haven’t found any issues. When do you think this may make it to a Stable version?

Leonardthall · April 10, 2023, 12:28am

Hi Chris, I think it went out with the last release.