PX4 1.11.2 won't work in position mode

Pixhawk
#1

Hi. I’m newbie here.

A few days ago, I flied the Pixhawk4 + PX4 1.11.2, and looks good in stabilized mode and altitude mode. But when I changed the Position mode, my quad look like soo cold. It looks trembling. When I move the position any directions, it moved like a stop and go and stop and go. I mean moved not smoothly.

Today, I downgrade the firmware to 1.9.2. And every problems go away. Position/Altitude/Stabilized mode working very nice. Would you let me know why PX4 1.11.2 firmware version is not working in my case? My drone is Quad and size is around 1000mm. I think PID looks good.

My flight log is gone because of my fault. Sorry. And also sorry for my poor english. I hope you can understand my words.

Thank you.

#2

Hello,
Any logs please?

#3

Hello ,
I am under firmware 1.11.2. I had the same problem as @Wuyong in position mode, it was very stable with a strong wind. I changed mode and since then the position mode no longer works. I did not change firmware version. What’s the cause ?

#4

Thanks for sharing your experience! Could you please share a flight log? Here is how you can do this: https://docs.px4.io/master/en/getting_started/flight_reporting.html

#5

Sorry for my late.
Actually a few days ago, I changed my quad’s firmware to v1.11.3. And I think it’s better than before.
But in position mode, my quad looks like wild horse. If I move my RC’s pitch to up, then quad tilt sharply.
As I said, my quad’s size is 1000mm. I don’t want to. But I don’t know how I change this situation.
My guess, this phenomenon is misleading like a unstable.

Here is my newest flight log.

Flight Review - Quadrotor (px4.io)

P.S.
Actually I tried to offboard control of this quad. In offboard mode, it looks good. I have no idea why offboard is good and position mode is strange. Here.

Flight Review - Quadrotor (px4.io)

#6

You need to re-tune your velocity controller (lower the MPC ACC P gain). The tuning guide is here:

@MaEtUgR might have better tips.

#7

@wuyong.yi @regis_carreg Thanks for reporting! As far as I can see from the first log from @wuyong.yi there are quick oscillations through the attitude setpoints during horizontal position control in Position mode which are gone in Altitude mode:

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Like @LorenzMeier suggested I would start by testing lower horizontal velocity control gains: https://docs.px4.io/master/en/advanced_config/parameter_reference.html#MPC_XY_VEL_D_ACC and https://docs.px4.io/master/en/advanced_config/parameter_reference.html#MPC_XY_VEL_P_ACC
The velocity gain scaling changed from 1.9 to 1.11.

Note that the horizontal vibration levels of ± half a g on the accelerometer are most likely part of the issue:

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The accelerometer vibrations lead to quick velocity estimate changes that have a strong influence on velocity control:

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For generally better flight performance I would double-check that the autopilot is mounted in a rigid way with only very slight isolation e.g. sticked with large surface douple sided tape to a frame plate or screwed down to the frame with orings under the screws. Also there should be no oscillating or rattling parts on the drone like lose screws or long thin GPS masts that can amplify oscillations.

If none of this helps there’s also the low pass filter for the accelerometer from which you can lower the cutoff frequency: https://docs.px4.io/master/en/advanced_config/parameter_reference.html#IMU_ACCEL_CUTOFF
If set too low this might have negative side effects but is worth a try after testing velocity control tuning and checking the autopilot mount.

Please let me know how it goes or if you have further questions.

#8

I also had a look at the second log provided with offboard mode flying and I do not seem any improvement over the flights in Position mode. The same oscillations are visible plus there are some smaller jumps in the x-axis position setpoints provided in offboard mode:

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I’d recommend to keep these setpoints as smooth as possbile.

#9

Thank you for your kindly help.
I will try again.

#10

Thank you for your help.
It will be helpful for me.