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Old Apr 24, 2015, 04:04 AM
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Quote:
Originally Posted by Andyclayton View Post
to be honest for the last month Iv messed around trying to get decent footage from a mobius on a gimbal. I come to the conclusion its just the wrong shape. I can take a gopro type camera and get ultra smooth footage but I think the mobius with its streamline shape is either acting like a control surface or wing causing lots of friction and vibrations. or the fact that its long causes it to wobble on the gimbal no matter what you do., for anyone else trying this you will know that the tripod mount is loose on the mobius holder, you wanna glue that in place. also theres play in the mobius holder itself which I have glued down. Still not as smooth as a go pro sj4000 style camera. Hobby kind do sell a gopro type adapter for the mobius. might be worth a shot although I have to say theres a lot of cams now that are out doing the mobius in that category!
The shape of the Mobius has little to do with the problems you are seeing. The lighter the camera, the harder it is for a gimbal to properly stabilize it (mass helps stabilize, since it changes the natural resonance frequency of the system). The Mobius, being one of the lightest cameras on the market, poses more challenges than a heavier GoPro. Especially if you have extra wires (power, video out), getting good video is hard. But even the motor or IMU wires are a challenge, since the "pull" of the wires is a significant portion of the Mobius mass (the heavier the camera, the less the wire influence it). So, yeah, it's hard...

But a properly designed and properly balanced gimbal with a good controller (e.g. STorM32) can produce video as stable as any GoPro gimbal in the same flying conditions.

Or you can cheat, and add enough mass to a Mobius to make it the same as a GoPro . That way you will clearly see that shape has nothing to do with the problems you are seeing, it's just mass and balance
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Old Apr 24, 2015, 05:39 AM
OlliW is online now
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I overall fully agree, but there is one point which might need clarification.

The natural resonance frequency of the system is actually quite similar for all gimbals, be it for small or large cameras. This is so because it is not only determined by the mass of the camera but also the size/strength of the motor, and one has to choose that combination to be in a proper ratio for the gimbal to work well, with the result that the natural resonance frequency has in fact to be a in a narrow range of values, with relatively little variation with camera size.

The major difference between small and large cameras/gimbals is the "sensitivity to external factors". One example would be the wires mentioned by robca, obviously for a huge camera setup the wires are no issue while for a mobius gimbal they can be a major issue. You'll find many of these things which are more or less independent of the camera/gimbal size, so that they tend to have a very important effect for small cameras while irrelevant for large cameras. Other examples could be the vibrations coming from the copter, friction in bearings, also the cogging torques in the motors, and so on and forth ... so, it's the low weight in relation to all external disturbances which makes a Mobius gimbal more challenging.

Cheers, Olli
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Old Apr 24, 2015, 05:31 PM
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Originally Posted by OlliW View Post
I overall fully agree, but there is one point which might need clarification.

The natural resonance frequency of the system is actually quite similar for all gimbals, be it for small or large cameras. This is so because it is not only determined by the mass of the camera but also the size/strength of the motor, and one has to choose that combination to be in a proper ratio for the gimbal to work well, with the result that the natural resonance frequency has in fact to be a in a narrow range of values, with relatively little variation with camera size.

The major difference between small and large cameras/gimbals is the "sensitivity to external factors". One example would be the wires mentioned by robca, obviously for a huge camera setup the wires are no issue while for a mobius gimbal they can be a major issue. You'll find many of these things which are more or less independent of the camera/gimbal size, so that they tend to have a very important effect for small cameras while irrelevant for large cameras. Other examples could be the vibrations coming from the copter, friction in bearings, also the cogging torques in the motors, and so on and forth ... so, it's the low weight in relation to all external disturbances which makes a Mobius gimbal more challenging.

Cheers, Olli
Thanks for chiming in Olli! This explains some of the behaviors I've see. Would more poles on the motors make it smoother?

I've given up on the Tarot, and I have a STorM32 coming from witespy, hopefully I can get this working before I leave.
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Last edited by rcboosted; Apr 24, 2015 at 05:44 PM.
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Old Apr 24, 2015, 05:54 PM
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well ... nearly all gimbals, and especially Mobius gimbals, will nearly always need some tweaking, and not only of the gimbal controller parameters, but also with the damping, vibrations and all sorts of things... it's IMHO exactly as robca said "Put it simply, the gimbal you want doesn't exist (yet) ..." ... your timing is IMHO extremely tight to bring all that to success ...
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Old Apr 24, 2015, 10:09 PM
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we shall see because HK do a mobius mopro conversion kit that weighs the same as a mobius there abouts

I also beleive that the mobius having a flat surface creates a bigger surface area for the prop air to press down on causing a bobbing effect. I got some different setups to test. I will post the results hopefully in video form
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Old Apr 25, 2015, 10:43 AM
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Old Apr 25, 2015, 10:46 AM
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Originally Posted by jpgilbert View Post
Modified the GoPro holder for this gimbal so I could attach my Mobius ActionCam. Seemed to balance out OK. Not perfect but does work. Also added pitch control with a DSMX remote receiver. That also works fine. Still a bit of jello but not too bad. Fog just a bit too high today to get above it.

The Mobius has the lastest FW and the 350 has its FW updated and GPS receiver moved and added the tall landing gear.
Joe
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Hey jpgilbert,

I did the same thing as you with the CGO1 mount. I added a 14 gm weight on the upper inside corner of the box and an 11 gm weight on the other side of the box to simulate the weight of the CGO1 camera with the Mobius mounted to the bottom with the tripod mount. However, if I mounted the Mobius towards the outside of the tray, it would flop over on its side, then straighten back up and flop over on its side again, and so on. If I mount it near the left side, or closer to the gimbal, it doesn't do that. It doesn't look like you have any balancing weights on your setup. Have you had any issues like I described? Or any vibrations or twitching?
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