Im trying to help another member here (Zhiran) get his p4p gimbal back working properly after a 6 foot fall. In my opinion the yaw motor has a shaft misalignment issue. If you look at the video you will notice when it yaws right it smacks the bump stop but when it yaws left it never makes it to the bump stop. The p3 has a flat spot on the shaft with a set screw so its pretty easy to realign the shaft. The problem with the p4 series is that the shafts are pressed on so there is no flat spot. My question is how do you identify the center point location on the shaft to line the motor mount back up with the shaft? Ive searched high and low and I cant find anything about it. We would certainly appreciate any help. Thanks.

  

Aloha Duchunter,

     This is a delicate issue.  As you noted the P3 series has the flat spot but the P4 series is a different story.  At one point it was recommended to use hand force manipulation to reset the center line.  We need the DJI Team to confirm if this is still an approved procedure.  Of course, DJI will prefer that you send the unit in so their technicians can do the manipulation for you to protect you and the company in case of a problem with the procedure.

     Hopefully a Team member will respond to this thread to give you better direction than I am able to provide.  If not, the crash may have already voided the warranty such that a DIY manipulation could be in order.  

     Obviously a manual override of the gimbal motors is not something that is good for the gimbal.  The hard landing was the first override of the gimbal motor, resetting it by hand will be another override of the gimbal motor.  Doing this too many times will wear out the friction necessary to allow proper function of the gimbal.  Then you potentially get disarticulation and a torn ribbon requiring a camera replacement or surgery.  Not a pretty picture.  There are also sensor distortions that can be created by this procedure.

     Under any circumstance, after any remedy, a gimbal calibration will obviously be in order and it will be very important to check the shaft set of the camera prior to and after any flight.  This would be to see if the motor is sliding off of the shaft.  If there should be a resultant tendency for the camera to slide off of the shaft, a preventer can be made out of a paper clip that can salvage the damaged gimbal to keep it from damaging the vulnerable ribbon.  I have done this before with P2s and P3s.

     Hope this helps!

Aloha and Drone On!

Cetacean Posted at 2017-7-1 05:11
Aloha Duchunter,

     This is a delicate issue.  As you noted the P3 series has the flat spot but the P4 series is a different story.  At one point it was recommended to use hand force manipulation to reset the center line.  We need the DJI Team to confirm if this is still an approved procedure.  Of course, DJI will prefer that you send the unit in so their technicians can do the manipulation for you to protect you and the company in case of a problem with the procedure.

Thank you very much for your input. I have already walked him through the disassembly of the gimbal so the yaw motor has been removed. He did a great job taking it apart so we just need some instruction on realignment of the top plate. He lives in Iraq so I imagine parts are hard to find and it seems to be such a waist is all it needs is to be realigned.

Duchunter Posted at 2017-7-1 09:02
Thank you very much for your input. I have already walked him through the disassembly of the gimbal so the yaw motor has been removed. He did a great job taking it apart so we just need some instruction on realignment of the top plate. He lives in Iraq so I imagine parts are hard to find and it seems to be such a waist is all it needs is to be realigned.

Aloha Duchunter,

     OK, does everything look workable?  Is there damage?  To get the "correct" alignment, without DJI input, he will have to do a forced hand manipulation as I noted above.  To keep unnecessary movement from reducing the friction, he will have to position or align himself to the extent that he knows the full yaw degrees available to him for the adjustment.  Then he needs to grasp the camera and align it so that it ends up centered when the start-up yaw procedure is completed.  

     He may have to run the yaw start-up procedure a few times to get the correct alignment.  But, remind him that the more movement he manually introduces, the more damage to the friction system is inflicted.

     The gimbal yaw calibration will be able to complete any small adjustments necessary, but the major adjustment will have to be manual.  Understanding what makes everything work is important to a successful result.

     Hope this helps!

Aloha and Drone On!

Cetacean Posted at 2017-7-1 16:43
Aloha Duchunter,

     OK, does everything look workable?  Is there damage?  To get the "correct" alignment, without DJI input, he will have to do a forced hand manipulation as I noted above.  To keep unnecessary movement from reducing the friction, he will have to position or align himself to the extent that he knows the full yaw degrees available to him for the adjustment.  Then he needs to grasp the camera and align it so that it ends up centered when the start-up yaw procedure is completed.  

Ok, that all makes sense but the yaw motor has 360 degrees of movement when you remove it. It has bump stops on the gimbal that stop it from going to far left or right but the motor itself has nothing limiting its range of movement. The motor has a sensor that tells it where center is. There is no obvious reference point to indicate the center point. What we need to know is how to identify the center of movement to square up the top plate on center. Thats what is keeping him from being able to realign it.

Duchunter Posted at 2017-7-1 17:30
Ok, that all makes sense but the yaw motor has 360 degrees of movement when you remove it. It has bump stops on the gimbal that stop it from going to far left or right but the motor itself has nothing limiting its range of movement. The motor has a sensor that tells it where center is. There is no obvious reference point to indicate the center point. What we need to know is how to identify the center of movement to square up the top plate on center. Thats what is keeping him from being able to realign it.

Aloha Duchunter,

     Yes, that is the problem nicely summed up.  Also it is the problem with the gimbal continuing to work because the realignment has to be done while the camera is on and showing its misalignment.  If it is done wrong, the sensor and/or the sensor system can be damaged.

     When it is on, you have to analyze the stable and moving parts.  You then hold the stable part and rotate the moving part back toward center.  First do it a little bit first to see if it makes a difference.  Then you have to go from there.  It is a hand force manipulation while the camera and gimbal are on.  That is the problem and that is the risk.  The P3 series was much easier to repair in this respect.

     Look at the situation and decide if it is worth the risk.  You may already have to replace the camera/gimbal.  In that case, doing the manipulation is almost no risk but it is your friend's decision - unless you plan to buy him the replacement camera!

     Hope this helps!

Aloha and Drone On!

Seems like it may be easier to just replace the yaw motor, especially since its already apart.

Since there is a sensor on the yaw motor that sends the center point location to the gimbal controller then certainly there must be some mechanical reference that triggers the sensor when the motor has reached the center point of its movement. I wonder if you separate the bell from the stator can you locate that mechanical position indicator. Im gonna see if I can get my hands on a bad yaw motor and come up with a better method.  

Cetacean Posted at 2017-7-2 11:13
Aloha Duchunter,

     Yes, that is the problem nicely summed up.  Also it is the problem with the gimbal continuing to work because the realignment has to be done while the camera is on and showing its misalignment.  If it is done wrong, the sensor and/or the sensor system can be damaged.

Realize an old thread.  Wondering what you meant by the P3 being much easier to fix; the misalignment of the gimbal.   Do you mean simply loosing the set screw and moving it away from the flat spot, where it is supposed to be?  If not, how is the misalignment corrected?   (Some say the magnet on the yaw motor must be released and moved, etc.  That, truthfully, is the only fixt I've found, and I don't care for it and it makes no sense to me.)  Thanks for your time and any information you may be willing to share.  

Harvey