I have build a 7 inch LongRange quadcopter using :
- Armattan Chameleon TI LR carbon frame
- Matek H743 SLIM running Arducopter 4.1.0-beta5 with bidir dshot firmware
- ESC : T-Motor F55A Pro II T-Motor - 3/6S -BLHeli_32 4in1 MCU F3
- Xing2 2506 - 1650KV motor
- Propeler : HQ Durable Prop 7 X 3.5 X 3V1S
- External GPS & COMPASS : M9N-5883
- External Lidar + Flow Sensor : Matek 3901-L0X
- RC : TBS CrossFire Nano RX with Yaapu script telemetry running on TX16S
- LIPO Battery Tattu 1800mha 100C
This quad ( and its predecessor based on GEPRC MARK4 7 inch frame) suffer from severe oscillations from 10Hz to 20Hz mainly on the roll/X axis, in STABILZE, ALTHOLD, POSHOLD modes. The issue is not produicible at all time.
I am running DSHOT 1200, in bi-direcionnal mode for high freq RPM motor telemetry.
I never tried to run older Arducopter 4.0.x since i need crossfire support and yaapu telemetry.
When the oscillation occurs, current drawn rise a lot from 8A (hover) to 20A/30A, but the quad remains under control from my RC.
Some time the oscillation last 5% of flight time, sometime 80%…
Here is some chart of a flight :
I have also tested with Betaflight 4.2.8 this quad : no oscillation appeared in angle mode. No feedback from INAV, since H743 is not yet supported.
Please find the BIN LOG file : https://drive.google.com/file/d/1mvKQycTC4ZzA_YW2cI6NDu4vfzPjrSC3/view?usp=sharing
In this log oscillations occurs at the following timestamps :
- 4min 6.0s during 5 sec - STABILIZE MODE
- 7min 35sec during 3 sec - POSHOLD MODE
- 8min 2sec during 3 sec - POSHOLD MODE
The Armattan Chameleon TI 7 inch LR frame is know to fly well, without issue of that kind.
Does anyone have any deterministic method to tackle this kind of low freq - high amplitude oscilations?
Any suggestions ?