Hello everyone,
I’m working with an 8 kg custom VTOL (Lift + Cruise) using a Pixhawk 6C running PX4 v1.16.2.
I’ve reduced MC_PITCHRATE_D and MC_ROLLRATE_D to 0.0001. My attitude P gains are currently MC_ROLL_P = 2.0 and MC_PITCH_P = 3.1. Since this is a custom frame, my flight logs indicate excessive vibration. I’ve already mounted the Pixhawk using the anti-vibration damping board along with double-sided tape.
I have a few questions:
-
Vibration suppression:
Being a custom frame my logs show there is excessive vibration. I have used the pixhawk anti vibration damping board and double sided tape to stick it. Are there any parameters I can tune to further suppress the vibrations, or is this likely to be a hardware issue?
-
Motor 2 saturation and overheating:
As shown in the logs, Motor 2 frequently reaches an output of nearly 1.0, and I’ve observed that it becomes significantly hotter than the other motors. Could the D-term contribute to this behavior? Also, this motor has a small section of its winding that was spliced internally. Could this be causing the issue?
-
Battery emergency warning:
Although each motor draws a maximum of about 35 A at full throttle (producing approximately 3.7 kg of thrust), I’m repeatedly getting a “Battery Level Emergency” warning.
My power setup is:
- Two 3S 5000 mAh 50C batteries connected in series (6S total)
- Pixhawk UBEC Power Monitor Module (2–12S, 200 A)
My understanding is that this power module should be more than capable of measuring the battery voltage and current accurately. Why might PX4 still be triggering this battery emergency warning?
Flight log:
https://review.px4.io/plot_app?log=d4f2b663-9343-4375-b358-f62c495d4227
“Also, this motor has a small section of its winding that was spliced internally”???..Can you swap the motor with another on the airframer? If the problem follows the motor, you have a bad motor.
Yeah I’ve done that previously and its the same issue with the motor output saturating to 1 after a point. I have somewhat achieved hover (only one time) at 3m altitude at this point. But after this point the motor with windings spliced becomes really hot. Is the last option to replace motor ?
Is this motor creating the high current/low volatge warning ?
Also my vibration level are way too high as seen from the log. Is this the issue with frame ? or I can choose cutoff frequency and remove this ?
Thanks for the reply
If the problem moves with the motor, very high probabilty (99%) the motor is bad. I would get a new motor.
A bad motor can cause vibration problems. A bad motor can cause your ESC to fail.
I would not fly again untill the motor is replaced. Get a new motor.
Hello John
Today I conducted yet another test with my 700gram payload removed. In this test from the logs I found that now my motor 2 is not saturating to 1. The VTOL was stable in hover and I executed pitch and roll and the VTOL didn’t show any oscillations.
But there is error that says emergency battery level land now which you can see from logs. Its just a warning and doesn’t trigger my VTOL to land. Is there anything I could do ? I am using 200A hall effect current sensor.
Second, the vibration level is still high so I’m assuming I need to make my frame stiffer ?
My power distribution board, wiring, and xt60 battery connectors are getting extremely hot to the point that it can burn fingers when trying to remove it. My wirings are all 12awg. Will replacing wiring / connectors to xt90 fix this heating issue?
Logs:
https://review.px4.io/plot_app?log=2a9afef6-577f-43fc-8541-733a7dd8b1f5
From what you have told us, you probably have a bad motor. One motor is getting realy hot and has some sort of internal splice on the windings. If you keep flying with that much power draw, I’m afraid you will lose an ESC and/or power disribution componets.
There maybe other problems, but one hot motor with spliced windings is a problem that needs to be fixed, did you replace the motor?
