theely
commented
4 years ago Update! Two more tests:
- Disabling bidirectional DShot, problem still present
- Added a 1k mF 35V capacitor, problem still present
I have noticed that most of the time when the ESC has issues to ramp up the motor the battery voltage drops heavily some times even below 3V per cel. If the underlaying problem is electrical this could explain why the problem gets worst on 48kHz PWM.
Test flights logs are available at: https://drive.google.com/drive/folders/11mEeKe6_ok3_siuswv1yySXTsgk_OoO7?usp=sharing
It appears that some Tekko32 F3 4in1 ESC 45A - Revision C (2 out of 3 that I tested) have issues when requested to quickly ramp up motor nr. 2 (yes only motor nr. 2) on sharp rolls or flips. In some occasions leadings to partial or full de-sync.
Furthermore the issue is accentuated when lowering PWM from 96kHz to 48kHz. On PWM at 48kHz the very first roll leads to an unrecoverable de-sync.
Testing method: I own two identical quadcopters, 5" running S4 battery with Tekko32 ESC and Kakute Mini FC, with NO capacitor installed.
The first quad I built had no issues and is flying amazing, the Tekko32 F3 (rev c.) installed on the quad was purchased on August 2020. Later in early October 2020 I purchased two more Tekko32 F3 (rev c.). Already on the maiden flight the second quad was manifesting the issues. I then replaced the ESC with the second one purchased in October but the issue persisted.
Finally I decided to swap the ESC from the working quad with the defective one and was able to confirm that the issue is indeed related to the ESC since it was the only variable that made the issue manifest or not.
The issue manifests as following: When the FC requests to increase RMP (yellow line) the ESC struggles to quickly spool up the motor in some occasion RMP even drops before catching up (blue line).
In some occasion the ESC goes in partial de-sync before being able to provide the requested throttle.
When testing PWM at 48kHz the issue was so sever that the first roll would result in an unrecoverable de-sync (motor two green line never reaches the required RMP).
To exclude issues related to low RPM I have increased Betaflight min idle RPM with no apparent improvement.
Test flights logs are available at: https://drive.google.com/drive/folders/11mEeKe6_ok3_siuswv1yySXTsgk_OoO7?usp=sharing