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Question HELP Needed !!!

Discussion in 'Motor actuators and drivers' started by George Amemiya, Oct 19, 2019.

  1. George Amemiya

    George Amemiya New Member

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    Hi everyone !
    I'm planning my 6 DOF, and reading here and there on this forums I don't know anymore how to proceed.
    1. Should I use worm gear or linear actuators ?
    2. Worm gear is the option that I'm thinking about and to which I dedicated most time, however I still have a lot of questions: the platform I'd like to move will be at least 500Kg (considering I'll be moving 2 persons in the platform + seats + controllers + others? ) So I was looking for a 24V 1500W 4.5Nm 3000rpm brushed motor with a 60:1 gearbox and 55% efficiency at that ratio. So my first question is about final rpm. Is 50rpm after the gearbox ok? I read on a post by Thanos that between 10-15 rpm is good. Can somebody confirm this ? I mean, is this is the case, I can look for a cheaper motor ;). This will be controlled with 2 MM in parallel for every motor, and SMC3 I think. Another option is to use brushless motors, but I don't know anything about this. Can they still be controlled by MMs ?
    Well, for now, I think this can help me a lot, or at least to find a way to keep going. Thanks !!! :thumbs
  2. SeatTime

    SeatTime Well-Known Member

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    For a 2 person heavy rig, go straight to big AC motors/gearboxes.
  3. George Amemiya

    George Amemiya New Member

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    Thanks for the advice. What should I be looking for in terms of:
    1. Motor (Power, Torque, RPM, and for around here, 220VAC)
    2. Gearbox Ratio
    3. What kind of drivers should I use?
    4. What are the benefits over 24V?
    Thank you !
  4. SeatTime

    SeatTime Well-Known Member

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    Not something that I would like to give advice on, as I have not built something of that weight and it is a expensive exercise. Power supplies and drivers for a DC motor of that size are not readily available or cheap, sorry a couple of MM will not do the job. AC motors have no brushes, so one less thing to go wrong/wear out. AC motors are normally cheaper/smaller for same rated power. You normally purchase a suitable matched driver (VFD) with the motor.

    Good quality strong gearboxes are readily available to match most AC servo motor types. AC motors can normally be powered by your house power - no array of batteries etc needed and cables connectors switches/relays can all be much smaller (less current). There are big AC sim rigs already built out there, so recommend you do some research on this and other sites. There are of course some cons - often VFDs (AC motor Drivers) produce high frequencies in operation, which can be annoying to some people.
  5. SilentChill

    SilentChill Problem Maker

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    @Thanos should be able to help you out, hes got plenty of experience with the bigger AC stuff :)
  6. Thanos

    Thanos Building the Future one AC Servo at a time... or 6

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    Perhaps you may want to do some more research before going for DC motors... check my blog for some interesting links:
    http://motionsim.blogspot.com/2019/10/amc-aasd15a-servo-controller.html

  7. George Amemiya

    George Amemiya New Member

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    Hi again @Thanos , I've been looking around your blog, but still can't find my proper way. Can you please help me with the calculations for the platform I'm trying to do? I've already made some calculations for DC motors and a reduction gearbox, but not sure if that applies to AC motor, AC servos or even actuators (DC or AC). Here is what I got so far:
    500Kg Platform: 6DoF ... Each set (motor+gearbox) should carry 83.33Kg.
    I was planning to use a 30cm leverarm so .... something around 25Kg.m on each set that becomes around 245Nm with the gravity accel
    Gearbox with a 60:1 reduction ratio ... 4.1 Nm on each motor without considering gearbox efficiency (around 60%), to make a final number of 6.83 Nm torque for each motor.
    After all this calculations, I've been looking around for a 24V DC motor that can handle this and found this that a 130ZYT156 motor with neodymium magnets that can handle 6.2 Nm (that's the best I found @ 24VDC). The gearbox I was thinking is a NMRV75. So, as I was trying to achieve more torque out of the gearbox I came to the question on whats a good number for rpms after the gearbox (my calculations are based on 50rpms), but if I lower this number I can get more torque, and therefore this thread.
    So, what do you think ?? As I already said, any experienced help will help me find a way.
  8. Thanos

    Thanos Building the Future one AC Servo at a time... or 6

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    The platform on the video uses 1605 leadscrew (250mm/s speed) 400mm stroke actuators, and is capable of loads 300kg dynamic load (500kg static load) by using 750watt AC servomotors.

    Its way more efficient than planetary or worm gearboxes type, about 90% as the ball bearing leadscrew has much less friction than the reduction gears used on planetary reduction gearboxes.
  9. joe extraknow

    joe extraknow Member Gold Contributor

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    For Racing, I see some of requirements for actuators need up to 2g.

    For 500kg, you would need 500kg x 2g = 9800Nf.

    below, they used 6 ac servo motors with 3kw each:

    • Informative Informative x 1
  10. Thanos

    Thanos Building the Future one AC Servo at a time... or 6

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    I wonder why they use external position sensors? That is so old technology by now...
  11. SeatTime

    SeatTime Well-Known Member

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    In my eyes, that whole rig is 'old school'.. No VR and no G systems.
  12. George Amemiya

    George Amemiya New Member

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    Hi ! Thanks for the post. The platform is for X-plane, won't be used for racing, but anyways, I get the 9800N (cause the 2g requirement) and I'm sorry for my ignorance, but what are the calculations to finally decide for 3KW motors ?
  13. joe extraknow

    joe extraknow Member Gold Contributor

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    I was there and saw the motors:

    Attached Files:

    • Informative Informative x 1
  14. joe extraknow

    joe extraknow Member Gold Contributor

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    Here is how to calculate:
    Say your actuators,,,,, has max movement x.
    You want to move (heave) the rig platform in max vertical distance of 400mm or 0.4m

    so the energy need is the potential gain:
    mgh = 500 x 9.8 x 0.4 = 1960 J

    now if you want to move the rig from min to max point (0.4m) at 2g acceralation, the time is needEd:
    T =sqt (o.4/9.8)= 0.2 sec.

    the power needed = 1960/0.2 = 9800 w
    Divide by 6 so you need 1600w motor each, but assume your motor is 70% efficiency then you really need 2300W motor though.

    hope this is helpful

    joe
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  15. SeatTime

    SeatTime Well-Known Member

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    I know the big moving rigs look cool, but looking at it from a different angle (yes I am pushing my G system barrow again :rolleyes:) and from all the work that I have done with sonics, G Seats and active harness systems, I wonder if a big expensive 'motion platform' is really even necessary, or even a good 'bang for buck' simulation wise, especially with VR. Apart from when I use No Limits 2, my 6DOF now is left to do small 'transitions' with the G systems simulating all the extended forces and actually doing a better job of it. I even think for multiple passengers were VR can get a bit complex, the use of wide displays and limiting the view of the outside world with screens would also work well. Anyway food for thought.
  16. SeatTime

    SeatTime Well-Known Member

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    To back up my work, just last week I had a friend on my simulator and he was flying in DCS. When he was 'banked' in a extended turn with the G systems/harness applying continuous forces to his body, I asked him what angle he thought the rig was at and he said 45 degrees when it was actually flat at horizontal :). Apply the right visual and pressure cues to the body and blank out the outside world and it will be fooled very easily. Of course as many people already know, VR in itself can do this, but adding the correct and well synchronised forces to the body really adds to immersion and can reduce the chance of VR sickness.
    • Agree Agree x 1
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    Last edited: Oct 21, 2019
  17. George Amemiya

    George Amemiya New Member

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    Thanks again Joe, but I think you're missing my point, I can buy 1KW motors (and you be here when they're delivered) but that doesn't mean my platform will work. What I mean is that there must be some sort of calculations before the decision of buying a motor that have some specific specs (3KW in the case you showed us).

    That's what I mean !!!! It was most than helpful !!! Thank you very much Joe !!
  18. George Amemiya

    George Amemiya New Member

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    I've been doing some math and this platform is getting more and more expensive as I keep reading the forums, so I think I'll be changing the design a little. Btw, as for a flying sim, I know 6DOF is the way to go, but, will 3DOF do the trick ? I think I'll run a poll on that. What do you think about that, both the poll and the change of plans ?
  19. George Amemiya

    George Amemiya New Member

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    Hey @Thanos, does induction AC motors can work accurately ? I'm guessing I'll still need a VFD for them ?? Does your AMC1280USB work with this motors ?
    Thanks !
  20. Thanos

    Thanos Building the Future one AC Servo at a time... or 6

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    AC motors with VFD inverters are low performance in slower speeds. They need at least a minimum 60hz signal to start moving instead of 0, meaning they will step in low speeds and won't be very accurate (overhooting etc.)

    See this article which explains mainly the difference between AC Servomotors and BLDC motors but also shows a bit about VFD inverter AC motors for comparison:
    https://www.orientalmotor.com/brush...rushless-dc-motors-servo-motors-inverter.html
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