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Camera shake due to low torque in gimbal, camera drifts left
3270 20 2015-7-23
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aek
lvl.2

Sweden
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Edit (Aug 4 2015):
Seems the trouble I describe below is gone after the 1.3.20 firware upgrade on Aug 4 2015.
I have to verify this more, although the first tests is 100% successful.
Thank you DJI  





Dear DJI,
I have seen this problem since I received my unit on July 3.
The firmware and the Android app are the latest (updated before my first flight).

The symptoms:
It seems the gimbal is way to weak when it should pan to the right. Strangely it is firm in all other directions.

A very slight touch on the camera, panning it to the left, is enough to get it out of sync, and it does not recover. It stays pointing to the left.
In all other directions it is very firm, and immediately returns to the correct position after a slight push.

If the camera is slightly pushed, for example by using a finger or simply by a gust of wind while flying, forcing it to:

pan to the left- it does not return to the correct position, the motor seems to weak, the camera stays panned/pointing to the left
pan to the right- it immediately and firmly returns, but overshoots to the left and then only sometimes returns to the correct position
tilt down- it immediately and firmly returns to the correct position, no problem
tilt up- it immediately and firmly returns to the correct position, no problem
rotate CW- it immediately and firmly returns to the correct horizontal position, no problem
rotate CCW- it immediately and firmly returns to the correct horizontal position, no problem

The symptoms are completely consistent and fully repeatable.

Is this a hardware problem or should I wait and hope for a firmware update to fix this?

(Also, I have seen other posts on the forums mention that the camera gets stuck pointing to the left, so maybe it is not just my unit?)

Best regards
/aek


Edit 1 (July 24 2015):

I found a workaround: leave the copter on for 2 minutes, and then turn it off and then on
This is consistent.

Let the copter warm up for 2 minutes (just let it sit with power on, but props turned off), and then cycle the power off and then on.
The gimbal does now have power enough to hold the camera in all directions and is rock steady!
The power cycling seems essential for this to work. A gimbal auto calibration did not have any effect on the problem even when the copter had been warmed up.

My testing today consisted of 38 powercycles, in 5 sets, letting the copter cool down between each set for at least 30 minutes.

I did all testing with the transmitter turned off, except for when trying the gimbal auto calibrations.
It does not matter if the transmitter is on or off otherwise.

Whenever the copter has been turned off for a while, for example for 30 minutes, the problem will be back.
The procedure must then be repeated (warm up for 2 minutes, and then turn off and then on).

This leads me to think that there is some gimbal calibration going on at startup, that fails if the copter is not already warmed up before it is turned on.

So before every flight, I have to let the copter sit powered on for 2 minutes and then cycle the power off/on before start.

Also, the gimbal auto calibration does not help even if the copter has warmed up. A power cycle is still needed.
I tried this by letting the copter sit for 4 minutes with power on, then verified that the problem was still there, then did the auto calibration, and problem was still there after the calibration. Then I did a power off/on and the problem then disappeared as expected, and not due to the gimbal auto calibration.

Here is a what it looks like.
First when the copter has not been warmed up, and then after it has been warmed up.

2015-7-23
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aek
lvl.2

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Example:



Here the shaking is seen from the start, and corrects itself @19s into the video.
Also, another example starting @32s, does not correct itself.
2015-7-23
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aek
lvl.2

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Another example:
Note that it is not the copter that is shaking, but the camera gimbal drifting to the left while shaking.
Here the shaking starts @15s into the video, and corrects itself @27s

2015-7-23
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terrylewis
Captain
Flight distance : 3517287 ft
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United States
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There is a small set screw on the gimbal shaft that some P3s did not have Loctite applied and the set screw vibrates loose. Customer reports that their gimbal buzzed. Look at this article and see if it applies I any way:
Gimbal Buzz The set screw is well down the thread....
2015-7-23
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aek
lvl.2

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terrylewis Posted at 2015-7-24 04:01
There is a small set screw on the gimbal shaft that some P3s did not have Loctite applied and the se ...

Thanks, but I checked that screw and it was firmly seated. It does not seem to be the problem.
Also, my gimbal does not make any noise like that.

The problem with my unit seems to be that the pan-motor is weak, and strangely only weak in one direction (when panning right).

2015-7-23
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terrylewis
Captain
Flight distance : 3517287 ft
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Always worth a shot before you look to DJI Support for a repair.
2015-7-23
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chris
lvl.1
Flight distance : 25820 ft
Canada
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I just got my P3 and noticed that the wind really effects the gimbal. I keep getting "gimbal overload" notice in high wind.. If i YAW so the wind is pushing the P3 forward its seems to correct. I think it does this because the camera is hugely unbalanced and front heavy and the wind is just enough to then overload the motor. The motors are working overtime to keep the camera level and get super hot..  First it happened i thought i hit a bird or something and had a mini panic attack! Im going to try to add some weight to the back of the camera and see if that helps.
2015-7-23
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L8again
lvl.4

Canada
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Did you try a gimbal auto calibration?
2015-7-23
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chris
lvl.1
Flight distance : 25820 ft
Canada
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L8again Posted at 2015-7-24 06:40
Did you try a gimbal auto calibration?

Auto cali is only good for setting the motor tension which wont correct the balance as the balance is mechanical and not corrected with software
2015-7-23
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aek
lvl.2

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chris@leckieins Posted at 2015-7-24 08:25
Auto cali is only good for setting the motor tension which wont correct the balance as the balance ...

I have successfully calibrated the IMU and the gimbal many times, each time thoroughly leveling the unit on a table before calibration, with the table leveled with a spirit, etc

It seems the problem simply is that the gimbal pan motor does not deliver much power in the direction left to right.
If this "power balance" somehow can be calibrated, I would like to know.

2015-7-23
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aek
lvl.2

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See edit in post #1 for a workaround
2015-7-24
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aek
lvl.2

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chris@leckieins Posted at 2015-7-24 05:59
I just got my P3 and noticed that the wind really effects the gimbal. I keep getting "gimbal overloa ...

Chris, have you tried to check the torque as I show in the video I added to the first post?

Power on the copter when it is cold (has been turned off for at least for 30 minutes), and see what happens if you lightly push the camera to the left, and see if it always returns to center.

If you can make the camera stay pointing slightly to the left you have the same problem as I do.

Then let the copter stay turned on for a few minutes (warming up) and then turn it off and on.
Now, try the same thing again.
2015-7-25
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aek
lvl.2

Sweden
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Very similar symptoms for this user:
http://forum.dji.com/thread-24725-1-1.html
2015-7-25
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Daninho
Second Officer

Germany
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chris@leckieins Posted at 2015-7-24 05:59
I just got my P3 and noticed that the wind really effects the gimbal. I keep getting "gimbal overloa ...

wind is a factor but the overload message is because of faulty gimbal if it is permanent. I have those warnings as soon as i am in the air, wind or not. I guess the gimbal cant take the vibrations from the copter and its faulty. Have already the 2nd gimbal like that.
2015-7-26
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aek
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Daninho Posted at 2015-7-27 00:54
wind is a factor but the overload message is because of faulty gimbal if it is permanent. I have t ...

Sorry to hear that, Daninho

Lets hope for a firmware fix soon.

Did you get a replacement gimbal or did you simply buy a new one?



2015-7-26
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Daninho
Second Officer

Germany
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aek Posted at 2015-7-27 03:12
Sorry to hear that, Daninho

Lets hope for a firmware fix soon.

no, they changed the gimbal during the 2nd RMA but it did not help. Thats why i asked to change again and this time the whole copter. It cant be that hard to get a P3 without jello, or?
2015-7-26
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aek
lvl.2

Sweden
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Yeah, the jello effect that some people have, and the unstable gimbal issue my copter has are similar, but not the exact same thing, I think.

The jello is more due to high frequency vibrations, for example from unbalanced propellers or incorrect gimbal attachment.

The unstable gimbal and shake has more to do with the gimbal motors and controllers not being able to hold the camera in position, for example due to low torque.

2015-7-27
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Fulgerite
First Officer

United States
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You guys are all assuming the issues are old school mechanical problems.  It's not.  It's not "low torque".

The reason you have a motor drifting left or right... Not level... etc...  It's ALL IMU and electronics issues.  This cymbal is being controlled by a COMPUTER and electronic gyros.  If the gimbal is not behaving correctly you need to recalibrate your IMU and then calibrate the gimbal.  If the problem persists it's a faulty IMU or gimbal controller issue.  (Bad position sensing potentiometers, etc...)

Most often jello is caused by unbalanced props or bent motor shafts.  Some users have failed to remove the packing foam transit lock for the gimbal.  This will cause jello.  

Another source of jello is that some gimbals have a servo oscillation problem that makes the gimbal servos vibrate.  This is an issue that is cause by faulty potentiometers or servo drivers in the gimbal.  The only way to fix that problem is to send it back for repair or replacement.
2015-7-27
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aek
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Fulgerite Posted at 2015-7-27 23:24
You guys are all assuming the issues are old school mechanical problems.  It's not.  It's not "low t ...

Not sure what you are rambling about. No one here is assuming mechanical problems.

And the symptom is most certainly low torque. Just watch the video in post #1.
2015-7-28
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Fulgerite
First Officer

United States
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aek Posted at 2015-7-29 00:42
Not sure what you are rambling about. No one here is assuming mechanical problems.

And the sympto ...

First of all...  I should have started by saying...  I am sorry you are experiencing this issue.  It's a bummer.  I am sure you are frustrated.

But... You are describing gimbal drift.

That drift may be 100% precision controlled high torque positioning that is responding to a completely BROKEN software program or motor controller that is driving the motor to drift & vibrate.  And... Vibration can be casued by many things including servo loop ocillation.  Not just low torque... but minor over corrections in the servo loop timing.

Or it might be a faulty motor controller FET that's blown.  Or it could be about 20 other things.  The least likely thing is that a direct drive permanent magnet motor suddenly stopped producing torque.  There is not much to break in a direct drive motor...  But the electronics that drive it can have a 100 things go wrong...

Again... I doubt it's a matter of a weak MOTOR that can't move the camera.  It's a motor being controlled by faulty motor controller, bad servo loop tuning,  faulty IMU, noisy position sensing pots, or bad software.  (Or all of the above.)
I am sorry you got stuck with a bad Phantom.  But I don''t think it will be an easy fix.  It probably needs to go back to DJI for diagnosis or replacment.  (Sorry.)




2015-7-30
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aek
lvl.2

Sweden
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Check my edit at the top of the first post.
Firmware 1.3.20 seems to have fixed this issue.
Will report back when I have done some more testing.

(Glad I did not send it in for repair )
2015-8-4
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