Every few seconds, the motors jiggle

Flight Testing & Log Analysis
1

Hi,

I am having a Pixhawk 6xpro, with PX4 1.16 Stable, with a fixed wing VTOL, that has 4 of these as vertical lift motors: T-Motor MN3510-13 Multirotor Fixed Wing UAV Motor KV700 ( MN3510 UAV / Drone Motor - Stability & Longer Flight Time ).

As ESC, I am using **Skystars Jupiter 35A 3-6S AM32 (**Skystars Jupiter 35A 3-6S AM32 | Rotorama).

Every few seconds, somehow my motors jiggle, meaning there is a short “desync”?

I uploaded a video on youtube showcasing my problem:

I think the smoking gun in this regards is the mavlink console output:

nsh> dshot status
INFO [dshot] Outputs initialized: yes
INFO [dshot] Outputs used: 0xf
INFO [dshot] Outputs on: yes
dshot: cycle: 68808 events, 1416021us elapsed, 20.58us avg, min 18us max 77us 1.941us rms
dshot: bdshot rpm: 17204 events
dshot: dshot telem: 0 events
INFO [mixer_module] Param prefix: PWM_AUX
control latency: 68811 events, 39411036us elapsed, 572.74us avg, min 470us max 5457us 306.846us rms
INFO [mixer_module] Switched to rate_ctrl work queue
Channel Configuration:
Channel 0: func: 101, value: 0, failsafe: 0, disarmed: 0, min: 109, max: 1999, center: 65535
Channel 1: func: 102, value: 0, failsafe: 0, disarmed: 0, min: 109, max: 1999, center: 65535
Channel 2: func: 103, value: 0, failsafe: 0, disarmed: 0, min: 109, max: 1999, center: 65535
Channel 3: func: 104, value: 0, failsafe: 0, disarmed: 0, min: 109, max: 1999, center: 65535
Channel 4: func: 0, value: 0, failsafe: 0, disarmed: 0, min: 109, max: 1999, center: 65535
Channel 5: func: 0, value: 0, failsafe: 0, disarmed: 0, min: 109, max: 1999, center: 65535
Channel 6: func: 0, value: 0, failsafe: 0, disarmed: 0, min: 109, max: 1999, center: 65535
Channel 7: func: 0, value: 0, failsafe: 0, disarmed: 0, min: 109, max: 1999, center: 65535
Channel 8: func: 0, value: 0, failsafe: 0, disarmed: 0, min: 109, max: 1999, center: 65535
INFO [arch_dshot] dshot driver stats:
INFO [arch_dshot] Bidirectional DShot enabled
INFO [arch_dshot] Timer 0, Channel 0: read 6367, failed nibble 0, failed CRC 0, invalid/zero 10841
INFO [arch_dshot] Timer 0, Channel 1: read 0, failed nibble 0, failed CRC 0, invalid/zero 17209
INFO [arch_dshot] Timer 0, Channel 2: read 0, failed nibble 8979, failed CRC 0, invalid/zero 8230
INFO [arch_dshot] Timer 0, Channel 3: read 0, failed nibble 0, failed CRC 0, invalid/zero 17209
nsh>

Especially

“INFO [arch_dshot] Timer 0, Channel 2: read 0, failed nibble 8979, failed CRC 0, invalid/zero 8230”

If I understand correctly, this means that many packages do not even transfer correctly?

I tried with many different AM32 settings, different timing advance, etc, but nothing really resolved the problem.

Can someone please help do name me what this problem refers to exactly?

2

Does this happen with the motor test with QGC? And does it also happen when you just try to arm and test it that way. You could force arming in the MAVLink console doing commander arm -f (and commander disarm -f.

3

Hi Julian,

when Arming and in manual flight, I don’t notice this behavior. Yes, this video is from the actuator test with QGC.

4

Yes, then that’s likely a communication issue between QGC and PX4 as QGC sends commands at a (too) high rate.

5

Is there a way how to fix this? Or a way how to dive deeper into the code of Qgroundcontrol and monitor the signals that arrive at the Autopilot?