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MMOS controller with cheap servo drive and motor

Discussion in 'Direct Drive Wheels' started by sikjar, May 22, 2017.

  1. Gadget999

    Gadget999 Active Member

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    i suggest you use a DC motor and a IBT-2 motordriver - you can use a arduino leonardo or a STM324f Discovery to control the Motor
  2. MegamanAT

    MegamanAT New Member

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    they are accepting digtal pulse and direction and analog (position mode) and -10 +10v analog (torque mode)
  3. MegamanAT

    MegamanAT New Member

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    yes, probably the only way for a cheap solution.
  4. MegamanAT

    MegamanAT New Member

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    But I realy don't see the benefit of a 5-6nm dd-whell. That's about the level of a T500RS... A 12nm stepper or 20nm servo would be much better in my opinion.
  5. Gadget999

    Gadget999 Active Member

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    if you find time - there is a video of a guy who is a racing driver and he tries out the osw

    first thing he does it reduce the ffb strength so the wheel feels more realistic

    i think it was reduced to approx 30%

    I have a dc motor from a winch - it looks like it would dislocate my arms !

    starter motors are several kw iirc
  6. wsx820919

    wsx820919 New Member

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    In fact,in the "Son of OpenSimwheel - An Experiment" page 1 videos It has been given to everyone Enough clues about design stepper wheel,People who have used stepper should know,when the stepper motor running but locked the rotor,the rotor must be Happen torque impact,This is a need to overcome,but,how do this,The rotation of the magnetic field is the key,when the stepper motor running but locked the rotor,but The motor controller is still continuing to input PWM,The magnetic field is still spinning,the rotor will be between have torque or have no torque cycle ,therefore used the encoder,encoder followed the position of the rotor,then controller KeepThe magnetic field of the first or next shot in the direction of rotation at any time,And then according to the duty cycle by stm32f4discovery PE9(MMOS),Real time change of current,This is probably the idea of development,I'm trying to do something about it。。。


    PS:Please forgive my bad English.....
  7. henrique fernandes

    henrique fernandes New Member

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    is this project dead? I`m also thinking about using these Chinese cheap drivers+stepper because the budget is a strong limitation for me LOL.My idea is to buy a NEMA 34 of 8.5NM and driver, which I found for 180 aud on ebay, but I don't have any hardware yet
    I read the whole topic and a possible issue that you guys have found made me think about a different technique to control the torque. One was thinking that the power supply was too weak, and because of this, the motor had no torque. Don't you think this can be the solution?
    what if we use this PWM out of the DISCOVERY to control the voltage supply on the "cheap driver"?
    my idea is to use the PWM direction on the driver to set the correct direction and the PWM signal we could reduce the voltage on the power supply pins of the Driver.This way for a low-intensity effect the voltage would be low, consequently the Direct drive weak, and for a strong effect the voltage would be close to the nominal, and then we would have the maximum torque of the motor. This way all the setting of the interface would keep working normally, and we would be able to set up stronger or weaker effects.
    Does anyone think this idea can work? and have the hardware to test?
    Suggestions?
    Possible side effects?
    so far I believe this can work, my only concern is about the minimum voltage of the Driver, that maybe we would need to respect in order to avoid damage. test.png
  8. sikjar

    sikjar Xiao Nie

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    I am not developing on this project any more, and I don't visit this forum very often, so most questions don't get any reply, sorry about that.
    As for your suggestion regarding about regulating the voltage, as far as I remember, the manual for the driver says that voltage only affects the motors speed (RPM), and not the torque.
    The torque is mainly influenced by the current (amperes) that the power supply can deliver.
    I tried hooking the driver up to a variable power supply, and it doesn't seem to make any difference to the torque whether it gets 24 volt or 80 volt.
  9. henrique fernandes

    henrique fernandes New Member

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    You're right, controlling this voltage the torque doesn't change, I would need to control the current of the coil to change the torque.
    I don't know if there is anyone still interested in building something like this, but I will spend some minutes to share what I took hours find out.
    Basic fact - to control the torque we need to control the current(not the voltage as I thought).
    Following this thinking, I made a lot of research and I found that the most of the "Chinese cheap drivers" have current control by chopping the current. The problem then was that the mode of we set this current control is mostly through switches, so we couldn't control it by Arduino.
    Searching a bit more about chopper stepper drivers I found some circuits DIY based on the chip Toshiba tb6600, which can drive steppers using 10 to 42VDC up to 4.5A, and the mode of control of this circuit is via 10K pot, so the plan is to use one of this driver ( I found for 10 aud from China), and replace this pot by a X9C103 Digital potentiometer, so we can control it via Arduino

    PS: As the intention is to build the steering wheel not the driver I'll jump this part and buy one of this,(if someone is interested just let me know that I can share the project of this driver and some more information that I found about Chinese drivers, because I am convicted that we can use this "mod" in any driver)
    Cheap Driver Alternative.png I will copy the main idea of this post, use an Arduino to convert the PWM coming drom the DISCOVERY board into a percentage of torque( or percentage of Amps applied to the coils), controling this way the toque
    the direction signal I will use to set direction and a constant speed, sending pulses to the driver ( I'm not sure about using a constant speed, but it looks like this is the way the commercial FFB wheels work, constant speed and variable torque depending on the effect)
    I would like to listen to a second opinion about this crazy plan. Do you guys think this would work? any suggestion about the circuit or the mode of control?
    • Like Like x 1
  10. gefa

    gefa New Member

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    Hello, I am really interested in Your project, Did it succeed and is it working? I would really appreciate if You send an answer to my e. gefa96(etta)gmail,com
  11. henrique fernandes

    henrique fernandes New Member

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    Hey mate. I'm still waiting for some stuff from China. I got my discovery board and made it work with my arduino. I'm using a Chinese clone of mega2560 and I made a program to read the pwm from the DISCO and depending on the duty circle control the digital potentiometer and send pulses to the driver to rotate the stepper.
    To proceed I need my stepper that is coming from China to test the current modulation but I believe it's gonna work
    On the next couple of weeks I may have more progress to post here

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