Omnidirectional wheels
Hi there,
I came across this little video on Youtube, here, and thought that it would be pretty cool to build something like that. Does anyone know where I could get those diagonally oriented omnidirectional wheels? I am look something in the 3-4cm diameter range. I have seen the other kind with the non-diagonal sub-wheels here, but they'd be too easy to push sideways and probably wouldn't work with more than 3 wheels anyway.
Gr,
Mightor
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| What the world needs is more geniuses with humility, there are so few of us left.
I came across this little video on Youtube, here, and thought that it would be pretty cool to build something like that. Does anyone know where I could get those diagonally oriented omnidirectional wheels? I am look something in the 3-4cm diameter range. I have seen the other kind with the non-diagonal sub-wheels here, but they'd be too easy to push sideways and probably wouldn't work with more than 3 wheels anyway.
Gr,
Mightor
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| What the world needs is more geniuses with humility, there are so few of us left.
Comments
By the way, how is it that your designation changes - where it normally says forum moderator or registered member - yours always has something interesting. My favorite was unstable element. Are the Parallax guys messing around with you?
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Whit+
"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
Post Edited (Whit) : 7/29/2007 5:30:50 PM GMT
Gr,
Mightor
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| What the world needs is more geniuses with humility, there are so few of us left.
Gr,
Mightor
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| What the world needs is more geniuses with humility, there are so few of us left.
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Whit+
"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
Post Edited (Whit) : 7/29/2007 7:19:29 PM GMT
Whit,
I think you forgot to attach said doc, but I get the feeling I saw that pdf already. The term swedish 45 degree thing sounds very familiar. I believe it was someone's thesis. I read through it quickly. I think machining something like that would be pretty tricky. Especially considering I don't even have access to a CNC machine.
Edit: seems you've attached it now [noparse]:)[/noparse]
Edit: Hrmm, gonna have to find a way to view this now. I don't have any kind of office-like program installed (yet).
Gr,
Mightor
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| What the world needs is more geniuses with humility, there are so few of us left.
| "Wait...if that was a compliment, why is my fist of death tingling?"
| - Alice from Dilbert
Here is the link to the complete PDF - http://autonomousmobilerobots.epfl.ch/doc/Slides2.pdf
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Whit+
"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
Post Edited (Whit) : 7/29/2007 7:24:08 PM GMT
Gr,
Mightor
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| What the world needs is more geniuses with humility, there are so few of us left.
| "Wait...if that was a compliment, why is my fist of death tingling?"
| - Alice from Dilbert
also
http://video.google.com/videosearch?q=mecanum
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- Stephen
Post Edited (Franklin) : 7/30/2007 3:03:16 AM GMT
Gr,
Mightor
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| What the world needs is more geniuses with humility, there are so few of us left.
| "Wait...if that was a compliment, why is my fist of death tingling?"
| - Alice from Dilbert
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Whit+
"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
which is based on this book - Introduction to Autonomous Mobile Robots by Roland Siegwart and Illah R. Nourbakhsh -
http://mitpress.mit.edu/catalog/item/default.asp?sid=19A582C1-8F4C-44B3-9108-96F2DDB530E7&ttype=2&tid=10138
It is pretty interesting stuff. Someone is bound to make an inexpensive wheel like this.
Here is a PDF about the robot (see figure 8)·in the you tube video, I believe - http://robotics.ee.uwa.edu.au/papers/1999-EyeBot-Family.pdf
They are called Mecanum Wheels - this slide has a little history - http://www.ese.upenn.edu/ee442/0405/0405posters/Group%201%20Poster.ppt
Still can't find a one though!
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Whit+
"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
Post Edited (Whit) : 7/30/2007 10:05:05 PM GMT
Thanks for all the links though. You must've been doing some serious detective work [noparse]:)[/noparse]
Edit: The picture has been removed, it looked a little Smile.
Gr,
Mightor
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| What the world needs is more geniuses with humility, there are so few of us left.
| "Wait...if that was a compliment, why is my fist of death tingling?"
| - Alice from Dilbert
That is to make a set of wheels like these sold for $375 - http://www.andymark.biz/am-0083.html
Plus check out the assembly instructions·http://lib.store.yahoo.net/lib/yhst-33833170891817/MecanumWheelAssemblyInstructions.pdf
And, these don't look nearly as cool as the one in the you tube video.
Two other interesting links on the bot in the you tube video.
Eye Bot site - http://robotics.ee.uwa.edu.au/eyebot/doc/index.html
http://robotics.ee.uwa.edu.au/eyebot/doc/robots/omni.html·- Check out the video here (with sound) - the wheels even sound good.
And this is the book, Embedded Robotics by Thomas Bräunl,·linked on the page above -http://robotics.ee.uwa.edu.au/eyebot/doc/emro.html
Wonder if Parallax has ever done any Omni-wheel work?
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Whit+
"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
Post Edited (Whit) : 7/31/2007 1:17:22 PM GMT
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D Faust
The wiki entry is here http://en.wikipedia.org/wiki/Mecanum_wheel
It includes a great link for a Fork Lift like the Navy is using in tight spaces, so...
Take a test drive! - http://www.airtrax.com/
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Whit+
"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
Post Edited (Whit) : 7/31/2007 2:39:17 PM GMT
The patent has expired (see the same wikipedia page), so it isn't that folks haven't bought the rights, but that there are just not many people making them on a small scale. Looking at the wheels offered, they are probably not high volume movers (see comments on control below), and the company needs to recover the costs of tooling for the stamped hubs. This also jacks up the price.
Other sources for rollers might be a "bearing house" or possibly and "arts and crafts" store - look in the beads area. I don't know if they would have plastic, but I've seen wooden beads that are the right shape.
Control of these things is not for the faint of heart either. You're going to need some form of feedback, probably both on actual wheel speed (or use stepper motors), and also on actual movement (possibly accelerometers??).
Any variation in speed or slip, and the robot will be wandering off in an unanticipated direction and/or rotating about the central axis.
The concept is more than a little intriguing, and I may take a shot at making some out in the wood shop once I've got a couple other things squared away (meaning winter or possibly next year).
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John R.
Click here to see my Nomad Build Log
Yikes! $60 per wheel and they're not even tapered - I don't think so.
Gr,
Mightor
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| What the world needs is more geniuses with humility, there are so few of us left.
| "Wait...if that was a compliment, why is my fist of death tingling?"
| - Alice from Dilbert
Click on "Control Panel", "Edit Options". From there you can put in a custom user title to replace "Registered Member".
I think I might play around with one of those holonomic drives some time soon, using the normal Omniwheels, at least I can get those at slightly less than $OMGWTH and I'll only need 3 wheels, not four! Such savings!
Gr,
Mightor
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| What the world needs is more geniuses with humility, there are so few of us left.
| "Wait...if that was a compliment, why is my fist of death tingling?"
| - Alice from Dilbert
Yeah, I figured out what Mightor was doing. After he said it was him doing it - I went looking.
Mightor,
I guess we will have to dream. I found a good article during my search using a normal omniwheel for a tail wheel. Don't stop dreaming though.
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Whit+
"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
http://www.omniwheel.com/robot-wheels.htm
Here's a video of them in action as well..
http://www.kornylak.com/images/video/MinhoVideo.mpeg
Matt
Thanks! I have seen those. I guess I don't have a good idea how the 3 wheel system with these works. The 4 wheel system with diagonal rollers intuitively makes sense. They are like screws. I can't picture exactly how these work. Does anyone know of an article that describes how this works. I will do a little looking myself too.
Later entry - Just found this http://www-scf.usc.edu/~csci445/CS445_final_contest/CS445_FA04contest_RobotSoccer/Locomotion/omni_4wheel_encoders/omni_drive.pdf
Now I get it. With wheels on the each side of a triangle, two wheels on adjacent sides turn in opposite directions toward the rear (which ever point at the time will the rear) point of the triangle. These two "screws" push the robot away from the direction they are turning. They can also pull to make the robot move in the opposite direction. The rollers on the wheels don't need to be at 45 degrees, because the orientation of the wheels are at an angle to one another. Pretty neat.
Mightor,
Nice Avitar.
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Whit+
"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
Post Edited (Whit) : 8/3/2007 7:10:15 PM GMT
I have sent them an email inquiring about purchasing just the rollers....
Obviously, based on the versions that AndyMark sells (they appear to use cylindrical rollers, not spherical) this doesn't have to be perfect.
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John R.
Click here to see my Nomad Build Log