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Discussion: Issues with 6DOF

Discussion in 'Ready, set, go - Start your engines' started by Trip Rodriguez, May 29, 2019.

  1. apointner

    apointner Siddhartha

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    I don´t understand that. In my 360 Pit i do real 360° loop.
    My Belttension System is pulling, all the time of the loop, Butt, Shoulders, Legs with 5kN into the Jetseat. Yes it´s not like real 6Gs pressure but it feels really quit the same like RL.
    Still blood is pressing into my head...this is a immersion braker too. But i don´t have a soultion for that.
    Last edited: Jun 11, 2019 at 12:13
  2. apointner

    apointner Siddhartha

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    Please read my text!
    You are the last to exchange anything!

    But you/we should advance the 6DOF Filters to get Position into your 6DOF!
  3. Dirty

    Dirty Active Member Gold Contributor

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    You can only tell that because you know in advance that you are on your rig, and what you feel can only be a rotation ;) The "world" and the "world as presented in hour head" are two very different things and have less to do with each other than your brain will make you believe.
    There are hundreds of incidents every year where experienced pilots (who learned about this for years in their training) fall into that trap.

    Read this. Every line in this article was written with blood, sweat and tears!

    Or at least watch this.


    ...or even better: Come over for some more coffee and cake some time. It will be an "eye opener" for you (literally)! :)
  4. Dirty

    Dirty Active Member Gold Contributor

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    Position information is the last thing you need on a 6DOF rig.

    OMG,... lots of coffee and cake needed, I guess :grin But ya know, I have a good appetite :)
  5. pmvcda

    pmvcda aka FlyPT

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    I have read, and I don't agree.
  6. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    Human sensory systems are not infallable.

    The Kraken motion simulator at the Captain Ashton Graybiel Acceleration Research Facility is specifically designed to
    "allow the exhaustive research necessary for a comprehensive understanding of spatial disorientation and other motion and acceleration-based phenomenon...[the] Air Force report estimated that motion related mishaps have cost the Air Force $2 billion in lost aircraft. But more important are the lost lives". https://www.wpafb.af.mil/News/Article-Display/Article/818426/namru-d-releases-the-kraken/
  7. hexpod

    hexpod http://heXpod.xyz

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    You have to understand that the tilt coordination has to be properly tuned AND combine with surge AND with a proper center of rotation in order to cheat you.

    You can’t achieve the accel effect only with pitch.

    I think that’s the point of desagreament here
    • Agree Agree x 1
  8. Dirty

    Dirty Active Member Gold Contributor

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    A Hexpod delivers some small cues that were carefully selected (filtered) to allow a few correct cues to be perceived and false cues to be minimised. It is not perfect, but the best compromise you can get. Some minor improvements on algorithms are being discussed in the scientific community. But at its core this is what is going on in FullFlightSims around the world.

    Your rig gives a thrill ride of inputs to the occupant, that consists of huge and scary cues, that are mostly not matching what the occupant of an aircraft feels. Some exceptions: Vertical climbs (unless engines at idle), sustained inverted flight & quick aerobatic rolls (no barrel rolls) are displayed with very little false cues, but for a big chunk of the time the cues generated by such a rig would have to be seen as "thrilling but wrong". At least from a technical/professional standpoint.

    I'm not putting your thing down! It is great! It is the very reason I entered into this hobby (remember in late 2017?). When I tried it last time, I stepped out of it saying just: "WOW!!!" Because it does feel amazing,... just not "correct".

    That's why it's not the path I or others want to pursue.

    On a sidenote:
    These hexpods...
    SSJ100_FFS_1_(9318513805).jpg
    ...are certified for "Zero Flighttime Training". That means you can get a license without ever even having seen the real aircraft. It is not because they provide 90% correct cues (which they don't), it is because they avoid 99% of the false cues.


    Dirty :)

    ...oh, and did I mention that I'm hungry for coffee and cake?
    • Agree Agree x 2
    Last edited: Jun 11, 2019 at 13:03
  9. BlazinH

    BlazinH Well-Known Member

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    And if you have the $ to take it to the next level
    • Like Like x 3
  10. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    Does anyone know what thread here on the forums gives the most comprehensive guide to building a good (and affordable) G-seat with harness tensioners? I need the "G-seat for dummies" version! Exact details so I can buy what I need and follow step by step to build it. I've looked at a number of G-Seat threads but most don't have enough detail for me to be confident in trying to replicate them.
  11. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    Those graphics though! D= And 2D!

    I would sure love to have a huge sway/surge table like that though.. plus at least 50 feet of heave and 360 pitch, roll, and yaw. =D Sadly I'll have to settle for the "poor man's" solution of a Stewart platform plus G-seat.... poor me! =P
  12. apointner

    apointner Siddhartha

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    No one here is even close in understanding what i want to explain with position. Thing is, i can´t descripe it better. I give up.
  13. BlazinH

    BlazinH Well-Known Member

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    Look on the FAQ's page under g-seat to get some links. Basically there's two types utilizing either paddles or air bags.

    But this site is not the same as "Instructables" so you're not likely to find step by step instructions.
    • Agree Agree x 1
  14. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    Maybe I overstated my case. =P

    I don't need my hand held 100%, but I'd like to be able to put together a complete list of electrical, electronic, and mechanical parts at the outset, as well as being directed to the software needed and photos of the assemblies. I'll check the FAQ's page, I didn't know there was that kind of stuff there, thanks!
  15. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    I think we understand @apointner . We are just being difficult. =P
  16. Trip Rodriguez

    Trip Rodriguez VR Pilot

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    Well folks, I'm not ready to show my modifications to the world yet but thanks to hexpod helping me out and promptly responding to my emails I've got it moving pretty nice so I thought I'd give you guys an early look. @Dirty @pmvcda @hexpod

    This requires an explanation for sure, I know it's far from an ideal setup and there are a few other odd things too! Fortunately Hexpod's software allowed me to get correct kinematics even with my bizarre servo ranges! I very highly recommend his interface for 6DOF sims. I'll be trying out FlyPT Mover very soon too, but haven't yet.

    1) Electrically actuated, hydraulically damped!:

    Backlash has been a HUGE problem for me since I got my rig initially built. I would not recommend these gearboxes to anyone who wants to use the rig as a flight sim. For racing they are OK, but for flying I just could not achieve smoothness. In particular large downward heave motions caused a bone jarring shudder that was terrible. I basically had to use almost no heave in my profiles to avoid the violent shake! Pitch was also particularly bad. The VW Type 1 shock absorbers I used are also gas shocks, so they act as a spring and keep some tension against the backlash too.

    Now the down side is that I had to give up quite a bit of displacement and angle in order to do this. These shocks have 150mm travel which is pretty good. Since the shocks are on a 160mm radius and the motion sim actuator rods (legs) are on 190mm radius this theoretically gives me about 178 mm of actuator travel. That's pretty decent, but sadly that's not all usable. First off, I have to use less so that small overshoots and such don't hit the mechanical limits. Second, because my angles are so strange I get a bit less actual sim travel out of the actuator travel. As of right now I only wound up with 130mm of travel, but I think I'll be able to get a couple more degrees out of it.

    I could put the shocks on a shorter radius, but that would make them a bit less effective, and wouldn't help much because I can't use much additional travel anyway without the actuator rods (legs) interfering with the upper shock mounts.

    The saving grace here is that it's pretty much universally agreed that you use much less angle with VR than with screens. More heave would sure be nice though! Roll is the main thing that suffered, but it feels better than it looks and I intend to add a G-Seat anyway. =) I think it was Seattime that recently posted that with a G-seat you will wind up using smaller movements from the 6DOF so it should all work out well ultimately.

    2) Platform pitch up when sim is "neutral"

    Well, one of the complaints I've had (previously using Ian's BFF) was that if I tuned the sim for a satisfying feeling of acceleration (pitch up) in race cars and on takeoff runs, hitting the brakes felt like I was standing on my nose.

    My (terrible I know) solution which I've found surprisingly satisfactory was to shorten the back actuator rods (legs) a bit so that the sim is normally tilted back. I don't even notice with the VR headset on, and now my accelerations feel much more satisfying, and my decelerations no longer feel super exaggerated. Mind you, with SimTools/heXpod the difference in available travel can be easily adjusted out, but still if you do that you are failing to take advantage of the opportunity for bigger forward acceleration cues. When I have to move my sim, I will almost certainly rebuild it so it's oriented the standard direction to get more pitch up travel out of it.

    3) The Start position is higher than it should be.

    This is very soon to be solved. I had to request that Hexpod increase the range of a couple sliders in his software to accommodate the compromises I made to get the hydraulic dampers on the sim. As soon as I get my numbers all punched into the new version of heXpod and readjust my servo sensors to match I'll be able to achieve the ideal "home" position within my (oddball) range, and I'll also get just a touch more total travel added at the bottom.

    --------------------------

    Try to ignore the mess, it's been heavy construction on this thing for months and there's a ways to go yet! The sim can move a good bit quicker than this, but any faster and the motors start having bigger and bigger sync issues. Here you will see small errors, I'll run it as fast as I can without getting sync errors after smoothing filters. That might be a bit faster than this video, but it might be slower too, I'm not sure how it's going to work out.



    I would say to let me know what you think, but you might make me cry!
    • Like Like x 1
    Last edited: Jun 16, 2019 at 03:08