VOXL2 PX4 not flying

vivek rk

I have a VOXL2 using the following configuration

Frame -> dragonfly 230 (check this image https://cdn.shopify.com/s/files/1/0101/1977/4259/files/3mav_desk_1_2048x2048.png?v=1616628087)
ESC -> VOXL ESC v2
Flight Controller -> VOXL2 using PX4

I was able to setup the VOXL2 and run PX4 on it. I did the calibration of all sensors and could get it to arm, but when i fly it I see a very weird jittery motion. When I check the ulog file on PX4 flight review I see the following on the pitch, roll and thrust setpoints where it oscillates between the setpoint provided using the RC and another setpoint which is different

pitch setpoints oscillates between the value set by the RC and -35 degrees (max tilit)
thrust setpoint oscillates between the value set by the RC and 0

The review for ulog is here

https://review.px4.io/plot_app?log=444738f8-fc52-4c52-a53d-831342feeba3

I have also tried different PX4 versions that are available here https://github.com/modalai/px4-firmware/ by manually compiling for the rb5 platform and all of them have the same issue.

Is there anyone here who has had a similar experience and was able to solve this issue ?

Regards
Vivek

Chad Sweet

Have you performed PX4 Multi-rotor PID tuning? That is required for every new platform

https://docs.px4.io/main/en/config_mc/pid_tuning_guide_multicopter.html

We have starling PID parameters published here for VOXL 2: https://gitlab.com/voxl-public/flight-core-px4/px4-parameters/-/blob/master/platforms/v1.12/Starling/Starling_V2_param_rev_D.params

vivek rk

Hi Chad,
Im not sure if the problem lies with PID tuning, as the pitch and thrust setpoints (directly taken from the RC) are the ones that create the problem in the first place. If you have a look at the PX4 flight review, you will see the following

Between time 21:26 and 21:36 the RC input received on the pitch is 0 but the pitch setpoint oscillates between -35 and 0 (degrees).
In the same time my thrust setpoint at the RC is between 0.9 and 1.0, whereas the thrust setpoint is also oscillating between 0.08 and 1.0 or 0.9

This behavior cant be explained by a bad PID tune as the thrust and pitch setpoints should follow the RC directly.

Another thing i see is that in the link provided, I see that voxl2 has PX4 v1.12 but the github repo has v1.4.24 as the latest version. Is there a dev build for v1.12 that i could access somewhere else ?

James Strawson

Are you using a Spektrum radio with satellite receiver to control the drone? Or something else?

vivek rk

Im using the spektrum DX8 radio with the satellite receiver

Daniel Mellinger

Hi Vivek,
This is a strange issue. It would be good to rule out an issue with the radio transmitter and receiver. Are you able to try a test with a different radio transmitter? Could you also try with a different satellite receiver? Thank you!

vivek rk

@Daniel-Mellinger
I am still facing the issue with the remote, but i believe its only with the remote as I was able to get it flying in offboard mode using the VIO onboard. Its flying and is quite stable at the moment. Due to the nature of our research, we dont fly with the manual remote (we only use that for initial tests).
But from my experience im not sure if the remote controller could be at fault, because

I have used the same RC / receiver pair on the VOXL (version 1) and its able to fly in manual mode without any problems
If you look at the Manual Control input plot in the px4 review mentioned in the 1st post, you will see that there are no discontinuities present in the signal. The setpoint thrust and pitch curves look fine. Whereas the setpoint pitch and thrust going into the attitude controller is quite discontinuous

In summary, we are just using the remote to change modes and trigger emergency kill switch and thus this bug is not affecting us anymore