strange behaviour of pixhawk-request help to understand

Hi

I am building a 1300mm octocopter with 30AH lipo. I want to be using a tegra tx1 for onboard visual processing coming from a sony a6000. 

I have built the drone and assembled it. I have configured it as usual. I was using the external compass on the m8n gps. and when the compass calibration happened both of them had similar reading all under 150. I have also done a compass motor calibration for the offset.

however when I took it to the field and wanted to test it in autonomous mode, it started behaving weirdly. below is the auto diagnosis of the data log and also please find attached the flight log.

I fail to understand what could have gone wrong. I would appreciate any help solving it. I wish to fly the machine and then work the tegra part.

Size (kb) 856.1298828125
No of lines 10433
Duration 0:00:28
Vehicletype ArduCopter
Firmware Version V3.5.3
Firmware Hash 1a85c237
Hardware Type
Free Mem 0
Skipped Lines 0
Test: Autotune = UNKNOWN - No ATUN log data
Test: Brownout = GOOD -
Test: Compass = FAIL - Large change in mag_field (257.75%)
Max mag field length (1112.76) > recommended (550.00)

Test: Dupe Log Data = GOOD -
Test: Empty = GOOD -
Test: Event/Failsafe = FAIL - ERRs found: CRASH GPS_GLITCH
Test: GPS = UNKNOWN - join() takes exactly one argument (2 given)
Test: IMU Mismatch = WARN - Check vibration or accelerometer calibration. (Mismatch: 0.81, WARN: 0.75, FAIL: 1.50)
Test: Motor Balance = FAIL - Motor channel averages = [1722, 1684, 1360, 1314, 1480, 1441, 1754, 1650]
Average motor output = 1550
Difference between min and max motor averages = 440
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 = WARN - VCC min/max diff 0.563965v, should be <0.3v

thanks in advance 

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Hi Javier,

Thanks for the Suggestion. I shall check on the Battery and the Motors. But how do you explain the volatility in the voltage and the magnetic field. some flights show good voltage some show a bad difference and same is the case with eh magnetic interference

Cheers

Javier Cerna said:

Hi,

Judging from your flight log, you have a really high voltage drop. I'm not sure if that's the issue, but going from 24 V to 17 V on launch seems unusual. Maybe the C parameter of your battery is too low, or they are not in good shape. The peak of 90 A seems to cause this voltage drop, but the voltage drop is too high to be acceptable.

Regarding the motor balance, it could be that your motors are indeed not well balanced (test them with a level tool, just in case).

Best,

Javier

moriarty said:

HI all

today I performed my flight after much suggested changes in the power module and other power issues.

FIRST FLIGHT:

Test: Autotune = UNKNOWN - No ATUN log data
Test: Brownout = GOOD -
Test: Compass = FAIL - Large change in mag_field (59.65%)

Test: Dupe Log Data = GOOD -
Test: Empty = GOOD -
Test: Event/Failsafe = FAIL - ERR found: CRASH
Test: GPS = GOOD -
Test: IMU Mismatch = GOOD - (Mismatch: 0.46, WARN: 0.75, FAIL: 1.50)
Test: Motor Balance = FAIL - Motor channel averages = [1768, 1679, 1535, 1441, 1543, 1457, 1736, 1726]
Average motor output = 1610
Difference between min and max motor averages = 327
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 = WARN - VCC min/max diff 0.338379v, should be <0.3v

SECOND FLIGHT:

No of lines 5584
Duration 0:00:13
Vehicletype ArduCopter
Firmware Version V3.5.4
Firmware Hash 284349c3
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 (1.09%)

Test: Dupe Log Data = GOOD -
Test: Empty = FAIL - Empty log? Throttle never above 20%
Test: Event/Failsafe = FAIL - ERR found: CRASH
Test: GPS = GOOD -
Test: IMU Mismatch = GOOD - (Mismatch: 0.14, WARN: 0.75, FAIL: 1.50)
Test: Motor Balance = WARN - Motor channel averages = [1231, 1229, 1167, 1176, 1220, 1216, 1253, 1201]
Average motor output = 1211
Difference between min and max motor averages = 86
Test: NaNs = GOOD -
Test: OpticalFlow = FAIL - FAIL: no optical flow data

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

THIRD FLIGHT:

No of lines 51355
Duration 0:05:26
Vehicletype ArduCopter
Firmware Version V3.5.4
Firmware Hash 284349c3
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 (9.63%)

Test: Dupe Log Data = GOOD -
Test: Empty = GOOD -
Test: Event/Failsafe = FAIL - ERR found: CRASH
Test: GPS = GOOD -
Test: IMU Mismatch = GOOD - (Mismatch: 0.19, WARN: 0.75, FAIL: 1.50)
Test: Motor Balance = WARN - Motor channel averages = [1196, 1268, 1246, 1289, 1178, 1237, 1179, 1277]
Average motor output = 1233
Difference between min and max motor averages = 111
Test: NaNs = GOOD -
Test: OpticalFlow = FAIL - FAIL: no optical flow data

Test: Parameters = FAIL - 'THR_MIN' not found
Test: PM = GOOD -
Test: Pitch/Roll = GOOD -
Test: Thrust = GOOD -
Test: VCC = WARN - VCC min/max diff 0.362548v, should be <0.3v

Now firstly all these three flights were on the same machine without changing anything on the machine, except the first flight was where the drone took off and crashed and the following two were flights with the drone tied down(bench tested). I fail to understand the following:

1) The volatility in the vcc when its all the same battery(TATTU 30AH 6S) same current sensor(ATTOPILOT 180AMP).

2) The volatility in the magnetic field.(my last bench tests, to which I uploaded the logs just a while ago, showed the magnetic fields in check when throttled all the way up and down and thru the other channels of roll/pitch/yaw.however today all of them had different values on the exact same setup)

3) the second and the third flights were actually bench tests with the drone tied down. I fail to understand why it has a crash error. further, I had the same issue bench testing the drone the other day, when it was absolutely static and tied down . still  had the same error message. following is a read from that log

No of lines 10375
Duration 0:00:28
Vehicletype ArduCopter
Firmware Version V3.5.4
Firmware Hash 284349c3
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 (1.91%)

Test: Dupe Log Data = GOOD -
Test: Empty = GOOD -
Test: Event/Failsafe = FAIL - ERR found: CRASH
Test: GPS = GOOD -
Test: IMU Mismatch = GOOD - (Mismatch: 0.18, WARN: 0.75, FAIL: 1.50)
Test: Motor Balance = FAIL - Motor channel averages = [1570, 1422, 1558, 1453, 1386, 1209, 1369, 1605]
Average motor output = 1446
Difference between min and max motor averages = 396
Test: NaNs = GOOD -
Test: OpticalFlow = FAIL - FAIL: no optical flow data

Test: Parameters = FAIL - 'THR_MIN' not found
Test: PM = GOOD -
Test: Pitch/Roll = GOOD -
Test: Thrust = GOOD -
Test: VCC = FAIL - VCC below minimum of 4.6v (4.485938v)

4) I don't understand why all these flights have the following error messages:

a) Test: Motor Balance = FAIL - 

b) Test: Parameters = FAIL - 'THR_MIN' not found

*any help is greatly appreciated. I have been trying to build this huge 1300mm octocopter with a 30AH battery and haven't been able to have a successful flight yet bcos of a lot of issues encountered 

Thanks in Advance

Cheers

To be completely honest, I'm not sure why that's happening. But try to flight the drone first in Stabilize Mode. In one of your logs, it seems that you start in Loiter and go up to 2 m and then crash it. I'm not quite sure how it influences the current, but maybe one of your gains is too high. To simplify the troubleshooting of your flight logs, try to make sure the drone flies well in Stabilize, please.

Best,

Javier

 Thanks Javier,

I shall do a flight test with stabilize mode see how that performs

Javier Cerna said:

To be completely honest, I'm not sure why that's happening. But try to flight the drone first in Stabilize Mode. In one of your logs, it seems that you start in Loiter and go up to 2 m and then crash it. I'm not quite sure how it influences the current, but maybe one of your gains is too high. To simplify the troubleshooting of your flight logs, try to make sure the drone flies well in Stabilize, please.

Best,

Javier

hello moriaty,

I have just looked at some of your latest logs. Same critical problem exists, bad voltage to the pixhawk, excessive battery voltage drop from idle to flight.

your power

bad%20power.PNG

power from my copter

good%20voltage.PNG

It is also very badly tuned apparently. The real attitude is not fallowing the desired attitude. Most likely because your large machine does not fit the default values. Do you have the corrrect props for your motors ect.? I don't know,but your machine has a lot of issues that would cause me to ground it until i figured it out. Below is a desired(by the FC) angle and the actual. Your copter and then mine as an example as with the power thing above.

bad%20tune.PNG

good%20tune.PNG

Other than that I don't know what, but I do know that that machine is not safe to fly as it is. Can you advise what your motor/props are. A picture of this machine would be nice.

Be carfull!

Hi Greg,

thank you for the insights. I am using a 30AH,25c TATTU battery with foxtech S5010 288kv motors with 17"*5.5" propellers.

Also do you think the magnetic field is in check now? and what is this about motor balance .I was not able to get that.

Regarding the tuning. I was hoping to auto tune the machine if it flies, but if the apparent reason for bad flight is its tuning, how do you suggest I solve it.

Also PFA the image of the copter and a video.The image has the older configuration of the copter. the lastest configuration after changing the FC has the FC right on the top plate, where the gps mast is screwed to. the battery is way more than 20 cms below the compass on the mast. the Fc is also quiet far away from the battery and reasonably far away from the PDB.



Greg Fletcher said:

hello moriaty,

I have just looked at some of your latest logs. Same critical problem exists, bad voltage to the pixhawk, excessive battery voltage drop from idle to flight.

your power

bad%20power.PNG

power from my copter

good%20voltage.PNG

It is also very badly tuned apparently. The real attitude is not fallowing the desired attitude. Most likely because your large machine does not fit the default values. Do you have the corrrect props for your motors ect.? I don't know,but your machine has a lot of issues that would cause me to ground it until i figured it out. Below is a desired(by the FC) angle and the actual. Your copter and then mine as an example as with the power thing above.

bad%20tune.PNG

good%20tune.PNG

Other than that I don't know what, but I do know that that machine is not safe to fly as it is. Can you advise what your motor/props are. A picture of this machine would be nice.

Be carfull!

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