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Slow Speed Testing

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by JAD, Apr 8, 2020.

  1. cubexxx

    cubexxx Member

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    The thing with these videos is, even if you can't see the "jerkyness" you will be able to feel it very clearly if you touch to rotor with your fingers. On a direct drive wheel this is even more important, the simucube 2 states: "Encoder Resolution 22Bit (4,194.304 CPR)"! Also just because an actuator resolution of 0.01 mm sounds impressive, it doesn't mean that you can't feel it, you'd have to make experiments. I think you can feel a vibration with an amplitude of 0.01 mm and a frequency of say 10Hz.
    • Agree Agree x 1
  2. pmvcda

    pmvcda aka FlyPT

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    My Motion Simulator:
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    It's not comparable.
    Because the wheel is direct drive in your hands and we are speaking of rotation.
    The actuator is linear and indirectly connected to you and you get play in all the joints.
    Not saying that you don't feel nothing, but it will be so subtle and your brain is in another place, it's not like the wheel.
    It's going to be just road noise.
    My actuator is low resolution, and in normal use it's OK. Yes could be better, but $€

    And the games! Yes some famous ones are awful in road noise, specially some laser scanned tracks! Never thought saying it, but some feel baaaaad.
    • Funny Funny x 1
  3. cubexxx

    cubexxx Member

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    All true, was just trying to say that your hands may be a better tool to judge smoothness than your eyes. Resolution-wise I think the 10000 cpr of the AASD and the 8192 cpr of the AMT102 (commonly used with the odrive) with a pitch of 5mm/rev are ok, but I wouldn't go lower personally. I think higher resolution would still be beneficial for smoothness of control, especially for slow movements
    • Agree Agree x 1
  4. JAD

    JAD Active Member

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    I think the resolution of the encoders we are all using are easily sufficient and wouldnt be much of a factor in this notchiness feeling Im seeing and feeling.
    My understanding at the moment is we are observing the differences in motor construction.
    Im my case, I think using the DC brushed motor is inherantly going to give the most notchiness
    I guess the main factor is the brushed commutator and to a lessor degree, the low pole count.
    Im actually impressed these motor drivers can achieve the accuracy that they do given there are only 18 contacts on the commutator and 2 or 4 poles(Im not sure how to count what Im looking at here).
    Heres a pic of an old burnt out unit I have in my rig.
    upload_2020-4-26_14-8-42.png

    It looks like there is a good improvement going to BLDC and then another improvement going to full AC servo motors.

    Having thought about it now.
    Im now in the market for 80ST-M02430 for my next upgrade.
    The best price I can find right now on Aliexpress is AUD$302 each inc delivery + GST.
    Im in no rush so just watching the prices ready to jump on a bargain.
    Just gotta wait for some of the better prices that I saw last year. I thought it got down to AUD$250 ea back then.
    But it might be as good as it gets for the next 6 months.
    upload_2020-4-26_14-28-27.png
    • Like Like x 1
  5. JAD

    JAD Active Member

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    I just spotted that there was a cheaper delivery option,
    so the price is down to AU$292 ea inc delivery +GST
    upload_2020-4-26_16-2-27.png
  6. JAD

    JAD Active Member

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    Just a note to conclude the main reason I started this thread.

    The upgrade to AC Servo is done and Im happy with the result.
    • Like Like x 2
    • Winner Winner x 2
  7. Gadget999

    Gadget999 Well-Known Member

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    My Motion Simulator:
    2DOF, DC motor, Arduino, 6DOF
    Sim looks great :)