Swerve Drive

[AlecMataloni]

Originally Posted by Ether

Omni and mecanum wheels don't need to be slippery to operate properly. The rollers need to spin freely though. But even with grippier wheels, they lack the pushing force of a standard wheel because the floor reaction forces are larger.



It sounds like what you are describing is crab, not swerve. A swerve has no problem turning with a long wheelbase.

Whoops. My bad. Sorry.

[Peyton Yeung]

Team 45 is prototyping a swerve drive right now.
Advantages
-omnidirectional movement
-pushing power
-wow factor(if done right it makes people wow)

Disadvantages
-complex
-heavy
-expensive
-time consuming (design, build, then the enormous time that will be spent coding followed by hours of practice)
-requires many motors

[Joe Johnson]

Implementation matters.

Some go with swerve (steerable drive wheels) on two wheels and omnis on another two. Some go with 4 wheel swerve. Even with 4 wheel swerve there are differences. Do you have 4 wheel independent steering or perhaps 2 sets of two steerable drives.

There are resource differences in each.

And then there is the big kahuna: power to the driven wheel.

Most swerve implementations have independent motors on each wheel that provide the power. In this way you only have to feed wires to the motor and viola! you have your torque source for your wheel.

BUT... ...others have chosen to get the torque to the drive wheels via mechanical means (typically a shaft through the pivot and a pair of bevel gears).

On the one hand, I hate bevel gears (in FIRST applications especially). They can be done well (Note to self: talk to John V about his championship robot and inspect that dang bevel gear set up). On the other hand, having a remote motor can make swerve a more compact package (swinging motors in space uses a lot of room and the wiring challenges are less problematic). It also makes shifting somewhat easier if that is how you roll because there is morel likely room if you have a stationary motor/gearbox.

Still other use a long chain and drive multiple wheels via this arrangement. It has its own set of strange behaviors to deal with.

Then there is the question of how many revolutions do you allow? Some swear by infinite. I think I am more of a +/-180 kind of a guy. In many cases even +/-90 is enough. Depends on the game.

In all cases, driver skill is as important as the feature. If you don't have a chassis to practice on, your drive will be learning at a regional. I can tell you from experience this seldom ends well.

Oh... ...one more thing. wheel power. The one wheel one motor method limits you in a pushing match in that if you ever get rocked back the motors that are driving wheels that are in the air are giving you no help at all. You have the advantage that you can move sideways to get the right angles to push at, but that is not always enough.

Joe J.