Help Please, Gimbal seems unstable and glitchy.

Discussion in '3 Axis Gimbal' started by Darren Brower, Nov 4, 2013.

  1. Darren Brower

    Darren Brower Member

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    I have tried every adjustment i can think of on this Gimbal, but despite my efforts i cannot seem to get a steady picture. Could someone please look at this footage, or some of it and give me suggestions as to what might be going on. This was shot on my Canon 2Ti with an 18-135 lens open to its widest. The gimbal is the Freefly 360 radian stabilized dual operator. Disregard the quality of the picture as everything was set to auto and it was a crappy day. I shot a full round of all the booms to see if anything looks unusual but i couldn't see anything. Thank you in advance for your help.
    Here is the link:
     
  2. Steve Maller

    Steve Maller UAV Grief Counselor

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    A few thoughts...
    • At least one of your motors appeared to me to be significantly out of vertical. This can cause instability in the copter, which in turn can cause the Radians to overwork. You should correct that.
    • The 18-135 lens is a curious choice. It's a lot of unused glass in there, and the weight could be an issue. a 10-22 or something is a much more compact and suitable lens.
    • You said that everything was set to "auto". If that includes auto focus, a hunting autofocus could cause the weight to shift enough to throw off the balance in the gimbal.
    Other than that, it can be helpful to upload your videos in HD rather than super low res, and there are sometimes telling details visible at higher resolution.
     
  3. Darren Brower

    Darren Brower Member

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    Thank you Steve, I guess i should explain myself a little more. Camera was set to manual focus, everything else was on Auto. The lens is the only one i have right now and is for testing purpose only. I haven't decided which camera to go with yet so didn't want to buy the 11/16 Tokina lens just yet. I checked all the motors and they are all perfectly vertical.
    I put on my Sony cx760 today and tested it out. Now, there is no excuse for shaky cam with this camera mounted but yet i am getting similar results. Not as bad, but still not acceptable for this Gimbal in my opinion. This thing should be real smooth, but its not.
    So, is it my O-ring's, the gain on the Radians, Props ? im out of ideas. For the price of this Gimbal i expect it to be almost perfect, with the least amount of post stabilization in most conditions, but i just cant seem to get it to that point. i find it impossible to balance the cameras so they are perfect and can be put in any position without movement.
    I will try and post the HD footage i shot today so you can check it out.
    Regards
     
  4. Dave King

    Dave King Well-Known Member

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    HI Darren

    I see some roll twitching which can be caused from strong wind (which you had in the sample) or the roll axis being balanced perfectly. It's very easy to think you have the roll balanced when in all actuality its not close enough. From my experiences the radians are very sensitive and the roll has to be dialed in perfectly to avoid roll twitches.
     
  5. Steve Maller

    Steve Maller UAV Grief Counselor

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    Make sure your belts are tight. I'd also fly it with the Radians disabled and see how it looks. It will be bumpy and jittery, but you may notice something (like excessive vibration). It's easier to tune the Radian gains once everything else is right.

    And with respect to your comment, "For the price of this Gimbal i expect it to be almost perfect", welcome to the frontier, amigo. We're all blazing trails out here, and if somebody sold you a system with the expectation that this is a mature market with infallible products, I'm sorry to say you were misled. We're all inventors to one degree or another, and in my experience there is a lot of blood, sweat and tears required to get decent results. :(
     
  6. Darren Brower

    Darren Brower Member

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    Thank you Steve, ill check things out again and see if i might of missed something. I do feel however a little misled and disappointed in this system. I have had a number of failures on my Cinestar 8 and 360 Gimbal since i bought them 7 months ago. Perhaps my expectations are too high and my experience too low, im not sure. I come from the film industry and understand the high price of film equipment, however it is usually justified by the end result. I was led to believe that this is the best of the best when it comes to the merging of the film industry and multirotors, and that people request the Cinestar by name. This is far from reality. I have made a very big investment in this system and i just want it to work properly so i can start to recoup some of that investment.
    Sorry for the rant.
     
  7. Darren Brower

    Darren Brower Member

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    Thank you Dave, ill take a closer look at that. Since you mentioned that, i took a closer look at my footage and noticed that allot of the movement and glitches seem to be coming from the roll radian. that might explain the up and down movement in the corners of the screen.
     
  8. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    As Steve says, Darren, we're operating out on the "bleeding edge" of this technology. Getting a gimbal to work right means you need to really understand how to tune it and that takes time, I'm afraid.

    Could you do some basic checks please -- and let's focus on the roll axis as that seems to be giving you the most trouble.

    1. Can you hold the gimbal at the junction where the rear transverse tube meets either the left or right side tube (that's at the rear of the gimbal), and then, with the other hand, grab the large roll pulley. Gently try to raise and lower the gimbal and see if there is any play in the system -- there should be a very small amount.

    2. Check the tightness of the roll servo belt by pushing with your finger gently at the mid-point between the small pulley and the large pulley. The deflection should be about 2-3 mm at most. If there's more, you'll need to loosen the boom clamps that hold the servo on and slide the servo further away from the large pulley to remove the slack. It's also possible that (a) the small pulley on the servo has come loose -- check with a 2.5mm hex wrench that it's tight or (b) that the big pulley is loose on the roll shaft (that needs a 2mm wrench (I think) to tighten a small grub screw that holds it on the shaft. Also check all the bolts holding the rear of the U-part of the gimbal together.

    3. Can you connect up the Radian software to the roll Radian, Read the current settings, and take a screen capture of the resulting window showing the values and then post it as part of a message on this thread. If you're not familiar with screen captures, do a Google search with the search phrase:

    Windows X screen capture​

    where X is the version of Windows that you're running (XP, 7, or 8). Save the screen capture as a file on your computer in a place that you can get to easily, and then create a new posting and click on the "Upload a file" button and navigate to and select that file you just saved.

    4. Can you also take some well-lit images of the camera on the gimbal. I say "well lit" only because black carbon fiber doesn't show up vary well in most images!

    Those are the first major steps to take....we can work into more details depending upon what you find.
    Andy.
     
  9. Darren Brower

    Darren Brower Member

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    Hi Andy,

    Thank you for your response, i really appreciate it.
    Ok, I spent the weekend really trying to find out what was going on. I pretty much took the whole thing apart and put it back together.
    I took great care going over all of your points to make sure things were nice and tight. Screws, check! Belts, Check! unusual movement, Check! At this point everything looks kosher but i have not had the time to go and test fly it yet. The only play i see in the system is small notch on the servos, but that seems normal to me. I took off the Canon with the crazy lens and put back the Sony cx760. Now i know that is somewhat cheating but i could never really get a smooth enough picture with that camera, and that is saying something.
    The problem im having is that i really don't know what is acceptable movement. Ive watched hundreds of hours of footage all over the web. Some was great and some was total rubbish. some was from people on this forum and some was not. My point is however, that if someone can stick a gopro on a phantom and get better results than i can.... well that is not acceptable to me. I have spent the past 7 months and many many $1000 really trying to learn this new trade, fighting off temptation to go and and find clients. I always strive to be the best at what i do, but i have really been struggling with this product. I really want this to work out and i don't want to lose faith in the Cinestar brand.
    Here are the photos you requested. I shot them overexposed on purpose so the carbon pops out. Please let me know if you would like to see anything else. Next chance ill get to fly will be Thursday, ill post a video from that flight for you to see.

    Cheers, tilt radian.jpg Roll Radian.jpg pan radian.jpg IMG_9971.jpg IMG_9969.jpg IMG_9968.jpg IMG_9967.jpg IMG_9966.jpg
     
  10. Steve Maller

    Steve Maller UAV Grief Counselor

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    One curious thing I see in one of your photos is the cloverleaf antenna. If I was you, I wouldn't have that mounted on the gimbal. Not only is it a potential sail in the wind, but it's going to bounce and possibly create some unwanted jittering on the gimbal. I would mount it on one of the legs or somewhere else that's not part of the suspended area of the camera mount. But maybe it's a red herring.
     
  11. Shaun Stanton

    Shaun Stanton Active Member

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  12. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Thanks for the images Darren. Nicely done!

    The other consideration is that clover leaf is radiating radio frequency power at around 1.2 Ghz and it's very close to a radio receiver listing at 2.4 Ghz -- and the first harmonic of 1.2 Ghz is......you guessed it 2.4 Ghz -- so I'd follow Steve's advice.

    Your gains are Pan 50, Roll 125, Tilt 95.
    Based on what I've been seeing on the forum (and bearing in mind, this varies with payload and placement of components), typical settings are Pan 70, Roll 130, Tilt 150.

    Your Roll setting looks good, but I worry that Tilt is quite low. Pan also seems a bit low.

    When you adjust these gains you might want to go up and down by 5%, but for fine tuning drop to up or down by 1%. I've seen the "sweet spot" hiding in there between three or four percentage points and it's easy to blow right by it.

    Andy.
     

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