Launcher: turret, flywheels, hood, and auto-aim

The launcher consists of a rotating corner turret (TurretSubsystem), dual flywheels (Flywheels), and an adjustable hood (Hood), all coordinated by LauncherSubsystem. A singleton LaunchCalculator continuously solves for the correct hood angle, flywheel RPS, and turret angle using a Newton-Raphson time-of-flight iteration with pose-differentiated defense compensation.

Architecture

LauncherSubsystem
├── TurretSubsystem    (CAN ID 23 — rotating mount)
├── Flywheels          (CAN IDs 20, 21 — dual TalonFX)
├── Hood               (CAN ID 22 — position-controlled TalonFX)
└── LaunchCalculator   (singleton solver)

LauncherSubsystem public API

Method	Returns	Description
`launcherAimCommand()`	`Command`	Runs every loop: calls `LaunchCalculator.getParameters()`, sets hood position and flywheel RPS, publishes NT goals
`isAtTarget()`	`boolean`	Returns true when flywheel + hood + turret are at target AND safety gates pass
`rawStowCommand()`	`Command`	Sets hood to 0, stops flywheels
`zeroSubsystemCommand()`	`Command`	Delegates to `hood.zeroHoodCommand()`

`launcherAimCommand()` internals

public Command launcherAimCommand() {
    return Commands.run(
            () -> {
                LaunchingParameters para =
                    LaunchCalculator.getInstance()
                        .getParameters(s.drivebaseSubsystem, s.turretSubsystem);
                this.launchParameters = para;
                hoodGoal = para.targetHood();
                flywheelsGoal = para.targetFlywheels();

                hoodGoalPub.set(hoodGoal);
                flywheelGoalPub.set(flywheelsGoal);

                s.hood.setHoodPosition(hoodGoal);
                s.flywheels.setVelocityRPS(flywheelsGoal);
            })
        .withName("Launcher Aim Command");
}

`isAtTarget()` gates

All five conditions must be simultaneously true:

flywheelAtTarget — within FLYWHEEL_TOLERANCE (10 RPS) of goal; tolerance widens to 30 RPS beyond 6 m
hoodAtTarget — within 0.23 motor rotations of goal, and driver station is enabled
turretAtTarget — within dynamic tolerance clamped between 4° and 20°, derived from atan(0.3 / distToHub)
notUnderClimb — LaunchCalculator.isUnderClimb() returns false
notGoingToBeUnderTrench — LaunchCalculator.isApproachingTrench() returns false

All five gate booleans are published to NetworkTables for debugging:

/AutoAim/hoodGoal — current hood setpoint (motor rotations)
/AutoAim/flywheelGoal — current flywheel setpoint (RPS)
/AutoAim/hoodAtTarget — hood within tolerance
/AutoAim/turretAtTarget — turret within tolerance
/AutoAim/flywheelAtTarget — flywheels within tolerance
/AutoAim/NotUnderClimb — climb safety gate
/AutoAim/NotUnderTrench — trench safety gate

TurretSubsystem

A single TalonFX (CAN ID TURRET_MOTOR_ID = 23) through a gear reduction, with a hall-effect sensor (analog input HALL_EFFECT_SENSOR_ID = 0) for homing.

Constants

Parameter	Comp bot	Alpha bot
kP	200	25
kD	2	0
kS	0.65	0.41
Gear ratio	40	24
`TURRET_MAX`	350°	190°
`TURRET_MIN`	-90°	0°
`TURRET_DEGREE_TOLERANCE`	10°	10°
Stator limit	40 A	40 A

Public API

Method	Description
`setTurretPosition(double pos)`	`runOnce` — sets `PositionVoltage` request to `pos` (rotations), runs once
`rotateToTargetWithCalc()`	Default command — calls `LaunchCalculator.getParameters()` every loop for continuous SOTM targeting
`pointFacingJoystick(xSupplier, ySupplier)`	Manual aiming — maps joystick angle to turret position relative to robot and field heading
`zeroTurret()`	`runOnce` — sets encoder to 0
`getTurretPosition()`	Returns current position in rotations
`atTarget()`	Within `TURRET_DEGREE_TOLERANCE` (10°) of target
`atTarget(DoubleSupplier)`	Within a supplied tolerance (radians, converted to rotations)
`brakeTurret()`	Switch neutral mode to `Brake`
`coastTurret()`	Switch neutral mode to `Coast`
`getOmega()`	Returns angular velocity in rad/s

`rotateToTargetWithCalc()` — shoot-on-the-move

The default turret command solves for the best reachable target degree within soft limits, normalizing across ±360° candidates:

double[] candidates = {
    normalizedTarget, normalizedTarget + 360, normalizedTarget - 360,
};

double finalTarget = /* best in-range candidate */;
setTurretRawPosition(Units.degreesToRotations(finalTarget), -FFV);

The velocity feedforward (-FFV) cancels the turret angular velocity required to track a moving robot.

Driver Y button toggles turretKillActive. When active, the turret holds its current position and the auto-rotate drive mode is also disabled. A second press re-enables shoot-on-the-move. The NT topic /SmartDashboard/Turret/Position shows the current position in rotations during debugging.

Flywheels

Two TalonFX motors (CAN IDs FLYWHEEL_ONE_ID = 20, FLYWHEEL_TWO_ID = 21) running VelocityTorqueCurrentFOC.

Parameter	Value
kP	10 (comp) / 5 (alpha)
kS	5.0
kA	0.5
Supply limit	80 A
Stator limit	80 A
`FLYWHEEL_TOLERANCE`	10 RPS
Neutral mode	Coast

Key methods

Method	Description
`setVelocityRPS(double rps)`	Applies `VelocityTorqueCurrentFOC` to both flywheels
`atTargetVelocity(double targetRPS, double toleranceRPS)`	Returns true when flywheel 1 is within tolerance
`stop()`	Stops both motors
`isOutOfFuel()`	Detects a velocity dip and debounced recovery — used for fuel count estimation

Hood

A single TalonFX (CAN ID HOOD_MOTOR_ID = 22) with PositionVoltage control. Homing is performed by driving the hood at AUTO_ZERO_VOLTAGE (-1.5 V) to the hard stop, then zeroing the encoder — no hall-effect sensor is used for the hood.

Parameter	Value
kP (real)	10
kD (real)	0.2
kS (real)	0.155
Forward soft limit	9 motor rotations
Reverse soft limit	-0.01224 motor rotations
`TARGET_TOLERANCE`	0.23 motor rotations
`AUTO_ZERO_VOLTAGE`	-1.5 V
Stator limit	30 A
Neutral mode	Brake

Key methods

Method	Description
`setHoodPosition(double positionRotations)`	Issues `PositionVoltage` request
`autoZeroCommand()`	Drives hood at -1.5 V to hard stop, then zeros encoder
`zeroHoodCommand()`	Sets encoder to 0 and marks `hoodZeroed = true`
`atTargetPosition()`	True when within `TARGET_TOLERANCE` and driver station enabled
`isHoodZeroed()`	Returns `hoodZeroed` flag

LaunchCalculator

A singleton (LaunchCalculator.getInstance()) that computes LaunchingParameters every loop, with aggressive caching to avoid re-solving when the robot has not moved significantly.

LaunchingParameters record

public record LaunchingParameters(
    double targetHood,          // motor rotations for hood
    Rotation2d targetTurret,    // field-relative angle for turret
    double targetFlywheels,     // RPS for flywheels
    double targetTurretFeedforward, // angular velocity feedforward (rad/s)
    Pose2d turretPose           // estimated turret pose at launch time
) {}

Caching / throttling

The cache is preserved (and returned immediately) if all of the following are true:

Pose has not moved more than 1 inch
Heading has not changed more than 0.5°
Chassis speed is below 0.5 in/s on both axes and 0.5°/s rotationally
Turret angular velocity change is below 0.05 rad/s
Filtered linear acceleration is below 0.3 m/s²
Filtered angular acceleration is below 0.5 rad/s²

Moving-shot solver

Defense/push compensation

Pose-differentiated velocity (Lie-algebra Twist2d log) is blended with wheel speeds. The blend weight scales from POSE_VELOCITY_BLEND = 0.9 at MIN_POSE_DT = 5 ms down to 0 at MAX_POSE_DT = 50 ms. When the robot is stationary (wheel speed < 0.05 m/s) pose-diff is disabled entirely to suppress estimator noise.

Phase delay prediction

Robot state is advanced by PHASE_DELAY = 20 ms using second-order kinematics: x = x₀ + v·t + ½a·t². The velocity at the end of the phase delay (launchSpeeds) is treated as constant for all subsequent calculations — post-launch acceleration does not affect the ball.

Newton-Raphson TOF convergence

Up to 5 iterations of Newton’s method converge on the true time-of-flight accounting for robot velocity. Each iteration adjusts the distance estimate using:

trueDistanceX = distanceX - turretVelocityX * t
trueDistanceY = distanceY - turretVelocityY * t
t_new = t - f / f'

Convergence is declared when |t_new - t_prev| < 0.001 s.

Lookup table interpolation

LauncherConstants holds an InterpolatingDoubleTreeMap for flywheel RPS, hood angle, and time-of-flight vs. distance, populated from compDistanceData (12 points from 1 m to 8 m).

Safety gates

isApproachingTrench(Pose2d, ChassisSpeeds) samples 10 lookahead poses over 0.5 seconds at the current velocity. If any sample places the turret within ±12 in (X) × ±24.97 in (Y) of a trench AprilTag (IDs 1, 6, 7, 12, 17, 22, 23, 28), the hood is forced to 0 and isAtTarget() returns false. isUnderClimb(Pose2d turretPose) checks whether the turret is within the climb structure envelope (±23.5 in X × ±11.38 in Y of tags 15 or 31). If true, isAtTarget() returns false.

Get Started

Subsystems

Autonomous

Simulation

Configuration & Tuning

Launcher: turret, flywheels, hood, and auto-aim

Architecture

LauncherSubsystem public API

`launcherAimCommand()` internals

`isAtTarget()` gates

TurretSubsystem

Constants

Public API

`rotateToTargetWithCalc()` — shoot-on-the-move

Flywheels

Key methods

Hood

Key methods

LaunchCalculator

LaunchingParameters record

Caching / throttling

Moving-shot solver

Safety gates

Build docs developers (and LLMs) love

Get Started

Subsystems

Autonomous

Simulation

Configuration & Tuning

Documentation Index

​Architecture

​LauncherSubsystem public API

​launcherAimCommand() internals

​isAtTarget() gates

​TurretSubsystem

​Constants

​Public API

​rotateToTargetWithCalc() — shoot-on-the-move

​Flywheels

​Key methods

​Hood

​Key methods

​LaunchCalculator

​LaunchingParameters record

​Caching / throttling

​Moving-shot solver

​Safety gates

Build docs developers (and LLMs) love

Architecture

LauncherSubsystem public API

`launcherAimCommand()` internals

`isAtTarget()` gates

TurretSubsystem

Constants

Public API

`rotateToTargetWithCalc()` — shoot-on-the-move

Flywheels

Key methods

Hood

Key methods

LaunchCalculator

LaunchingParameters record

Caching / throttling

Moving-shot solver

Safety gates