Elevators

Basic Elevator Config

Given the tutorial and how to find your mechanism circumference, we have a basic config below.

SmartMotorControllerConfig smcConfig = new SmartMotorControllerConfig(this)
  .withControlMode(ControlMode.CLOSED_LOOP)
  // Mechanism Circumference is the distance traveled by each mechanism rotation converting rotations to meters.
  .withMechanismCircumference(Meters.of(Inches.of(0.25).in(Meters) * 22))
  // Feedback Constants (PID Constants)
  .withClosedLoopController(4, 0, 0, MetersPerSecond.of(0.5), MetersPerSecondPerSecond.of(0.5))
  .withSimClosedLoopController(4, 0, 0, MetersPerSecond.of(0.5), MetersPerSecondPerSecond.of(0.5))
  // Feedforward Constants
  .withFeedforward(new ElevatorFeedforward(0, 0, 0))
  .withSimFeedforward(new ElevatorFeedforward(0, 0, 0))
  // Telemetry name and verbosity level
  .withTelemetry("ElevatorMotor", TelemetryVerbosity.HIGH)
  // Gearing from the motor rotor to final shaft.
  // In this example gearbox(3,4) is the same as gearbox("3:1","4:1") which corresponds to the gearbox attached to your motor.
  .withGearing(new MechanismGearing(GearBox.fromReductionStages(3, 4)))
  // Motor properties to prevent over currenting.
  .withMotorInverted(false)
  .withIdleMode(MotorMode.BRAKE)
  .withStatorCurrentLimit(Amps.of(40))
  .withClosedLoopRampRate(Seconds.of(0.25))
  .withOpenLoopRampRate(Seconds.of(0.25));

// Vendor motor controller object
SparkMax spark = new SparkMax(4, MotorType.kBrushless);

// Create our SmartMotorController from our Spark and config with the NEO.
SmartMotorController sparkSmartMotorController = new SparkWrapper(spark, DCMotor.getNEO(1), smcConfig);

ElevatorConfig elevconfig = new ElevatorConfig(sparkSmartMotorController)
      .withStartingHeight(Meters.of(0.5)) // Starting height of the Elevator
      .withHardLimits(Meters.of(0), Meters.of(3)) // Hard limits defined
      .withTelemetry("Elevator", TelemetryVerbosity.HIGH) // Telemetry Name
      .withMass(Pounds.of(16)); // Mass of the carraige

Starting Height

An Elevators starting height is the starting height of the elevator when the robot boots up. This value is translated using the Mechanism Circumference to rotations and the encoder of the SmartMotorController is set to the equivalent Mechanism rotations.

ElevatorConfig elevconfig = new ElevatorConfig(sparkSmartMotorController)
      .withStartingHeight(Meters.of(0.5)) // Starting height of the Elevator

If you want to control your elevators height relative to the ground you should set the starting height to be the height relative to the ground.

Mass

The mass defined .withMass is used for simulation of the elevator. The mass given should be the carriage weight. Any changes in Mass will require a retuning of the PID and FF, and could necessitate a sim only PID and FF to maintain an easy comparison.

ElevatorConfig elevconfig = new ElevatorConfig(sparkSmartMotorController)
      .withMass(Pounds.of(16)); // Weight of the carriage.

Cascading Elevators

Cascading elevators need their gearings divided by the number of stages there are in the elevator.

// Cascading Elevator with a 3:1 and 4:1 gearbox and 2 stages.
new MechanismGearing(GearBox.fromReductionStages(3, 4).div(2));
new MechanismGearing(GearBox.fromReductionStages(3, 4)).div(2);

Linear Slides and Slanted Elevators

A linear slide is still an elevator! Just with an angle of 0deg! You can set the angle of an Elevator with .withAngle

ElevatorConfig elevconfig = new ElevatorConfig(sparkSmartMotorController)
      .withAngle(Degrees.of(0)); // Parallel to the ground, linear slide.

A linear slide is guaranteed to have a different sim PID and FF, so be sure to set them!

Hard Limits and Soft Limits

The difference between hard limits and soft limits are ubiquitous among all mechanisms.

• Hard Limits are where physical stops that should not break are located along the mechanisms movement.

• Soft Limits are where the motor controller PID should limit itself to. It does not always limit itself within these limits which is why Hard Limits should also be used.

Hard limits are the simulation maximum boundaries.

ElevatorConfig elevconfig = new ElevatorConfig(sparkSmartMotorController)
      .withHardLimits(Meters.of(0), Meters.of(3)) // Hard limits defined
      .withSoftLimits(Meters.of(0), Meters.of(2.5)); // Limits imposed on the PID controller.