Good evening,
During startup, when the rotor has reached the required rpm (1800), the tail vibrates violently in the horizontal plane. This phenomenon persists during takeoff and stops after a few seconds of hovering. What could be the cause and how can I resolve it? Can anyone please help me?
I’m attaching the flight log: https://drive.google.com/file/d/1hXEDppLN2Ru-rX4TttMSKmA-IKLTxeV8/view?usp=drive_link
Thank you.
The only thing I can see is the tail rotor trim is off, so the controller may be hunting to stabilize the yaw. Try SERVO6_TRIM,1640.
Edit: I also noticed the Z vibrations are very high, so you will need to likely adjust the blade tracking before you go too much further.
Could it be ground resonance vibration or what its called?
A video might help people identify where to investigate if its practical.
Hi Walter,
Your parameters ATC_RAT_YAW_I and ATC_RAT_YAW_P both have the exact same value of 0.02448343.
Recommended initial values are 0.12 for YAW_I, and 0.18 for YAW_P.
Maybe one or both need to be adjusted.
1 Like
Hi Walter,
first it would help enabling the PID logging.
Looks like your yaw axis could use some more integrative. I’d suggest to increase ATC_RAT_YAW_I to at least 0.15.
Also, looking through your ATC params, all axises ANG_P parameters have been set to 10, was this intentional?
Thanks for the replies. I haven’t changed the values of ATC_RAT_YAW_I and ATC_RAT_YAW_IATC_RAT_YAW_P, nor the ANG_P axes. I just performed autotune. I’ll enable PID recording and increase ATC_RAT_yaw_i to 0.15. Is it appropriate to change other parameters before the next test flight?
Thanks
I suggest to perform one flight with atc_rat_yaw_I increased to 0.15 and one subsequent flight with atc_ang_pit/rol/yaw_p set to 5 (keep atc_rat_yaw_I at 0.15).
I flew two flights: the first with atc_rat_yaw_i set to 0.15, and the second with atc_ang_pit/rll/yaw_p set to 5. I saw no reduction in tail vibration. On the second flight, the helicopter rolled to the left much more than on the first flight.
I’m attaching the flight logs and a video of the flight with only atc_rat_yaw_i adjusted.
Thank you.
Hi Walter,
tail response look much better once in the air. I believe the initial shaking is due to a large over rpm while on the ground with the collective bottomed:
Remember each tune is valid only for the specific rpm setpoint you tuned at.
The governor is trying to compensate for this over-rpm, but it would help lowering H_RSC_THRCRV_0 , here you can see the governor output in relation to rpm:
Hi Ferruccio, I lowered h_rsc_thrcrv_0 and the other h_rsc_thrcrvs as indicated on the arducopter wiki, but with the collective at minimum, the tail continues to vibrate. I also attempted a landing and subsequent takeoff, and even then, with the collective at minimum, the tail vibrates.
I’m attaching the flight log: https://drive.google.com/file/d/1gsI9MMtpJ0OZhNnAofZe8c4mqaV93IIb/view?usp=drive_link
Thank you for your guidance.
Hi Walter,
file attached is a .rlog, can you please provide the .bin file ?
Hi Ferruccio,
sorry, I made a mistake. Here’s the correct flight log.
Thanks
Hi Walter,
try reducing ATC_RAT_YAW_D. I suggest to use transmitter based tuning to find the correct value (TUNE set to 26, TUNE_MAX set to your current ATC_RAT_YAW_D and TUNE_MIN to ATC_RAT_YAW_D/2) .
Hi Ferruccio,
Today I took my first flight with atc_rat_yaw_d: 0.0025. The vibration on the ground is much less and disappears when increasing the collective pitch. In flight, the tail response feels good. On landing, the vibration is low and stops when increasing the collective pitch.
I took a second flight with atc_rat_yaw_d set to about 0.00375. The vibration is much greater, even on landing, and it doesn’t decrease as quickly as increasing the collective pitch. In flight, I felt at times that the tail was jerky. I’ll leave the flight logs.
Thank you
Hi Walter,
What servo are you using on the tail?
Hi Ferruccio,
the helicopter uses the original Align servo, namely the Align DS520. Do you think it might be malfunctioning?
Thanks