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Cousin of OSW (Open Sim Wheel)

Discussion in 'DIY Motion Simulator Projects' started by Gadget999, Sep 23, 2017.

  1. Frederiksen

    Frederiksen New Member

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    Thanks for your reply. I will watch those videos.
    I was just asking about the wiper motors because I get them for free and I thought that could save me some money but I guess that is not the case.
    I'd like to build a dd wheel with a budget of about $150USD.
    Motor: my1020 500w for $40. If I want the 1000w it would cost me $60. Is it worth the difference?
    Encoder: 600ppr for $10
    Power Supply: 2 modified PC power supplies for $20 each
    Motor driver: 2 BTS7960b for $14
    Arduino Leonardo for $8 or STM32F4 for $10
    Does everything on that list look good? Also for the steering wheel could I get one from the junkyard and remove the airbag? Or would that be too heavy?
  2. danove_b

    danove_b Member

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    In Theory it might be a good motor. If you reverse calculate, it should give 3.18 Nm @ 18 Amps. My guess is that you may be able to push a little more amps at stall with 12 V, but not much. So maybe 4 Nm if you use 12 V and the double (8 Nm) if you run it at 24 V. The BTS7960 works good with 24 VDC. You can just measure the resistance and calculate the stall current with 12 respective 24 volts. The motor should produce 3.18/18= 0.177 Nm/A at stall.
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  3. Frederiksen

    Frederiksen New Member

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    Would you recommend I buy it? It's $10 cheaper than a my1020 and I read that treadmill motors are much easier to attach an encoder to. Also how sure can you be that it will produce about 4nm? Is 4nm a good amount or should I go higher?
  4. danove_b

    danove_b Member

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    I cannot guarantee anything. Do you have a link to the motor? If we know the resistance of the winding we can easily calculate the stall current/torque. 4 Nm is not enough for me, even that I have a small wheel. (Logitech momo red)
  5. Frederiksen

    Frederiksen New Member

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  6. Gadget999

    Gadget999 Active Member

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    My Motion Simulator:
    2DOF, Arduino
    I am struggling to get the encoder working with the STM32F4 disco

    i assume it wont work at the 5v i am feeding it from the board

    what encoder do you guys use - does it work ok at 5v ?

    here is the one i am using -- https://www.minikits.com.au/ENC-360-6
  7. Gadget999

    Gadget999 Active Member

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    My Motion Simulator:
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    problem solved - encoder a and b were sharing the same pullup resistor
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  8. Frederiksen

    Frederiksen New Member

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  9. danove_b

    danove_b Member

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    The label states 6700 rpm and that means that the theoretical torque will be even less that my reversed calculation gave. I'm a little bit skeptical...
  10. Frederiksen

    Frederiksen New Member

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    Thanks for the reply. If you think it's still a reasonable torque at 24v maybe I should buy it at $30. I had seen two my1020s for $40 each but those have gone up in price to $60. Therefore I'm kind of stuck. Do you have any idea where I could find a <$40 motor that would serve this purpose? Also, I read that a power steering motor from a car might work. What do you think of that idea?
    Last edited: Dec 22, 2018
  11. danove_b

    danove_b Member

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    When I look at the motor, it just look a little bit "thin" for the job... I have also thought about using a complete power steering rack from a car, but according to a guy that have tried (I think there is a link in this tread somewhere), it is to much inertia because of the gearbox. If you think you are satisfied with a lower torque solution, I should go with a 36 VDC version of the MY1016 or similar.
  12. Gadget999

    Gadget999 Active Member

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    At that price just buy it - at 6700 rpm it may make an excellent motor for a ballscrew linear actuator !
  13. Alexey

    Alexey Well-Known Member

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    Not worth it, go with the MY1020. Tried and tested.
  14. danove_b

    danove_b Member

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    After some hours of reading on internet, the best option to build a DD wheel now must be with a Hoverboard motor and the Odrive card.
    The only thing that i yet haven't any good idea about, is how to connect the rotary encoder. Remove the tire from the wheel and then connect the encoder with a belt maybe. I tested my MY1020 in a similar way and it should work ok i think. Maybe someone have a better idea?

    The Odrive card:

    https://odriverobotics.com/shop/odrive-v35

    159$ for the 48 VDC version

    I searched the internet for the torque data for hours... finally found it on the odriverobotics site... almost 13 Nm!
    https://docs.google.com/spreadsheets/d/12vzz7XVEK6YNIOqH0jAz51F5VUpc-lJEs3mmkWP1H4Y/edit#gid=0

    You can buy a hoverboard motor for about 40$

    From what I have read until now, the standard firmware should do the job.
    - It has PWM input, but for now only for RC PWM, but expecting 0-100% duty cycle PWM in future releases...
    - It has serial interface where you can send torque/current command until they release a PWM function (one arduino in the middle that CCP the PWM from MMos and send it out on serial to Odrive card)
  15. Gadget999

    Gadget999 Active Member

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    I did think a hoverboard motor would make a good candidate for a ballscrew motor

    Being brushless it may have cogging as you rotate it

    If you buy a broken hoverboard you will get 2 to play with !
  16. Alexey

    Alexey Well-Known Member

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    My Motion Simulator:
    3DOF, DC motor, Arduino
    Most of the cogging will be eliminated by the controller, if it has the required control methods though..

    I'll be going through this myself shortly. I bought a 3 phase AC servo motor used in industrial sewing machines for $50 from a local workshop.
    I then bought a 3 phase servo drive from ebay for $90 and have stripped out the micro controller so that I have direct access to the 6 pwm lines.

    What I am going to try to do is make my own phase vectoring drive or Field Orientated Control (FOC). This is pretty much how to control torque motors. What I was thinking of doing was to
    determine the exact position of the rotor in relation to the 3 phases and create a constant force in the required direction by balancing out the phases (something like, a phase vector of 30 degrees to the rotor, increasing/decreasing in relation to required torque). This is certainly going to be a deep dive for me in terms of coding so any advice would be much appreciated.

    https://en.wikipedia.org/wiki/Vector_control_(motor) a good explanation of what I will be trying to implement.
  17. danove_b

    danove_b Member

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    Sounds exiting indeed! I have also spent the last month thinking of this from time to time. I'm no expert here, but I will give some advise based on my own ideas, experience and what I have learned from internet so far:

    - don't waste time (or cpu time) by doing a closed loop trying to regulate the current. The motor is going to work in stall mode or near stall mode 100% of time = current is proportional to the voltage. It may have some meaning if you are a "drifting" driver where you let the wheel turn of it self in a higher speed, but I doubt it is noticeable for the driver.

    - I don't know what Kind of hardware you have planned to use, but I think there is no "Arduino" chip that can handle 6 PWM channels with the precise timing that's demands here. Maybe if you make a lookup table with a pwm constant for every electrical degree it may be possible...

    -If you have a STM32 card, I will gladly buy you a beer or two if you could try the BLDC output function of the MMos hardware/firmware. It should be a minor job if you already have the 6 pwm lines ready! (Hey, If you don't have a card, skip the beer, I order a card for you)
  18. Alexey

    Alexey Well-Known Member

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    Unfortunately the BLDC mode does nothing on the MMos software, I did try it and found that it doesn't output anything.

    I don't actually need 6 pwm channels as the secondary channels are just complimentary (inverted). Even if I do need them I have an Arduino due.
    I do have a few other chips in mind but arduino will suffice for now.
  19. danove_b

    danove_b Member

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    https://discourse.odriverobotics.com/t/idea-direct-drive-sim-racing-wheel/544/2

    This has already been tested with negative results...
  20. Gadget999

    Gadget999 Active Member

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    do you have a link to the negative result ?