PX4 Community Q&A: May 03, 2023==

rroche · April 26, 2023, 5:00pm

May 03, 2023

Join us

Agenda

Community Announcement
Community Q&A
General Discussions

Community Announcement

A.1 :

Community Q&A (No deep technical discussions)

Guideline for asking a Question

Specify what you are trying to achieve
Specify what environment / platform you are using
Prepare a Link or Document to help understand if possible
First, ask the question on Discord or create a Github Issue!
If you take over 5 minutes for the question, please continue in Discord or a Github Issue.

Q.1: Offboard swarm control

Answer:

Q.2: PX4 Dev Summit 2023 CFP Deadline

Find the details here:

CFP Closes: Sunday, July 9, at 11:59 PM PDT
CFP Notifications: Monday, August 14

Q.3: Multirotor control equation

General Discussions

D.1 : DroneCAN 15 Servos support

github.com/PX4/PX4-Autopilot

Support 15 servos on DroneCAN

PX4:main ← henrykotze:support-more-servos-on-outputs

opened 01:25PM - 21 Apr 23 UTC

henrykotze

+44 -17

Currently only 8 servos can be command simultaneously over DroneCAN, but `uavcan…::equipment::actuator::ArrayCommand` takes up to 15 Servo commands (`uavcan::equipment::actuator::Command`) This changes bring the number of servos which can be commanded simultaneously to 15. ## Testing Using a Hitec Servo and setting its ID to 15, and by using the actuator tab on QGC it was following the slider commands as expected.

DroneCAN supports 20 servos (DSDL array length limited)
We could probably go to 16 servos support, just need to take care of FLASH overflow

D.2: RC Driver discussion

github.com/PX4/PX4-Autopilot

Fix uncalibrated RC input being used

PX4:main ← PX4:maetugr/rc-uncalibrated-fix

opened 10:17AM - 03 May 23 UTC

MaEtUgR

+139 -89

### Solved Problem When testing for https://github.com/PX4/PX4-Autopilot/issues/21506 I often reset all parameters to go through a fresh setup and found that my RC input data from a crossfire receiver was used even though I didn't calibrate it yet. The values were all static zero because it was uncalibrated but still assuming to have pilot input even though there is none is a safety concern. ### Solution - (Refactor topic object naming in RCInput.) - Start using the `valid` flag in the `manual_control_input` topic to signal that the input is not actually calibrated and shouldn't be considered valid and used. The RC is considered calibrated if the channel count parameter `RC_CHAN_CNT` is set and at least one of the stick axes roll, pitch, yaw or throttle is mapped to an RC channel. Further the input is only considered valid if the number of channels in it actually matches what was calibrated (`RC_CHAN_CNT`). ### Changelog Entry For release notes: ``` Bugfix: Uncalibrated remote input is now considered invalid ``` ### Alternatives What's not ideal in my eyes is the reporting to the user. He cannot screw up anymore by accidentally using uncalibrated stick input but he's not informed about the details about why the stick input does not get used. QGC shows a red remote icon but feedback could be better. Should I duplicate all these checks into the RC calibration check here? https://github.com/PX4/PX4-Autopilot/blob/1d4b66fcbc103eb2e81eb708d863595679989884/src/modules/commander/HealthAndArmingChecks/checks/rcCalibrationCheck.cpp#L81 I considered that but then we need to change the workflow of default RC configuration because it will immediately fail and you will not be able to fly without RC without disabling it. I think this is the way to go but I don't feel comfortable introducing this change for 1.14 since we don't have UI changes and RC disabled by default to go with it yet. ### Test coverage I did bench testing using the same setup that I found the issue with. On a fresh setup the `manual_control_input` is published with the uncalibrated values but flagged as invalid and therefore does not get selected/used. <img src="https://user-images.githubusercontent.com/4668506/235889619-a3b5c50d-3d84-437d-a6d2-54e7c6189739.png" width="350"> Once the RC is successfully calibrated it gets flagged valid and is normally used. <img src="https://user-images.githubusercontent.com/4668506/235889949-ac6ff101-515f-4a68-895a-1cdc77681f81.png" width="350">

Further discussion on the splitting the RC drivers PR: [WIP] split drivers/rc_input per protocol by dagar · Pull Request #20829 · PX4/PX4-Autopilot · GitHub

We need to have a context on which protocol is used, to remove hard-coded logic!

D.3: DDS Documentation

Ramon will run the XRCE-DDS again, and then will merge the docs PR: [dds] DDS documentation & User workflow testing · Issue #21383 · PX4/PX4-Autopilot · GitHub

D.4: Release candidate for v1.14

Release candidate before next week. We will continue to compile the high level release notes.

Remaining 2 release blockers will be resolved with small fixes. Regarding 100% thrust issue, it is likely not happening with 1.14, we should keep that in mind.

D.5: Multi EKF sensor priority

Multi EKF is currently enabled for most targets. The improvement PR would add logic in EKF selection to prioritize external magnetometers.

princealy · May 2, 2023, 5:54pm

Hi!
Wnated to follow up and see if there is an update on the support for swarm flight and simulation with PX4. Looking tor a way to have offboard control functioning with PX4 for multi vehicle flight. This would allow the implementation of swarm logic. I believe this would be of interested to many researchers as well. I couldn’t find any guide online that worked for me.
Would love to learn if:

This is currently supported on the main branch
How that can be configured and if there is documentation in place.
If this is not in place, what would it take? If someone can take the lead, I am happy to help with the implantation.
If any of the community members have working examples of using swarm algorithms with PX4.

Thanks!

Benja · May 2, 2023, 6:42pm

Hi @princealy , I’ll not be able to attend tomorrow, so here is the answer for your questions.
You can simulate multiple drones with PX4 and apply offboard control on them. Everything is in the docs and it refers to the current main branch:

Multiple drone simulations: I am most familiar with Gazebo Classic (default gazebo version up to Ubuntu 20.04) and Gazebo Garden (default Gazebo version from Ubuntu 22.04). In both cases you can spawn multiple drone in different location and have them connected to a PX4 instance.
Offboard control: Once you have the simulation running you can either use offboard through mavlink (mavsdk, mavros, the one that you prefer) or you can use the new PX4 - ROS 2 bridge and its support for multi-vehicle simulations and have all the UORB topics that you want available as ROS 2 topics. Then you can implement any swarm logic on your companion computer / offboard computer.

To be clear, PX4 does not implement any swarm control algorithm. However you can send offboard commands and implements your controllers offboard.

Does this suit your needs? Feel free to open a specific topic if you have other specific needs.

Other relevant resources: