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Permalink Reply by Ammar Husain on November 8, 2011 at 5:38pm

The same thing happened again.... Here are the logs:

MOT: 1337, 1349, 1381, 1313

ATT, -61, 156, 1566, 38, -636, 132

MOT: 1356, 1362, 1270, 1396

ATT, -113, 181, 1564, 293, 202, -30

MOT: 1315, 1373, 1370, 1330

ATT, -164, 173, 1565, 72, -338, 0

MOT: 1340, 1354, 1314, 1380

ATT, -125, 224, 1577, -63, -230, 26

MOT: 1356, 1344, 1323, 1369

ATT, -78, 328, 1628, -152, -1024, -270

MOT: 1337, 1307, 1274, 1478

ATT, 467, 1406, 1981, -1513, -2500, -857

MOT: 1438, 1207, 1207, 1707

ATT, 1236, 3081, 2690, -1441, -2500, -1215

MOT: 1424, 1207, 1272, 1772

ATT, 2054, 4734, 3406, -1986, -2500, -1653

MOT: 1485, 1207, 1332, 1832

ATT, 2891, 5809, 4167, -1733, -2500, -1966

MOT: 1476, 1207, 1332, 1832

ATT, 4127, 6120, 5200, -2040, -1944, -2488

MOT: 1454, 1207, 1444, 1832

ATT, 5896, 5836, 6439, -2500, -2500, -1079

MOT: 1383, 1207, 1207, 1597

ATT, 9294, 4896, 8227, -2500, -2500, -1942

MOT: 1077, 1077, 1077, 1077

ATT, 12795, 2901, 9978, -2500, -2500, -1676

MOT: 1077, 1077, 1077, 1077

ATT, 16241, 817, 10885, -2500, -2500, 364

 

Motor 4 gets a really high PWM when it stalls.. What could this be ?

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Permalink Reply by Ellison Chan on November 8, 2011 at 7:06pm

Those are the PPM values sent to the motor.  It goes up to max because the motor is stalled, and the APM increases the PPM to that motor thinking that side needs more power.  Is the motor or esc that's stalling getting hotter than the others, after this happens?

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Permalink Reply by Ammar Husain on November 8, 2011 at 8:15pm

Ummm not really.. It seems fairly normal when I stop it...

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Permalink Reply by Ellison Chan on November 8, 2011 at 8:51pm

I was thinking bad bearings causing the motors and esc to overheat.  However, since you say there's no overheating, could be a bad connection causing the motor to cut out.  Like I said, what it seems like is that the software thinks that there's not enough thrust at one motor and keeps trying to increase speed on that motor until the max is reached.  The APM has no feedback on the motor's actual speed, but from an error status point of view, it should be able to tell by the fact that one motor's output is so different from the other four that the Arducopter is in a bad state.  It seems that there's no code in the Arducopter, right now to detect this state and take corrective action. I'm not sure what corrective action can be done, except maybe disarm all motors so they don't continue to  run and cause more damage.  Maybe it's a feature we can request in the next release.

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Permalink Reply by Ammar Husain on November 8, 2011 at 9:01pm

Oh I see what you mean.. To think about it I have been getting some drift in the direction of motor 4. That is the motor 4 was dipping a little lower causing the quadrotor to translate. Could these be related problem?? Also how can I narrow down if it is my ESC or the motor that has the problem,so I can get spares accordingly.

Thanks

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Permalink Reply by Ellison Chan on November 8, 2011 at 9:16pm

First, I wouldn't continue to fly it, if this problem happens repeatedly.  Eventually, you will have a bad crash.

What I suggest is to first take all your propellers off, and then alternately swap the suspected bad motor with another motor on another arm.  If the problem follows the motor, then the problem is at the motor.  If the problem stays at the old arm, then it's at the esc.  Check all the power and connections from the esc to the motors, and look for bad connections.

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Permalink Reply by Ammar Husain on November 9, 2011 at 6:43am

I actually have it tied down right now.. So I ll try to narrow down between my ESC and motor... What surprises me though is that this does not happen that frequently but when it does, it ll stall for a few times back to back.

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Permalink Reply by Ammar Husain on November 9, 2011 at 8:20am

Hi Ellison, 

I ran it again tied down to some posts. This time seems like my motor 4 gave up as usual and then motor 2 did something weird...

MOT: 1361, 1331, 1285, 1331

ATT, 61, 67, 971, -64, 203, 60

MOT: 1340, 1328, 1342, 1302

ATT, 116, 368, 1081, -860, -1905, -274

MOT: 1387, 1215, 1207, 1545

ATT, 749, 1928, 1490, -1439, -2500, -390

MOT: 1449, 1207, 1207, 1634

ATT, 1071, 3364, 1791, -140, -2500, -318

MOT: 1365, 1337, 1207, 1663

ATT, -163, 2949, 1288, 1575, -242, 768

MOT: 1302, 1616, 1283, 1331

ATT, -795, 1492, 725, -3, 370, 1227

MOT: 1408, 1408, 1207, 1207

ATT, 142, 1015, 333, -2362, 76, 304

MOT: 1367, 1207, 1207, 1207

ATT, 890, 1334, 930, -437, -2437, -1090

MOT: 1077, 1077, 1077, 1077

 

Seems like 4 had recovered a little before I stopped it... Any ideas?

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Permalink Reply by Ellison Chan on November 9, 2011 at 8:46am

Now that you have it tethered, the motor logs are not going to help you diagnose the problem.  It's the same situation as the stalled motor.  The APM keeps trying to change the attitude of the quad, and increase the motor throttle, but being tethered, it doesn't change and the APM continues to feed throttle.

 

If the same motor keeps cutting out, then I would recommend replacing it.  If the motor on the same arm fails, and you've swap a known good motor there, it sounds like and ESC problem.  I would check all the solder connections to make sure nothing is loose.

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Permalink Reply by Ammar Husain on November 9, 2011 at 9:27am

Thanks Ellison! I ll try switching them around now and see where the problem lies..

BTW, does anyone know where I can find details on the different logs that I can collect. For example: I am not sure what each of the 8 values PM means. I looked up in the code and it says imu.adc_constraints or dcm.get_health.. However what do these convey??

 

Similarly for the Atiitude readings, I understand from the code that the first three are roll, pitch and yaw. However I do not know what rc.servo_out is??

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Permalink Reply by Ammar Husain on November 13, 2011 at 11:58am

So I took the props out and am now running the motors. And they seem to be working perfectly. Could vibrations cause motor to stall?? Since I see the arm 4 has slightly more vibration than the other three arms?

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