The Simulacrum - The Altenative to an ODT

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zalo
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Re: The Simulacrum - The Altenative to an ODT

Post by zalo »

It's a really inefficient solution but I'm using a Sparkfun Pressure sensor ( http://www.sparkfun.com/products/9376 ) with a 10k pull resistor (as outlined at the end of its docs). Any resistance value over 900 (out of 1024) is considered a foot "down".

Don't strap the sensor to anything, always use some form of adhesive or velcro to avoid tripping the sensor all the time.

Or better yet, use a piece of bent tinfoil, or bent wire or something that you can step on to cause it to complete the circuit and trip the switch. It will be infinitely cheaper than using a full on sparkfun sensor. Or one of those SMD push-buttons that they sell oughta do the trick too.

How much promise the project has remains to be seen. My next steps are to build a harness of some sort for hands-free motion forward and backward on the level surface. Also, I wish I knew that WD-40 dissolved plastic before slathering my belt with it. It's not terrible now, but not any better.
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Re: The Simulacrum - The Altenative to an ODT

Post by brantlew »

You know, I started thinking about those silly LED shoes that kids wear. I bet those could be modded for walking sensors. Stangely enough, I can't find them for adults, but a kids pair could probably be scavenged for parts.
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Re: The Simulacrum - The Altenative to an ODT

Post by android78 »

brantlew wrote:You know, I started thinking about those silly LED shoes that kids wear. I bet those could be modded for walking sensors. Stangely enough, I can't find them for adults, but a kids pair could probably be scavenged for parts.
They probably just use a flat pressure switch under the lining of the sole. Probably be just as easy to make one yourself with a couple of strips of metal and plastic barrier.

Or one of these:
http://www.ebay.com.au/itm/50pcs-Moment ... 231ca3c3b4
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Re: The Simulacrum - The Altenative to an ODT

Post by FingerFlinger »

Zalo, have you thought about using an optical mouse to measure the belt speed? That should obliterate your 100ms latency.

Also Brantlew, for detecting foot pressure, I would recommend membrane switches. They are pretty reliable and simple. I might be able to scrounge some up at work from other broken parts. If I can, I'll PM you.
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Re: The Simulacrum - The Altenative to an ODT

Post by zalo »

The latency is pretty much self induced in the software side. I could make it instant, but because the sensor is so sensitive, I get a lot of false positives (w is full-on go, even though you only moved 1 tick, gets annoying). So I accumulate the signal over time to kinda damp it. Also, because a mouse would be even more sensitive, I would need to add even more damping to it. If I had a way to feed the raw data into a game (bypassing w), it would work perfectly without the need for any kind of filtering or speed measuring at all (1301 ticks mapped to 4'7" exactly) Also, I think mice the would suffer from more dead-reckoning drift error than my rotary encoders do.

Luckily, 100 ms is an arbitrary number, and there's no reason I can't count the accumulated ticks over a 10ms period of time as opposed to a 100ms period of time. I just lose a little resolution in measuring the speed over time.

Also, in terms of a better pressure switch, I have a few of these, I just have yet to find a need to rewire my setup to use them: https://www.sparkfun.com/products/8720

Maybe if I start making this setup for other people, I'll use these.

EDIT: Since the treadmill itself doesn't have any side rails, I'm thinking of using a hammock stand for the harness mounts.
This seems like a good candidate since I can fit the treadmill in there length-wise to restrict forward and backward movements: http://www.campmor.com/texsport-hammock-stand.shtml
The actual harness itself would be fashioned from some ratcheting straps that I have.
The harness itself is necessary to restrict real-world motion on the level treadmill surface. I'm just dismayed that I'll have to fork out another $80 or so to solve this problem (raising the overall cost of the system to over $300, more than a rift!).
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Re: The Simulacrum - The Altenative to an ODT

Post by FingerFlinger »

Cool, keep us updated! I might grab a treadmill and try this out come winter-time.
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Re: The Simulacrum - Update (8/13/12)

Post by colocolo »

zalo wrote:The Treadmill and have Encoder arrived. The treadmill is a little sticky, but bearable (mostly static friction).
It also had no place where encoder could be attached, so I had to get a little creative:
http://vid34.photobucket.com/albums/d14 ... G_0591.mp4

The whole setup looks alright, though:
Image
The platform that the laptop is sitting on is just for looks and debugging.
The incline will be a thornier issue (fantastic for walking forward, terrible for backward).

Ran out of solder, need to buy some more to wire it up and get data out of it.

EDIT: Remind me to never EVER get lead-free solder again. That sh*t is terrible!

Also, my brother just broke my quarter setup. So much for creativity!


I reply on your thread cause i had a really great idea about a bidirectional treadmill. and i was wondering where i saw somthing like it in VR forum.
it was the pressure sensor which let me remember.
i am thinking very much about a bidirectional treadmill and how to realize it. yesterday i saw a device that gave my thoughts a new impulse. the gamerunner.
so, the cool thing about it was that you can control the treadmill with a button. i immediately thought that u can hold a wiimote gun in your hand and control back and forward of the treadmill.
for not falling off you make some rubber walls (or something else). So the main idea is controlling the treadmill by a button which can give a really accurate response.
Why not controlling it by a pressure sensor. this would be perfect.
also connecting the motor of a treadmill with a back and forward button would be trivaly easy.
example : connect the motor with 2 buttons and attach them onto 2 buttons on the wii nunchuck controller for walking for and backward
press them simultaneously.... :D
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Re: The Simulacrum - The Altenative to an ODT

Post by zalo »

colocolo wrote:it would be so cool if u did a 2 hour workout and game.
i am currently looking for a used treadmill at ebay.
i also will buy an arduino controller. i will try to control the motor by foot contact.
if you raise one foot it would automatically start to move. if u put both down it will stop.
sounds very easy.... :D
for moving left and right i would use the nunchuk controller on a wii gun.
later i could locate the peak of the gun with Leap Motion.
Wait, don't! It sounds good in theory, but very quickly the treadmill will throw you off (or some other consequence) because people tend to lift their feet a lot more often than you'd think when they walk.

I wish I was in your position where I could afford a motorized treadmill for experimenting, but here's my advice:
1. Get the Arduino, the Treadmill, and an Ultrasonic Rangefinder or an Infrared Rangefinder.
2. Hook up arduino to treadmill like you normally (lol) would, and mount rangefinder to the front end of the treadmill facing you.
3. Use rangefinder values to move the treadmill. The closer you are to the rangefinder, the more the treadmill should move to move you farther away. Or visa-versa when you step backward.

Despite the fact that this method is patented, it's already proven to work and be intuitive. Also, it now allows you to walk backwards (Hooray! (You actually really need this, this isn't the place to skimp)).

Move left and right however you want, I haven't gotten that part down yet ;)
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Re: The Simulacrum - The Altenative to an ODT

Post by FingerFlinger »

I'll also mention that for any motorized solution you'll want much better speed control than ON/OFF.
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Re: The Simulacrum - The Altenative to an ODT

Post by colocolo »

it wouldnt throw me off cause i would make some kind of soft safety barriers. ;)
but anyway the solution you offered me sounds much more elegant.
i only have to fix out how to seperate main current circuit from control circuit properly.
just for safety reasons :D
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Re: The Simulacrum - The Altenative to an ODT

Post by zalo »

Well, FingerFlinger is much more of an expert on this, but you should be able to find a wire leading from the terminal (control unit on the top of the treadmill) to a motor driver of some sort (which will then connect directly to the motors).

From there, it shouldn't be too difficult to replace it with your own PWM signal. The motor driver circuit should then take that signal and amplify it to "dangerous current/voltage levels" for direct consumption by the motor.

A thought just crossed my mind: can you even run a normal treadmill backwards with the existing driver?
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Re: The Simulacrum - The Altenative to an ODT

Post by FingerFlinger »

Hmm, not really with out additional circuitry you'd need to reverse the polarity on the motor leads to run it in reverse. Should be relatively simple to do with a relay, though. Also, on our treadmills at least, the console sends serial data to the power board, which generates a PWM with an on board processor.
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Re: The Simulacrum - The Altenative to an ODT

Post by calebkraft »

Hey, Caleb from hackaday.com here.

I really like where you're going with this. The treadmill is a good addition. It might actually be easier to just build your own circuit to run the treadmill motor if it has no reverse built in. I can probably help you cobble something together if you're not comfortable with that part of it.

Your project will hit hackaday this morning, so watch there for some possible feedback as well.
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Re: The Simulacrum - The Altenative to an ODT

Post by colocolo »

@calebkraft
that would be very nice. i must confess, that i am not much into programming. i am studying mechanical engineering. but i will get more into programming. arduino seems to be very easy stuff. i always wanted to start some programming, but i had not much ideas what to program. so this time VR will give me a really big motivation.
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Re: The Simulacrum - The Altenative to an ODT

Post by MSat »

I'm sort of curious - what if you mounted a "gun" to the front of the treadmill which you leverage your body against to keep you oriented and positioned correctly, instead of holding on to rails? Might not be perfect, but it might feel a bit more immersive for FPSs. You could even possibly mount it in such a way that allows it to swivel up and down.

edit: Just to clarify, by "gun" I mean something like a shotgun/rifle that you hold with two hands which allows for better grip.
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Re: The Simulacrum - The Altenative to an ODT

Post by zalo »

Thanks caleb for the offer. I will come to you and FF if I ever scrounge up enough money to get a motorized treadmill to experiment with. I also hope the other readers of hackaday are inspired to explore their own solutions to the ODT problem.

MSat, there was a treadmill a while back called the "Gamerunner" or something where you hold onto the controller while moving on the (motorized) treadmill.

It looked a little like a stand-up bicycle setup to me.
I am not aiming to have the player hold onto the rails, though, I'm planning on implementing a waist-harness.

My recent tests have shown that it is feasible if you can overcome the static friction from standing on the treadmill. You may end up having to "jump" a little to get it moving from a stand-still, but walking is easy from there. I'm just worried what the motion will be like when wearing the foot platforms.
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Re: The Simulacrum - The Altenative to an ODT

Post by MSat »

Just looked up the gamerunner - eh, a treadmill with a rotating handlebar. Your setup definitely allows for more natural movement. Waist or body harness mounting is probably one of the better methods to integrate movement in a virtual world, so I can see why you would want to go that route, though I imagine it would have to be quite sturdy. I'm wondering, does your treadmill have a mechanism that purposely increases the rolling resistance? If so, could it be disabled?


I'm starting to get pretty interested in a similar setup. What I'm thinking about trying out is also a pivoting shoe, with 4 wheels (mounted more along the side than on the bottom like a roller skate) and measuring one wheels rotation. The pivot would be spring loaded to return the bottom section back to the correction orientation when the foot is lifted.

I would really like to know what a mounted gun-like handlebar would feel like. Is there any way you can quickly rig something up (even if it's just a broom handle or something) and try moving around with your eyes closed? If it feels even remotely natural, I'd be definitely interested in building a similar setup. I'd probably interface all the sensors with a Parallax Propeller (since that's what I'm most comfortable with) and emulate a PS2 mouse or something.
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Re: The Simulacrum - The Altenative to an ODT

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Last night I had a brainwave. Instead of using a waist-mounted harness, I can use a backpack harness. This way, I can lean into and against the backpack with much more confidence, and I can generate much more motive force because of the increased leaning. Also, if I had the treadmill near a wall, I can build a rigid backpack wall-mount that will lock it in place without the use of ropes or anything. Whether or not it needs to carry anything is your choice, but there are opportunities to use much stronger desktop computers placed beside the setup.

Sadly, there is no mechanism on my treadmill that I can just "turn off" (or smash apart) that would decrease friction. It's all generated from my foot pushing the belt onto the stage. It rolls just fine without anyone on it, but once you step on, it gets difficult. The flywheel on the belt actually does makes it easier to maintain motion once you have it.

I'm using some treadmill lube but spraying it under the belt hasn't seemed to have much of an effect. I'm considering spreading it under there with a butter knife just to get more surface area.

Now I just have to get off my lazy butt and build the darn thing. Luckily, I have a leisurely 3 months (maybe more) left with which to complete the build.
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Re: The Simulacrum - The Altenative to an ODT

Post by Okta »

picture14749-size1.jpg
Rather than the complexity of a treadmill, use one of these walkers with your rotation disks mounted on the foot platforms for turning with an outward twist of the foot? Kind of a hybrid of your Simulacrum and the wizdish.
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Re: The Simulacrum - The Altenative to an ODT

Post by zalo »

Perhaps that could work.

The only problem I see is that it would do nothing that the WizDish doesn't already do better.
Maybe if one could get retractable legs and selective resistance (for stepping) it could work better.
Heck, maybe you could even use it to simulate stairs if you could to actuate the retraction.

Unfortunately for the simulacrum, it's mostly dead. The cheapo treadmill I went with turned out to
be too crappy/frictiony, and I don't have the resources to make foot platforms that are remotely comfortable.
This is one of those ideas that you have to execute perfectly, otherwise the magic stays hidden.
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Re: The Simulacrum - The Altenative to an ODT

Post by MSat »

zalo, I think your idea for using a backpack-style harness would be good with something like the WizDish. That way you can take actual steps, instead of shimmying about, which would also help with the aspect of safety (Hate to say it, but the WizDish without a harness is a lawsuit waiting to happen - at least in the States). I thought of a fairly simple backpack harness system that prevents body rotations and major forwards/sideways translations while still allowing vertical movements for jumping/crouching - with selectable range limiters.

Using a low friction walking surface may not be the perfect solution (is there any?), but I don't think the simplicity and cost effectiveness can be beat. It shouldn't be too difficult to simulate inclines either, but something like steps is far too complex unfortunately. Still, even a rudimentary VR walking platform that people can afford to own would be awesome!
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Re: The Simulacrum - The Altenative to an ODT

Post by Namielus »

I can picture the wizdish with a bungee style harness that let you bounce up and down but stay in place.
Once I get my hands on a wizdish I will definitely try to make something like that
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Re: The Simulacrum - The Altenative to an ODT

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Namielus wrote:I can picture the wizdish with a bungee style harness that let you bounce up and down but stay in place.
Once I get my hands on a wizdish I will definitely try to make something like that
Cumbersome to setup and mount but a good idea. It could take away the danger of falling while reducing friction of walking and fatigue of crouching and jumping. Could also allow some sideways foot dragging for strafing. It would even be a great idea even without a wizdish.
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Re: The Simulacrum - The Altenative to an ODT

Post by Flassan »

Do you mean this kind of thing?
http://www.inglesport.com/climbing/clim ... -harnesses

With a hook into a ceiling joist I suppose you could adjust it to either make you weightless or catch you if you were to lose balance.
Great for public demos too.
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Re: The Simulacrum - The Altenative to an ODT

Post by Okta »

Flassan wrote:Do you mean this kind of thing?
http://www.inglesport.com/climbing/clim ... -harnesses

With a hook into a ceiling joist I suppose you could adjust it to either make you weightless or catch you if you were to lose balance.
Great for public demos too.
I was eyeing off those before but after some thought i believe those harnesses are for climbing in a seated position, so no good for vertical. It would be difficult to rig a comfortable and practical vertical harness perhaps.
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Re: The Simulacrum - The Altenative to an ODT

Post by Flassan »

They are commonly used for things like Treetop adventures (http://goape.com/) as well as climbing and abseiling.
Most of the time they just hang loose so you're not aware you're wearing them.
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Re: The Simulacrum - The Altenative to an ODT

Post by Okta »

They would be great as a safety precaution for sure but i interpreted Namielus idea as a bungee style setup with a sprung harness taking some body weight to aid in crouching/jumping. That would probably need a full body harness with a high back fixing point to remain vertical with getting wedgee'd to death :lol:
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Re: The Simulacrum - The Altenative to an ODT

Post by Flassan »

Yeah, I see that now. http://www.amazon.com/Muddy-Outdoors-Sa ... _sbs_sg_10
It might let you hang in the air a moment when you jump.
Tell me if I'm crazy but could that be used to convalesce someone with a leg injury, by gradually increasing the weight they bear while distracting them with a game? Might be more fun than physiotherapy.
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Re: The Simulacrum - The Altenative to an ODT

Post by FingerFlinger »

Yes, you'll want a full-body harness, especially if you want to do public demos. Source: I am a climber. Seat harnesses are for a specific application, and I suspect a user could up-end him/herself if they do not understand how the harness will react to being weighted.
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Re: The Simulacrum - The Altenative to an ODT

Post by MSat »

For a commercial device, the suspension platform should probably be part of the walking platform. Something robust like a workout machine. I also don't think you have to physically be able to rotate your body - only the foot platform needs to detect that you're "turning".
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Re: The Simulacrum - The Altenative to an ODT

Post by Flassan »

MSat wrote:For a commercial device, the suspension platform should probably be part of the walking platform. Something robust like a workout machine. I also don't think you have to physically be able to rotate your body - only the foot platform needs to detect that you're "turning".
Agreed. You wouldn't want to bring the ceiling down on you, and the bungie might have to be quite long to be effective. Re turning, I believe the inner ear is crucial because there is no way it's going to think you've turned round unless you have.
Imagine a VR experience based on the T-Rex scene in Jurassic Park. You are stood in the jungle and feel something through your feet even before you hear it. You turn around and around looking for the source and when it happens again and you spot ripples on a puddle. If you are standing and able to 'walk' in any direction your instinctive response will be to feel that you're in mortal danger. Same thing when you turn around and find yourself standing face to face with a Zombie. That isn't lame and will blow any 5D cinema experience out of the water.
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Re: The Simulacrum - The Altenative to an ODT

Post by zalo »

MSat wrote:only the foot platform needs to detect that you're "turning".
That's the spirit! Some GVS oughtta fix the inner ear turning issue in due time.

On a pure Wizdish note, you can take advantage of the fact that (on a Wizdish) the feet are always moving in opposite directions to do tracking with just an IMU and a Pressure sensor on one foot. Let's just say for the sake of example that this is your right foot. Here's how you would interpret the data:
  • High Pressure + Moving = Player is moving opposite the direction of the IMU
    Low Pressure + Moving = Player is moving the same direction as the IMU

    Very High Pressure to No Pressure + Upwards movement = Jump
    Normal Pressure to No Pressure + Upwards movement = Kick

    Gyro + Magnetometer = Absolute Orientation
The pressure indicator works because we assume that you're shifting your weight when you shuffle with the intent to move forward or backward. Eventually this would all be integrated with the custom shoes (or shoe mods) that you buy with the wizdish.

I might test this if I ever get a wizdish, and one of Oculus's 9dof trackers.
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Re: The Simulacrum - The Altenative to an ODT

Post by MSat »

I don't know how much the inner ear plays a role - particularly if you're turning slowly. Keep in mind, you head is still free to move on its own. Regardless, it should still be a good VR stepping stone.

I've mentioned before that having a fixed backpack-style harness might also trick your body into sensing accelerations from walking/turning. For example, if you're trying to walk forward, the fixed harness acts as leverage for you to overcome the little bit of friction from the "floor". The sensation will be a slight push against your chest (in essence, you are walking into the front of the harness) - which is exactly what happens when you try walking/running with a hiking backpack. When you try to turn, one side of your body will be pushing against the backpack, while the other side is pushing into the harness. I think this is a good way to trick your body into believing (to some extent) that you're actually moving. Of course it's not perfect, but it might be simpler (cheaper) and more practical than other walking solutions.

I don't imagine any sensors being necessary for the feet/legs, because they could probably be integrated in the floor platform - utilizing technology similar to resistive or capacitive touchscreens. This way the foot location/rotation can be tracked precisely (at least when it's touching). Perhaps an even better solution would be to use something like the Leap Motion to track the feet/legs both in the air and on the ground.
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