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Rotorpixel gimbal - How does it actually work?

Discussion in 'Phantom 2 Vision Discussion' started by DKDarkness, Feb 11, 2014.

  1. DKDarkness

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    Before you reply, I am looking for actual answers, not "It works great!" or "I think it looks perfect!" or even "I ordered one, can't wait" these questions have been answered in full in other topics.

    I have been looking at videos for the Rotorpixel gimbal (http://www.youtube.com/watch?v=3E85L4FPRVQ) and the Dronexpert gimbal (http://www.youtube.com/watch?v=tkYnkfw02_8) I can understand how the Dronexpert gimbal works, I can see that it draws power from the FC200 jack, and the IMU is attached to the camera along with the 3.5mm jack. I am not looking for an answer to which of the two is best, this also has been discussed at length in other topics.

    When reading up on the Rotorpixel gimbal, the homepage says:
    -----
    SIMPLE PLUG-AND-PLAY INSTALLATION
    No soldering. No disassembling the Phantom frame. Simply detach the Vision camera, attach our gimbal, and plug in 2 cables, and you're ready to fly! It really couldn't be any easier.
    -----
    Which is great, but I can for the life of me not figure out, how it draws power, or where the IMU is located, let alone how the tilt is controlled? The videos show it keeping the camera level, but not operated via the remote/phone app. The stills show the gimbal without cables attached.

    Anybody knows how it ACTUALLY works?
     
  2. Pull_Up

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    I don't know because I haven't got it yet, but if there is no disassembly required the only two cables that are available from outside the shell are the jack plug into the camera (camera power and data), and the stock gimbal servo power cable that comes out of the shell into the top of the stock gimbal mount.
     
  3. tizzl10

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    good question..i was wondering the same thing.
     
  4. ZonComGMZ

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    I'm trying to wrap my head around how these work also. Let me know if this is correct.

    The FC200 has a Camera, 2.4Ghz WiFi with 2 antennae & an IMU. These plug into the P2V via 2 cables. The white one supplies power and data to the FC200 & the servo cable supplies power to the servo.

    If another gimbal is to be used it would have the IMU on the gimbal and not need the one in the FC200. Therefore I think they would have the white plug go into the IMU on the gimbal. Then I think it would have another plug that went out of the gimbal to get the Power & Video to the camera. I don't think this actually goes through any electronics in the gimbal but would need to be added so the one cable that supplies Power, Video, & IMU signals. Does this sound correct?

    White Cable

    P2V Gimbal
    FC200 (Video, Power & IMU)----------P2V

    3rd Party Gimbal with FC200
    FC200 (Video & Power)------------Gimbal (IMU)--------------P2V
     
  5. semaj

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    I think it's a lot simpler than that... All they are doing is replacing the built-in gimbal with there's... Nothing changes with the camera and it's plug... The flat cable that powers and controls the stock P2V gimbal is now the cable that powers and receives the tilt commands...

    That's pretty plug and play to me...
     
  6. DKDarkness

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    Thank you for your input. The FC200 does however not have a IMU. I tested this simply by detaching the FC200 from the P2V and tilting it. Nothing happend. Then I kept the camera level and tilted the PV2. The camera tilted. The camera seems to be controlled by the PV2's stabilizer. This also explains why the stock gimbal does such a crappy job at keeping level, and has the drop-off... The PV2 just assumes the position the FC200 is in, and adjusts accordingly. I am getting more and more curious about the Rotorpixel solution. Those who have ordered one, Pull_up :), I am looking very much forward to an in depth review :)
     
  7. gfredrone

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  8. DKDarkness

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    The IMU needs to be mounted on the camera platform:
    The principle of the camera stabilization using brushless direct drive motors

    In fact, gimbal based on BLDC motors is very similar to regular gimbal based on hobby servo. The main difference - each axis of rotation passes through the center of gravity (CG) of the "Camera + frame" system and rigidly connected to the BLDC motor. The absence of gear - a fundamental point that lets you use the inertia of the system is not to harm, but for good. In case of ideal balance of the camera, the rotor rotates freely without resistance and even without need of applying extra control force, which allows the camera to unleash from the disturbance from UAV frame. In addition, there is no backlash inherent gears or belts.

    To control the motors, a special controller was designed. It receives information from gyroscopes and accelerometers mounted on the camera platform. A standard IMU algorithm is used to define camera inclination angles. With the remote control, operator sets desired tilt angle. PID-controller calculates the amount of compensation and send command to the power unit, which controls the current in the windings and thus the direction of the vector of magnetic field in the stator. Magnetic field moves the rotor to the right position.

    Due to using IMU, mechanical part of the system is a very simple. There is no need in complex and expensive high-definition encoders for each axis. Just mount tiny IMU board on the camera platform, connect wires to controller and motors and all done!

    It gives impressive quality of stabilization compared with regular servos.

    (Source: http://www.basecamelectronics.com/company/)
     
  9. gfredrone

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    It receives information from gyroscopes and accelerometers mounted on the camera platform.

    The P2V is the camera platform. I would assume the info comes from the flat connector that's attached to the stock gimbal.
     
  10. ZonComGMZ

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    So the FC200 servo uses the NAZA IMU? The FC200 Tilt correction is actually the NAZA IMU sending opposite signals on how it thinks the P2V is tilted and not how the camera is tilted? If this is the case does that mean that tilt control signals to an external gimbal would include the corrected tilt from the NAZA IMU as well?

    What would be awesome is if a gimbal would have it's own IMU on the mount and then we could control the Tilt action of the gimbal with the 7e channel. I know this is how most other ones are done but to me it seems like it may be harder with the P2V especially if the tilt control from the 7e channel has the corrected signal from the NAZA IMU.
     
  11. Rotorpixel

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    We designed and manufactured a custom circuit board which accepts the thick white cable coming from the Phantom 2 Vision body. power is pulled from this white cable, and sent to the gimbal control board, and a thin/flexible custom cable plugs into the back of the Vision camera to maintain all wi-fi/FPV/telemetry information.

    The IMU is mounted on the top of the camera (not shown in the images online, but we're updating things soon) in a small protective plastic case, and thin wire runs alongside the thin white cable plugging into the back of the Vision.

    The 3-pin cable which normally goes to the Vision camera's crummy servo, instead plugs into our gimbal control board with another custom cable (thanks to DJI's choice of non-standard 2.0mm pitch connector...), which allows the pitch control to be maintained through the smartphone app.

    So, as our product description says, you just need to plug in 2 wires... the standard white cable into our custom circuit, and the 3-pin servo cable into our board.

    I hope that was helpful!

    Keri
     
  12. Itmustbemagic

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    Brill thanks for that
     
  13. DKDarkness

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    THANK YOU KERI!

    Facts and specifications directly from the manufacturer beats speculation and guesswork any day! :) Thank you again!
     
  14. ZonComGMZ

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    Thanks. So does that mean the Rotopixel is using it's own IMU for Roll & the IMU on the P2V for Pitch?
     
  15. gfredrone

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    You can see the IMU chip on the camera in the video on the Roterpixel website. Here is a SS of the IMU chip. I'm betting the complete setup will be neater than what you see in the picture as this is probably a proof of concept prototype. Looking forward to seeing the updated pics of the final product that will be shipping soon.

    Keri, any chance we can get some mesh wire loom on those wires to give everything a neater appearance?
     

    Attached Files:

  16. gfredrone

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    Yes I saw that but no picture was provided. Some people are visual learners and would probably appreciate the picture.