The helicopter banked at a large Angle during takeoff

@bnsgeyer @Leonardthall

Hello,

Our helicopter tilted a lot when it took off from the ground. I noticed that in Stabilize mode the helicopter was smooth off the ground, but in Loiter mode and Auto mode when it took off from the ground, the helicopter tilted at a large Angle.


By analyzing the log data, I found that the helicopter has a relatively large attitude control integral value when it is off the ground. I guess the reason is that the helicopter has a large integral correction when it is on the ground.

My flight control version is 4.1.5. H_OPTIONS parameter is 0. This is my flight log data.
The helicopter banked at a large Angle as it lifted off the ground

Hope to get help, thank you very much!

When the collective pitch starts to increase, the helicopter is actually still on the ground, but the integral control has already begun. As a result, the final integral control quantity is relatively large, and the helicopter tilts at a large Angle when it lifts off the ground.

Is it possible to set a takeoff parameter value with respect to collective pitch in the flight control firmware? When the collective pitch is greater than this parameter, the take-off is judged to be successful. Thus, the start time of integral control is delayed and the amount of integral control is reduced when taking off and leaving the ground

@Flying2015 good job on your analysis. It all makes sense. @Leonardthall has already made a change to the code to fix this issue. This change causes the throttle to be raised at a constant rate and the not landed flag is set when the aircraft determines it is flying rather than just setting the not landed flag at the beginning of the takeoff sequence. With the new change, the integrator is not released until the aircraft determines it is off the ground. This new behavior will come out with version 4.3.0 which is currently in beta at the moment.

Wow, that’s great. It’s an exciting new release. We are looking forward to it. Thank you for your wonderful and creative contributions!

@bnsgeyer
By the way, in loiter mode, what parameters can be adjusted to shorten the take-off time and accelerate the take-off process? We tried it a little bit, but it didn’t work very well. By data, it is found that the take-off timeis 1~2 seconds in Stabilize mode, while it takes 5~6 seconds in Loiter mode. In version 4.1.5, we suspect that shortening the take-off time should significantly reduce the impact of points.

The other thing to consider is to set the WP_NAVALT_MIN to 50 cm. This will keep the flight controller from trying to control the aircraft before liftoff. Be aware though that you may see it start to drift on takeoff and then it will quickly correct once it gets above 50 cm.

Thanks.
Best wishes.

@bnsgeyer
That is a good hint for me too. Always good to read the posts from you :wink:

Does this parameter also influence the behavior during start in Loiter-mode?

BR
Heri