Hi everyone. Yesterday I did a autotune flight with the X8 drone that me and my team are building.
Specs:
tarot 17 inch carbon props
tarot martin 4008 330kv motors
double tekko32 f4 4in1 mini 45a esc (one connected to top motors and other to bottom motors)
Matek H743 mini V3 FC
TOW 4.5kg in this flight
It was maybe the 4th autotune flight of this drone and before there was never any problem. However, this time when doing the pitch axis autotune the motors shutdown mid-air and it fell from an height of around 1.5m.
Our luck is that it seems it only shutoff the bottom motors because it fell leveled and had no damage. It seems like the 4in1 esc connected to the bottom motors had a problem but we can´t figure out what it was. Esc temp was around 80ºC and then the telemetry froze for a few seconds when it failed.
However, we already tested the motors and esc again and everything is working as it should. The drone flies like anything happened. Seems like the esc rebooted in-flight but we see no reason why. This said, even if this esc had rebooted, why did the drone fell and did not keep flying? It surely has the power to fly with only 4 motors.
If somebody could spend sometime analysing the log and pointing me to the possible problem I would be very gratefull.
Edit: While disassembling the drone to check for possible problems we found a loose motor signal wire from the 4in1 esc to the fc. We are not sure if this happened during the disassembly or if the wire was already damaged and making bad connection. However, because all four motors connected to this 4in1 esc failed at the same time and not just this one motor, we think this wire may be damaged during disassembly and should not be the cause. We believe that even if this motor wire was making bad connection, a problem would only manifest in this specific motor and not the entire 4in1 esc board Besides this, the motors were tested before the disassembly and everyone worked ok.
I understand what you say. I thought setting ATC_RATE_FF_ENAB to 0 was not a crucial part. Despite that the drone already completed many autotunes without issue.
The loose motor cable was the only wrong thing that we found but we are not sure that it is the smoking gun. It may have come loose during disassembly. Shouldn’t a loose motor just cause problems in that specific motor and not on all motors connected to that 4in1 esc?
On your first post you said that all four bottom motors stopped simultaneously.
Hence the probability that the cable got loose is high.
In the log you say that the telemetry of all four motors also got lost. The the cable that got loose is the GND cable, it could have been the cause.
The wire that was loose was the one connected to M4 position in the plug and not the GND. Do you still thing a bad contact in this wire could make all motors connected to this board stop and not just the one connected to M4?
It seems both 4in1 ESCs lost voltage, signal or reset, but the main voltage/current sensor did not. The flight controller did not falter and it was still sending commands to the ESCs and logging everything else.
So maybe a bad ground/0v connection, or something somewhere got too hot.
Are the ESC small signal ground wires connected to the servo output ground terminals?
Make sure the only connector in the main supply is directly to the battery and everything else is soldered, no string of XT60’s one after the other.
Hi @xfacta! Thanks for your time analizing the log.
These are exactly the graphs that I have been looking at without arriving to a definitive conclusion.
We did not find any damaged ground wire but can be an option. In terms of temperature the esc only got to 85ºC max. I don´t think this is enough to shut down or is it?
One ESC signal ground wire is directly connected to the servo output ground terminal in the FC. However, after this question me and the team realized the other ESC has signal ground wire connected to a ground bus shared with other sensors and this ground bus is connected to a normal ground port in the FC. Could this be a problem?
This is also an interesting question. For ease of maitenance we decided, while building this drone, to connect the battery using a XT90 and then Y split to two XT60 and then solder directly to the ESCs with the capacitors soldered also directly to the ESCs pads. Could this also be a problem?
The BLHeli software comes default with temp protection at 140ºC. I lowered it to 100ºC. So I don´t believe it would shutdown at 85ºC. I also investigated the datasheet of the F4 MCU in this ESC and it states it works well until 120ºC.
Next time me and my team disassemble the drone for improvements I will post.
True. And BLHELI32 will slowly limit the output too, not just cut out.
And these little MCUs lock up at about 120°C too, so if temperaturewas an issue it would be unlikely to just reset and return to normal operation within 3 seconds.
So the cut out you experienced is something else.
From the BLHELI32 manual:
/*
The ESC measures temperature within the MCU and limits motor power if the temperature is
too high. Motor power is limited over a range:
- If the temperature is above the threshold, motor power begins to be limited.
- If the temperature is above the threshold plus approximately 15°C, motor power is limited
to 25%. Motor power is not limited below 25%
*/
I wouldnt have any connectors at all in the power wiring, except where you need a main battery connector of course.
The XT60’s for example have a PEAK current rating of 60 amps, the continuous rating is 30 amps. They may still get hot and fail - you have to regularly check their pins are still tight, and re-tighten them if necessary. Use a small flat-blade screw driver (or similar) to carefully spread the split male pins so they grip tight in the female sockets.
Ok. We will check again if the XT60s are in good condition and if possible remove them as you suggest. Still, after reading the post you mentioned I think the ESC signal ground wire situation is the most problematic and we will surely change that.
Greetings ! I think the first thing to do is replace the 4in1 board, check the main power supply cables, batteries/4in1 board, correct power cable section, advice from a manufacturer of large multirotors for many years, use separate motor and ESC power plates.
