Build: S900, A2, GH4, Futaba 14SG

Here's a video the shows the problem...



You can see it starts off straight but then drifts to the right.  This happens no matter where or what direction I'm flying in.

* A2 has latest firmware (v2.7)
* Compass has been calibrated
* IMU has been calibrated
* GPS is currently pointing straight towards the front of the S900.  Also tried adjusting it slightly to the left (based on my location) but that didn't help either.
* Also thought the props might have something to do with it.  I've upgraded to the E1200 props and still have the problem.

The problem doesn't just create challenges with flying.  Because it's difficult to fly directly at or away from the subject all videos end up with a slight pan to them.

Has anyone seen this problem before?  Any help or suggestions are appreciated.

Here's what it looks like from the S900.  I'm trying to fly parallel to the guy cutting the lawn but you can see there's significant drifting to the right...

I have found that if you fly out and back several times in the same location the situation will self correct.  See if that works for you.  It does take about 3-4 trips out and back to see a difference.

Tahoe_Ed Posted at 2016-7-23 04:55
I have found that if you fly out and back several times in the same location the situation will self ...

I had been flying for a while when I took this video and had already done around 10 trips out and back.

Then if does not help, try to adjust the GPS puck based on the magnetic declination where you are located.  It can be more that just a little.  If that does not work, then I would suggest that you contact dji.com/support for additional assistance and possibly a RMA.

Tahoe_Ed Posted at 2016-7-23 08:22
Then if does not help, try to adjust the GPS puck based on the magnetic declination where you are lo ...

Thanks again for your reply Tahoe_Ed.  I had already tried that but it didn't help.

If there's a bad component, do you think it's the GPS COMPASS PRO PLUS?  I'm beyond the warranty period so hopefully can just buy the piece that's bad.

Since you have done the IMU calibrations, the Compass calibration and tried to physically adjust the GPS puck for declination, it could the the GPS or it could be the IMU.  At this point it is the process of elimination.  Let us know what finally works for you.

Tahoe_Ed Posted at 2016-7-24 08:20
Since you have done the IMU calibrations, the Compass calibration and tried to physically adjust the ...

Thanks again...  will start by replacing the GPS.

I replaced the GPS, did not fix the problem...



Note that if I fly in Atti mode it flies straight...



Also, if I use the IOC function - Banked Turns - it also flies straight.

На ваш компас может улавливать электромагнитные поля, которые возникают из проводов внутри модели. Вы сказали, что изменили ESC. Вы изменили что-то другое? Например, увеличение длины проводов от аккумулятора к ESC? Это может значительно увеличить магнитное поле, создаваемое ими рядом с компасом. Попробуйте провести провод, насколько это возможно от компаса. Используйте "бифилярно" (косичку) скрутить провода питания к двигателю. Обратите внимание на выравнивание воздушного винта, если бы вам пришлось снимать motomaunty.   В некоторых местах шайбу компаса приходится поворачивать больше, чем 30 градусов.

vladimir57 Posted at 2016-9-4 04:01
На ваш компас может улавливать электромагнитные поля,  ...

Thank you for your reply vladimir57.  I had to translate to English using google...

"On your compass can sense electromagnetic fields, which arise from the wires inside the model. You said that you changed the ESC. Have you changed something else? For example, increasing the length of wire from the battery to the ESC? This can greatly increase the magnetic field generated near their compass. Try to hold the wire as far as possible from the compass. Use "bifilar" (pigtail) to twist the power wires to the engine. Pay attention to the alignment of the propeller, if you had to shoot motomaunty. In some places, the compass puck has to turn more than 30 degrees."

I've had the S900 for over a year now and have always had this problem.  It occurred with the original props as well as the new E1200 props.  I've also had it setup as a two-person system (one radio to fly the other to control the gimbal) and have reconfigured the layout of the components (A2, Mark II, etc.) several times, all setups and configurations have resulted in the S900 drifting to the right.

What's interesting is that in GPS mode, using IOC - Banked Turn, the S900 does not drift to the right.  In this mode the S900 is not using the Yaw stick and is using 'Drift Damping'



From the A2 User Manual - "Once the aircraft performs side slip, adjust the drift damping value. Note that too big value may lead to aircraft vibration."  I wonder if this Drift Damping feature is correcting the problem I'm having when not using IOC.

I'll also take a look at the wiring, and, try mounting the compass at a different location on the top plate and see if that helps.

Dear "timonroesg", thank you very much for your reply!
  I understand and am sympathetic to your problem. Unfortunately, I do not know English. My native language is russian. It seems to me that programmatically You can not solve this problem. Let's think logically. In GPS mode off your model flies without departing from the course? If "YES" - is a consequence of magnetic fields.
Try to calibrate the compass only after the discovery of the satellites.
If there is no compass successful calibration, try to include a "black" wire from the battery last.
Try to move the compass as far away from the module "IMU" and from the motors Gimbal camera.
  It is possible that during transport in a vehicle, GPS compass is very close to the speaker system and feeling the effects of these components.
It is possible that in the ground where you calibrate the compass, are metal pipes for the irrigation system. I have encountered a problem when the compass is not working properly because of that.
  You might not see the display LED on the block "IMU"?
Are there any in a series of "green", "red" LED flash?
Maybe, in a series of LED flashes lies the answer to this question?

vladimir57 Posted at 2016-9-7 08:52
Dear "timonroesg", thank you very much for your reply!
  I understand and am sympathetic to your pro ...

Thanks again for your reply!  I will try your suggestions and report back anything that I find.

vladimir57 Posted at 2016-9-7 08:52
Dear "timonroesg", thank you very much for your reply!
  I understand and am sympathetic to your pro ...

Here's the layout of my components.



The compass was mounted at the center of the top plate.  I remounted it at the front of the copter.



Unfortunately, it's still drifting to the right.



I also recalibrated the compass at different locations in the field (after getting 14 satellites), and also flew in several directions.  Each time it still drifts to the right.

Have you tried to turn the GPS-compass to the left at an angle of 10-30 degrees? Your mount does not allow to do this without drilling additional holes in the drone. If you are flying directly into the "Atti mode", and "GPS mode", the model is rejected, then try to turn the GPS-compass deviation in the opposite direction from the direction at an angle of 30 degrees. You can use the correction for magnetic declination: http://www.ngdc.noaa.gov/geomag-web/#declination. Try using a higher mast for GPS-compass. Wish you luck!

vladimir57 Posted at 2016-9-21 12:22
Have you tried to turn the GPS-compass to the left at an angle of 10-30 degrees? Your mount does not ...

Thanks again vladimir57...  I appreciate your help on this.  Yes, I had to drill two holes in the top plate to remount the compass.  I've also tried turning the compass to the left based on my location...  this didn't work either.

I can try raising the GPS up higher but I think there's a faulty component...  assuming it's either the IMU or the Main FC unit.  Will need to decide how much more money/time I can invest into trying to resolve this issue though.

Tahoe_Ed Posted at 2016-7-24 08:20
Since you have done the IMU calibrations, the Compass calibration and tried to physically adjust the ...

Tahoe_Ed - I've replaced the GPS-Compass and that didn't fix the problem (see details above).  I'm now assuming I have a faulty IMU or maybe a bad Main FC unit.  Is there any way that you/DJI can send me an IMU that works, I'll try it out to see if it fixes my drifting problem, then pay you for it if it does.  If it doesn't fix the problem, I'll just ship it back.  I'll even take a used IMU if you know it's in good working condition.  I'd really like to get this resolved but it's difficult financially to continue paying for new parts that I don't need.

Timon: just a wild guess but I know my Naza Lite manual mentions magnetic fields, and magnetite (as though everyone is a geologist! )  What about trying a completely different flying location?

timonroecg@gmai Posted at 2016-9-21 21:18
Tahoe_Ed - I've replaced the GPS-Compass and that didn't fix the problem (see details above).  I'm ...

Iwould agree that it could be an issue with either the IMU or the Main Controller, but unfortunately those parts cannot be sent out and would require that the unit is sent in for further diagnosis and repair. Just to clarify, have you tried a completely different location like Beckler suggested?

Beckler Posted at 2016-9-21 22:57
Timon: just a wild guess but I know my Naza Lite manual mentions magnetic fields, and magnetite (as  ...

Beckler: thanks for the suggestion...  I've flown at several other locations and have had the drift problem at all of them.  The first video in this post is at a different location.  I also fly my Phantom, Inspire 1 and a F450 (Naza-M v2) in this park and none of them have this problem.

Try to place the Flight Controller "Naza" in the DJI S900. Each model has its magnetic field. Even being close to the wire, can change the flight characteristics and the course of your model. Do not despair! I think that the installation of Flight Controller "Naza" at  DJI S900 will respond to your question. Do not be afraid to experiment! With all my heart I wish you solve this problem!

vladimir57 Posted at 2016-9-23 03:29
Try to place the Flight Controller "Naza" in the DJI S900. Each model has its magnetic field. Even b ...

Thanks vladimir57...  I'm using the Naza on the F450 right now but when I get some time I'll give it a try.

Hi there ....just a thought ...looks like you have some awful vibration in your airframe , look at the left landing gear .Did you balance your E1200 props ...i did ..didn't require much but it will have an effect . Goodluck with it.

ckiffkool@talkt Posted at 2016-9-23 23:32
Hi there ....just a thought ...looks like you have some awful vibration in your airframe , look at t ...

Hey ckiffkool - thanks for the reply...  the first video in this post (with the shaky left landing gear) is from my original setup, which had the standard props that came with the S900.  When I upgraded to the E1200 props those vibrations went away.  I also epoxied the horizontal support bar that connects the left and right landing gear assemblies which probably helped as well.
How did you go about balancing your E1200 props?

Hi,

I used scotch tape and a tarot prop balancer . Easy to do .

I can not agree with the assertion that the right shift depends on the landing gear vibration or absence of a perfect balancing of propellers. A2 The controller is very well protected from vibration. Plastic propellers provide natural isolation. In many cases, the "jelly" video and "crazing" stabilization system "Gimbal" was eliminated using plastic propellers.
  Try it, without changing anything in the scheme, electric "S900", put on the platform already proven "Naza".
 I am sure that the shift to the right will disappear.
I wish you successfully solve this problem and to take another step towards a safe flight!

I confess to you that I have not been able to solve this problem for its "X6" ... In the module, "IMU" has a status display of this unit. Wherever occurred compass calibration (on the street or at home), but this would have to satellites would not have found the GPS module, no matter how many times calibrated IMD, the micro LED indicates one and the same sequence consisting of 9 outbreaks. The first outbreak - "Green", the second flash - "Red", the other seven outbreaks - "Green".
  Dear DJI, prompt, please, is this normal?

Dear "timonroesg"! You tell me, please, did you manage to solve the problem of displacement to the right flight at S900?
You do calibrate the compass after its rotation through a certain angle to the left?
Are you a calibrated module to him after that?
I am very interested in your results!
With all my heart I wish you success!

Hey vladimir57 - I still haven't figured this out and have done everything that I can think of (and that has been recommended to me) to correct it...  even replaced the GPS and that didn't work.  At this point I'm guessing I have a bad IMU or FC but don't have the time/money right now to purchase a new one.  I've got almost $10,000 (US) into this build so would really like to get this resolved some day.

Dear "timonroesg"!
Could you describe the sequence of a small LED display, which is located on the IMU module?
In all three (!!!) my A2 sets have this sequence.
The first outbreak - green, second - red rest seven - green.
This state does not depend on how many satellites found A2.
GPS compass calibration, the calibration of the IMU unit do not change the sequence of flashes.
What sequence of micro LED flashes IMU on your block?
The code of these outbreaks - the key to understanding our problem?
And, as an addition, I would like to ask you - did not occur if you have not controlled buildup of the model after a smooth flight?
The buildup with batteries fully charged?

timonroecg@gmai Posted at 2016-10-27 22:13
Hey vladimir57 - I still haven't figured this out and have done everything that I can think of (and  ...

I believe that the best course of action would be to send the unit in for repair. The technicians would be able to further diagnose and help rectify the issue.

Hey timonroecg, I've actually come across the exact same problem. s900, A2, drifting when trying to go straight, except mine tends to be to the left when going out and to the right when coming back. I've had the issue for awhile, but just realized today that it was probably related to the GPS being off. I've done a GPS calibration many times, but the problem persists, regardless of location. I even flew in in Hawaii a few months back and had the drifting issue. I know this post is pretty old, but curious if you ever came across a solution. I haven't re-calibrated the IMU yet, so that's my next step. Like you said it doesn't inhibit flying, its just annoying.

quality Posted at 2017-5-18 16:08
Hey timonroecg, I've actually come across the exact same problem. s900, A2, drifting when trying to go straight, except mine tends to be to the left when going out and to the right when coming back. I've had the issue for awhile, but just realized today that it was probably related to the GPS being off. I've done a GPS calibration many times, but the problem persists, regardless of location. I even flew in in Hawaii a few months back and had the drifting issue. I know this post is pretty old, but curious if you ever came across a solution. I haven't re-calibrated the IMU yet, so that's my next step. Like you said it doesn't inhibit flying, its just annoying.

Bought a new GPS/Compass, recalibrated the IMU many times and still not fixed.

Haven't used my S900 for a while and just bought the new Pixhawk 2.  Will give this a try and see if I can get the S900 to fly straight.

fansbf647da2 Posted at 2017-5-30 08:29
Bought a new GPS/Compass, recalibrated the IMU many times and still not fixed.

Haven't used my S900 for a while and just bought the new Pixhawk 2.  Will give this a try and see if I can get the S900 to fly straight.

When you lift the model into the air, pause for a few seconds. Is the model drifting? If not, start moving forward. Does the model deviate from the course? Very often, the drift disappears after such a hang above the start point. Check the alignment of the motors. You have a well-proven flight controller "Naza-M V2". You still have not decided to transfer it to the "S900"?
  Speaking about the "IMU" block, the flashes of its LED in such a sequence: "green", "red", and the other seven "green" ones - this is a normal indication for this device.