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Jul 15, 2012, 08:43 AM
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nicnaimless's Avatar
Quote:
Originally Posted by blade strike View Post
Are you sure your Z value is correct? It seems with batteries that low it would atleast be around -3 -4?

Something you might want to look at
I've always understood the values to represent the distance to the center of the craft. Not actual weight distribution. I don't think the value should change if the battery was mounted 12 inches below the frame or 3 inches to the right of center. The value needs to be changes in relation to the distance the IMU is from center of the aircraft. I don't believe we are concerned with weight distribution here.... Please correct me if I'm wrong.
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Jul 15, 2012, 08:46 AM
DJI Testing / US Support
blade strike's Avatar
Sorry to say yoou are wrong They want distance to the CoG
Jul 15, 2012, 08:49 AM
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nicnaimless's Avatar
Quote:
Originally Posted by blade strike View Post
Sorry to say yoou are wrong They want distance to the CoG
So if you added a big camera mount to the bottom of your craft you would change your Z value? Is this what you are doing?
Jul 15, 2012, 09:01 AM
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VerticalVue's Avatar
Quote:
Originally Posted by nicnaimless View Post
So if you added a big camera mount to the bottom of your craft you would change your Z value? Is this what you are doing?
That is correct. I fly with camera ballast so that i dont have to keep changing settings. Its all in the manual....
Jul 15, 2012, 09:10 AM
DJI Testing / US Support
blade strike's Avatar
Quote:
Originally Posted by Bengit View Post
That is correct. I fly with camera ballast so that i dont have to keep changing settings. Its all in the manual....
What he said ^^^^^
Jul 15, 2012, 09:17 AM
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nicnaimless's Avatar
Quote:
Originally Posted by Bengit View Post
That is correct. I fly with camera ballast so that i dont have to keep changing settings.
This is very interesting. I think we have a language issue in the manual. You can hang a lipo off one arm of a tuned WKM craft and it will hold position the same as if the craft was balanced perfectly. All this without changing the X Y or Z values. The GPS and Compass are not concern about the center of gravity but concernd with the center of the craft. GPS and compass are measured the same as IMU. I think this language problem in the WKM manual has caused A LOT of headaches. Once WKM knows the center of the craft it's good to go. I've never adjusted these from initial setup and I swap out little point and shoot cameras all the way up to Pro cameras over 4 lbs. It flies the same. Of course I adjust gains but IMU just wants to know where the center is not where the weight is.

Hmmmm.... I think DJI wrote CoG when the IMU is mostly concerned with CoC.
Jul 15, 2012, 09:28 AM
Registered User
When i first got it, i just placed my IMU dead centre, never added values, as i saw it, there were no values to add as the centre point is the CoG point, as for GPS, what are we saying exactly?

If the GPS is set to the rear and up, do i measure its distance from the CoG and enter a minus value? and measure distance up, then enter a Minus figure?

never did this earlier, but all used to be fine.
Jul 15, 2012, 09:28 AM
Registered User
bcollydas's Avatar
OK Blade then help me out here.
This is a quick diagram of my setup.
The bird is at work and I don't have it in front of me.
According to the diagram, what are the position numbers from the IMu and the GPS?

Right now I have my GPS set at -3cm for the Z axis.

Cheers
Bill
Jul 15, 2012, 09:35 AM
Registered User
so this pic, what would my values be for the GPS negative?

Centre is also CoG
Jul 15, 2012, 09:36 AM
Registered User
VerticalVue's Avatar
Quote:
Originally Posted by nicnaimless View Post
This is very interesting. I think we have a language issue in the manual. You can hang a lipo off one arm of a tuned WKM craft and it will hold position the same as if the craft was balanced perfectly. All this without changing the X Y or Z values. The GPS and Compass are not concern about the center of gravity but concernd with the center of the craft. GPS and compass are measured the same as IMU. I think this language problem in the WKM manual has caused A LOT of headaches. Once WKM knows the center of the craft it's good to go. I've never adjusted these from initial setup and I swap out little point and shoot cameras all the way up to Pro cameras over 4 lbs. It flies the same. Of course I adjust gains but IMU just wants to know where the center is not where the weight is.

Hmmmm.... I think DJI wrote CoG when the IMU is mostly concerned with CoC.
Refer to pages 11,12 and 13 of the Manual 2.9. Everything refers to the C of G, its makes sense....If you have never compensated for Cg (large) changes I would suggest that you have been very lucky. The M will compensate for small changes.

I always try to get my Cg at aircraft centre (X and Y), this makes life easy when taking measurements, the only problem comes with estimating the Z value...this is the one that in most affected by increasing battery weight/adding gimbals and cameras.

The IMU and GPS want/need to know where the copter Cg is, NOT the CoC. Cheers
Jul 15, 2012, 09:37 AM
Im the eye In the sky
epedemi's Avatar

Perfect flyer


Ok guys...

I dont think perfect is a term in this business... But I think I have achieved something very close to it.

Firmware 5,12

This is in windy conditions.
Gps-atti mode.
Frame = Dji F550
AUW = 2,5 kilos.
Graupner 10x5
Maytech esc = 30amp.
Zippy flightmax 5800
Torxpower ( tigermotor ) 2216 ( 900kv )
Gymbal enabled.
Last edited by epedemi; Jul 15, 2012 at 09:44 AM.
Jul 15, 2012, 09:42 AM
Registered User
bcollydas's Avatar
do you have a picture of the craft?
Jul 15, 2012, 09:43 AM
Registered User
VerticalVue's Avatar
Quote:
Originally Posted by Davebbb View Post
so this pic, what would my values be for the GPS negative?

Centre is also CoG
Assuming Cg is at centre then the GPS would have negative X and Z.
Jul 15, 2012, 09:45 AM
Registered User
Quote:
Originally Posted by Bengit View Post
Assuming Cg is at centre then the GPS would have negative X and Z.
okay, thanks Bengit
Jul 15, 2012, 09:47 AM
Registered User
Quote:
Originally Posted by epedemi View Post
Ok guys...

I dont think perfect is a term in this business... But I think I have achieved something very close to it.

Firmware 5,12

This is in windy conditions.
Gps-atti mode.
Frame = Dji F550
AUW = 2,5 kilos.
Graupner 10x5
Maytech esc = 30amp.
Zippy flightmax 5800
Torxpower ( tigermotor ) 2216 ( 900kv )
Gymbal enabled.


Correct me if I am wrong but do you have the IMU 4cm below your CG?


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