[WIP] Multicopter Controllers Muxing #14754

Pedro-Roque · 2020-04-24T22:47:16Z

A configurable low-level control chain
The objective for this WIP PR is to modularize the low-level control chain so that it is easier to integrate different controllers for rate / attitude / position on multicopters. The framework shall be extendable to other systems afterwards, but I will start with these. We hope that this makes it easier for everyone to incorporate novel controllers into the stack, as well as provide researchers with an easy way into PX4 to test their own control approaches.

Describe your solution
Involved devs/users: @dagar @Jaeyoung-Lim @bresch @PepMS
The solution will be a muxing of which low-level controllers are active for a specific flight. The user selects (or doesn't, hence leaving default) the controllers for MC Position, MC Attitude and MC Rate that he wishes to use on a given flight, before the vehicle is armed. For all runs, the default PX4 controllers are initiated and ready, but are not running in parallel - they stay dormant but will takeover once the user leaves OFFBOARD mode.

Gdrive Doc (ongoing discussion moved there):
https://docs.google.com/document/d/1bexM6KeLv73wtiiRvYTqrCHi-HpvmC5YHYHy5CTjibQ/edit?usp=sharing

On the one hand, this allows for sandboxing of controllers under test, providing a safer environment to test new research. On the other hand, I will also provide basic templates that will allow for anyone to implement their own control laws on the low-level system and test them in SITL.

NOTE: this will be WIP for at least a few months. However, interested devs are welcome. I will be working on this at my own pace.

stale · 2020-07-25T04:24:23Z

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

bresch · 2020-08-03T07:45:51Z

@Pedro-Roque This still seems really interesting. Any progress/testing?

Pedro-Roque · 2020-08-03T11:50:05Z

@Pedro-Roque This still seems really interesting. Any progress/testing?

@bresch TBH I didn't proceed any further since I didn't know how much interest it had, and maybe it would be better to focus on fixing other things first (the SITL is one of those I want to fix once I'm "free").

You think it would be interesting to have this for v1.12 ?

bresch · 2020-08-10T10:11:15Z

You think it would be interesting to have this for v1.12 ?

If possible, yes.

PepMS · 2020-11-03T11:45:50Z

Hi @Pedro-Roque and @bresch , I've been looking for something like this for very long. I'm very interested.
I have some doubts though. If I have understood correctly, the lower you can get with this development is to control the rates, right? What if we want to control directly the speed of the motors?

I think that this would be very interesting since several model-based control techniques outputs the thrust of the motors (or, equivalently, the wrench in the flying body). For that purpose, sometime ago I did this. I wasn't sure of the development though, since a modification of the mixer module was required and I was afraid of messing something up.

Pedro-Roque · 2020-11-03T11:50:17Z

Hi @Pedro-Roque and @bresch , I've been looking for something like this for very long. I'm very interested.
I have some doubts though. If I have understood correctly, the lower you can get with this development is to control the rates, right? What if we want to control directly the speed of the motors?

I think that this would be very interesting since several model-based control techniques outputs the thrust of the motors (or, equivalently, the wrench in the flying body). For that purpose, sometime ago I did this. I wasn't sure of the development though, since a modification of the mixer module was required and I was afraid of messing something up.

@PepMS , if you disable the rate controllers ( {0} option ), then you need to set individual motor speeds directly - with all the Pro's and Con's that come with it.

Essentially you would get this chain for a position-control MPC:

User Setpoint -> {MPC position control} -> {0} -> {0} -> Mixers , since MPC will output motor controllers directly

PepMS · 2020-11-03T12:07:30Z

I see. Would you need a special mixer for that? To which uORB topic should the controller publish so that the commands are applied directly to the motors?

Pedro-Roque · 2020-11-03T12:08:41Z

I see. Would you need a special mixer for that? To which uORB topic should the controller write so that the commands are applied directly to the motors?

You would have to send the inputs to the same topics (unless you want to extend the chain to {PX4 mixer, custom mixer 1, custom mixer 2, ... , 0}. The analogy would be the same in that case.

PepMS · 2020-11-03T12:22:08Z

You would have to send the inputs to the same topics

Sorry to insist on this. So in case in the example you said, where you are omitting the attitude and rate controller, the MPC position control should publish to the topic that the original rate controller was publishing, right? Which at the same turn is the input to the mixer. Is that correct?

Pedro-Roque · 2020-11-03T12:30:27Z

You would have to send the inputs to the same topics

Sorry to insist on this. So in case in the example you said, where you are omitting the attitude and rate controller, the MPC position control should publish to the topic that the original rate controller was publishing, right? Which at the same turn is the input to the mixer. Is that correct?

Yes exactly. But the mixer could also be disabled in the same way, leading the MPC to control directly the actuators.

PepMS · 2020-11-03T12:35:50Z

Yes exactly. But the mixer could also be disabled in the same way, leading the MPC to control directly the actuators.

That would be the most appropriate thing for my case. How should we proceed? I could take over, but I certainly need some advice with the development.

Pedro-Roque · 2020-11-03T15:12:51Z

If there are more people interested, we could do a quick Zoom call on this and distribute some tasks?

Pedro-Roque · 2020-11-09T19:04:41Z

Takeaways:

Granularity of PX4 Default Controllers vs Custom controllers -> moves to the existing OFFBOARD mode, where the OFFBOARD model specifies which which controllers are enabled or disabled (like the current position and attitude setpoints that disable specific controllers);
Provide meaningful examples where it is clear what triggers the FAILSAFE. Examples of the above functionality, for each of the cases ( position override @Jaeyoung-Lim, attitude override @Pedro-Roque );
Quoting @dagar : "If you want to do a Wrench, do whatever you want" -> as in, be sure that you want to go with that extra effort. Use the body rates and force instead (most likely you can do this anyways), @lowjunen;
EXTRA BUT IMPORTANT: Clean the OFFBOARD mode (BIG BIG task: @dagar , please refer to specific components that we should be careful with and that we should start cleaning)

dagar · 2020-12-20T19:29:46Z

.vscode/settings.json

@@ -178,5 +178,6 @@
        "workbench.statusBar.feedback.visible": false,
        "yaml.schemas": {
                "${workspaceRoot}/validation/module_schema.yaml": "${workspaceRoot}/src/modules/*/module.yaml"
-        }
+        },
+        "C_Cpp.errorSquiggles": "Disabled"


I'd like to see if we can keep them in certain circumstances.

Pedro-Roque added 2 commits April 25, 2020 00:33

Starting MC CTL Muxing.

d04717f

Starting mavlink interface.

52f89df

weekly-digest bot mentioned this pull request Apr 26, 2020

Weekly Digest (19 April, 2020 - 26 April, 2020) #14761

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stale bot added the stale label Jul 25, 2020

weekly-digest bot mentioned this pull request Jul 26, 2020

Weekly Digest (19 July, 2020 - 26 July, 2020) #15419

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bresch removed the stale label Aug 3, 2020

dagar reviewed Dec 20, 2020

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junwoo091400 added the Multirotor 🛸 label Mar 5, 2023

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[WIP] Multicopter Controllers Muxing #14754

[WIP] Multicopter Controllers Muxing #14754

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[WIP] Multicopter Controllers Muxing #14754

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[WIP] Multicopter Controllers Muxing #14754

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