Sunday, June 14, 2015

F450 Quadcopter Mods: Walkera G-2D Gimbal and XIaomi Yi Camera



I built my F450 with aerial video in mind. Once I got it flying, it was time to select a camera and gimbal. 

The camera needs to be able to record at high framerates to reduce the "jello" effect of rolling shutter. If you try to strap a cheap keychain camera to the frame of your quad, it is very likely that the result will be a garbled mess of distortion. This is because the CMOS sensors in those cameras scan each frame into memory over a small period of time. Vibration causes the frame to move as it is being captured. 

Additionally, even if you get the vibration under control, the rapid movements in all directions as the quad flies around will make you ill. It's not a lot of fun to watch. 

The solution is a camera that can record at 60 fps and a motorized gimbal to compensate for the motion of the quadcopter and keep the camera level. There are gimbals that use servo motors, but the best use brushless motors, which are quiet and smooth. They nearly instantly compensate for the motion in pitch and roll that occurs from pilot inputs and wind gusts.

I selected the Xiaomi Yi camera. This has the same imaging sensor as a GoPro without some of the frills, and is much less expensive. They are currently available on Amazon Prime for $88. The don't come with a case, or even a lens cap. The Android version of the app is rather untrustworthy looking - it is currently distributed off of a file sharing site I normally associate with pirated software, rather than from the company's website. "Here! Run this random APK from the Internet on your phone! It will be fine!"

Yeah. I dug out an old phone that doesn't have access to any of my important stuff and used that. I used the app to set up the video mode (60 fps at 1080p) and timelapse mode (still frame every 3 seconds). You can toggle between these modes with the camera's button - you really only need the app once.


I also ordered a Walkera G-2D 2-axis gimbal. This only compensates for pitch and roll, but uncommanded yaw motions don't seem to be much of a problem. I am extremely pleased with this gimbal for the money. It has an onboard regulator, so you can run it straight off your 3S lipo pack. I connected it to my main power line on the quad and it fired right up. It supports the use of auxilliary channels on your receiver to aim it in roll and/or pitch, but it doesn't require it - you can set the tilt and roll angle with a couple of trim pots and leave it alone, and it requires no connection to your receiver. It even comes with a small tool to adjust the pots with and the needed Allen keys. It worked right out of the box, and bolted directly onto the lower frame of the F450, aligning nicely with the slots on the lower frame. I secured it with 4 bolts.

One note: the gimbal is not designed for the Xiaomi Yi and the existing mount doesn't fit. I found that the frame could easily be removed, a 1/4" cardboard shim cut to level off the mounting plate, and a large zip tie easily secures the camera to the gimbal. There is probably a more dignified way, but that works just fine.

I am really pleased with this combo. I am still seeing some vibration in the video that I want to eliminate, but it's by far the best video I've gotten from an RC model so far. More to come on the vibration problem as I work it out. (Update on how to fix this below)

Here are a couple of still frames of a local park, shot in timelapse mode.



And some video....



Video Test Flight 3 - Xiaomi Yi and Walkera G-2D Gimbal on F450 from Jason Bowling on Vimeo.


Update on the vibration problem, and a note about the camera:

1) The vibration was improved by changing the vibration dampeners that came with the gimbal with more rigid ones from HobbyKing. The dampeners that it comes with are too soft.

2) Additional improvements were made by inserting soft foam earplugs into all four vibration dampeners.



3) The lens rectification function on the Xiaomi Yi makes the edges of the video very blurry. Once I fixed the vibration, the edges were still bad. I turned the lens rectification off, and it's much better. Here's a test flight with these improvements.





TestFlightNoFisheyeCompensation from Jason Bowling on Vimeo.

6 comments:

  1. Awesome, ty! I just got the same gimbal for my f450 after seeing your setup. What bolts did you use to attach it to the frame?

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    1. Cool, I'm glad you found it useful. The bolts used to attach to the frame were something out of my junk box - little stubby 4/40 or 6/32 nuts and bolts, I think. I'm sorry I can't be more specific.

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  2. Thanks Jason! I got mine mounted with some of my spare screws too! Took it out for a flight, it was a little shaky. Which dampeners did you go with? And where/how did you put in the foam earplugs?
    Thanks again for responding!

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    1. I'm sorry, a friend had picked them up for me and I had them in my parts box. They were stiffer than the ones that come with the gimbal, which I believe are too soft. I'd recommend getting a couple in different stiffnesses from Hobby King and seeing what works best.

      The ear plugs are the little disposable ones about 1/2" or 1.25 cm long I found mine in the health and beauty section at Walmart near the ear care stuff - they also have them in sporting goods. They were very cheap. The vibration dampeners are like a hollow barrel with the ends removed - twirl the ear plug between your fingers to roll it up and compress it, and shove it down into the vibration dampener. Pull it through the other end with tweezers until it sticks out a touch from both ends and then let it expand. It did wonders for mine.

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  3. Hi Jason have same issue with vibrations in my records, have xiaomi yi and walkera 2d gimbal. What dampers you buy to fix this problem?
    Because I see in hobbyking some differents dampers, i don´t know the correct one.

    Thanks

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