Mecanum

[HadeBe]

I want to build an autonomous robot with mecanum wheels. Andymark is a company where you can buy these wheels, so thats not the problem..

My discomforts are about the control system. I can control the turns with a compass.
But my question is about the encoders. I know that lateral movement is not possible when only using encoders for position control. but if the robot moves just forward, is slippage then a problem?

[Ro-Bot-X]

I would suggest the use of an optical mouse sensor instead of encoders. This way you get movement in all directions regardless of wheel slippage. Search the forum for mouse optical sensor hack. It has been done and documented.

[Admin]

Optical mouse sensors are horrible, actually. Lift your optical computer mouse above the table about 1mm, and watch what happens. You'll see error gets really large if its not always perfectly flush with the table.

[Joker94]

Optical mouse sensors are not good like admin said. I just mounted the one i had lying around on my robot and it didnot work well at all.

[Ro-Bot-X]

Optical mouse sensors are not good like admin said. I just mounted the one i had lying around on my robot and it didnot work well at all.

Of course it doesn't work. The lens is made so the beam is focused on the mouse pad (really close distance). So at a greater distance, you need to modify (change) the lens. Please look up the optical mouse sensor on this forum, there is someone who did it and it worked.

[Joker94]

i had it mounted skimming the floor. not hovering in mid air but i get what your saying

[wil.hamilton]

you could always use gyros and accelerometers to get relative motion.
you can get ones that are accurate within a few degrees for not too much.

[FingerTech Robotics]

I would like to offer a link to FingerTech's Mecanum Wheels.  They are much cheaper than others and might be a more manageable size (2.125" diameter).
http://www.fingertechrobotics.com/products.php?cat=Wheels+%26+Hubs

[youtube]http://www.youtube.com/watch?v=DhNm0FOIiG0[/youtube]

Hope that helps!

[blackbeard]

i'd so buy those wheels if you mounted a flame thrower on that robot while it passed through the buildings