Everything was normal during flight, then the motors abruptly stopped spinning and it plummeted.
Thrust loss on Motor 4. This craft is underpowered/overweight perhaps the ESC was overtemp. Describe the components on this craft.
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Thank you for your help. The details are as follows, and I have one more question:
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Weight: 5 kg
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Diagonal Length: 65 cm
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Flight Controller & ESC: SpeedyBee F405 V4 60a
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Motor：XRotor 2807 1300kv
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Propeller blade ：7×4×3
Since we turned off the Voltage Compensation function, we suspect this might be the cause. How did you analyze and draw the above conclusions?
I don’t think so. It’s way too heavy for that kit of components. Buy a subscription to eCalc and see for yourself. It aligns with what the log is showing. Average output at hover is 1700us and the Motor 4 is commanded to max.
Just to be sure it’s 5kg with the battery (take-off-weight)?
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Yes. The total weight (including the battery) is 5 kg. With voltage compensation enabled, the flight time is only about 2 minutes. We tried disabling voltage compensation to improve endurance, but the drone crashed as a result.
Are you saying that the motors will suddenly stall once they exceed a certain RPM?
No. That is dangerous, you should only deplete batteries to a certain point. To increase endurance you need to reduce weight or improve efficiency.
No, it is saying that the ESC is overloaded and shuts down due to temperature.
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Could you please explain how you concluded that there was an overload and over-temperature condition? From my analysis of the graph above, I see that the current suddenly dropped to zero. Did you draw the conclusion of overload/over-temperature from this specific point?
Additionally, if that is the case, how can we avoid this? Would limiting the value of ‘MOT_SPIN_MAX’ help prevent this issue?
You avoid the problem by:
- Reduce the weight of the drone (best option), or
- Increase the efficiency of the propulsion system (second best option), or
- Increase the cooling of the ESC and motors (not as good as the others).
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Normally, my operation is quite gentle with the throttle around 40%. However, during this specific flight, my maneuvers were more aggressive, causing the throttle to reach 70%.
Years of experience with this failure mode.
From your first graph, with the command to Motor 4 going high, that says that the flight controller is asking for more thrust from that motor than it is receiving. It could simply be that the control line for that motor became unplugged (very unlikely here due to the 4in1), or the supply lines to that motor becoming disconnected (possible but you’d be able to tell after the fact), or more likely overdriven motors leading to temperature excursions, cooking the motor and seizing it, and or causing the esc chip to self protect due to temperature (and it’s a 4in1 so you lose all 4), or the power supply feeding the motors quits while keeping the avionics alive, also unlikely)
Your current readings drop after because the motors aren’t spinning anymore, which is expected, but this signal alone is unlikely to tell you which part of the system caused the failure.
If the propellers are too big for your motors, then you can end up cooking things because your propulsion system is trying too hard. Things might be fine at hover, but not if you go harder.
As others have said, buy eCalc and learn it.
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This is mostly irrelevant. It’s simple. This craft is too heavy for the components and battery power you have. It needs to lose a significant amount of weight to be stable with Arducopter.
5 kg is at limit of 7" drone, the Motor 4 output reaches 85% throttle at some points, and is loaded more than others.
You can enable bdshot edt, or read your ESC data via telemetry wire, your ESC supports temperature readouts afaik.
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Check your center of gravity as well.
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All you need to see is Hover @ throttle (linear) to know this craft is overweight. It should be 50% or less.
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Thank you for your technical recommendations
Thanks for your analysis. I’m going to run the test.
Obviously I was referring to eCalc.
Or, you can look at Thrust:Weight. 1:4 to 1 is not going to work.
So, before you can do anything else this needs to be addressed.
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With very little time, I could only take a quick look at what was discussed. I believe that my colleagues’ comments about insufficient motorisation (motor and/or propellers and/or ESC) are the most likely answer.
What I want to add is that although ECALC is a great tool, it is still only a simulation/estimate. Sometimes it will be very accurate, and other times (as in this case) there will be a huge difference. According to ECALC, your UAV will have a maximum (electrical) power of 840.4 W. The reality is that it was 1525.58 W (maximum value) and 1168.13 W (average value). Clearly, ECALC’s proposal is far below reality, and if you followed that proposal, your UAV is underpowered.
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