Swerve drive chassis dimensions

Hey everyone, second year into our 2 year swerve drive implementation plan! Trying to get some discussion going on the the pros and cons of a rectangular shaped chassis for swerve drive (MK4). Does everyone just use a square chassis?
Team 3512

lots of teams use rectangular bots with swerve, and with wpilib and sdslib its very easy to use a nonsquare chassis. Im not sure how the performance compares however.

We used swerve for the first time this year although we had been playing around with it for about 2. Our choice for square frame was helpful with our concept for this year’s game. However, our choice of square vs. rectangular may be game-driven in the future.

I don’t think the challenge is programming the robot itself. If you have a rectangular robot frame, it may be tippy in either the “front/back” or the “left/right” direction if it is too narrow and/or the center of gravity is too high. With the brushless motors, the acceleration can make robots tippy.

The “tippiness factor” may require extra programming to help the driver or the driver will need to remember not to accelerate/decelerate too fast.

It could be any shape. We’ve chosen to do square and haven’t really explored rectangular (or any other shape) at this point.

There’s no requirement for swerve modules o be arranged in a square, or a rectangle. There’s also no requirement that you have four modules; in theory you can use any number over two for full dimensional control. As long as the modules are in known positions relative to the robot you’ll be fine, just a matter of setting up the code accordingly.

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Many teams do use the square as it is simple (like us) but then there are teams that don’t (eg 1706).

The code for the swerve in wpilib has a kinematics object (SwerveDriveKinematics) that takes a list of Translation2d objects representing the offset of each module from the center of the chassis.

And then there’s 2481

The determining factor for swerve shape is going to come down to meeting the game challenge. Unless there’s specifc reason otherwise, a square or other regular polygon is going to be the logical choice. There are at least two basic reasons go irregular:

  1. You need to fit in a narrow space (between obstructions, on a bridge, packing 3 robots on the hanging bar).
  2. You need to have greater length in one direction than frame perimeter rules would allow for a regular polygon. As an example, a climber this year which skips the high rung on the way to traverse would benefit from this. A game tasks which required great force in one direction (pushing a heavy mobile goal?) would also indicate length in one direction being beneficial.

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