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Mini 6DOF Servo-Powered Motion Platform

Discussion in '3D Printing' started by Zed, May 16, 2018.

  1. Zed

    Zed VR Simming w/Vive

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    I drew this up and printed it to be able to experiment with 6 DOF platform control.

    The servo mounts fit Futaba S3003 and compatible servos. The bolt holes in the base to hold the petals together fit M3x8 screws. The bolts that hold the Traxxas links to the upper frame and also hold the upper frame together are M3x20, and the bolts that hold the Traxxas links to the servo arms are M3x12.

    You'll need support to hold the shelf overhang where the pieces bolt together during printing.

    The pieces are drawn to fit in a 4x5x5" print volume.

    You just print three base pieces and three top pieces, and bolt them together to get a respectable-sized platform. The links I'm using are Traxxas 3645 Turnbuckles / Toe Links, 61 mm (pair) (http://a.co/0WOcN2x). They fit an M3 bolt just about perfectly.

    8FCF01ED-D1DA-478B-A1A7-D4C9D1BD6061.jpeg 29CA55DF-BE3B-4431-87A0-97D6C9C8E691.jpeg 18C97B84-CAA1-48EF-A777-706D3492876F.jpeg singlet.jpg 414A5F42-1593-4FA5-824A-750026556D6E.jpeg TopPiece.jpg

    The Traxxas links are 2 for $10 so $30 total. The servos are $11 each at Tower Hobbies.

    I’m really impressed by the Traxxas links. They swivel totally freely but have virtually no slop. I need to get this wired up now but can already tell it’s going to be precise as all hell. It’s totally not necessary for experimenting with @Thanos' AMC1280, but I might turn it into one of the ball bearing balance tables once I get done with testing.

    I printed a plate with a stand for a toy plane so now it has the ubiquitous model on top. Both a blank and pedestal insert are in the Inserts .zip. Here it is all mounted up with a toy plane model from Thingiverse (https://www.thingiverse.com/thing:1341481) printed at 65% scale. It has a pocket underneath that the post engages to hold it on the platform. The pedestal post is in the very center of the insert.

    5E6E3BFB-A4B6-48CA-83DF-8B48717378C8.jpeg 24406A47-234A-4D4D-8E36-AABE2198125F.jpeg

    Today I wire it up...

    Attached Files:

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    Last edited: May 20, 2018
  2. Jerry Atrick

    Jerry Atrick this is my sim Gold Contributor

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    Nice job Zed, I will look forward to see it working.

    Jerry.
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  3. Zed

    Zed VR Simming w/Vive

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    @Jerry Atrick - I am kind of proud of it. Photos and .stl files posted.

    It’s trivially easy to build and I think will work like a champ. Haven’t powered it up yet though.

    If only building the real thing was this easy!
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  4. paulopsx2

    paulopsx2 Active Member

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    is it possible to create a "real" dof sim with this project? Something like a 1:1 scale ?
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  5. Zed

    Zed VR Simming w/Vive

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    Hey @paulopsx2 - I don’t know about that but some concepts may apply. In spite of the complexity, I do like the three identical pieces that bolt together concept instead of one big base or top. It would make it much easier to build or move. The servos are essentially gear motors with the feedback already built in so nothing really new there. Besides interfacing and power handling, the electronics don’t care about scaling.

    Printing parts full size is an interesting thought and somebody put a list together of the biggest 3D printers available: https://www.aniwaa.com/largest-3d-printers/

    The Erectorbot could print this full size which would be kind of a trip. It would be cool to just get six big hunks of plastic in boxes and bolt them together to have an instant 6dof Stewart platform. It a very interesting thought. :thumbs

    I’m pretty sure I’m going to build a 6dof and am sorting how to do it. I might have a shop make the base petals and upper frame pieces out of aluminum and then add my own stuff to it. Lots of details to work out on the best way forward.
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    Last edited: May 21, 2018
  6. FoxONe42

    FoxONe42 6DOF newbie

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    @Zed Very nice setup. Building a scale model 6DOF with RC servo is a great well to get some knowledge about motion platform and simtools. I did the exact same thing as you :) (also 3D printed with RC servo, but different layout though) and I am now in the learning process using LFS as a free demo for some testing.
    Where are you with your project ? Your intention is to use it with a flight sim I guess, which one ?
    Let me know as I would be interrested in your axis assignement.
    20180602_140707[1].jpg 20180602_182559[1].jpg
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  7. Zed

    Zed VR Simming w/Vive

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    Hey @FoxONe42 - it's built and it works. I havent integrated it with SimTools though since I havent wanted to disconnect my current 2 dof. I'm using @Thanos AMC1280USB controller with the mini platform and it has dedicated buttons on the front panel for heave and yaw and that's all I've done with it so far. Axis assignment is the same as in this video by Thanos, but I start at the nose and go clockwise from there for the actual connections numbering 1 to 6:



    I'm trying to sort strategies on a full-size 6dof before I start building but am getting closer. I am planning to use it more for flying and the arrangement for the full scale version kind of lops off the top of the vertical travel compared to a linear actuator 6dof. (https://www.xsimulator.net/community/threads/some-interesting-takes-on-stewart-platforms.12012/) I'd be using it mostly for P3D but also XP11 and AFS2.

    Nice looking platform! Congrats! And I agree - best to get bearings first to understand more about this stuff before diving in!
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  8. Thanos

    Thanos Active Member

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    Better control for 6DOF platforms in Simtools is coming soon:


    Thanks
    Thanos
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  9. Zed

    Zed VR Simming w/Vive

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    @Thanos - thanks for posting that video! This might be the missing link for the platform I'm thinking about building.

    A few questions:

    Do you use the "Linear Actuators" checkbox to differentiate between worm gear and linear actuators and if so, does that try to linearize the worm gear positions to better approximate linear actuators?

    I'm guessing that had the Linear Actuators checkbox not been checked, the Servo Arm Length and Servo Limit values wouldn't be grayed out?

    Since you appear to be compensating for the differences between linear and rotary actuators, I'm also guessing that turns out to be important? Is this something that has always been done for 6 dof setups? In another thread people are speculating about how much spurious movement you get with non-linear actuators and I'm sure they are correct that there will be some. Is that why you are appearing to correct for non-linear actuators?
  10. FoxONe42

    FoxONe42 6DOF newbie

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    Wow, awsome. Exactely what was missing for simtools. A advanced setup for 6DOF platform. That is just a perfect timing, I'll be able to test it on my 6DOF Scale model better I start the full size.
    Any idea of the release date by chance ?
  11. Thanos

    Thanos Active Member

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    Hi Zed,

    You are right, The worm gear actuators (with arm-rod configuration) need additional computations to calculate their speed and position according on the angle of the a arm of the actuator. Otherwise they are fast when the angle between arm-rod is around 90degrees, and slower near the top and bottom position.

    The linear actuators do not suffer from this issue and have same speed all along their travel.



    The servo arm length and servo limits values are indeed grayed out when linear actuator is selected (on motion from x-sim), but I haven't implemented that change yet for the simtools input.


    Thanks
    Thanos
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  12. Thanos

    Thanos Active Member

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    I'm stuck trying to learn some deeper C++ to fix the conversion issues I have. Simtools exports on String output (VB .NET) then I can capture them as CHAR which I then convert to string, and then convert again to INT... Which works well until certain values that shift the output of the simtools value in memory because of leading zeros are hard to capture as they appear a NULL in C++!!

    Anyway, I hope I get to the bottom of this soon, as I want it released yesterday!!! :)

    Thanks
    Thanos
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  13. Zed

    Zed VR Simming w/Vive

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    Thanks for answering, @Thanos! Very helpful! Looking forward to it!
  14. FoxONe42

    FoxONe42 6DOF newbie

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    @Thanos Just for my understanding: Is this going to be part of Simtools or is this a separate piece of software ?
    Thanks
  15. Thanos

    Thanos Active Member

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  16. FoxONe42

    FoxONe42 6DOF newbie

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    That looks very very promising. Hope it will be available soon, I'm looking forward to testing it with my scale model, and the "virtual" scale model designed with Sketchup Physics. 20180607_232256[1].jpg