swerve math quiz

[brennonbrimhall]

Originally Posted by Jon Stratis

Define "standard" swerve...

Either http://www.andymark.com/product-p/am-0537.htm or http://www.andymark.com/product-p/am-0760.htm.

My definition of a standard swerve drive are four independently controlled modules, such that each can have its own velocity vectors (i.e., independent direction AND magnitude). Anything less than that is not a swerve (or so I've gathered from CD searching and speaking with mentors) -- my understanding is that a crab drive is a derivative of a swerve drive where the vectors must all be parallel (and most always have the same velocity magnitude too, though this is not a mechanical limitation).

Originally Posted by Jon Stratis

Unicorn is "4-wheel independent-steering and independent-driven drivetrain, with unlimited rotation of the wheels and sensors, and no gaps in the sensor feedback?" http://www.chiefdelphi.com/forums/sh...07&postcount=9 Oh, and it was so named by none other than JVN!

You might also call it an idealized swerve drive.

Gotcha. A true, pure swerve.

Originally Posted by Jon Stratis

A more common approach is coaxial swerve, where each side rotates together, and has a limited range of rotation (usually no more than 360 degrees).

Originally Posted by Jon Stratis

Another approach might be to have all 4 swerve modules rotate together.

I'm a little confused here -- I don't really understand what you're trying to convey with your examples, unless you're just mentioning common implementations of what are commonly referred to as swerve drives.

Assuming you're using continuous potentiometers or some other sort of continuous sensor solution and have independent direction and magnitude control of each module, how is a coaxial swerve drive like 118's Revolution design NOT a unicorn swerve drive?

Per Nate Laverdure's paper (page 2, available here), wouldn't the proper term for what you describe in quote 2 be a crab drive? That's most certainly not a unicorn swerve drive.

EDIT: Nate beat me to his paper.