FRC 4265 Secret City Wildbots Shifting Swerve CAD Release

Team 4265 The Secret City Wildbots is proud to present the second iteration of our two-speed swerve design.

V4 SS GIF

After our success running the previous iteration of these shifting modules during the 2021 season we decided to deign a new module from the ground up with the primary goal being simplification and weight reduction. The current design has free speeds of 8.38 ft/s in low gear and 22.85 ft/s in high gear as that was what we were using for our 2021 robot; however, other possible and more realistic gearings are detailed in this spreadsheet for both 4" and 5" wheel configurations:

Shifting Swerve Gearings.xlsx (18.3 KB)

The total dimensions of this module are 5.75" x 5.75" x 11" including the motors and it weighs just under 6.25 pounds. The major design changes for this module over our previous iteration are the addition of a 3D printed gearbox cover and the complete removal of the absolute encoder. Instead of a dedicated azimuth absolute encoder we are using a series of safeties to ensure that even if the falcon loses power we can keep driving.

A short description from Amelie, our programming lead:
Our swerve drive automatically handles failures and calibrations. If an azimuth module fails, we switch the motor to coast mode, disable the drive motor for the affected module, and remove the module from the robot pose calculations. To prevent the swerve module from opposing each other, we slow down any module that is going against the others. Instead of the integration of absolute encoders for brownout situations, we use the azimuth position from both the Falcon and the roboRIO, both of which can be re-initialized.

For more information about how we are controlling our modules check out our code release:

Because we only machined and assembled one of these modules to make sure there weren’t any issues before the season starts to save resources, we don’t have any footage of a robot driving with all 4; however, here is a quick video of the one module running through a shifting sequence.

Download CAD files here:
https://grabcad.com/library/v4-shifting-swerve-1

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