
Cable Robot Simulator [video] - alex_marchant
https://www.youtube.com/watch?v=cJCsomGwdk0
======
jameshart
This seems like a poor fit for VR motion simulation - actual movement through
space is generally unnecessary, you just need to gimbal the platform to
simulate accelerations. Actual linear acceleration is of limited value in
simulation because you can't maintain that acceleration indefinitely - you run
out of room and have to apply an opposite acceleration, which can conflict
with the simulation needs.

On the other hand this looks more useful for something like movie making, to
throw actors around in front of a greenscreen.

~~~
ghgr
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 accelerating). You cannot
recreate this acceleration by suddenly rotating. The angular accelerations
would ruin the experience. Rather, you make a linear movement, and THEN you
rotate the simulator (if you need to sustain the acceleration).

> you run out of room and have to apply an opposite acceleration, which can
> conflict with the simulation needs.

wrong again. If you move the simulator at slow speed, you can actually come
back to the optimal position and the subject does not notice it (washout
filter [1])

[1]
[https://en.wikipedia.org/wiki/Motion_simulator#Implementatio...](https://en.wikipedia.org/wiki/Motion_simulator#Implementation_using_washout_filters)

~~~
ljk
> _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?

~~~
ryandamm
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.

~~~
RobertoG
[http://cb.nowan.net/blog/2008/12/02/redirected-walking-
playi...](http://cb.nowan.net/blog/2008/12/02/redirected-walking-playing-with-
your-perceptions-limits/)

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

~~~
ryandamm
That's the one. YourGoogleFu >> myGoogleFu.

------
eps
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](http://motionsim.blogspot.ch)

~~~
lotharbot
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](https://youtu.be/rrUF8Dz84rE?t=329)

------
TrevorJ
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
unpowered/uncommanded state simply leads to the platform settling in a stable
configuration.

Having said that: I still want one. :D

~~~
irl_zebra
Around 25 seconds into the video you can see how thick the cable is. I would
guess probably an inch thick. With regular wire rope, the breaking strength of
that diameter would be in the neighborhood of 80,000lbs[1] with the safe load
strength closer to 16,000lbs. I'm guessing with regular maintenance and
checking, it would be exceedingly rare to have a mechanical failure.

Additionally, the occupant is harnessed into the chair, bolted into what is
essentially a spherical roll cage. Even with failure, I'm guessing there would
be a crash but no serious injuries.

[1] - [http://www.engineeringtoolbox.com/wire-rope-strength-
d_1518....](http://www.engineeringtoolbox.com/wire-rope-strength-d_1518.html)

~~~
TrevorJ
It's more about how the cable is managed in terms of slack, keeping the cage
from flipping over, etc. I agree with you, the cable itself is an unlikely
point of failure.

------
beambot
Cable Robots are generally a very interesting technology. I wrote a bit about
them (eg. for 3D printing, as a crane, etc) a while back:
[http://www.hizook.com/blog/2014/07/15/stadium-
sized-3d-print...](http://www.hizook.com/blog/2014/07/15/stadium-
sized-3d-printers-using-winch-robots-aka-cable-robots-or-rope-robots)

------
aresant
I purchased a commercial motion simulator as part of research for a vr tech
we're working on and while you can immediately see the potential, it's not
quite there yet.

Some resources to share

If you buy a simulator - offsetting to the chair with the rift is a work in
progress
[https://forums.oculus.com/viewtopic.php?t=7933](https://forums.oculus.com/viewtopic.php?t=7933)
\- and not currently supported in the Oculus SDK. I can't find the thread but
Oculus has said that's a "future tech" goal.

Excellent thread on currently available options / configurations -
[https://forums.oculus.com/viewtopic.php?t=1673](https://forums.oculus.com/viewtopic.php?t=1673)

A great resource with a community of enthusiasts that have tried nearly every
sim on the market (racing specific, but still the best) is here -
[http://www.isrtv.com/forums/](http://www.isrtv.com/forums/)

------
Animats
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](https://www.youtube.com/watch?v=VkjM9leyQPc)

------
usaphp
Somehow it reminds me of this:
[http://www.youtube.com/watch?v=G-N3XDc-3QQ](http://www.youtube.com/watch?v=G-N3XDc-3QQ)

------
amdolan
Looks a lot like University of Iowa's National Advanced Driving Simulator
NADS-1 [1]. NADS-1 has an entire dome on tracks, hydraulics and a bunch of
other cool stuff going on. I guess it's used mostly for research.

[1] [https://www.nads-sc.uiowa.edu/sim_nads1.php](https://www.nads-
sc.uiowa.edu/sim_nads1.php)

------
condiment
Here's the press release from the Max Planck Institute:

[http://www.ipa.fraunhofer.de/en/cable-
driven_parallel_robots...](http://www.ipa.fraunhofer.de/en/cable-
driven_parallel_robots.html)

------
jonah
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?

~~~
networkjester
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](http://www.nist.gov/el/isd/gantry-2.cfm)

------
audleman
I want one. I'll replace the walls/stairs in my house with this and just zoom
exactly where I need to go. Think of the space savings; I could mount my
computer 6" from the ceiling!

------
earlyadapter
This would actually be dope for flight training. As a student pilot there are
some things like unusual attitudes training, that rely on motion to fool the
senses.

------
JDDunn9
I'd like to know more about the winches, since they aren't made for constant
use. They have planetary gears with very high gear ratios, which can overheat
if used too long. I believe many linear actuators (with high gear ratios, used
to lift beds/tvs) have ~20% duty cycle (use for 2 minutes requires 8 minutes
of cool down).

------
tetraodonpuffer
it looks really cool, however with cables wouldn't this limit the amount of
"instant Gs" you can generate? it seems motion simulators based on pistons
would be able to simulate better things like driving on a bumpy road and
sudden changes of direction as there isn't the slack of the cable to take into
account or the inertia of a large suspended mass (cables are heavy too)

Still given enough space and light enough cables that support enough tension
(to minimize slack) it seems this could be scaled up very cost effectively
compared to other technologies to enable longer sustained accelerations

~~~
njharman
> slack

why cables are loaded at 1.5tons. Electric motors have incredible torque and
those looked like some honking big motors.

------
eatonphil
Hopefully not a completely ridiculous question, is there any chance cable
technology like this could be used as public transportation in the future
similar to in Pixar's Robots?

~~~
vpribish
Come visit beautiful San Francisco!
[https://en.wikipedia.org/wiki/San_Francisco_cable_car_system](https://en.wikipedia.org/wiki/San_Francisco_cable_car_system)

I think the wires would get in each other's way if you had pods in the same
volume.

~~~
eatonphil
Ah of course, that was silly of me. I guess I meant suspended cable travel.

~~~
Retric
Sure:
[https://en.wikipedia.org/wiki/Ski_lift](https://en.wikipedia.org/wiki/Ski_lift)
or
[https://en.wikipedia.org/wiki/Gondola_lift](https://en.wikipedia.org/wiki/Gondola_lift)

~~~
eatonphil
You are right! But it is now apparent that the question I had in mind is
completely different from the one I actually asked. nbadg caught on to what I
meant which was more along the lines of: could suspended cable transportation
be a feasible mode of public transportation in cities?

~~~
AdamTReineke
Yes. The biggest benefit is very low ground footprint and highly predictable
traffic flow. A few articles discuss it as a reasonable form of mass transit.

[http://urbanland.uli.org/infrastructure-transit/public-
trans...](http://urbanland.uli.org/infrastructure-transit/public-transit-
takes-sky-cable-car-gondola/)

[http://www.seattletimes.com/seattle-news/commute-by-
gondola-...](http://www.seattletimes.com/seattle-news/commute-by-gondola-
kirkland-may-be-up-for-the-idea/)

~~~
eatonphil
This is really cool. Thank you for sharing!

------
jastanton
Cool, it's the same concept as the NFL skycam! I wonder if there are any
practical uses for it, say military or civilian training?

~~~
lucb1e
Do you get sick from driving a car or riding a bus though? Because I guess you
could make the experience to be exactly like that. It's supposed to feel like
a normal, natural motion.

------
robodale
Very fascinating, but I also feel left out. I get sick just by riding a Ferris
wheel.

------
oskenso
This could make for an interesting Disney ride!

~~~
ljk
Anyone knows scalable it would be? To start, everyone would need a VR headset,
not that amusement parks are short on cash

~~~
iridium127
with those same cables, they would probably be able to carry hundreds of
people at the same time... just make the platform a bit bigger and maybe
upgrade the winches.

------
kk3399
looks like we are getting close to VR with some (unreal) experience

------
jakobegger
It's a holodeck!

------
sandworm101
All well and good with the standard little girl model, but what does this look
like with ten fat disney tourists? What would the machinery look like to swing
10 or 50 times the weight? (Same question if this is to be used for flight
simulators.) Is there a point at which linear hydraulic actuators are easier?

~~~
hn9780470248775
> All well and good with the standard little girl model

"The software developer Maria Lächele from the 8-person developers team at the
Max-Planck Institute is seen amongst others as a passenger of the robot."

~~~
sandworm101
So? She could be the chief engineer, but in the video she is the model, the
stand-in, the demonstration person. Call it sexist if you want, but it is
standard marketing practice to use young women/girls in promotional vids.
Where movement is involved, models with long hair are also preferred as it
shows the motion, something that again tends towards young girls. Smaller
people also make products seem larger. Where the product involves a seat
(cars, air travel etc) a really tiny person makes things look much roomier and
more comfortable. Where the action is recorded at a distance people with clear
skin but darker lips and larger eyes are more expressive, again trending
towards females. Where there is any sort of perceived physical danger you pick
models that, rightly or wrongly, are perceived delicate. Use a 250lb Army
grunt with massive muscles (of any sex) and viewers might think they also need
to be tough to enjoy the product. So this vid is following standard marketing
practices in selecting a very standard model.

My point still stands. What would rigging for several non-small people on this
thing involve? Looking at the angles on those cables, a 10-fold increase in
payload might need a 20 or 30-fold increase in cable strength ... adding
weight ... needing stronger cables.

After watching it a couple times more, I'm also interested in how it would
handle asymmetric loads. How much before it tips into a cats cradle of wire?
Is there any feedback into the system to detect such situations?

