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Old Mar 07, 2014, 01:54 PM
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Wobble Issue

It sounds like my weekend is getting busy.

I'll be doing a lot of trouble shooting this weekend, and I'll do my best to record what I do, and the results that I get. I have a Bluetooth module on its way from Witespy, so that'll get here some day, and today after work I am headed to Costco to look at their offerings of Android tablets, so that should help a little.

Things to do:
-check motors individually, with and without props. What should I be looking for in regards to a motor misbehaving besides a balance issue?
-run up quad with all motors/props and move on all axis to see if I can induce a wobble.
-try reducing Ps to see if that makes any difference.

Anything else I am missing?

I'll provide updates throughout the weekend. I'm confident that we'll get this sorted, and I'm very thankful for all of your help and suggestions.
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Old Mar 07, 2014, 02:20 PM
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Quote:
Originally Posted by kapu View Post
motopreserve - There are three lines to enable the ESC calibration. In my MW code, they look like this by default:

#define ESC_CALIB_LOW MINCOMMAND
#define ESC_CALIB_HIGH 2000
//#define ESC_CALIB_CANNOT_FLY // uncomment to activate

So all I have to do is uncomment the last line and flash to calibrate. Then I recomment and reflash. That's it.
That's what I did. Thanks for the clarification!
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Old Mar 07, 2014, 02:25 PM
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Another quick question: I have been testing by doing ACC and MAG calibration while on the deck which is the closest thing to perfectly level for me. Then after it calibrates, I pick it up and set it on the driveway - which isn't horrible, but is definitely not as level.

Will this throw off the "level?" Am i better off doing the calibration in the driveway on the slightly unlevel ground? I am having some drift - but it's hard to tell what's causing it. Not sure if this discrepancy would cause it, but I'd like to rule it out if I'm causing myself issues.
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Old Mar 07, 2014, 03:05 PM
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I don't think you ever need to recalibrate ACC or Mag, unless you reflash firmware. But remembr that gyros are calibrated every time you power up. You don't need to be level for this, but you do have to be stationary. If you are moving the quad during power up (and how do you avoid this really, when plugging in the battery pack), you can screw up the gyro calibration. I was having problems with this for a while. I would set everything up on my work bench at home, then when I went to the field and plugged in the battery, my BT GUI would show everything off, and the quad would drift like crazy. I finally enabled this line in config.h:

#define GYROCALIBRATIONFAILSAFE

and I never had the problem again. This setting detects motion during gyro calibration and repeats it if there is motion. You can plug the battery in and set it on the ground, and it will calibrate properly. Something worth trying.
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Old Mar 07, 2014, 03:18 PM
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Quote:
Originally Posted by kapu View Post
motopreserve - There are three lines to enable the ESC calibration. In my MW code, they look like this by default:

#define ESC_CALIB_LOW MINCOMMAND
#define ESC_CALIB_HIGH 2000
//#define ESC_CALIB_CANNOT_FLY // uncomment to activate

So all I have to do is uncomment the last line and flash to calibrate. Then I recomment and reflash. That's it.
If you're using the default value of MAXTHROTTLE, which is 1850, then using the code as above will calibrate the ESCs to expect 2000 for full throttle while the FC will only output MAXTHROTTLE (1850).

To get full throttle range, the code above should be

#define ESC_CALIB_HIGH MAXTHROTTLE
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Old Mar 07, 2014, 03:22 PM
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Kapu, I was recalibrating because I just had to reflash die to the ESC calibration I did following your directions. I'll try that code for safety's sake.

Moto (am I the "other Moto???),

To confirm, that line you listed replaces the 2nd line???
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Old Mar 07, 2014, 03:24 PM
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Quote:
Originally Posted by motopreserve View Post

To confirm, that line you listed replaces the 2nd line???
yes.
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Old Mar 07, 2014, 03:33 PM
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Originally Posted by motopreserve View Post
Moto (am I the "other Moto???)
"The name so nice, when you say it twice"

Madagascar - Moto Moto scene (0 min 52 sec)
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Old Mar 07, 2014, 03:39 PM
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Originally Posted by scf2k View Post
yes.
Great. Thanks!
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Old Mar 07, 2014, 03:55 PM
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[QUOTE=Moto Moto;27720499]If you're using the default value of MAXTHROTTLE, which is 1850, then using the code as above will calibrate the ESCs to expect 2000 for full throttle while the FC will only output MAXTHROTTLE (1850).

Good catch Moto-squared. My Maxthrottle is set at 2000, but that's because I changed it. I wonder why the default value for ESC_CALIB_HIGH isn't MAXTHROTTLE?
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Old Mar 07, 2014, 04:03 PM
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[QUOTE=kapu;27720862]
Quote:
Originally Posted by Moto Moto View Post
If you're using the default value of MAXTHROTTLE, which is 1850, then using the code as above will calibrate the ESCs to expect 2000 for full throttle while the FC will only output MAXTHROTTLE (1850).

Good catch Moto-squared. My Maxthrottle is set at 2000, but that's because I changed it. I wonder why the default value for ESC_CALIB_HIGH isn't MAXTHROTTLE?
Yep, good call Moto. Just changed it. Got a chance to do a little PID testing since it broke the 32 degree mark here today. I can't tell if I'm going round and round or getting somewhere...it's definitely one or the other!

Thanks for all the help folks.
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Old Mar 07, 2014, 05:51 PM
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Quote:
Originally Posted by kapu View Post
Good catch Moto-squared. My Maxthrottle is set at 2000, but that's because I changed it. I wonder why the default value for ESC_CALIB_HIGH isn't MAXTHROTTLE?
I wonder the same thing.
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Old Mar 07, 2014, 06:17 PM
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It's not MaxThrottle because you want headroom between maxthrottle and 2000. Scenario: You're at full throttle and want to go straight up. Your bird is not perfectly balanced. If you're at 2000 for max throttle, then the motor has no headroom to spin one faster, only slower. This could result in your bird going sideways and you have no way to adjust.
Having a maxthrottle lower than the capabilities allows the multirotor to keep itself at an angle in a high throttle situation. i personally set mine to 1950 or 1900 depending on the model and flying style I will use. It's always good to have some leeway for the controller to keep it stable.
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Old Mar 07, 2014, 06:54 PM
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That's pretty interesting 1eleven. So the ESC_CALIB_HIGH needs to be the true maximum throttle (2000 usually), but there are reasons to back off the MAXTHROTTLE setting, which is the maximum throttle that the stick can send. You are saying that the FC can still access that delta between MAXTHROTTLE and ESC_CALIB_HIGH to maintain stability. I did not know that.

I should probably consider backing my MAXTHROTTLE off slightly, though I don't peg the stick very often..
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Old Mar 07, 2014, 07:00 PM
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Quote:
Originally Posted by 1eleven View Post
It's not MaxThrottle because you want headroom between maxthrottle and 2000. Scenario: You're at full throttle and want to go straight up. Your bird is not perfectly balanced. If you're at 2000 for max throttle, then the motor has no headroom to spin one faster, only slower. This could result in your bird going sideways and you have no way to adjust.
Having a maxthrottle lower than the capabilities allows the multirotor to keep itself at an angle in a high throttle situation. i personally set mine to 1950 or 1900 depending on the model and flying style I will use. It's always good to have some leeway for the controller to keep it stable.
That's what i believed at one time too, but MultiWii never actually outputs throttle levels above MAXTHROTTLE. You can see it on the GUI.

It maintains stability by reducing the opposite motor at high throttle settings.
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