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My first build. Another budget flightsim 2DOF rig.

Discussion in 'DIY Motion Simulator Projects' started by Tean33, Mar 18, 2023.

  1. Tean33

    Tean33 New Member

    Joined:
    Jan 12, 2023
    Messages:
    25
    Balance:
    175Coins
    Ratings:
    +11 / 0 / -0
    My Motion Simulator:
    2DOF
    The motor link doesn't show in my last post. This is the motor.
    upload_2023-5-30_1-15-18.png
  2. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

    Joined:
    Jul 13, 2014
    Messages:
    20,551
    Occupation:
    Innovative tech specialist for NGOs
    Location:
    St Helens, Tasmania, Australia
    Balance:
    145,124Coins
    Ratings:
    +10,779 / 52 / -2
    My Motion Simulator:
    3DOF, DC motor, JRK
    Yes the Tuning Center is SimTools specific. That said, not knowing the settings for whatever used, in your case FlyPT, leaves out significant context when others are trying to offer suggestions and things to try.

    I would suggest reducing the lever to CTC to 60mm, particularly for a rig that can be back driven. And ensure appropriate FlyPT settings. Those may not eliminate cogging, if that is a feature of the motors (more common with steppers), but should significantly improve things.

    Again, DIY linear actuators are also a possibility if nothing else helps address your concerns, particularly if you want to maintain large axis movements.
  3. Richardamo1

    Richardamo1 Member

    Joined:
    Apr 2, 2023
    Messages:
    50
    Balance:
    241Coins
    Ratings:
    +10 / 0 / -0
    My Motion Simulator:
    2DOF, DC motor, Arduino, JRK, Motion platform
    Hi there
    Yes this stepping ..if that's what we call it is a pain,when going slowly in flight Sims it's awfull..just like it's not smooth almost like it's moving bit by bit and jerky..
    When in hard out combat you don't notice it so much,I have 2x dayton audio tranducers and they do mask some of the stepping feeling for sure but not all of it I'm afraid.
    It's almost like a resolution thing,I have 180 hall effect pots which should be fine.

    Yup I removed the springs last night after getting a very hot motor on one side,in reality your asking a lot if your motors to move me and a loaded spring as well,especially in a sustained bank..
    Anyway I have ordered the steering dampers from aliexpress and will try those.
    Also i am experimenting with pneumatic rams and reducing valves...
    See how that goes.
    I'm sure that will only help the backlash issue not the cogging or stepping as we say
  4. Tean33

    Tean33 New Member

    Joined:
    Jan 12, 2023
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    25
    Balance:
    175Coins
    Ratings:
    +11 / 0 / -0
    My Motion Simulator:
    2DOF
    Yes, the slower and gentler the movement, the more noticeable the steps become. For ages I was convinced it was some sort of digital resolution thing, and perhaps it still is, but the motors are now my prime suspect. Maybe it's the toothed belt drive I have to the position sensors but I don't think so.
    I've attached my FlyPT and SMC3 settings to this and if anyone wants to take a look and see if I've got something wrong then I'd be very grateful. The only slight oddity I've noticed is that any I gain at all, even just a value of 2 or 3 in SMC3 seems to cause the motors to randomly kick and twitch every few seconds so I just leave it at zero, hence the small error visible in the trace due to my weight pushing down on the motors. I have read of this behaviour elsewhere on here.

    I still haven't got my force-feedback stick moved onto the rig but I had a first combat session in DCS, not online yet, just against some AIs, and it was absolutely amazing. The ROLLOVER filter in FlyPT is genius for aerobatics and dogfighting and yes, the plane shakes when the guns are fired. Such joy.

    So my multi-point plan is:
    1. Stop being grumpy about the stepping. It's distracting and annoying but it's not THAT bad and it's barely noticeable in combat or other 'spirited' flying. For what it's cost me so far the rig is actually really good and I'll cure the stepping eventually.
    2. Try @noorbeast 's suggestion (thank you) of shortening the arms and see if any improvement in stepping is worth the loss of movement range.
    3. Fit some sort of sound/haptic system, which I was going to look at anyway, to see if it masks the stepping.
    4. Read up on alternative motors/actuators.

    Attached Files:

    • Like Like x 1
  5. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

    Joined:
    Jul 13, 2014
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    Occupation:
    Innovative tech specialist for NGOs
    Location:
    St Helens, Tasmania, Australia
    Balance:
    145,124Coins
    Ratings:
    +10,779 / 52 / -2
    My Motion Simulator:
    3DOF, DC motor, JRK
    May I suggest refining your SMC3 settings from scratch, as they are not smooth nor precise. Try increasing Kp and run Sine so we have an idea of how your hardware tracks.

    smc-grab-010623.png
    • Informative Informative x 1
  6. Tean33

    Tean33 New Member

    Joined:
    Jan 12, 2023
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    Balance:
    175Coins
    Ratings:
    +11 / 0 / -0
    My Motion Simulator:
    2DOF
    If I increase the P gain then, as you'd expect, the feedback and setpoint curves match more closely, but the motion starts to become uneven. The motor seems to pulsate at about 2Hz. It does this regardless of load. The pulsing shows quite well on the PWM curve. I don't know what's causing this. It's not like the sort of oscillation I'd expect if the P gain was too high and it's persisted through two types of motor driver and two types of position sensor.

    I'm going off on a boat for a few weeks so please don't think me rude if appear to ignore any replies.

    Attached Files:

  7. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

    Joined:
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    Occupation:
    Innovative tech specialist for NGOs
    Location:
    St Helens, Tasmania, Australia
    Balance:
    145,124Coins
    Ratings:
    +10,779 / 52 / -2
    My Motion Simulator:
    3DOF, DC motor, JRK
    May I suggest starting from scratch and follow the SMC3 instructions, please note at what value the response starts, run Sine and please post a picture of that.
  8. Radje748

    Radje748 Member Gold Contributor

    Joined:
    Dec 26, 2022
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    203Coins
    Ratings:
    +35 / 0 / -0
    My Motion Simulator:
    2DOF
    I have exact the same motors, but run with much higher KP (420) and I run with the IBT's.
    What I can confirm is that even with slow movements, there is no stepping, so the issue is definitely not your motors. What voltage are you using, as I am using these engines on 19v. Maybe this is somewhat low on your side? My first build was with 12v motors and IBT's, where the IBT's got really hot, now with bigger motors and 19v... the IBT;s never get warmer than 40c where the motors are max 25C
    Last edited: Jun 5, 2023
  9. Tean33

    Tean33 New Member

    Joined:
    Jan 12, 2023
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    25
    Balance:
    175Coins
    Ratings:
    +11 / 0 / -0
    My Motion Simulator:
    2DOF
    Thanks for chiming in @Radje748 I'm away from home for the next couple of months so my project is on hold for now, but I'm feeding my motors with around 23.8 volts and I have used IBT2s before I got the Sabertooth. I guess perhaps if you can find decent ones (or just get lucky) then these drivers are great, but the ones I had hardly had time to get hot before they died, or just never worked from new, and the stepping issue was still present. There's also the fact that I tried driving my motors from a simple RC source thus bypassing all the Arduino/software/feedback stuff and they still stepped. Perhaps, in a world full of fake/cloned Arduinos and IBTs the same might apply to motors too. My setup is basically a copy of the one shown by SCK Gaming on Youtube and I notice his motors have a logo (UniteMotor) cast into the gearbox whereas mine are just plain. I can perhaps see some other small differences in the casting so who knows.... They were very cheap.
    But glad to hear your motors are working for you and that there could be hope for mine. Hopefully I'll get to the bottom of it when I get home.
    • Like Like x 1
  10. Radje748

    Radje748 Member Gold Contributor

    Joined:
    Dec 26, 2022
    Messages:
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    Balance:
    203Coins
    Ratings:
    +35 / 0 / -0
    My Motion Simulator:
    2DOF
    It eventually all will work :) also costed me some time and strange issues.
    23.8V is somewhat High for these IBT's, when I tested them on 22-24v, they were getting very warm quickly.
    Now I am running 19v, and the temp is always between 25-45C(depending on the outside temp). I also placed a fan above the IBT to cool them extra....
    • Informative Informative x 1
  11. Tean33

    Tean33 New Member

    Joined:
    Jan 12, 2023
    Messages:
    25
    Balance:
    175Coins
    Ratings:
    +11 / 0 / -0
    My Motion Simulator:
    2DOF
    Happy 2024 to everyone.
    I last posted here back in the summer before I disappeared off to sea for a few months. Since I've been back I've been quietly tweeking away at my rig which is proving to be surprisingly reliable given the wild thrashings it gets whenever I get shot down in DCS. I now have VR motion compensation working and have spent many hours learning how to set up FlyPT and also learning the tricks that can be used to trick the human brain into thinking there's more going on than just a little rocking in two axes. I still have the stepping issue but it's masked a bit by the addition of an HF8 haptic pad.
    And the result is that I'm really liking my little rig. So much so that I just splashed out on a fancy new computer with all the latest and greatest stuff to upgrade my VR experience.
    So in 2024 I'm think I'm going to look around for some alternative motors which may or may not cure my stepping issue, but also there is some backlash in the gearboxes of the current motors which I find a bit disturbing. I'm also going to look at adding a yaw axis, so the journey isn't over yet.
    • Like Like x 1