DJI Naza-M with GPS Toilet Bowl Effect on a F550 everything stock 8" props

[bruce365]

Bruce – Adelaide Sth Australia:- Hi everyone thought I would share my experiences in the hope it migh help someone else:-

First time I flew my hex I lost control and it ended up in trees, broke an arm and prop.
I did not know why at the time, it was set on GPS Altitude hold, but it just did it own thing.
I know now it was suffering from extreme TBE.

I know to you experienced guys this is nothing new, been there done that, but for someone new its perplexing.
I read so much about how stable Naza was even in wind and how GPS/atidude hold mode was so good.
All my settings were as per manual with GPS sensor facing forward 0 degrees.

I did more reading in the forums and it seems even now there is still divided opinion about how to cure TBE.
I had to start somewhere, I knew all my configurations Radio and Naza assistant were correct.

I offset the GPS sensor by the Adelaide declination of 8 degreesEast, rotating sensor CLOCKWISE – this really had NO Effect at all.
Then 16 degrees, this was better, it would not initiate the TBE but when purposleyput into one it took 3/4 to 1 minute to sort itself out and stop (still doingquite a few rotations). Well at least I was on the right track and it isimproving.

Finally I set the GPS sensor to 30 degrees clockwise from the forward axis ofthe hex and all is cured, even if trying to manually initiate the TBE as soonas controls are released the hex stops. SUCCESS.

I question the logic 8 degrees East of actual magneticdeclination and the sensor having to be set to 30 degrees to totally neutralisethe effect, this does not make sense to me.

Anyway I'm glad its sorted and the hex is behaving as it should.
Thank for reading this and I hope it helps some who might have the same problem.
Regards - bruce

 

[Fxt4me]

I had the TBE when my sensor was at 0deg, my magnetic declination is about 16 too but I also have a better position lock at 20-30deg. I just put velcro on the bottom of the sensor so I can change it quickly. Bruce if you are using the DJI 8" props get some APC 8x6 or Grupner props ASAP.

 

[bruce365]

Hi Fxt4me, I used the original double sided tape supplied to attach the sensor and simply used a sharp kitchen knife to pry it loose and then reposition. Did not have any velcro at time of building but it is a very good idea. I have read about the broken props issue and ordered graupners 8" and 10" from electronica.com but they have not arrived yet and I was itching to try out my hex.

Perhaps the cold weather has an effect on the plastic props causing them to fracture and break. As mentioned above on my first flight (never having flown remote control devices before, my previous hobby being hovercraft) the hex crashed into trees at a high level. It broke an arm, the top fibreglass plate and one prop was mangelled and twisted but not actually broken. The temperature was a comfortable 21 degrees. As soon as the graupners arrive I will be putting them on the craft.

Regards - bruce

 

[E-Copter]

Hi,

did you calibrate the compass first and then had also to manualy adjust the magnetic declination offset of antenna ??

BEst regards,

Fabien

 

[bruce365]

Hi Fabien, Yes I did calibrate the compass (clockwise circular motion in horizontal and vertical, amber light then green then off) before my first flight. Each time I adjusted the magnetic declination offset, before flying the hex I would go through the calibration. As far as I know each time the GPS antenna is moved it should be calibrated before flying. I understand there one member who calibrates his copter every time he takes it out. Are you also having problems?
Regards - bruce

 

[E-Copter]

Hi Bruce,

i do not use Naza anymore but as far as i remember, when i did setup the Naza's GPS for my friends, once the calibration was done, it was necssary to check the magnetic declination of the area and tune the offset (strange after a compass.. calibration).

Something that shocked me is that none of my friend could tell me what was the exact position and height needed for the compass on the frame, which is more than important ( X, Y and Z offset from CG).

You can try for example to mount the compass on the frame CG location ( x,Y) and lower the mast as much as you can without having magnetic disturbance from frames and battery. YOu should note a much better behaviour of the frames when compass is closer to the center of gravity.

Regarding magnetic declination, i admit i do not understand how their compass calibration works as normally, if made correctly, you should not have to work on the offset, except if there is a exact position to respect of the compass height and location on the frames ?

Best regards,

Fabien

 

[Razzil]

I ended up attaching an arm from my hobbyking talon frame out the back and mounting the GPS, to be away from everything.
GPS worked perfect, Return to Home worked perfect ... then only recently I've been noticing the TBE.
So, like ya would, you move it as recommended and its perfect again.

My quesiton is ... why? does the GPS go bad?
For it to work perfect, then all of a sudden turn into this Toilet Bowl Effect, shouldn't be.

Having the cable stick out that tube, then be off-centered, annoys the @#$% outta me the most.

View attachment 6946

 

[E-Copter]

Hi,

this could be due to several things :

- GPS conditions : number of sats you catch and accuracy ( HACC). Over some accuracy level, then you will get a TBE.
- Batteries you use : some can generate strong EMI disturbing the compass that is enclosed with the GPS sensor)
- External EMI source: for example i can't lock ANYTHING decently in my garden due to my house metallic structure.. If i move away 40 meters all works.. Crap, but true lol ! I spent over 8 hours to try to setup a Compass and frame to get it locked and never succeeded at home. At the field down my hill, everything perfect in just 30 seconds !
-Your compass has moved on the horizontal plan( it's not levelled correctly after a landing or a shock or whatever ?

Hope you will find the little culprit
BEst regards,

Fabien

 

[bruce365]

Hi Fabien, I set my gps sensor lower than others I have seen on this forum. I attached it centrally at the front on the bottom plate to try and protect it a little more so it's not so vulnerable. I think I have the xyz correct (8cm, 0cm, -11cm) just followed instructions in manual.

Actually mounting the sensor at the centre of gravity is very difficult and not necessary because you can set the offsets in the software.

Regards - bruceView attachment 6957

 

[dhani_n]

Hi .. friends, I'm still new at this, I want to know the problem with DJI NAZA-M & GPS, I was confused by my DJI, why after hover hover around 2 ~ 3 minutes suddenly roll right and fall down, it happens always to the right, if there is a problem of the motor or ESC section right? ... I hope that from friends can provide a solution, Thanks

 

[Leslie LP]

Hi Bruce, I noticed that you have the GPS connected to the bottom plate. That will actually make your Z axis -7cm not -11cm. I have also seen these numbers on a few Youtube videos. But if you measure the height of the GPS antenna from the bottom of the provided stand its closer to 9cm not 11.
Just a thought.

 

[DesJardins]

You should be measuring from COG & that can change on what your flying.

 

[Leslie LP]

You should be measuring from COG & that can change on what your flying.

Nice rig, does look a lot more complicated than that Jpeg you showed above. So I guess when you have to fly with the GoPro you move the battery pack to the back to maintain CG at current center point? Does that change the Z axis a bit lower as well?

 

[Crash404]

Dipping problem

Hi

If you are using the DJI motors there is a easy fix. It turns out that there is a problem with the bullet connectors on the motors. They are not soldered on properly. I had to re-solder mine and it fixed the problem. Give it a try.

Hi .. friends, I'm still new at this, I want to know the problem with DJI NAZA-M & GPS, I was confused by my DJI, why after hover hover around 2 ~ 3 minutes suddenly roll right and fall down, it happens always to the right, if there is a problem of the motor or ESC section right? ... I hope that from friends can provide a solution, Thanks

 

[dhani_n]

Hi

If you are using the DJI motors there is a easy fix. It turns out that there is a problem with the bullet connectors on the motors. They are not soldered on properly. I had to re-solder mine and it fixed the problem. Give it a try.

Thank you Crash404 ... for your advice, I'll give it a try, all the conditions of the ESC to the motor conector no soldered ... and I think should replace 1 motor to the right .... thank you very much

 

[Crash404]

Thank you Crash404 ... for your advice, I'll give it a try, all the conditions of the ESC to the motor conector no soldered ... and I think should replace 1 motor to the right .... thank you very much

No Problem. Because the motors plug into the ESC it seems fine bit it turns out the gold connector on the motor wire that plugs into the ESC is covered with heat shrink and it hides the fact that in being mass produced the connectors are not loose but they make a bad connection. If you strip off the black heat shrink and then heat the gold connector until the wire can move out freely and then re-seat it the connection works properly. It is a good idea to replace the motor if it is faulty. Maybe try to swap it with one of the other motors and see if the problem moves with it. If it does it is a faulty motor or bad connection. If the problem stays at the same location but with a different motor it could be the ESC that is faulty. That way you don't replace the motor just to find it is something else.

 

[bruce365]

@ Leslie LP Hi Leslie, I supported my F550 and let it hang down vertically until my spirit level indicated that the top hexa plate was level vertically. The balance point I assume is my vertical "Z" axis center of gravity, I measured from that point to the center of the NAZA GPS sensor and that is how I arrived at 11cm. Please let me know if my methodology is wrong.
Regards - Bruce

 

[bruce365]

@ DesJardins, Hi Des, I notice your hexa is at an angle other than 90 degrees to the horizontal, is this the way you calculate your "Z" axis COG. Could you please explain.
Thanks - Rgards Bruce

 

[kev333d]

So your center of gravity in this picture is where? And are you balancing this? Whats the technique?

You should be measuring from COG & that can change on what your flying.