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Showroom my 6dof (reproduction of ckas)

Discussion in 'DIY Motion Simulator Projects' started by vulbas, Mar 27, 2014.

  1. Konrad

    Konrad Gdynia

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    My Motion Simulator:
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    Hi,

    control signals for the inverters are pwm??

    Regards
  2. vulbas

    vulbas Active Member

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  3. speedy

    speedy Well-Known Member

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    My Motion Simulator:
    3DOF, AC motor, Arduino, Motion platform
    actually this is very sophisticated and expensive circuit board for a " pwm to 0-10v " conversion ...
    @yobuddy did that cuircuit before and I confirm it is working perfectly ...
    here ...
    Yobuddy’s ~EZ~ Series Layouts!
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  4. eaorobbie

    eaorobbie Well-Known Member Staff Member SimTools Developer Gold Contributor

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    My Motion Simulator:
    2DOF, DC motor, JRK, SimforceGT, 6DOF
    And then can be driven with a cheap Ard too.
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  5. tronicgr

    tronicgr

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    -Except that you missed the SPI DAC chip on the 6DOF extension board before the amplifiers... and the high power transistor arrays to drive the 24v signals for all 6 inverters... Its not using PWM!

    -That was my original circuit, that was redesigned in better PCB layout. Author forgot to provide source...
    Last edited by a moderator: Sep 11, 2014
  6. vulbas

    vulbas Active Member

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    here's a video with dirt 3.
    Limiting axis 60%
    I made another video with axis Limiting to 100%. it's very violent.
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  7. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    My Motion Simulator:
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    Great video @vulbas! It really is a wild ride you have there.
  8. vulbas

    vulbas Active Member

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    My Motion Simulator:
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    limit axis 100%



    100% at 2mn50
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    Last edited: Sep 25, 2014
  9. SeatTime

    SeatTime Well-Known Member

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    My Motion Simulator:
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    Nice sim :thumbs . Recommend though that you fit a harness, as just like in a real race car it saves you from having to hold yourself in the seat with just your arms when things get rough.
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  10. Tino

    Tino Member

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    Hi @vulbas,

    Motion looks really good!
    How long are your gearbox crank arms?
    Do you know approximately how much mm/s speed are you getting from your platform?

    I'm trying to decide whether to go for higher RPM and shorter
    crank arm, or lower RPM and longer crank arm
    ?

    With longer crank arm and lower RPM I should get approximate the same speed in mm/s and more motion
    but I've hear that you need higher RPM for racing sims...

    Does anyone know if there is a minimum RPM for a good racing simulator, or can you use lower RPM if the crank arm is long enough?

    All the best, Tino.
  11. bsft

    bsft

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    @Tino , rpm of motor and linear travel are 2 different things.
    Yes a longer lever on a slower motor will give you the linear travel speed you need, but at the cost of torque.
    Generally, the minimum linear speed for racing is 200mm travel per second. Faster is better, although I know some will disagree.
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  12. Tino

    Tino Member

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    Hi @bsft ,
    Thanks for your reply.

    Yes, but using the same motor with lower RPM for a sprocket system means that I'm using a higher gear ratio, which would increase the torque.

    120RPM 14Nm motor with 3:1 sprocket system results in:

    40 RPM, 42Nm torque, and could lift 42 KG with 10 cm lever, and if my math is correct;
    63Nm and 63Kg lift with 7.5cm lever.

    Linear speed with 7.5cm lever would be 310 mm/s

    With 4:1 sprocket system I would get:
    30 RPM, 56Nm, 56Kg lift with 10cm lever, liner speed = 310 mm/s

    I'd get about the same liner speed and slightly less torque (56Nm vs 63 Nm = 11.2% difference), but with much longer lever!
    7.5 cm vs 10 cm is 25% difference in motion.

    I'm sure I could find better example with different lever lengths and RPM, but these are easy to calculate.

    That's what I was hoping to her, I think that using higher gear ratio would give me almost the same speed and torque, but I'd be able to get a bit more motion :)

    P.S. @vulbas , sorry for going off topic :)


    Regards,
    Tino.
  13. riton

    riton Active Member

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    must increase power!
    in my case
    30Rpm 330Nm 1.1kW 480mm / s
    240mm Lever

    it is understood that the right speed is at about 30 RPM

    then it is necessary to increase the range of effects for a range of good effects.

    otherwise the effects are saturated.

    more the simulator is fast and more the range of effects gives a better definition.
    if the simulator is fast increases the range of effects.

    effects that were "invisible" not felt, then this becomes.

    you must also remove the ramp, otherwise the effects are reduced.

    you must take into account the inertia



    how you calculate the speed of 310mm / s?
    30 RPm 310 mm / s ?

    180 ° of cam movement.
    30Rpm = 0.5t / s =1 / 2tr / s =
    180 ° / s .
    with 10 cm lever =
    200mm / s
    Last edited: Sep 28, 2014
  14. Scratch

    Scratch Active Member Gold Contributor

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    Wow, this ride really looks cool. Definitely you need a harness in this thing, like @SeatTime proposed :eek:
  15. vulbas

    vulbas Active Member

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  16. Tino

    Tino Member

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    Hi @riton,

    Liner speed is just the lever distance traveled in one second.

    Instead of levers, think of a wheel.
    To have the same speed, bigger wheel rotates slower than smaller wheel.

    V = r x ω

    You can get ω (rad/sec) by dividing rpm with 9.5493 or with this calculator

    30 rpm = 3.141 rad/sec

    3.141 * 0.1 m = 0.3141 m/s

    You can have the same speed with 5cm lever spinning at 60 rpm, or 20 cm lever spinning at 15rpm.

    Slower rpm and longer lever have same speed, but also more motion range.

    I'll be using chain and sprocket system for my platform so I might go with longer lever and higher gear ratio to get a bit more motion.
  17. riton

    riton Active Member

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    sorry but it's not correct for heave.


    30 RPM , for 180° = 1/2 RPM by s
    180° /s with 24 cm =480 mm/s


    180 ° of cam movement.
    30Rpm = 0.5t / s =1 / 2tr / s =
    180 ° / s .
    with 10 cm lever =
    200mm / s

    for a 6DOF, for heave it's the same thing.


    your calculation is just for a circular motion.
    but then we have linear displacement of 180 ° (or less)

    Then according to the attachment point on the platform we need to talk angular velocity and consider the lever (attachment point on the platform, and the angle
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    Last edited: Sep 28, 2014
  18. Tino

    Tino Member

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    Hi @riton,

    You're right, I'm not talking about heave.

    I'm talking about choosing appropriate lever length and gear ratio.
    Let's take my 120RPM 14Nm torque motor, for example

    I can have 31cm/s linear speed either with:
    • 5cm lever spinning at 60RPM, motor should lift 56kg (56Nm torque)
    • or 10cm lever spinning at 30RPM, motor should lift 56kg (56Nm torque)
    • or (to take it to extreme) 20cm lever spinning at 15RPM, also 56Nm torque
    Longer lever means having more motion, so I would like to know why is it understood that "the right speed is at about 30 RPM"?

    Can you please explain why is 30 (or some say 50-60RPM) the right motor speed?

    I though that liner speed (mm/s) can describe motion better than just rpm (if you you have different sized wheel spinning at same rpm, their speed will not be the same)

    Here is one fast and smooth sim with long lever:


    Does this sim also looks fast to you?

    Best regards,
    Tino.
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  19. riton

    riton Active Member

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    I determine the distance of mechanical movement that I would have, for example 48 cm.
    I determine the torque I need with this lever arm, 24 cm so.
    (your math is correct for the couple and the length of the lever arm, of course.)

    the heave speed becomes 480 mm / s !!
    for directions: surge, sway, heave, it will be that speed
    the cam moves less than 180 ° on a 6DOF, but considered that it was 180 degrees with mixed effects.

    the other effects there will be a rotation angle speed is different.
    can be considered to be the inclination "X" degrees / s

    in 1s the cam runs through 180 °.

    my reasoning with the displacement of 180 ° of the cam.
    and the lenght of this cam.
    That's why I think 30 is very good.

    if your cam is 15 cm to 30 tr = 30cm / s!
    not enough ??

    30trs at 50 Hz of course can become 60 rpm at 100Hz !!
    if the couple is correct with the power margin, you have think of inertia.


    Why 60 rpm? even faster? it is no longer reasonable !!
    with 60rpm speed X 2 = 960mm/s !! crazy ! 1 meter /s!!

    with 15 cm arm = 600mm/s

    some take 60 rpm, and i see 120 rpm DC motor , but there is a lack of power, the engine runs more slowly because of inertia and lack of power.



    your simulator moves fast!
    I think it's not bad!
    I tried to time the movements, around 1s for travel Surg heave, sway.

    what is the length of your cam?
    and motor speed?
    Last edited: Sep 30, 2014
  20. Tino

    Tino Member

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    Hi @riton

    Unfortunately this is not my simulator (I wish it was mine :)
    I think BFG10K (Yue Qi) made this simulator, I found it on Thanos blog.

    I want to make much smaller simulator, so six motors have to lift less than 110Kg total;
    me (80Kg)+ seat(12Kg)+ oculus rift(0.3kg) and wheel or joystick (5-10kg).
    With 4 to 1 sprocket system I should get about 56Nm torque with 10 cm lever at 30RPM, each motor should be able to lift 56Kg. Speed should be 31cm/s.

    I think it's better to go for a longer lever and slower RPM, but please let me know if this is not correct.

    Best regards,
    Tino.