Hi everyone,

I am very newbie here, and would like to get some help on log analysis.

My drone is for agricultural application to spray pesticide, and crashed whiling I am returning to my side.

Drone Specification

- 10 Liter, 8 Axis 16 rotors.

- Max 29kg weight

- uses 2 parallel x 22000mah 6s 25C batterry

- runtime 5-8 min depen ding on half tank or full tank pesticide

Crash:

Flying about 3 min, whiling returning to my side.. 200-300m away from me.

It just crashed suddenly without no symptom of altitude drop or power decrease from battery low.

Literally fell down to the ground vertically.

After crash, my battery cell was 3.80-3.8 around 3.5 showing not any dead cells or significant cell difference (both battery)

Manufacturer Analysis Result:

Manufacturer analized log, and said it is because of battery low volatage showing sudden drop from 23 to 20V causing crash. because I did not use their brand battery, they keep saying it is not their drone issue, but my battery

I do not agree with them because I have been doing this for more than 3 years, and even worst battery (ballooned or not even have good cell balance) never had this kind of crash before.

I also belive that ESC or motor failed during the flight causing this crash, and battery amp draw caused by hardware (ESC, motor or FC)

Log Analysis (auto):

Log File C:\Users\MJ Park\AppData\Local\Temp\tmp26ED.tmp.log
Size (kb) 4766.681640625
No of lines 57556
Duration 0:03:07
Vehicletype ArduCopter
Firmware Version V3.4.6
Firmware Hash e707341b
Hardware Type
Free Mem 0
Skipped Lines 0
Test: Autotune = UNKNOWN - No ATUN log data
Test: Brownout = GOOD -
Test: Compass = GOOD - mag_field interference within limits (17.87%)
Max mag field length (626.75) > recommended (550.00)

Test: Dupe Log Data = GOOD -
Test: Empty = GOOD -
Test: Event/Failsafe = FAIL - ERR found: CRASH
Test: GPS = GOOD -
Test: IMU Mismatch = GOOD - (Mismatch: 0.53, WARN: 0.75, FAIL: 1.50)
Test: Motor Balance = WARN - Motor channel averages = [1553, 1547, 1500, 1563, 1521, 1578, 1534, 1531]
Average motor output = 1540
Difference between min and max motor averages = 78
Test: NaNs = GOOD -
Test: OpticalFlow = FAIL - FAIL: no optical flow data

Test: Parameters = FAIL - 'THR_MIN' not found
Test: PM = GOOD -
Test: Pitch/Roll = UNKNOWN - 'BarAlt'
Test: Thrust = GOOD -
Test: VCC = GOOD -

Mechnical Failure:

Battery Issue:

I am not very familiar with this and researched alot on the forum, but could not have any idea what should I see closely based on given parameters.

Please help me on this, so I can effeectively debate with manufacturer in terms of technical perspective.

Thanks

Views: 105

Attachments:

Reply to This

Replies to This Discussion

What voltage you see *after* the crash, is not very relevant, when the load goes away, the voltage will increase.

I would ask: is the voltage properly calibrated ?

I am asking because 22.8v(3.8v/cell) is the point at which it seems to enter  a VRS , and high throttle demand only reduces voltage.

During the VRS / and drop, the lowest voltage was 21.6v (3.6v/cell)

At the impact (showed in accelerometer data) the voltage dropped to 21v , but that's not relevant, as the motors got heavily overloaded by contact with ground at that point.

So my best guess would be if the voltage sensor were badly calibrated, and the voltage were too low.  otherwise, 3.6v/cell should not be too little on this rig that were flying at 35% throttle.

- it's a shame this RPAS don't have a current sensor, that would tell us valuable information about the power consumed during the final moments, a big drop in power would suggest battery issue.

Finally, the payload seem to slush around inside a lot, you might save some energy (and have better thrust surplus) by preventing that.

Sorry Andre K

My mistake to inform you wrong.

voltage after the crash was around 3.5 not 3.8

so you think this case is the battery issue?

Andre K. said:

What voltage you see *after* the crash, is not very relevant, when the load goes away, the voltage will increase.

I would ask: is the voltage properly calibrated ?

I am asking because 22.8v(3.8v/cell) is the point at which it seems to enter  a VRS , and high throttle demand only reduces voltage.

During the VRS / and drop, the lowest voltage was 21.6v (3.6v/cell)

At the impact (showed in accelerometer data) the voltage dropped to 21v , but that's not relevant, as the motors got heavily overloaded by contact with ground at that point.

So my best guess would be if the voltage sensor were badly calibrated, and the voltage were too low.  otherwise, 3.6v/cell should not be too little on this rig that were flying at 35% throttle.

- it's a shame this RPAS don't have a current sensor, that would tell us valuable information about the power consumed during the final moments, a big drop in power would suggest battery issue.

Finally, the payload seem to slush around inside a lot, you might save some energy (and have better thrust surplus) by preventing that.

Yes, with 3,5v with no load, it is very likely that the battery fell even below  3v with load.

There is one thing you could do:

power up the remains, and verify the telemetry-reported voltage using a multimeter.

If the telemetry voltage is not properly calibrated, and report higher than actual voltage, I would say it is the cause, or at least strongly contributing factor of the crash.

Reply to Discussion

RSS

Groups

Season Two of the Trust Time Trial (T3) Contest 
A list of all T3 contests is here. The current round, the Vertical Horizontal one, is here

© 2018   Created by Chris Anderson.   Powered by

Badges  |  Report an Issue  |  Terms of Service