Skip to main content

Roller Mechanism

The roller mechanism is designed for rotating drums or wheels that intake or outtake game pieces. It supports position, velocity, and duty cycle control.

Common Use Cases​

  • Intakes
  • Indexers
  • Conveyors
  • Hood angle adjustments

Typical Controls​

  • Velocity control for consistent intake/outtake.
  • Duty cycle for manual control.
  • Position control if you need a precise indexer rotation or hood angle.
  • Motion profile for smooth position changes (TalonFX only).

Constructor Parameters​

The RollerMech constructor requires the following parameters:

  • logging_prefix - String prefix for logging (typically from getSubsystemKey())
  • mech_name - Optional name for multiple instances (pass null if only one roller)
  • motor_configs - List of MotorConfig objects, leader first
  • gear_ratio - Gear ratio as motor rotations / mechanism rotations
  • roller_inertia - Optional moment of inertia in kg·m² (default: 0.00001, used for simulation)

Example Construction​

// Simple roller for intake
roller_ = new RollerMech(
    getSubsystemKey(),           // Logging prefix
    "Roller",                     // Mechanism name
    List.of(CONSTANTS.ROLLER_MOTOR_CONFIG),  // Motor configs
    CONSTANTS.ROLLER_GEAR_RATIO   // Gear ratio
);

// Hood roller with position control
hood_ = new RollerMech(
    getSubsystemKey(),
    "Hood",
    List.of(CONSTANTS.HOOD_MOTOR_CONFIGS),
    CONSTANTS.HOOD_GEAR_RATIO
);
hood_.setCurrentPosition(CONSTANTS.HOOD_HOME_POSITION);

Common Methods​

Control Methods​

  • setTargetPosition(angle_rad) - Standard position control
  • setTargetPositionMotionProfile(angle_rad) - Position control with motion profiling
  • setTargetPositionWithFF(angle_rad, feedforward) - Position control with arbitrary feedforward
  • setTargetPositionMotionProfileWithFF(angle_rad, feedforward) - Motion profile with feedforward
  • setTargetVelocity(velocity_rad_per_sec) - Velocity control
  • setTargetVelocityMotionProfile(velocity_rad_per_sec) - Velocity control with motion profiling
  • setTargetDutyCycle(duty_cycle) - Open-loop voltage control (-1.0 to 1.0)

Feedback Methods​

  • getCurrentPosition() - Returns current angle in radians
  • getCurrentVelocity() - Returns current velocity in radians per second
  • getLeaderCurrent() - Returns leader motor current draw in amps

Calibration​

  • setCurrentPosition(angle_rad) - Sets the current position (for zeroing/homing)

Tips​

  • Use current sensing or beam break sensors in your subsystem to detect game pieces.
  • Position control is useful for indexers with fixed pockets or adjustable hoods.
  • For simple intake/outtake, duty cycle control is often sufficient.
  • Use motion profile control when you need smooth, controlled position changes.
  • Keep units consistent (radians for angles, radians per second for velocities).