jerky video

[new2mavic]

I thought I tried to start the motors in the past with the props off and it would not run for more than a second or two. I did think about doing that with the props on since I don't need it to takeoff. I guess I will work on that.

Just tried that on my M2P, if the motors are started manually by pushing the sticks towards each other, the motor will keep spinning with the props taken off. It wont stop even if the throttle stick is subsequently pushed fully up. However, if you use auto take off, the motor will stop after a couple of seconds.

 

[ruggb]

Yeah, that works EXCEPT as soon as I tip the AC I get a motor/prop error and the motors stop.
However, I did get another clue..as soon as I start the motors I get a squeaking sound. It isn't the motors and it does not appear to be the fan. It sounds like it is coming from the gimble. When I stop the motors, the sound continues, then stops after about 5 seconds == which coincides with the jerking of the video.

 

[ruggb]

All the F/W is up to date.
I have had a couple hard landing and tree incidents.
This is a link to my video on my Google drive - too big to upload
2020_01_06_14_12_44.mp4
It starts with AC not running. "Takeoff" is motor start, no props.
As soon as the motors start the jerking and squeaking sound starts.
I think one of the jerks at the beginning I caused.
Then the motors stop but the jerking and noise continues.
Then both stop.

 

[new2mavic]

It seems to me that the yaw motor of the gimbal is damaged. As the entire weight of the gimbal is supported by the yaw motor, it is often the victim of hard landing / crash. You may want to take the gimbal out and examine :

The squeaking is likely caused by the oscillation of the yaw motor which is controlled by something called "PID controller" . Those who have built drones from components should know what PID controller is and that the PID parameter values need be tuned to the characteristics of the device under control in order to achieve the wanted degree of stability. The values for the gimbal motors has already been optimized for the original characteristics of the motors and fixed in the firmware. The oscillation suggests that the characteristics of the yaw motor has changed. For example, the core of the motor is no longer perfectly centered so the acceleration becomes different for the same input signal / current.

As explained in my previous post, it appears that there are two sets of PID parameter with one set used when the craft is flying ( prop motor turning ) and the other used when the craft is at rest ( prop motor stopped ). That explains why the jerking only appears when the prop motors are spinning.

I am afraid the gimbal will need be replaced. If you plan to do it by yourself, someone is selling this on ebay : Genuine Dji mavic 2 zoom gimbal please read the add carefully | eBay

the gimbal arm + motor is very cheap on Aliexpress :

52.65US $ |Repair Parts Mavic 2 Pro Gimbal Motor Replacement For DJI Mavic 2 Pro / zoom Gimbal Accessories|Drone Accessories Kits| - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

 

[ruggb]

new2mavic
thanks for the explanation. That was my thought but I wanted to understand the system b4 I jumped into it.

I didn't realize AliExpress had those. They are used parts, but if they do not work I am sure Ali will take care of it. I think I keep them in business, well, I guess the word got out so maybe not.

I have had the gimble off, but not ventured to disassemble it. At that point the screws got much smaller. It will be a challenge for my big hands and poor eye sight, but that is what the mag glasses are for.

It is silly to replace the whole assy if I can replace just what is broken. Tried to get a quote from a repair house but all they can tell me is $149. labor so I have no clue if they replace parts or assy. I am assuming assy so at $149 + $350 for the gimble, it is worth spending $24.