fw_pos_ctrl: subtract trim pitch setpoint before TECS everywhere

[CarlOlsson]

@sfuhrer @RomanBapst As discussed on Slack I don't understand why we would not subtract the trim pitch setpoint everywhere before pushing it into TECS. I noticed that the plane behaved differently when flying in position control mode compared to mission. I also added the change to places which I could not test, e.g. fw takeoff, so please review that more carefully.

Describe problem solved by this pull request
The limitation of the pitch setpoint was different in mission and position control

Describe your solution
Subract the trim pitch sp for position control mode in the same way as it is done for mission

Describe possible alternatives
A massive cleanup of the fw pos controller

Test data / coverage
I only tested position control so far

[dagar]

There was a question of interpretation of the various pitch limits in the fixedwing position controller (relative to the pitch setpoint offset or not). Let's settle this and make sure handled uniformly.

[dagar]

#9243

[sfuhrer]

For me it would make sense to treat pitch in the absolute way everywhere outside of TECS, and then relatively inside TECS - and thus this PR makes total sense for me.
@dagar what's the big blocker for #9243 and #11845 , I haven't quite understood the implications for FW takeoff yet.

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[CarlOlsson]

still relevant @sfuhrer

[CarlOlsson]

Is there a reason this wasn't just merged?

[dagar]

Is there a reason this wasn't just merged?

I've lost context here, but I recall there was confusion about the pitch (and various parameters) being an inconsistent mix of relative to the vehicle body frame and other cases that are relative to the pitch offset.

I propose we all take a few minutes to review and schedule a short call to settle this. @CarlOlsson @sfuhrer @RomanBapst

• fw_pos_control_l1: apply pitch setpoint offsets centrally #11845 (and Consider FW PSP in pitch limits #7098)
• fw_pos_ctrl: subtract trim pitch setpoint before TECS everywhere #14907
• FW position control add takeoff minimum pitch parameter #9243
• New Parameter request: "minimum takeoff pitch" #6787

We also need to make sure it's a clean/safe upgrade for existing users.

• FW_PSP_OFF
• FW_P_LIM_MIN/FW_P_LIM_MAX
• pitch for TECS
• runway takeoff (RWTO_PSP, RWTO_MAX_PITCH)
• landing pitch limits (FW_LND_FL_PMIN/FW_LND_FL_PMAX)
• hand launch minimum pitch (FW position control add takeoff minimum pitch parameter #9243)
• OFFBOARD considerations? (@Jaeyoung-Lim)

[dagar]

After brief discussion on slack the current consensus is to push the pitch offset into TECS itself so that the rest of the FW position controller can be kept simple and oblivious to the offset. All limits and configurable pitch settings are in the vehicle body frame. Does anyone have a different opinion?

[ryanjAA]

Probably just some clear documentation but will test it once I’m clear on the effects the changes will have. Having a pitch down on takeoff rollout is annoying so that will be good to get rid of.

[Jaeyoung-Lim]

@dagar Also makes sense to me and shouldn't have effect on offboard, since it uses the same setpoint types

[stale]

This issue has been automatically marked as stale because it has not had recent activity. Thank you for your contributions.