PX4 Community Q&A: April 05, 2023

April 05, 2023

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  • Community Announcement
  • Community Q&A
  • General Discussions

:loudspeaker: Community Announcement

A.1 : v1.14 beta testing

:people_holding_hands: Community Q&A (No deep technical discussions)

:exclamation: Guideline for asking a Question

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

Q.1: Crash report - Jw

  • Without companion computer, it flew perfectly. But after having companion computer (sending commands of 0?), it showed the weird behavior.

Q.2: ESC update through passthrough

  • This is a nice feature for sure.
  • BLHeli use case, we just need someone to implement it
  • Need to find contributor interested in this

Q.3: Reset speed when switching modes

  • Intuitively, it does make sense that we don’t *carry over the speed limit from another mode, to the new mode
  • But, we need more discussion on how to interpret this, what does it mean to change speed between flight modes?
  • Setting different cruise speeds for different modes of operation, is this what we desire?
  • E.g. we have “cruise speed” parameter for MC and FW, and for changing that (which should affect in long-term), it probably would be Service to change the parameter. But for temporarily changing the cruise speed shouldn’t incorporate parameter.

Q.3.5: Geofence

Geofence predictor is predicting the breach too early/wrong. Anyone with more context?


  • Setting ‘terimnate action’ can be very dangerous (e.g. lead to crash, as in the forum post), as there will be lots of false positive
  • This feature in general has a lot of false positives!


  • How can we improve this?
  • For now there’s quite a lot of Geofence issues

Q.4: Tilting multirotor support / testing

  • Implemented new Actuator Effectiveness Matrix method
  • How can we collaborate with PX4 team to get this incorporated properly?
  • In different labs, they rely on custom firmware, and has different problems. So using PX4 and fully supporting it would be much better for the research / industry! :muscle:


  • @sfuhrer has enabled this in control allocation side, so could be nice to sync
  • This is for sure interesting. Cleanup to make it generic and not specific to this use-case would be better
  • Output of position is 3d force, and that gets interpolated by control allocator.
  • This would be a nice addition to control allocator
  • CMU had another PX4 fork that implemented 6 DOF implementation. We could check that out as well.

Action Item:

  • Can create a new branch and add as Pull Request in PX4-Autopilot main repository. That will show what diff exists & continue discussion- @salmarc
  • Set the base branch to main, add videos!

Q.5: SUI04 - Ultrasonic sensor compatibility

  • In docs, Obstacle sensing is presumably supported through Companion computer
  • Brochere mentions this sensor is capable of MAVLink / up to 6 instances


  • Just for interfacing, companion computer isn’t needed, and can take data just through I2C
  • Quality wise, ultrasonic sensors probably aren’t the best, but still should work.
  • The driver for this is presumably implemented. So enabling the sensor via the "SR05" parameter, then trying it out would be great!
  • Recommend using a better sensor as well: SF45/B (50 m)

Q: PX4Flow

If anyone has experience with PX4Flow, Mark (Sauder) will appreciate some help in setting it up (currently doing it in progress)

:thinking: General Discussions

D.1 :

PX4 v1.13.2
Cube orange/ nvidea jetson xavier companion computer
Homebuild quadcopter 16" props, 4.9Kg

Hi all,
I’ve had a crash with my drone whilst flying in position mode with RC (without using the companion computer). I tried to switch back to manual but unfortunately could not save the drone anymore. Whilst analyzing the log files, I can’t directly find what might have caused the crash. I do see at the point where it went wrong a sudden jump in the roll and pitch set points, shortly after followed by one of the motors going to max thrust. The velocity controller seems to give some oscillations with a rather low damping. If there is anyone who might be able to shed some light on what might have gone wrong, it would be highly appreciated.

log: https://logs.px4.io/plot_app?log=62d094c4-0e64-43c1-bb9d-1c6f23de4eba
files: Homebuild quadcopter crash in position mode · Issue #21416 · PX4/PX4-Autopilot · GitHub

I put in a feature request for passthrough to update ESCs at Passthrough to update ESC's. · Issue #21420 · PX4/PX4-Autopilot · GitHub. Not a big deal if it’s not possible, or there is an easier way these days to get it done. But if there is a reason it cannot, or will not be implemented, I would be interested to here why that is. Thanks in advance!


Hoping to talk about this PR, and how set speeds should be handled between switching flight modes

Also hoping to get a bit more information and context around Geofence Predictor in relation to my discussion post. This led to an early termination. It is a user error, but I can see others making easily making this mistake

I made this customization to introduce the “tilting multicopters” airframe class.
This has been tested in simulation and on two real platforms ( PX4 customization for tilting multirotors - YouTube , PX4 for tilting drones - test on platform - YouTube).
I would like to propose that to the developers but I have some questions:

  1. how stable must the solution be to propose that to you? it has been tested but of course, there are things that will need to be checked or maybe changed
  2. would it be possible to have someone collaborating on it in order to improve and perform other tests? I’m not a PX4 developer so of course there will be something wrong with it, but I’m trying to learn to improve

Is the RadioLink Ultrasonic Sensor SUI04 compatible with PX4 for obstacle sensing . The brochure indicates it is Mavlink / Pixhawk compatible OR do we require any special drivers here similar to TF LUNA setup from Benwake .

RadioLink Ultrasonic Sensor SUI04 Obstacle Avoidance

If you could start a forum post that would be great, but I think I heard you mention something about publishing certain topics from your onboard computer. Could you create a forum post and mention the message topics you are publishing from?

I added the topic that is being published in the Quadcopter crash in position mode · Issue #21416 · PX4/PX4-Autopilot · GitHub. Given that the flight was performed in position mode without switching to the offboard mode, I expected there to be no influence of the offboard computer.

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