Mini-Project 5: Integrating a COTS Swerve Module

The goal#

Go from a boxed COTS swerve module to a driving drivetrain. Modern FRC swerve is almost entirely COTS, so the project is integration, not invention.

Step 1 — Pick a module and motors#

Good current options:

• REV 3in MAXSwerve (REV-21-3005) with a NEO 2.0 or Kraken X60 drive motor and a NEO 550 steer motor. The 15T Spline Input Kit (REV-21-3009) adapts a NEO 2.0 or Kraken X60 to the module (the Kraken needs the included spacer plate).
• SDS MK4i / MK4n / MK5n: the MK5n steering ratio is 287:11 (~26.09:1). Its drive motor is a Kraken X60 (or REV NEO V1.1 / NEO Vortex) and its steer motor is a compact Kraken X44.
• WCP Swerve X2 / X2S: built around the Kraken X60 for drive (the X2S adds a Kraken X44 for steer). The older WCP Swerve X also runs a Kraken X60.

Pick a drive gear ratio by trading top speed vs pushing force. Faster ratios give a higher free speed but lower traction-limited acceleration; most teams land near a 5:1-6:1 drive reduction for a ~15-17 ft/s robot.

Step 2 — Mount it square#

All four modules must be parallel and square to the frame. A few degrees of toe causes scrub, wasted current, and a robot that fights itself. Use the manufacturer's mounting holes and a machined or laser-cut bellypan; do not hand-drill module mounts. Record each module's CANcoder/absolute steer offset so wheels zero pointing forward.

Step 3 — Characterize with SysId#

The drive motors closely obey V = kS*sgn(v) + kV*v + kA*a. Run a SysId quasistatic + dynamic routine to get kS, kV, kA per WPILib. These feed your drive feedforward so the robot tracks commanded speeds and drives straight (mismatched wheel kV is a top cause of veering).

Step 4 — Stand up kinematics#

SwerveDriveKinematics kin = new SwerveDriveKinematics(
    fl, fr, bl, br); // Translation2d module locations from robot center
ChassisSpeeds speeds = new ChassisSpeeds(vx, vy, omega);
SwerveModuleState[] states = kin.toSwerveModuleStates(speeds);
SwerveDriveKinematics.desaturateWheelSpeeds(states, MAX_SPEED);
for (int i = 0; i < 4; i++) modules[i].setDesiredState(states[i]);

Always call desaturateWheelSpeeds so a high omega + vy command never exceeds a module's max speed and de-syncs the drive.

Step 5 — First-drive checklist#

1. Push the robot by hand and watch each module's reported angle/velocity flip sign correctly.
2. With wheels off the ground, drive +X slowly; confirm all four wheels point and spin forward.
3. Verify steer absolute offsets, then drive field-relative with a fresh gyro zero.
4. Set drive current limits (e.g. 40-60 A) to stay under the 120 A main breaker during a full-speed push.