Cable Robot Simulator [video] • Hacker News Board

Re: Cable Robot Simulator [video]

#61

Post by Animats » Wed, Sep 23, 2015, 8:43 PM UTC

Multiple computer-controlled winch systems have been used for movie special effects for years. Here's a 2010 system test for a flying taxi, which shows the controller as well as the taxi.[1] Disney's Aladdin at Tuacahn Amphitheater has a magic carpet which flies out over the audience with two performers on it. That's done with four computer-controlled winches.

The robot simulator looks like it's using the same winches Kirby's AFX uses for theatrical work. That's not surprising; few companies make high speed precision-controllable winches rated for human safety.

[1] https://www.youtube.com/watch?v=VkjM9leyQPc

Re: Cable Robot Simulator [video]

#62

Post by jameshart » Wed, Sep 23, 2015, 8:47 PM UTC

ljk wrote: post #59

jimm wrote: post #48

Earlier quoted context omitted.

Let's say I want to simulate acceleration going forward. First, there's the burst of forward motion provided by the cable rig, and that can be > 1G. By also gradually flipping the person onto their back you can simulate continued acceleration of 1G because lying on your back feels the same as 1G of acceleration forward. The VR rig would still show you accelerating forward. I am guessing that if the rig also slowly mo…

Thanks for explaining, I kind of understand it now, but what if the acceleration is > 2G, then gravity won't be enough to simulate it, and I'm still a little skeptical that the user won't feel the rotating and "slowly move back" to original position, but I've never used a VR headset so I might be completely wrong here

Your body's not that good at measuring acceleration. Sure, it'll be hard to convince your brain that blood's pooling in your feet, but being leaned way back will provide a pretty convincing >1g forward acceleration feeling if the visuals are right.

Re: Cable Robot Simulator [video]

#63

Post by ryandamm » Wed, Sep 23, 2015, 9:18 PM UTC

ljk wrote: post #39

ghgr wrote: post #16

Earlier quoted context omitted.

I've been working with full motion simulators for the past two years (I even rode that simulator last week at MPI) and I must say that this is plain wrong. This is actually a great fit for VR simulation (see below): > Actual linear acceleration is of limited value in simulation because... Linear acceleration is immensely useful for sudden accelerations. Image a sudden linear acceleration (e.g. a racing car accelerati…

> Rather, you make a linear movement, and THEN you rotate the simulator (if you need to sustain the acceleration). Am I understanding this wrong or are you saying long accelerations can be achieved by accelerating, turn, accelerating, .... etc? Wouldn't the person wearing VR headset feel the turn?

Another way of saying this: we're good at sensing the delta of acceleration, not the absolute acceleration. Also, we tend not to notice small DC values of either acceleration or rotation, so you can manipulate the user's perception.

Someone published a similar hack for full-room VR, showing you can 'bend' someone's trajectory, to create the false sense that they're walking straight when in fact they're curving. In a large enough space you could simulate an infinite hallway (by having the user walk in a circle).

Sorry, I tried but can't dig up the link right now... but it's out there somewhere.

Re: Cable Robot Simulator [video]

#64

Post by jakeogh » Wed, Sep 23, 2015, 10:11 PM UTC

TrevorJ wrote: post #37

The concern I have is that failures in the control software or mechanical failure would have grave consequences. Maybe that's a solved problem and the cable capstans have mechanical arrestors that kick in, etc but the setup looks inherently unstable unless under active computer control (due largely to the crossed cable attach points). This is quite a bit different than a more typical hydraulic setup where an unpowere…

I'm surprised they have the computers right next to it... and people standing there. I wonder how they mitigate the possibility of unintentional (error driven) movement?

Re: Cable Robot Simulator [video]

#65

Post by jonah » Wed, Sep 23, 2015, 10:24 PM UTC

I didn't see any Yaw motion in this video. (Rotation about the Y axis.)

Does it support it? Is it not necessary for the motions they're trying to induce? Would you have to make the seat rotate on the platform?

Re: Cable Robot Simulator [video]

#66

Post by networkjester » Wed, Sep 23, 2015, 10:37 PM UTC

jonah wrote: post #65

I didn't see any Yaw motion in this video. (Rotation about the Y axis.) Does it support it? Is it not necessary for the motions they're trying to induce? Would you have to make the seat rotate on the platform?

I believe with that cable configuration, Yaw motion isn't really possible. I'm sure it would help with motion programming with the VR, but perhaps true Yaw wouldn't be entirely necessary. Good questions though.

For your last question, I do think that's the way they would need to add Yaw if desired. Otherwise more cables and/or a different configuration would be needed.

As an example, check out the robocrane design from NIST: http://www.nist.gov/el/isd/gantry-2.cfm

Re: Cable Robot Simulator [video]

#67

Post by darkmighty » Wed, Sep 23, 2015, 10:40 PM UTC

jonah wrote: post #65

I didn't see any Yaw motion in this video. (Rotation about the Y axis.) Does it support it? Is it not necessary for the motions they're trying to induce? Would you have to make the seat rotate on the platform?

It says "freely programmable trajectory in six dimensions", and there are indeed six cables, so yes it's supported. But any rotation of that object is going to be limited of course.

Re: Cable Robot Simulator [video]

#68

Post by lotharbot » Thu, Sep 24, 2015, 2:37 AM UTC

eps wrote: post #8

If you like this, lookup "6DOF platform" - there's an active scene of people who tinker with home-made motion platforms, primarily for simulator games. Some very impressive stuff there, e.g. http://motionsim.blogspot.ch

I would love to see one of these platforms that's capable enough to feel right when playing Descent.

[0] https://youtu.be/rrUF8Dz84rE?t=329

Re: Cable Robot Simulator [video]

#69

Post by sounds » Thu, Sep 24, 2015, 4:31 AM UTC

jonah wrote: post #65

I didn't see any Yaw motion in this video. (Rotation about the Y axis.) Does it support it? Is it not necessary for the motions they're trying to induce? Would you have to make the seat rotate on the platform?

A motor under the platform that swivels the user, chair, and floor inside the cage would do it. But I agree with the other commenters that the video does not seem to demonstrate a yaw capability.

Re: Cable Robot Simulator [video]

#70

Post by RobertoG » Thu, Sep 24, 2015, 6:10 AM UTC

ryandamm wrote: post #63

ljk wrote: post #39

Earlier quoted context omitted.

> Rather, you make a linear movement, and THEN you rotate the simulator (if you need to sustain the acceleration). Am I understanding this wrong or are you saying long accelerations can be achieved by accelerating, turn, accelerating, .... etc? Wouldn't the person wearing VR headset feel the turn?

Another way of saying this: we're good at sensing the delta of acceleration, not the absolute acceleration. Also, we tend not to notice small DC values of either acceleration or rotation, so you can manipulate the user's perception. Someone published a similar hack for full-room VR, showing you can 'bend' someone's trajectory, to create the false sense that they're walking straight when in fact they're curving. In a…

http://cb.nowan.net/blog/2008/12/02/redirected-walking-playi...

I think you were searching for that. It seems it also comes from the Max Plank institute.