Tuner constants: swerve drive PID and module config

CompTunerConstants and AlphaTunerConstants are generated by Phoenix 6 Tuner X and define swerve module geometry, PID gains, and maximum speeds for each physical robot. The correct file is selected at runtime by Subsystems.java based on RobotType.TYPE.

These files are generated from a tuner-swerve-project.json that is checked into the repository. To regenerate them — for example after re-running sysid or changing hardware — open that JSON in Tuner X’s Swerve Project Generator and export the updated Java files. Do not manually edit the class bodies unless you know exactly which downstream code consumes each constant.

Key constants at a glance

Constant	Competition	Alpha	Description
`kSpeedAt12Volts`	5.30 m/s	5.48 m/s	Theoretical free speed at 12 V; used as `MaxSpeed` throughout drive code
`kCANBus`	`"Drivebase"`	`"Drivebase"`	CAN bus name for all swerve devices
`kWheelRadius`	1.924 in	1.84 in	Effective wheel radius (used for odometry and characterization)
`kDriveGearRatio`	5.357…	5.357…	Drive motor rotations per wheel rotation
`kSteerGearRatio`	18.75	18.75	Steer motor rotations per azimuth rotation
`kCoupleRatio`	3.125	3.125	Drive motor turns per azimuth rotation (coupling compensation)
`kSlipCurrent`	80 A	120 A	Stator current at which wheels begin to slip
`kPigeonId`	10	10	Pigeon 2 CAN ID

PID and feedforward gains

Steer gains (Slot 0)

Gain	Competition	Alpha	Notes
kP	100	100	Position proportional
kI	0	0
kD	0.5	0.5
kS	0.1	0.1	Static friction feedforward (V)
kV	1.79	2.33	Velocity feedforward (V/RPS) — differs between robots
kA	0	0

Drive gains (Slot 0)

Gain	Competition	Alpha	Notes
kP	0.1	0.1	Velocity proportional
kI	0	0
kD	0	0
kS	0	0
kV	0.124	0.124	Velocity feedforward (V/RPS)

Both steer and drive use ClosedLoopOutputType.Voltage.

Module positions

Competition bot

Module positions are measured from the robot center in inches, then converted to a Distance at compile time.

Module	X (in)	Y (in)	Drive ID	Steer ID	Encoder ID
Front Left	+9.375	+12.375	1	2	3
Front Right	+9.375	−12.375	4	5	6
Back Left	−9.375	+12.375	10	50	12
Back Right	−9.375	−12.375	7	8	9

Alpha bot

Module	X (in)	Y (in)	Drive ID	Steer ID	Encoder ID
Front Left	+12.375	+10.5	1	2	3
Front Right	+12.375	−10.5	4	5	6
Back Left	−12.375	+10.5	7	8	9
Back Right	−12.375	−10.5	10	11	12

`createDrivetrain()` factory method

Each tuner constants class exposes a static factory that constructs the CommandSwerveDrivetrain with all four module constants pre-populated. Subsystems.java calls the appropriate factory depending on robot type:

// Subsystems.java
drivebaseSubsystem =
    (RobotType.TYPE == RobotTypesEnum.ALPHA)
        ? AlphaTunerConstants.createDrivetrain()
        : CompTunerConstants.createDrivetrain();

The factory itself:

// CompTunerConstants.java
public static CommandSwerveDrivetrain createDrivetrain() {
  return new CommandSwerveDrivetrain(
      DrivetrainConstants, FrontLeft, FrontRight, BackLeft, BackRight);
}

Wheel radius characterization

WheelRadiusCharacterization is a utility Command that spins the robot in place while measuring gyro rotation and wheel encoder deltas, then calculates the effective wheel radius:

wheelRadius = (gyroDelta × driveBaseRadius) / wheelDelta

The result is logged via DataLogManager at command end. To run it, hold Y on the launcherTuningController (port assigned in Controls.java):

// Controls.java
connected(launcherTuningController)
    .and(launcherTuningController.y())
    .whileTrue(
        WheelRadiusCharacterization.wheelRadiusCharacterizationCommand(s.drivebaseSubsystem));

The drive-base radius used in the calculation is computed automatically from the module LocationX/LocationY values in CompTunerConstants:

public static final double DRIVE_BASE_RADIUS =
    Math.max(
        Math.max(
            Math.hypot(CompTunerConstants.FrontLeft.LocationX,  CompTunerConstants.FrontLeft.LocationY),
            Math.hypot(CompTunerConstants.FrontRight.LocationX, CompTunerConstants.FrontRight.LocationY)),
        Math.max(
            Math.hypot(CompTunerConstants.BackLeft.LocationX,   CompTunerConstants.BackLeft.LocationY),
            Math.hypot(CompTunerConstants.BackRight.LocationX,  CompTunerConstants.BackRight.LocationY)));

After running characterization, update kWheelRadius in the appropriate tuner constants file with the measured value, then redeploy.

Do not hand-edit kSpeedAt12Volts. This constant is passed directly to SwerveModuleConstantsFactory and is used as MaxSpeed throughout the drive and auto code. Changing it without re-characterizing will cause path following speeds to be scaled incorrectly.

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Configuration & Tuning

Tuner constants: swerve drive PID and module config

Key constants at a glance

PID and feedforward gains

Steer gains (Slot 0)

Drive gains (Slot 0)

Module positions

Competition bot

Alpha bot

`createDrivetrain()` factory method

Wheel radius characterization

​Key constants at a glance

​PID and feedforward gains

​Steer gains (Slot 0)

​Drive gains (Slot 0)

​Module positions

​Competition bot

​Alpha bot

​createDrivetrain() factory method

​Wheel radius characterization

Key constants at a glance

PID and feedforward gains

Steer gains (Slot 0)

Drive gains (Slot 0)

Module positions

Competition bot

Alpha bot

`createDrivetrain()` factory method

Wheel radius characterization