And you thought you had cool omni-wheels

[greencactus3]

Originally Posted by RogerR

not quite...
when they are going "forward" the rollers on the wheels don't roll, and the mechanum/ilon wheels act as a normal wheel would. this allows it to put 100% of its power forward, where a "traditional" holonomic platform (with four wheels) would only be able to put out approx. 71% of its full motor power.

ahhh, yes, you're right.. so where a "traditional" holonomic platform goes twice(well, for simplicity's sake, allow me to say twice) the speed going at a 45 degree angle than going straight forward or sideways, this "new" one will go twice as fast forwards and daigonally than sideways... am i right? or am i just getting even more confused?

[sanddrag]

Originally Posted by greencactus3

am i right? or am i just getting even more confused?

I'm not sure but I do know you got me more confused. I think I'll just stick with plain 'ol wheels.

[RogerR]

Originally Posted by greencactus3

ahhh, yes, you're right.. so where a "traditional" holonomic platform goes twice(well, for simplicity's sake, allow me to say twice) the speed going at a 45 degree angle than going straight forward or sideways, this "new" one will go twice as fast forwards and daigonally than sideways... am i right? or am i just getting even more confused?

actually with the "new" one, it'll be twice (again, for simplicity) as powerful going forward, and i believe sideways (<--subject to some debate), than it would going a a 45 degree angle.

[Solace]

Originally Posted by sanddrag

I'm not sure but I do know you got me more confused. I think I'll just stick with plain 'ol wheels.

yeah. me, i like round ones. how about you?

[George1902]

Originally Posted by RogerR

not quite...
when they are going "forward" the rollers on the wheels don't roll, and the mechanum/ilon wheels act as a normal wheel would. this allows it to put 100% of its power forward, where a "traditional" holonomic platform (with four wheels) would only be able to put out approx. 71% of its full motor power.

Roger,

Let's try some inductive reasoning:

Assume the mecanum wheels do put 100% of the power forward. We know the gearboxes can't output more than 100%, so there can't be any force sideways. Therefore, the robot could not strafe sideways.

However, we know that the robot can strafe sideways. Therefore our assumption is false.

The mecanum wheels do not put 100% of the power forward. They behave just like regular omnis at 45* angles. You get a maximum of 71% [1/sqrt(2) as Warren put it] power by moving forward, reverse, left, or right.

[RogerR]

<grumble> second time i typed this...$#%! jumpy touchpad</grumble>

Originally Posted by George1083

...However, we know that the robot can strafe sideways. Therefore our assumption is false.

Originally Posted by George1083

The mecanum wheels do not put 100% of the power forward. They behave just like regular omnis at 45* angles. You get a maximum of 71% [1/sqrt(2) as Warren put it] power by moving forward, reverse, left, or right.

assume that the robot is going forward, and the wheels are all spinning at the same speed (and going the same direction). the design of the wheels is what keeps the bot from moving from side to side. the front left wheel's rollers are 90 degrees to the front right rollers (and same for the back), and the front left wheel is 90 degrees to the rear left wheel (and same on the right). for a wheel to roll sideways, it would force the rollers from two other wheels to move 90 degrees perpendicular to the direction that they roll. notice that the motors don't do anything other than keep the wheels spinning at the same speed and direction.

[Max Lobovsky]

I've been having a hard time proving this, but I believe this is the way both holonomic systems work:

efficiency as compared with wheels facing forward

100% speed
100% power output
1/sqrt(2) max force (obviously, at stall)

It is pretty clear that force is 1/sqrt(2) because when the robot is pushing against something fixed, the force vector that the motor is creating is 45deg to the direction force is being applied.

The other two claims aren't as simple. The only way I can attempt to prove them is through conservation of energy stuff, when I try to look at force vectors, they don't make sense.

Anyway, assuming lossless omniwheels (no friction in lateral movement), 100% of power output goes in the forward direction. Even though there should be a force vector perpendicular to direction of movement, it does not use any energy because it the lateral movement is lossless. If power output is constant, speed must be also constant because max speed is is just the point where f_friction(v) = f_motor(v). (I think equivalent holonomic and straight wheels systems would require different gearing, though, because even if wheels are same sized, a revolution of a straight wheel covers further linear distance than what at 45deg)

[tiffany34990]

coolness!!!!

i must say these look way cool-- i bet many will try next year if the game can use them--that's what we did-- we found them useful fro the 2004 game


later y'all

enjoy the summer!!!