I am troubleshooting an issue that led to a crash while in Loiter mode. The drone in question is a heavier drone (~6-7 kg).
Before this test, we had flown the same drone successfully at 100m altitude, traveling 150-200m forward without any issues. As we were testing the impact of setting:
LOIT_SPEED = 3500 cm/s (35 m/s)
LOIT_ANG_MAX = 10°
Later during the next flight after changing the battery and re-flying, when we were specifically testing the impact of setting:
LOIT_SPEED = 3500 cm/s (35 m/s)
LOIT_ANG_MAX = 5°
We observed a motor failure when reversing yaw direction.
Critical Issue Observed:
When the pilot yaws the drone anticlockwise and then applies a small clockwise yaw command,
→ Motor (C4) suddenly loses power, causing the drone to fall.
This can be seen in log using ATT>YAW and RCOU>C1, C2, C3, C4 and RCIN>C2
Additionally you can also plot the GPS>ALT to see when the altitude drops.
Observed Logs & Parameter Settings:
1. Yaw Instability (ATT Log)
2. High Vibrations (VIBE Log)
3. Motor Output Imbalance (RCOU Log)
4. Pilot Command for YAW (RCIN Log)
Current Parameter Settings:
Yaw PID Tuning (ATC_RAT_YAW)
Parameter
Current Value
Default Value
ATC_RAT_YAW_P
0.462
0.18
ATC_RAT_YAW_I
0.0462
0.018
ATC_RAT_YAW_D
0.0024
0
Other setting for YAW can be seen using the log.
Loiter Mode Parameters
Parameter
Current Value
Default Value
LOIT_ACC_MAX
300 cm/s²
500 cm/s²
LOIT_ANG_MAX
5°
N/A
LOIT_SPEED
3500 cm/s
1250 cm/s
Acceleration and Jerk Limits
Parameter
Current Value
Default Value
ATC_ACCEL_Y_MAX
6500 cdeg/s²
27000 cdeg/s²
Request for Help:
How should I further refine my Yaw PID tuning?
Could my ESC/motor combination be causing desync in yaw transitions?
Would increasing ATC_ACCEL_Y_MAX significantly improve yaw response?
Are there any known firmware issues or flight controller settings that could cause this behavior?
I have attached log files with parameter settings for reference. Any recommendations would be greatly appreciated!
Motor 4 failed, the controller drops 3 to control torque. The current flow also drops at this point suggesting that nothing is happening with motor 4 given it’s full power command.
All the motors and ESC are tested and working fine.
This test was done after the crash, we took out all the motors and individually checked all the motors with its corresponding ESC. No unusual behavior or anomaly found. The battery was also tested and it turned out to be working fine. In my observation the issue does not lie in the motors, or ESC or battery. It was something else.
Wiring could be an issue, but the main point is, how come this crash happened after 2-3 consecutive flights, and just the previous flight before the crash, we have flown the drone to 200 meters and back at height of around 70-80 meters.
When we landed and after 4-5 minutes (ample time given to the motors for cooling down) we changed the battery for the next flight, then this crash happened as we fly to approx 15 meters height and then positioning the drone using the yaw command. Then the crash happened.
If the connections were perfect mechanically and electrically, there would be no failure.
If the connections were total junk you never would have taken off.
You may have been somewhere in the middle. Good enough to get in the air, but with time, heat, movement, vibration, and all the other stresses that occur to drone components it failed. It happens. This forum is full of posts saying the same thing: Why did it fail after we already flew x and y.
Sure - but the comment from the user makes me think it could also be a hardware issue given the stated maneuver requires the motor to go to min throttle and then ramp up to a higher throttle fairly quickly (which can lead to desync).
@sam_copter Could you share specs about your propulsion system?
When the users user the ArduPilot Methodic Configurator software, and configure their vehicles until the program finishes, a .zip file is automatically created that contains:
information on all their components (including propulsion system),
their connections,
all the parameters and
all the reasons why they choose those parameter values.
That .zip file, when shared here in the forum, is a valuable tool in diagnosing configuration/tuning issues. BTW that .zip file is small enough that it can be shared directly in the forum, without dropbox or google drive.
That is one of the reasons we keep recommending that the users use it. It makes their and our lives easier.
