Mecanum wheels friction coeff- will it work?

[Alan Anderson]

Originally Posted by CidTeach

on a prototype we have, we are able to drive fwd,rev and srafe (sp?) sideways. however when we try to do a 360, or even 180 the robot jumps/jitters and barely rotates(<90deg.)

This can happen if you have the wheels swapped. The wheels will try to push toward or away from the center of the robot instead of spinning the robot. If you can turn it by hand without any power applied, you definitely have the wheels swapped.

[Ether]

Originally Posted by Alan Anderson

This can happen if you have the wheels swapped. The wheels will try to push toward or away from the center of the robot instead of spinning the robot. If you can turn it by hand without any power applied, you definitely have the wheels swapped.

Is it my imagination, or are both Figure 2 and Figure 4 in the following link incorrect:

http://www.scipub.org/fulltext/ajas/ajas351831-1835.pdf

( the link appears on AndyMark's page at
http://store.andymark.biz/am-0083.html )

[Alan Anderson]

Originally Posted by Ether

Is it my imagination, or are both Figure 2 and Figure 4 in the following link incorrect:

http://www.scipub.org/fulltext/ajas/ajas351831-1835.pdf

Figure 4 is definitely wrong. I think that robot would have real difficulty going straight.

Figure 2 might be wrong, or it might just be a bottom view. Since it's showing the force vectors, it actually makes sense to be showing the spot where the wheels contact the floor.

[Ether]

Originally Posted by Alan Anderson

Figure 2 might be wrong, or it might just be a bottom view. Since it's showing the force vectors, it actually makes sense to be showing the spot where the wheels contact the floor.

OK, agreed, if it's bottom view it's OK. If it's top view it's not going to spin in place well. The side vectors will be trying to spin in one direction while the forward/reverse vectors will be trying to spin in the other.


~

[joek]

the only mechanum problems we've encountered is that they don't fit into the KOP brackets, but we're already at work on that

[McGurky]

Having done the calculations, and real world testing, Team 1716 has found that the 8" mecanum wheels will successfuly go over the hump. Unfortunatly we did have to modify the KOP wheel brackets. Once that had been accomplished, we had no problems!

Happy Building
-Mcgurky

[Ether]

Originally Posted by McGurky

Having done the calculations, and real world testing, Team 1716 has found that the 8" mecanum wheels will successfuly go over the hump. Unfortunatly we did have to modify the KOP wheel brackets. Once that had been accomplished, we had no problems!

Happy Building
-Mcgurky

Just curious... How are you planning on configuring your operator interface for controlling the mecanum wheels?

e.g.

Joystick1 y-axis controls fwd/rev for all 4 wheels and
Joystick1 x-axis controls right/left slide and
Joystick2 x-axis control right/left spin

OR

Joystick1 y-axis controls fwd/rev for left wheels and
Joystick2 y-axis controls fwd/rev for right wheels and
Joystick1 x-axis controls right/left slide

OR

something else??



~

[McGurky]

we are using a single 3 Axis Joystick vs. the ones provided in the KOP.

y-Axis=Forward/Reverse
x-Axis=Left/Right
"z"-Axis=Spin Left/Right

We are using a Joystick similar to this in which you can spin the joystick left and right.

Hope this helps!
-McGurky