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Basecam 32 (Alexmos 32). Too weak motors?
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Colleagues!
Two weeks passed and I am still trying to make my Canon EOS 100D stable during the flight (coaxial octa)
On the ground in hands gimbal wors perfect. But YAW and ROLL stab seems to be weak: a little vibration or a finger touch force gimbal to miss steps and rotate. Because of this YAW and ROLL axis do not work well during the flight: spontaneous rotations (wind blows, small vibrations, multirotor tilting etc). Increasing the power causes motors heating, but makes the situation a LITTLE better. I am using manually set PID parameters, but auto paremeters works the same.
Pictures of the gimbal and settings screen:
http://habrastorage.org/files/31e/6b7/7a5/31e6b77a59014b00a70752c76f5c0b3e.png
http://habrastorage.org/files/3bc/e4b/4ac/3bce4b4ac9b3415c896a38efca69962c.jpg
http://habrastorage.org/files/ea1/8d0/488/ea18d0488c9d40328a276638c91029ac.jpg
Canon EOS 100D + lens = 800g.
Gimbal 3-axis:
http://aliexpress.com/item/FC-Model-Carbon-Fiber-3-axis-Brushless-Camera-Gimbal-Mount-Kit-w-Motors-GBM5210-150T-for/1931896902.html?recommendVersion=1
Motors:
http://aliexpress.com/item/iPower-Gimbal-Brushless-Motor-GBM5208-180T-Featuring-a-Sealed-Casing/1553915978.html
Gimbal + Camera = ~1800g.
3S Lipo or 12V UBEC.
Thank you! -
I would:
1. compact the gimbal. Make the roll gage narrower, move the Pitch assembly/camera back and shorten the tube above roll motor. As much as maintaining balance allows.
2. Improve the camera installation, that is probably the biggest problem, a second supporting point (flash shoe) would probably help a lot. Also make sure there is no loose mass. Is the ferrite on video cable loose?
3. make sure basic setup is ok. All gimbal axis accurately 90 degrees to each other, well balanced, IMU(s?) well installed and calibrated, motor inverted status set with auto and pole numbers corrected manually. Power as high as those motors allow without over heating.
The motor could be too weak for Yaw, for Roll it probably will be ok after compacting the gimbal.
Using filters will help to vibrations after everything else is ok. -
Thank you very much, Graud, for your detailed response.
I will try the first item you are talking about: there is some potential to compact the gimbal for roll motors. Also 1 cm to compact for yaw motor.
Tha camera mount seems very good. I'v made a short video for you to check. Also, you can see the ferrite monting is good too:
VIDEO: https://youtu.be/VpzGJUM4mx8
In this video I touch the gimbal with se same strength, and you can see roll is very bad. Pitch is OK and PICH power is only 100.
The POWER of yaw and roll motors is 130. 150 causes overheating after 3-5 minutes of work. IMU calibration was done like on this video
and GUI shows correct camera position with no vibrations on display screen.
This is my second video with gimbal overview:
https://youtu.be/UP7ci7XdMLw
Thank you again! -
The ferrite is ok, I am not sure of camera installation, it is question of very small flex and the plate does not look that strong and many Canon bodies have not that good installation, but maybe it is ok.
The roll balancing is not very good, there is something strange on that. Also yaw flex strangely, it is difficult to see from video, is it the installation stand, the vibration damper or is there free play on yaw motor? Is the Yaw well balanced, with weak motors balancing is very important. -
Graud, I have rebalanced the gimbal and will send here a video shortly. Today I am going to check again in the air.
Your help is very important. Thank you! -
Graud, I couldn't shot a video, but after re balancing it has become a little better. Now, when the gimbal is off, I can put camera in every position and it will be static. I flew indoors and there were no problems. Outside there was moderate wind and there were some problems: 1 time in 10 - 20 seconds the gimbal turned yaw and roll direction by himself. Also there were big translational vibrations. These vibrations were on the frequency of dampeners. May be 2-3-4 Hz, 1-2 cm amplitude.
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And one else question. Now I use ubec 12V 2A to power all gimbal. Could it be too little? Should I power from 5S? I think increasing the number of S in LiPo is the same as increasing the POWER in GUI. Am I right?
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Yes, adding voltage has same affect than adding power. You should add voltage only if your power is already maxed out (above 220 as there is good to have some reserve for voltage compensation to work). If your power is less than 220 no reason to add voltage, it would not make it any better.
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Hello limon, Garug
I'm currently facing pretty much same issue. My gimbal seems to be fine on the ground and indoor, however while flying it attached to the copter it seems to lacking power in roll (BLDC 5010) and yaw (GBM5208 024-)200T motors. This is happening in gust of wind and I guess turbulence caused by copter itself while flying with high speed.
Here you can see exactly what I'm talking about
https://youtu.be/_S3xOAfCbPY
I was wondering whether going from 3s to 4s would improve anything but now after reading this thread I can see that no need to do that unless I'm reaching about 220 of power ( which is not the case for me so far - 150 for roll and 180 for yaw).
I have to admit that since I made the video above I was able to improve the situation quite a bit however it is not yet what it supposed to be. In order to achieve the results I'm looking for I think I need to understand few things first:
1 - up to what wind I should be able to fly without negative impact to the footage with such setup?
2 - What is the best way to identify Max power that can be set for the motor?
3 - Which parameter is better to keep high to get max power in order to keep position in gust of wind, motor power or maybe "P" gain ?
4 - is there any other parameter I should consider while tuning for copter purposes ? I can easily imagine that second IMU will be much more exposed to vibrations coming from the copter as it's mounted directly to the copter frame while the first IMU is much less (if at all)
Thanks in advance for all your suggestions -
Rotating landing gear (RLG) )is always difficult as it has huge inertia, it is easily vibrating, prone to wind and gimbal could get confused during takeoff.
I think your gimbal got confused during takeoff and looks like there is not much vibration dampening and second IMU would help. Put the second IMU below yaw. You should have different profile for takeoff, look for (RLG setups at the different forums) in any case do not start the gimbal/take off in follow mode.
Setting the max power, after changing power, just monitor that the motors do not get hot to touch during the time you will normally use the gimbal. -
Hi Garug,
Many thanks for your comments.
I wasn't really aware of the challenges around RLG. I thought it will be kind of "additional safety level" for the camera and the gimbal itself in case of potential crash.
If it comes to takeoff ... I'm switching gombal's motors off to avoid copter rotation (once it's in air I'm switching motors back ON) ... do you believe gimbal can still get confused this way ?
Second IMU is already in place (above YAW) .. Shall I move it below ? (after reading the manual it became quite obvious that above YAW option is more reasonable - but as I can see I might misunderstand that point :)
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"If it comes to takeoff ... I'm switching gombal's motors off to avoid copter rotation (once it's in air I'm switching motors back ON) ... do you believe gimbal can still get confused this way ?"
That should be ok.
Frame IMU below yaw works better for me. Also shorter IMU cables and less likely i2c errors. Your problem could be i2c errors. There is much electrical noise when the multicopter is flying. If you have BT connection available, you could have the GUI open and see if any i2c errors. (normally I would keep BT disconnected during flight)
Have you well balanced the Yaw? i.e. tilt multicopter 90 degrees, does the yaw stay in any position you put it to?
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Hello, wzbart_pl!
You are lucky that you can put power = 180. My motors heat at this power in 30-60 seconds.
The seller from China advises me to buy BGM-5208H-200T or DYS BGM-5208-200T, but now I see this may not help, because they do not look much stronger.
I have find this one (F06458 DYS BGM8108-90T 5KG Torque)
http://www.aliexpress.com/item/F06458-DYS-BGM8108-90T-5KG-Torque-Brushless-Gimbal-Motor-for-DSLR-Red-Epic-Camera-FPV-Aerial/1508860348.html
for 5!!! kg.
But the price is three times bigger. I am searching now something between 2kg (50$) and (5kg)150$... And also today I am going to compact the gimbal if I have enough time in the evening... -
@Garug
.. to be honest I was quite sure my YAW is balanced quite well. I followed lot's of "tutorial" videos out there and balanced my YAW up to 45 degrees only. Today I have checked how does it behave when I tilt it 90 degree and it seems it's far away from perfection. I will try to find perfect YAW balance and move second IMU below YAW motor ... of course I will let you know whether it helped or not. Also I have ordered Bluetooth module as it might be helpful in troubleshooting while flying.
@limon
I would really like to be able advice anything to you, but as you can see I'm struggling similar issues myself. I have seen lot's of videos on youtube where the guys used same class motors for big DSLR cameras with success. I'm wondering whether motor's brand could make a difference. I know people like to use RCtimer motors and they're usually satisfied with them. I'm using GBM5208 200T for YAW and in my case it needs to handle whole landing gear with gimbal and the camera (it's a bit more than 2kg) although it's still quite far from perfection I'm starting to believe that with proper balancing and a bit of work over the PID values I will be quite satisfied. I think you should follow Garug's suggestions ... the more I play with these things the more I understand on how important precision is ;) .. small things (like something out of balance) can make huge difference in the end. -
There is one thing that bothers me if it comes to YAW balancing ... while rotating the yaw (copter tilted 90 degree) gimbal will never stay in one position as the roll (mostly) and pitch motors moves and therefore center of balance will move as well.
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@wzbart_pl,
As I understand, if your have well balanced pitch, than "pitching" will never move the center of gravity, because pitch will rotate camera around its local center of gravity and it will not affect on the centers of gravity for roll and yaw. -
If all axis are well balanced, the gimbal can be put to any position and it will stay there.
This reguires also all axis to be exactly 90 degrees to each other. Often the yaw axis will flex some and never be perfect.
Always start balansig from pitch, then roll and last yaw -
Yep. It turned out that roll axis was loose a bit (one screw was not tightened enough) .. now everything is perfectly balanced (pitch, roll and yaw stays always where I put them)
Now I need to move second IMU below the YAW + shorter these long IMU cables. Install Bluetooth and I think I will be able to test. Will let you know how it goes in a while.
@Garug - another thought that came to my mind. Will follow YAW mode be anyhow affected by moving second IMU below YAW motor ? -
Follow yaw works well even with camera IMU only.
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Finally I had a time and no rain weather to test perfectly balanced gimbal and the second IMU moved below YAW. I have to say that Garug's suggestions brought significant improvement. MANY THANKS FOR THAT. No obvious issues at all. Below I'm posting the video that wa taken this morning.
https://youtu.be/QR_t7xyhLPY
As you can see the footage is pretty much stable and no obvious jerky movement like on previous video I posted.
What I could see afterwards is that gimbal tent to tilt a bit while moving to the side (02:07) or shake in roll (02:39). There are also some yaw shakes, especially when stopping the Yaw movement after rotation (03:23).
Do you have any suggestions to fix that tilting issue and the shaky roll and yaw?
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