Let's Make Robots!

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Crazyrabbit's picture

 I am also a fan of the basic stamp and use the BS2PE stamp for my robots. I experimented with 4 wheel omniwheel robots last year without much sucess. I think rubber or silicon coated wheels would work much better. Put that idea on the shelf until until wheels get better. Higher speed DC motors I have also seen and a bit better. Check some of my older stuff under Prettybird on this site. I am moving in the direction of using the Parallax Propeller chip. Your 3 wheel design does seem to work a bit better. I was wondering if you could send be the code. As I mentioned, I also use basic stamp some and like the BS2PE because you don't have to change the servo and freqout commands like you do with other higher power basic stamps.

Tman's picture

Thanks for the comment.  There are fairly good wheel choices available now.  Just do a web search and you'll find bunches of sources for these wheels.  The holonomic wheels I used for my omniBOT are 4cm black poly with 8mm center bore that I found through the Acroname Robotics website.  The black rubberized feature grants proper friction that the plastic wheels do not.  They also have larger diameter wheels.  The larger diameter is best for carpeted surfaces.  A gear motor would afford the proper torque for any surface.  I used standard Parallax continuous rotation servos for this bot.  With proper torque, the movement geometry is really cool with 4 wheels, affording multiple degrees of movement depending on spin and rate of spin of each wheel.  Gear motors would work better on a four wheel chassis.  A regular four wheel drive chassis design with holonomic wheels provides and entirely different robot programming experience.  Everything changes when holonomic wheels are brought into the picture.  truly cool.

DoCDoC's picture

Have you though about switching from a stamp to arduino?

DoCDoC

 

Tman's picture

I actually have delved into the Arduino.  It's just that I have a few of these BOEs lying around with Basic Stamps plugged into them.  I am Stamp happy.  Arduino seems very flexible and a bit more cost effective.  Plus the Arduino community has grown dramatically.  So, yes, I do plan on jumping into Arduino with both feet in the future.  Thanks for the comment.

DoCDoC's picture

First off very nice and clean design. Also nice scanning movments via that drive system.

I do have a small question. How did you go about attaching the omni wheels to the servos?

DoCDoC

 

Tman's picture

I simply clear epoxied a servo horn onto each wheel.  The wheel then affixes to the servo axle with the set screw.  I trimmed the ends off four horns and applied the epoxy and lightly clamped that sucker.  Just make sure your servo horn hole and wheel hole are aligned perfectly...or else you'll end up with holonomic wobble.   If you don't like the clear epoxy route, you can seek an alternate assembly pathway.  There's all sorts of gizmos for attaching wheels onto motors and servos nowadays.  There is an old Acroname tutorial concerning this very topic.  I included the address link below...

 http://www.acroname.com/robotics/info/ideas/omnimod/omni_mod.html

Hope this is helpful.  Thanks for the comment.

JAX's picture

If you just watch the sensor it just seems to knowingly float along while a bunch of unassociated things whirl below it. Great stuff. I heard that James A. Folger thinks you are a very talented person.

Tman's picture

Holonomic movement is cool.  And Folgers keeps me awake late at night so I can mess with autonomous machines.  Take care.