Dynamic control allocation for VTOL & others #18776

bkueng · 2021-12-03T13:24:21Z

This brings the ideas from #18701 and #18558, based on the valuable input from @sfuhrer, @dagar and others.

Details:

handle reversible motors
adds separate servo range reversal params (bitset) for simplified configuration
adds trim + slew rate configuration
adds support for multiple matrices in control_allocator. This is used for the existing VTOL control modules.
adds control surfaces + tilt configuration. The tilt captures the physical properties, like min and max tilt angles and direction of tilt. Motors can be assigned to a tilt. For tiltrotors, this is then used to automatically update the motor axis and disable non-tiltable motors during fixed-wing flight (see example UI below).
generalizes and extends ActuatorEffectiveness:
- classes can be used hierarchically. For example a VTOL can include motors + control surfaces.
- adds updateSetpoint callback method to allow it to manipulate the actuator setpoint after allocation (e.g. to add flaps or any kind of non-linear control)
- handle motor stopping (disable existing vtol logic to manipulate pwm's directly)
handle standard vtol + tiltrotor
adds support for rovers (with a fixed effectiveness - this can later still be a bit generalized)
adds 6DOF vectored thrust UI, used and tested with the UUV gazebo model
performance on F4 running a vtol (400hz): 4KB more RAM, interestingly ~1% less CPU, and doing matrix inversion @ 10Hz uses about 1% CPU.

Tiltrotor example:

There's still a few more to be added, like tailsitter or tiltable MC's. I also intend to make the motor thrust axis a bit more configurable in the UI, but likely this goes along with some UI changes.

Test flown on a tiltrotor (convergence) - there's still a couple of details to iron out, but it generally works nicely.

We still need to define the control surface torque convention (which we can use to then fill out the constraints table), but I leave that up to others to decide.

See commit messages for further details.

bkueng · 2021-12-03T13:28:12Z

src/modules/control_allocator/ControlAllocation/ControlAllocationPseudoInverse.cpp

 	// Allocate
-	_actuator_sp = _actuator_trim + _mix * (_control_sp - _control_trim);


@jlecoeur what was the original intent for _control_trim? My use here is to add an offset to an actuator, but the _control_trim logic leads to undesired effects, and I did not just want to remove it w/o knowing the background.

Linearization around a specific actuator state. In a linear system the equation above reduces and trim could be removed. However in a non-linear case --for example a tiltrotor-- it is required.
What are the undesired effects?

Makes sense. For example I added a trim of 0.2 to the right aileron for a FW setup, that resulted in a roll=pitch=0.2 control trim, which then overall resulted in an aileron setpoint of -0.2410.
Sounds like we need both then, as it's 2 different use-cases.

jlecoeur · 2021-12-03T15:09:59Z

@bkueng and @sfuhrer should I review?
I just read that you introduced two matrices for VTOL, I fear that this defeats the purpose of effectiveness matrix inversion -- almost back to the former mixer system right?

sfuhrer · 2021-12-03T16:12:15Z

@bkueng I pushed some additional VTOL fixes. de380c4 shows one way to handle the throttle allocation for tiltrotor without needing to change too much on the legacy mixing system. Happy to discuss other ideas.

sfuhrer · 2021-12-03T16:25:48Z

@bkueng and @sfuhrer should I review? I just read that you introduced two matrices for VTOL, I fear that this defeats the purpose of effectiveness matrix inversion -- almost back to the former mixer system right?

Yes it's two matrices. We chose that approach to be able to bring in dynamic control allocation without the need to change the whole VTOL control pipeline. Benefits compared to the legacy mixing system: much easier setup without the need to recompile, enables actuator failure handling and improves tiltrotor control by taking into account the motor tilts.
The step to an unified effectiveness matrix is a much bigger step that will help us to get rid of a lot of vtol specialties all over px4, but a user would not notice a lot, as the interface doesn't have to change.

sfuhrer · 2021-12-10T09:57:07Z

@bkueng and @sfuhrer should I review?

Hi @jlecoeur , yes would be cool if you could review. We're adding smaller fixer here and there while we go through all the vehicle types and test them in SITL and real hardware, but the core algorithm/concept will likely not change drastically anymore unless we find something.

bkueng · 2021-12-10T12:23:07Z

@bkueng and @sfuhrer should I review?

You're welcome to review, yes.

I also added a 'Custom' effectiveness that serves as a catch-all. I think everything should be possible now, except for helicopters, and some mixers that mix in RC aux channels.

sfuhrer · 2021-12-21T18:04:24Z

Testflown on this bunch of illustrious VTOLs today:

FunCub Standard VTOL: https://review.px4.io/plot_app?log=118268e4-5bfa-462a-88d5-63543afe6d82
Convergence Tiltrotor VTOL: https://review.px4.io/plot_app?log=0c3141ee-407d-4147-9d3f-5b89c06fb116
Xvert Tailsitter VTOL: https://review.px4.io/plot_app?log=f1bab1e5-4e73-49c4-ae73-56be56c8ebdc

All flew fine in hover and fixed-wing modes without too much rate controller tuning, though we could in general tweak the FW rate defaults a bit (less FF, more P and I). This is though not particularly related to this PR.
The tiltrotor (dynamically updated matrix depending on combined tilt) and the tailsitter flew better than I ever saw them, on the standard VTOL no difference was noticeable.

@dagar @jlecoeur, or anybody else: a review would still be very much appreciated!

dagar · 2021-12-22T15:59:24Z

I'm still working through this, but in the meantime we have a small flash overflow on fmu-v2. https://github.com/PX4/PX4-Autopilot/runs/4606740563?check_suite_focus=true

Wasn't correctly updated during a rebase.

…l_prefix)

…ing param Makes it a bit easier to configure. Reversing by setting MIN > MAX is still supported.

…tpoint

preparation for dynamic control allocation, where we won't have MAIN vs AUX anymore (at least for the generic frames).

…nd hover thrust In the tiltrotor case, beside an F_z thrust setpoint also a F_x setpoint must be passed to the allocator as the matrix has non-zero thrust-x effectiveness when tilts are applied. Signed-off-by: Silvan Fuhrer <silvan@auterion.com>

- only normalize rpy for MC matrices - for thrust use the 3D vector, so it works for FW and tilt rotors as well This keeps MC unchanged.

…n sign - horizontal control surfaces: up=positive deflection - vertical control surfaces (rudder): right=positive deflection - mixed (V-Tail): up=positive deflection Signed-off-by: Silvan Fuhrer <silvan@auterion.com>

…que_setpoint Signed-off-by: Silvan Fuhrer <silvan@auterion.com>

…s enabled Signed-off-by: Silvan Fuhrer <silvan@auterion.com>

dagar · 2021-12-23T15:10:58Z

Flash overflow resolved and rebased on master.

dagar · 2021-12-23T15:27:10Z

Isn't having 2 mechanisms to reverse an output going to be potentially confusing?

output reversed if MIN > MAX
per output group REV bits (eg PWM_MAIN_REV)

Then in the old mixing world we already have a REV parameter per ouput (eg PWM_MAIN_REVx).
Can we keep PWM_MAIN_REVx instead?

dagar · 2021-12-23T16:09:51Z

One of the bigger takeaways I had from the discussion in #18558 was the handling of control surfaces by type and constraining torque appropriately (eg left vs right aileron).

Is there something else planned to do this with the GUI?

EDIT: I think I found it.

dagar · 2021-12-25T01:05:10Z

It took me a while to go through this, but overall it looks good and I'd like to get it in before it gets any bigger or harder to rebase or we run out of flash again, etc.

notes/questions/comments

I'd still like to revisit the reverse configuration (Dynamic control allocation for VTOL & others #18776 (comment))
control surface constraints handled firmware side, so that it's still possible to safely configure things directly without the GUI
per output trim (eg PWM_MAIN_TRIMx)
I'm hoping we'll ultimately be able to consolidate quite a lot of this into something more generally configurable rather than carrying every possible airframe specialization
can we try to do these things more incrementally going forward?

mengchaoheng · 2021-12-31T01:19:40Z

some idea in the book "Aircraft Control Allocation" maybe can help you, the author provides some simulation files which can also be downloaded at https://github.com/mengchaoheng/aircraft-control-allocation.git

Jawad-RoboLearn · 2022-01-08T03:08:27Z

I am trying to check out this PR but it gives error,
fatal: couldn't find remote ref refs/heads/control_allocation_vtol
exit status 128

Jaeyoung-Lim · 2022-01-08T04:40:59Z

@Jawad-RoboLearn The branch no longer exists from the PR since the branch was deleted after the merge. The commit is merged to the master branch, so you can check out there.

Jawad-RoboLearn · 2022-01-08T05:15:10Z

Thank You.

mengchaoheng · 2022-06-22T05:25:09Z

some idea in the book "Aircraft Control Allocation" maybe can help you, the author provides some simulation files which can also be downloaded at https://github.com/mengchaoheng/aircraft-control-allocation.git

I have fixed bugs in the source code of this reference book, which can be found in my repository. The qcat from Ola Härkegård's is very helpful!!
@bkueng

VTOLDavid · 2022-07-14T11:02:44Z

Wich motor gain matrix will result for a quadcopter in deadcat configuration (Front and rear motors same distance to CoG in x axis but different in y axis)?

bkueng commented Dec 3, 2021

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sfuhrer mentioned this pull request Dec 3, 2021

[RFC] Enable dynamic control allocation for VTOL/FW #18701

Closed

dagar added the Admin: Enhancement (improvement) 💡 label Dec 4, 2021

dagar mentioned this pull request Dec 4, 2021

DSHOT support on VTOL tailsitter configuration #18567

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bkueng force-pushed the control_allocation_vtol branch 2 times, most recently from 7423538 to ad1948b Compare December 10, 2021 09:21

bkueng mentioned this pull request Dec 10, 2021

PX4 Actuator & Geometry Configuration and Testing UI mavlink/qgroundcontrol#9952

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4 tasks

bkueng force-pushed the control_allocation_vtol branch 3 times, most recently from 989cb7c to e535990 Compare December 17, 2021 10:37

bkueng requested a review from dagar December 20, 2021 07:16

sfuhrer force-pushed the control_allocation_vtol branch from 4acf1b2 to cce735f Compare December 21, 2021 17:54

jlecoeur self-requested a review December 22, 2021 08:13

bkueng added 10 commits December 23, 2021 10:03

metadata: fix BOARD_WITH_IO detection

48b9708

Wasn't correctly updated during a rebase.

control_allocator: make effective source name a class member

eb6fd4e

Makefile: exclude src/lib/crypto/libtommath from validate_module_configs

c5261b9

ROMFS: add control_allocator to all types

1af8424

generate_actuators_metadata.py: add mixer rules support

001ebc7

generate_params.py: fix bitmask param type

1e81363

generate_actuators_metadata: minor additions (index_offset, item_labe…

269f725

…l_prefix)

actuator_motors.msg: add reversible flags & implement in mixer_module

f26b8d4

output drivers: add option to generate a separate output range revers…

92fcd5a

…ing param Makes it a bit easier to configure. Reversing by setting MIN > MAX is still supported.

vtol_att_control: publish vehicle_thrust_setpoint & vehicle_torque_se…

61b6a46

…tpoint

bkueng and others added 11 commits December 23, 2021 10:03

px4/fmu-v5x: add missing board variants to rc.board_mavlink

d0d6105

airframes: sitl cloudship: switch to dynamic control allocation

403e435

airframes: sitl boat: switch to dynamic control allocation

40a8d15

px4airframes doc: handle common outputs individually

3c10582

preparation for dynamic control allocation, where we won't have MAIN vs AUX anymore (at least for the generic frames).

control_allocator: update matrix normalization

2b6ea6a

- only normalize rpy for MC matrices - for thrust use the 3D vector, so it works for FW and tilt rotors as well This keeps MC unchanged.

Tailsitter: invert roll (make it NED-correct) for filling vehicle_tor…

e58fb0c

…que_setpoint Signed-off-by: Silvan Fuhrer <silvan@auterion.com>

Tiltrotor: disable tilt/thrust compensation when dynamic allocation i…

e01ab95

…s enabled Signed-off-by: Silvan Fuhrer <silvan@auterion.com>

control_allocator: add scope to reduce stack usage by 256B

ff35e05

boards: px4_fmu-v2_rover disable events module to save flash

04ae90e

dagar force-pushed the control_allocation_vtol branch from ca94835 to 04ae90e Compare December 23, 2021 15:10

dagar approved these changes Dec 25, 2021

View reviewed changes

dagar merged commit 98d7067 into master Dec 25, 2021

dagar deleted the control_allocation_vtol branch December 25, 2021 01:06

jlecoeur mentioned this pull request Jan 7, 2022

Dynamic Control Allocation/Mixer #18556

Closed

This was referenced Jan 7, 2022

WIP: Control Allocation #13351

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[RFC] control_allocator: Actuator Effectiveness with generalized configuration parameters (combined MC, VTOL, simple fixed wing support, custom torque, etc) #18558

Closed

Jaeyoung-Lim mentioned this pull request Feb 20, 2022

Rover does not move in SITL Gazebo due to missing mixers #19233

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junwoo091400 mentioned this pull request Apr 6, 2022

[Project Tracker] Control Allocation User experience improvement #19444

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Dynamic control allocation for VTOL & others #18776

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		// Allocate
		_actuator_sp = _actuator_trim + _mix * (_control_sp - _control_trim);

Dynamic control allocation for VTOL & others #18776

Dynamic control allocation for VTOL & others #18776

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