Alexmos 32bit

R

Ronan

Member
So of course after having great success with my Alexmos 32bit, today after putting the camera back on the 3 axis gimbal and turning it on... it vibrates... quite a LOT!

I have markings on the gimbal for the balancing points of my camera... but could it be that i simply didn't balance it properly after remounting it?
 



dazzab

dazzab

Member
Hate to mention something so simple but it caught me out. Check that the IMU is mounted firmly. If it comes even a little loose it can vibrate in place which will screw up everything. Are you using the two IMU setup? Obviously, check both.
 

R

Ronan

Member
It's driving me nuts, it was working perfectly fine and now after i turn it on, it starts making a weird buzzing sound comming from all motors...

I guess it fell out of calibration, so much i need to recheck everything. Very annoying...
 

R

Ronan

Member
Alright i rebalanced the camera, checked the gimbal/motor, reinstalled my profile...

Now the yaw axis (left right) is turning back and forth by itself... as soon i pick up the gimbal, it starts to vibrate and make weird noises...

What the heck?
 

dazzab

dazzab

Member
Are you using both the camera and frame IMUs? I had a terrible noise problem on the bus due to the second IMU of an AlexMos I bought from a company that mounts them in a nice case and cables them up.

It shows up as errors in the error count so see if that's counting up errors in red. If so, try running it with only the camera IMU. If it works fine without the frame IMU then you have a noise issue coming from how the second IMU is cabled. I'll tell you more about that if you determine it's an issue or not.
 

vulcan2go

vulcan2go

Member
Hi Ronin,

1st - It sounds suspiciously like a poor connection - Check the plugs are all tight, ensure all motor mounting screws are tight, check the IMU cables are good and that the IMU mountings are solid.
2nd - I assume there are no I2C errors? If there are then try and find out the source of the noise and see if that makes a difference.
3rd - Try each motor in turn to see if that highlights any issues.
4th - If you move the IMU cable in any way, does the noise from the motors change (ie get louder or softer)? If it does then you may have to adjust the noise filters - there's a great link here that talks about how to set them up: http://levitezer.com/styled-2/blog-2/index.html

Good luck with finding the problem.

Cheers,
 

R

Ronan

Member
I now got everything to work EXCEPT the pan axis... after i turn on the gimbal (wait 10 seconds) the pan axis moves back and forth almost violently. It travels about 2 inches both sides...

This was working completely fine before... so not sure what happen...

SOMETIMES i get a I2C error of motor skipping or something like that (haven't seen that error since yesterday).
 
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gtranquilla

gtranquilla

RadioActive
Maybe this will help.

1) Double check the number of poles configured for the yaw motor.
2) Move the pan motor wires away from possible sources of emi such as battery or battery regulator.
Switching/digital volt regulators produce emi as well as possible voltage supply ripples.
Make sure the BG controller is not getting supply power from two difference sources, i.e., should not come in from servo wires if all 3 wires are connected from the FC which is not good.
3) Re-calibrate the yaw IMU gyros..... they drift a lot......

other reference info.
Fit a ferrite ring around the motors outputs on the board and the I2C cable still right out of the board. Also, use a LC filter (Power Noise Filter) if you feed the gimbal right out from the main lipos.
I2C errors are worse when the sensor cable is running along aluminum parts or close to the motors / motor wires. Make sure to route it not too close to wires that emit RF noise.



Ronan said:
I now got everything to work EXCEPT the pan axis... after i turn on the gimbal (wait 10 seconds) the pan axis moves back and forth almost violently. It travels about 2 inches both sides...

This was working completely fine before... so not sure what happen...

SOMETIMES i get a I2C error of motor skipping or something like that (haven't seen that error since yesterday).
Click to expand...
 
Last edited by a moderator:

R

Ronan

Member
Thanks, i'll give it a shot.

How do i know if i have the right number of poles anyway? Mine came with a profile that was working great but not anymore...
 

gtranquilla

gtranquilla

RadioActive
Count the number of coils in the motor then add 2 or just count the magnets, or look up the yaw motor model number on the internet and it should be stated in the specs. Most are 14 but Alexmos firmware consistently calculates it to be 22 poles which is wrong.

Ronan said:
Thanks, i'll give it a shot.

How do i know if i have the right number of poles anyway? Mine came with a profile that was working great but not anymore...
Click to expand...
 

R

Ronan

Member
It's a ipower gmb5208h-180T and the utility shows it at 14 pole.

Those are the settings the auto function is finding... It's a medium size gimbal for camera's 300 to 900 gram in weight.

attachment.php
 

gtranquilla

gtranquilla

RadioActive
Unfortunately your attached image or video did not come thru.
Also before and after each activation of auto-tuning your system always check that the motor pole counts are correct.
The latest firmware tends to include pole count and motor direction each time during auto-tuning and will frequently assign incorrect pole count to the yaw motor.

Finally, it is also best to auto-tune each axis independently for more accurate tuning.



Ronan said:
It's a ipower gmb5208h-180T and the utility shows it at 14 pole.

Those are the settings the auto function is finding... It's a medium size gimbal for camera's 300 to 900 gram in weight.

attachment.php
Click to expand...
 



R

Ronan

Member
gtranquilla said:
Good to see photo......

I doubt very much that you will be able to purchase a 15 pole motor..... so BGC software auto-configuration is wrong again. Most likely all 3 motors are 14 pole..... but doublecheck all motor specs.
Click to expand...

Hmnn interesting, i'll change them to 14.
 

R

Ronan

Member
Ok this is interesting... i have reinstalled the software, reuploaded my profile, forced the poles to 14.

Works a LOT better now, but yaw has a slight shaking, also it's not centered. When moving the gimbal on it's yaw axis, it tries to compensate violently (hard yaw turn left/right).

Pics after the original profile has been put again:
http://oi57.tinypic.com/25511kk.jpg
 

R

Ronan

Member
YAW axis still acting fubard... :(

Now it doesn't even know where the front is and auto-tune's at a weird angle...
 

gtranquilla

gtranquilla

RadioActive
Ronan,
Yaw axis is always the biggest challenge. It works for the handheld gimbal systems but is more limited on a Multirotor.

You have to re-calibrate the gyros much more frequently for the Yaw axis IMU as they drift a lot.
If you have a heavy camera, the Yaw motor torque becomes a critical factor.
Also you have to first hang your BGC/camera system at 90 degrees to carefully balance the yaw axis..... critical!
For Multirotors you have to stick with the "Heading" mode for now versus "Follow Mode".
So get "Heading" mode working first before tackling bigger challenges.
I am going to assume that you pinned down the number of motor poles based on motor model number data and/or counted the motor coils then added 2 as best guess could lead you astray.
The weakness of the low cost IMUs used on BGCs becomes most apparent with the Yaw axis due to the gyro drift.
There is not enough sensor input information available from these to enable the BGC to maintain a "follow" mode with accuracy for a longer period of time.
In other words, the AlexMOS is not there yet relative to the Radian and other very expensive complete solutions.
 

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