State-Based Roller Subsystems

What is a Roller Subsystem?

A roller subsystem controls motors that intake, outtake, or hold game pieces using spinning rollers. These subsystems vary from simple single-motor controllers to more complex ones managing multiple motors working together.

There are two main patterns in our codebase for roller subsystems:

• Basic Single-Motor Roller Subsystems

• Composite Multi-Motor Roller Subsystems

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We no longer use these patterns, will update when I have time (Although it is fairly similar). See RobotController.java‘s endEffectorRollers for Basic roller subsystem replacement. See IntakeRollers.java for a composite Subsytsem replacement.

1. Basic Roller Subsystems

Example: EndEffectorRollers

The EndEffectorRollers class is a simple roller subsystem controlling one motor. It extends the base class:

class EndEffectorRollers extends BasicStateBasedRollerSubsystem<EndEffectorRollers.State>

• Each state in EndEffectorRollers.State represents a voltage to apply to the motor.

• The control mode is usually VOLTAGE, directly controlling motor output.

enum State implements BasicRollerState {
    IDLE(0.0),
    HOLD(-2.0),
    CORAL_INTAKE(-4.0),
    // other states...
}

When to use: This pattern is ideal for simple rollers with straightforward control requirements, like a single flywheel or a roller that only needs on/off/hold states.

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2. Composite Roller Subsystems

Example: IntakeRollers

IntakeRollers is an example of a multi-motor roller subsystem that controls several motors as one logical unit:

class IntakeRollers extends StateBasedRollerSubsystem<IntakeRollers.State>

• Controls three motors: intake roller, indexer bottom, and indexer sides.

• Each state provides an array of voltages for all three motors.

enum State implements RollerState {
    IDLE(0,0,0),
    INTAKING(10.0, 2.5, 8),
    EXHAUST(-6, -6, -6),
    // other states...
}

• Each motor can have its own voltage, but they are managed together as a single subsystem.

Benefits:

• Centralizes control logic for related motors.

• Simplifies coordination and reduces complexity in the superstructure.

• Ensures all intake and indexing rollers work in sync.

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3. Control Modes

Our roller subsystems primarily use three common control modes:

• ControlState.VOLTAGE Directly controls motor output voltage. Most common for rollers because it’s simple and effective for on/off or variable speed control.

• ControlState.VELOCITY Uses closed-loop velocity control with feedback (e.g., encoders) to maintain a target roller speed. Useful for precise speed regulation during intaking or shooting.

• ControlState.OPEN_LOOP Sends raw motor power commands without feedback or PID control. Good for very simple or manual control scenarios.