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Motion systems/platforms, VR latency, and Nausea?

Discussion in 'Commercial Simulators and Peripherie' started by WalkerYYJ, May 24, 2019.

  1. WalkerYYJ

    WalkerYYJ Member

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    Hey all, have a question I was hoping to get some insight on specifically regarding what people are achieving with respects to motion latency...

    We are looking at kicking off a motion platform project specifically aimed at VR. Big ticket items such as motion cancellation, queuing etc are all top of mind, however the one item I was hoping to start a conversation on is latency.

    We've had some first hand experience working on several models of big boy 6DOF platforms (Moog & Bosch) and it seems in all cases we've seen so far although a computer to controller loop speed in the ~60-90Hz range is standard, there's almost always also an ADDITIONAL 50-300ms in lag time if you do an actual measurement of motion to photon using a headset or accelerometer bolted to a platform.

    We have now seen this from 3 separate platform manufactures and I was curious if anyone here has had hands on experience with hardware that does NOT exhibit this sort of issue?

    For reference this is just sending direct commands to a platform and bypassing all middleware/game environment stuff. IE this is lag that's present somewhere between Controller->PLC->VFD->Motor->Mechanical.
  2. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
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    As background information I will add the information from the initial discussion on reddit, so members here can jump in with their own views, plus request details: https://old.reddit.com/r/virtualrea...otion_systemsplatforms_vr_latency_and_nausea/

    What platforms and software are being used and what is your testing process and what speed are those sims capable of, as cost is not necessarily a good indicator?

    Based on the wisdom of the motion sim community a well tuned and precise motion profile on a fast simulator(at least 150mm/s, though I would suggest 250+mm/s for VR) should help reduce VR sickness, as there are additional reinforcing cues, but a bad motion profile or slow simulator will make it worse, as there will be conflicting cues.

    We've done this on a Moog a Bosch and on a custom 3rd party unit running mostly Parker Hannifin (Big name industrial gear). All were running their own control/PLC hardware/software setup and we were dealing in two cases with making the middleware & interfacing with the game environment (but were quite sure we were not the bottleneck.) In all of these systems (including the one where we didn't do the middle-ware) top speed was in the ~300-500+mm/s range but the issue wasn't actuator speed but rather response speed (in ms) for the whole system (certainly some of that would have been motor acceleration, but not all). IE you send a command to move and by the time an outside sensor detected the move it may end up being several tens to a few hundred ms later.

    For test setups we would be running an accelerometer mounted to the platform, send a movement command and then start a stopwatch before we would see a commensurate amount of motion. Then have that setup to be running in game to keep a rolling lag log. The systems could be "tuned" to work if just replaying an experience, but with interactive setups the clients always had issues.

    Does anyone have any idea what sort of motion latency is ideal and who on earth makes a system that's actually suitable for VR?

    There is a wealth of experience with VR and motion at Xsimulator.net.

    Being a commercially related question you can start a thread in the commercial section: https://www.xsimulator.net/community/forums/commercial-simulators-and-peripherie.52/

    There are a range of physiological processes and capability at play when it comes to motion simulation, in addition to visual, which also have to be taken in to consideration: https://en.wikipedia.org/wiki/Motion_simulator

    If the system is fast enough then my best guess, on the limited information provided, is that software could be an issue, but even more likely is the refinement of the motion profile and/or issues with motion cancellation. When it come to VR and motion simulation the rule of thumb with motion profiles is less is more. In other words precision and speed of motion is more important than large axis movements. Motion cancellation is needed on large axis movement sims and you have not made mention if such refinements are in place or not.​
  3. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    Innovative tech specialist for NGOs
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    My Motion Simulator:
    3DOF, DC motor, JRK
    Is there a video that shows the movement of the rig and game screen at the same time, as set up for testing?

    What game is being used for testing and are the testers familiar/comfortable with VR?

    Is motion cancellation being used?

    What VR HMD and tracking is being used?