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Old Jun 17, 2013, 12:50 AM
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Setup and Trouble shooting AG DD gimbal

To get peak performance out of AG DD gimbal, ,you will need good setup and possibly tweaking of the tuning. I will be using this blog to update the latest setting and setup technique. of course, be sure to read the software setup guide from tppacks, which will be updated in the future with more information.


as stated in the guide good performance is all about
1) good balance
2) friction free setup
3) good balance.
4) tuning

without near perfect balance and smoothness, you won't get good performance. first sign of improper setup is bad buzzing. this occurs when motor is trying to compensate for small positional error, but can't and create a fine oscillation. The main cause is either due to balance or friction. (and rarely resonance oscillation caused by motor vibration)

Mechanical friction:

let talk about friction first. In most adjustable gimbal, you get friction when things are out of parallel. for example, the yoke arms is not parallel in both vertical and horizontal view. the gimbal should move freely and easily. this should be fairly easy to test and fix. mostly visual and moving the camera plate should give us clue.


Balancing

I start with roughly balancing the roll with camera on. lock the roll down once this is done.

I do the pitch balancing next. Pitch balancing is critical with camera at all the angles that camera will face. I start by setting up the camera balance with lens facing down. you need to adjust the distance between the pivot and camera tray until you have proper balance. once this is done, you can balance the pitch with camera facing forward. (simply move the camera forward/back until this is done)

once pitch is done, I do the fine balance on the roll. this is very sensitive and small amount can make big difference. if you get it close and have trouble getting it perfect, i would consider adding small weight on one side to get it perfect.

then now, you need to check balance at different frame attitude. What I've found is that you can see unbalance easier with frame pitched up or down. once this is good, you are considered done.


once balance is perfect, you can look at PID tuning.

well balanced setup should look like this with power off

gimbal balance (0 min 0 sec)




PID TUNING



Biggest cause of oscillation and buzzing besides mechanical issues are due to improper PID setting, especially Integral term. I would start to reduce integral term down and see how the oscillation in the data window look. If you see lower amplitude and frequency, you are on right track. lower frequency, same amplitude is typically caused by other issues. even when it is bit out of balance, you can tune the PID so that it work ok. the key is low enough PID so it does not cause buzzing, but I recommend balancing as good as possible.

tuning is bit of art and science and you may need to experiment with the setting to find a perfect PID. even a same run of gimbal may have slightly different PID setting due to difference in motor wind. so you may need to play with it a bit.

here is video tuning guide that was linked

New Alexmos GUI quick introduction / tuning guide (16 min 27 sec)




Trouble shooting:

1) make sure all electrical connection is good. especially motor
Each of 3 circuit of the motor should have about 10-15ohms resistance.

2) make sure the driver is ok. it should have high impedance, but not infinite. if it is open, you have bad driver

3) no I2C error. this can cause havocs,. you may need to add ferrite core toroid and wrap the i2c wire few times (3-4 times recommended)

4) try reloading the firmware and starting from scratch. remember that the gui has to match the version of firmware.
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Last edited by askman; Aug 13, 2013 at 08:51 AM.
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Old Jun 17, 2013, 08:17 AM
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United States, MO, KCMO
Joined Apr 2013
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Thanks for this Andrey!
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