pic: FRC973 Presents Emperor Swerve

[Ether]

By now the inverse kinematics¹ of mecanum or Unicorn are well known in the CD community.

Their 3 degrees of freedom are translation forward/reverse, translation sideways, and rotation.

All possible motions or maneuvers can be commanded in terms of these 3 inputs.

To rotate while driving forward, for example, all that is required is a field-centric "forward" command (which gets converted into separate time-varying robot-centric forward/reverse and sideways commands) plus a rotate command.

The devil is in the details though. Unless the vehicle is built with craftsmanship and attention to detail, it will drift off course due to friction and motor performance tolerances. Encoders can be added to the gearboxes to provide closed-loop control of wheelspeed and/or position to help mitigate these variations, but doing so adds extra complexity and failure modes. For swerve especially, the interaction between steering angle and wheel speed requires careful design of the software to help the driver avoid sudden commands that could in some cases actually result in the vehicle tipping over. So that's the challenge, and it's one of the reasons why teams who want to try their hand at swerve do so off-season.

Looks like Team 973 has engineered and crafted a fine specimen. It will be fun to see it perform.

¹ given a desired vehicle motion, convert that into the required 4 wheel speeds (for mecanum) or the required 4 wheelspeed/steeringAngle pairs (for swerve)