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6DOF sim / linear actuator diy / sabertooth-arduino

Discussion in 'DIY Motion Simulator Projects' started by baykah, Dec 12, 2016.

  1. OZHEAT

    OZHEAT Member

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    PWMmin This is the minimum duty cycle that is used to drive the motors to their target position. For example if the motors are already close to target they will not need to be driven as hard as if they are a long way from target (or they may overshoot and oscillate). The reason we don’t just use 0 is that due to friction, loads, and other factors, the motors will need a certain minimum current just to get them moving. This helps us set that minimum. Settings are in the range 0-255 (which are mapped to the range of 0-100% duty cycle) however cannot be greater than PWMmax setting.

    source https://www.xsimulator.net/communit...3dof-motor-driver-and-windows-utilities.4957/

    With the original SMC setting PWMmin to close to zero you will not get any small movement corrections, just large PWMmax moves.

    With SMC softstart you will still not get any small moves, but with softstart large moves it will ramp up from PWMmin to PWMmax in defualt 30 unit increases.
    With the example above PWMmin~1 .

    When commanded to move
    cycle 1 PWM=1 no movement
    cycle 2 PWM=31 no movement
    cycle 3 PWM=61 finally some movement
    cycle 4 PWM=91 faster movement
    cycle xx till it reaches PWMmax is reached.

    set your PWMmin =55
    cycle 1 PWM=55 start movement
    cycle 2 PWM=85 faster movement
    cycle 3 PWM=105 fast movement
    cycle xx till it reaches PWMmax is reached.

    Why subject the motor with pwm rates that isn't going to do anything but heat the motor for 2 cycles?

    NB. l don't really take downwards motion in to account but it is upwards motion which is important
  2. baykah

    baykah Active Member

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    Thanks for the update

    I have a few issues now that I added my weight on the rig (70kg)

    => The PSU are so easily going in safety, I need to check my sabertooth configuration, When I installed the resistor for the braking regeneration ... but I did not put diode between the saber and the PSU ...
    I will add some asap ... as I don't want batteries ...

    => 1 actuator go nuts, vibrating strongly even without my weight ?, puley is not loose, potentiometer is ok and the ONLY thing that can solve this is reboot of the arduino OR connect with SMC3 software...
    The strange thing is that it is only with simtool ..... not problem when testing with SMC3 soft ...
    I tuned done to 115200 in simtool (and the arduino) and it did not appeared again ... but did not tested long since ...

    Also, I have the feeling the USB wire are important, I think I saw on gregory topic the same behavior with his laptop, by using the front USB3.0 connector my case PC I get stange things ...

    To be looked at ...

    Last question in mind :

    Do you think I need to get my 6 PSU wired together ?
    Right now I've set things with 3 module of :
    - 2 PSU
    - 1 Saber
    - 1 Arduino
    They share commun ground (small wire) because the 5V supply of the first sabertooth module is going throught ALL the end stop of ALL the actuator and finaly in ALL the security input of the sabertooth.
    The other security is a relay on the 220V of the 6 powersupply with the emergency stop.

    rgds
  3. SilentChill

    SilentChill Problem Maker SimTools 2.0 Beta Tester

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    I am not disputing anything about how it works, however through experience using my actuators using any PWMmin just creates heat and noise I don't see any benefit with any movement setting it anything other than 0.
  4. SilentChill

    SilentChill Problem Maker SimTools 2.0 Beta Tester

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    Yes I would run them in parallel and also get a nice beefy battery and you can run the return voltage back to the battery. My server PSU's tripped all the time so I switched to LED psu's
  5. Tim McGuire

    Tim McGuire "Forever a work in progress"

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    @OZHEAT

    Having PWMMin set too high actually makes it harder for the sim to make small corrective movements, not easier. It means that if the setpoint moves downwards (working with gravity) the control loop will force the output harder than it needs to . It also causes the loop to go unstable faster than having a lower value would (the large minimum step means that the loop will oscillate at a lower proportional gain than it would otherwise, combining this with the backlash that most of the gearboxes have only makes it more difficult). You can get around having a lower PWMmin by increasing Kp and Ki to compensate for it. With a higher value of Kp the ramp up to minimum movement value should be nearly instantaneous anyways.

    Personally I've had the best results when I set PWMmin to the minimum value needed for the sim to move in the downwards direction, this provides a good balance between the two sides of the argument.You also get the added benefit of not having any coil whine when the sim is sitting still.

    Like I said though, this is just my personal experience.
    • Informative Informative x 1
  6. SilentChill

    SilentChill Problem Maker SimTools 2.0 Beta Tester

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    That's what we have matey "PERSONAL EXPERIENCE" this guy has none, I'm sure he just likes to try and piss people off with his theories and what he has read with no actual Rig to back up his claims or advice.
    • Like Like x 1
  7. Michał

    Michał New Member Gold Contributor

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    What about CV joint used in car's front wheel. Is it suitable for 6DOF actuators?
  8. SilentChill

    SilentChill Problem Maker SimTools 2.0 Beta Tester

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  9. Michał

    Michał New Member Gold Contributor

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    If the size doesn't matter and one side of cv joint is mounted and blocked to prvent turning, is there any other reason that it shouldn't be usen in 6DoF simulator
  10. baykah

    baykah Active Member

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    ok ok ok !

    I got some progress to share

    => Got my seat for 50€, great finding
    => The 100A diode + 47000µF capacitor solved surge on PSU problem
    => I changed 1 actuator to linear bearing, planning to do it for the others (I know it will be noisy)
    => Simtools USB setting solved the actutor jitter

    => I played with my quadcopter DIY google (2D, bad resolution) it's fun but DIY headtracking is not working for the moment.
    So for the moment, TV is ok (I don't want to go VR)

    => Bought dirt rally, made some first setup, I had to invert roll and pitch, don't really now if the other one are ok :D

    Don't, please don't, really don't say a work about my kill switch in the video, please.
    I just saw it now, I forgot to take it back with me :p

    Axe limiting to 25%
    Kp 200
    PWM max 200
    • Winner Winner x 3
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  11. wannabeaflyer2

    wannabeaflyer2 Well-Known Member

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    Hi @baykah not been here in a while lol but am impressed with your projects and would just like to say congratulation on ajob well done good buddy :)
  12. SilentChill

    SilentChill Problem Maker SimTools 2.0 Beta Tester

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    I dont care for the kill button but Arghhhhhhhh vertical video !!!!!! are you crazy :D lol

    Looking really good though dude well done :)

    Just need to sort ya profile out but I cant see whats going on really. Look forward to more videos ..................... in landscape not portrait ;) haha
    • Agree Agree x 1
  13. baykah

    baykah Active Member

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    Yeah I know, it was easier for me to hold my phone ..

    If you have any tips for profil tuning ... for 6dof .. my ears are open ..

    @Wanabeaflyer : Thanks to your drawings that sent me in this direction !
  14. baykah

    baykah Active Member

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    Hello everyone,

    I received my carbon 25x21x500 tube and the linear bearing

    The tube are 21mm internal diameter and fit great with the end bearing/3dprinter adaptor I putted on the ball screws (I hope no vibration anymore !)

    I bought a broken G25 (no force feedback) for 30€ !!, I modifed the brake pedal to fit a honda 600 master cylinder, testing soon :p
    I will also use the wheel and the shift gear plate on a 3D printed hub for .... ! no not a MIGE !, it's a Hirden a little bit cheaper, but yes DIRECT WHEEL DRIVE !!

    I got the simcube and a 36V PSU ready to go ..

    Last, but no picture, I welded on my rig motorwheel support & support for the screen.
    I'm looking to buy a 34" curved 21/9 2XXX x 1080 pixel ~350€

    Attached Files:

    • Like Like x 6
  15. baykah

    baykah Active Member

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    I added my 3D file sketchup with my part

    Carefull, it is not a complete drawing, nor a compete assembly guide

    Some progress : Allmost ready to test the direct drive wheel ..
    • Like Like x 4
  16. SixDegreesOfFlight

    SixDegreesOfFlight Well-Known Member

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    @baykah
    Thank you for the Sketchup file with all the 3D print parts. It really helps to get an understanding of how the actuator fits together. I only have Sketchup Pro for 30 days so I exported each part separately as .obj and .dae for Fusion 360. The .obj mesh allows you to find the dimensions of the parts. The .dae is for import into Cura 15. I didn't find a way to get an editable model but they will help when I have to create my own.

    Thanks again :thumbs
    • Agree Agree x 1
  17. baykah

    baykah Active Member

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    Maybe with the pro version you can export a .STEP / STP ?

    Anyway, I use only the free version, there is a plugin free to create a STL for printing ... but it is not usefull for exporting to another 3D software.
  18. baykah

    baykah Active Member

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    Small update :

    => Chassit is ok for now (not light :p)

    => Actuator seems ok for now ! (kangaroo and rotary encoder next year)

    => DDW !!, working :D, MMOS ok and SIMCUBE ok, I just need to try it :)
    (my motor is not a mige, it is a hirden, just a little bit cheaper, i'm following the thread of a french guy who use it)

    => Hydaulic brake !, I received leobodnar adaptor for my pedal / shifter of the broken G25 I got, I modified the brake to fit a HONDA 600 Master cylinder, I added a pressure sensor 0/5V (also following another topic)
    For now, it's working great :D :D, I need to try it, but even with the slightly reduced travel, it's now working "in force"

    => Wheel, I used a moteino from lowpowerlab to send via 433mhz the shifting gear button to an arduino leonardo emulating a joystick in windows (off course with a battery)
    Everything is on a 3D printed quick release

    Attached Files:

    • Like Like x 2
    Last edited: Jul 25, 2017
  19. lilted86

    lilted86 Member

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    Great job and progress!..ive been watching you thread and hoping that 1 day i can made mine!..and out of curiosity..what is the link for you direct drive that using hirden servo?
  20. baykah

    baykah Active Member

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