mc_pos_control: fix takeoff ramp gets amended by feed-forward #14821
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…keoff ramp Because the takeoff ramp is a vertical velocity limit ramp for the nice user experience but the acceleration feed-forward can add on top of the output and depending on trajectory generation result in unwanted thrust changes during the ramp.
bresch
approved these changes
May 4, 2020
I'm totally aware of that but it's IMHO far less of an issue than a glitch at the beginning of the ramp. This is thought of as a hotfix. Thanks for reviewing! |
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Describe problem solved by this pull request
I found an issue with the takeoff ramp when real world testing #14749 on the Holybro QAV250. But I found the issue is independent of that pr.
The thrust doesn't ramp nicely anymore like it was designed but depending on stick input can go up and down unexpectedly during the ramp up. This can lead to early land detection if the thrust goes up high enough and then back down because the ramp is not yet high enough.
The problem is: Because the takeoff ramp is a vertical velocity limit ramp for the nice user experience but the acceleration feed-forward can add on top of the output and depending on trajectory generation result in unwanted thrust changes during the ramp.
Describe your solution
I suppress the vertical acceleration feed-forward during the ramp.
Test data / coverage
It's reproducable in SITL with the correct configuration:
MPC_TKO_RAMP_T5,MPC_JERK_MAX20Before: https://review.px4.io/plot_app?log=ba57f51e-abaf-4990-ad34-64b3cef56d11
After: https://review.px4.io/plot_app?log=532b6cdd-5101-4007-82b6-529b1491e85b