allwpilib/robotpyExamples/examples/RomiReference/commands/turndegrees.py

#
# Copyright (c) FIRST and other WPILib contributors.
# Open Source Software; you can modify and/or share it under the terms of
# the WPILib BSD license file in the root directory of this project.
#

import math
import commands2

from subsystems.drivetrain import Drivetrain


class TurnDegrees(commands2.Command):
    def __init__(self, velocity: float, degrees: float, drive: Drivetrain) -> None:
        """Creates a new TurnDegrees. This command will turn your robot for a desired rotation (in
        degrees) and rotational velocity.

        :param velocity:   The velocity which the robot will drive. Negative is in reverse.
        :param degrees: Degrees to turn. Leverages encoders to compare distance.
        :param drive:   The drive subsystem on which this command will run
        """

        self.degrees = degrees
        self.velocity = velocity
        self.drive = drive
        self.addRequirements(drive)

    def initialize(self) -> None:
        """Called when the command is initially scheduled."""
        # Set motors to stop, read encoder values for starting point
        self.drive.arcadeDrive(0, 0)
        self.drive.resetEncoders()

    def execute(self) -> None:
        """Called every time the scheduler runs while the command is scheduled."""
        self.drive.arcadeDrive(0, self.velocity)

    def end(self, interrupted: bool) -> None:
        """Called once the command ends or is interrupted."""
        self.drive.arcadeDrive(0, 0)

    def isFinished(self) -> bool:
        """Returns true when the command should end."""

        # Need to convert distance travelled to degrees. The Standard
        # Romi Chassis found here, https://www.pololu.com/category/203/romi-chassis-kits,
        # has a wheel placement diameter (149 mm) - width of the wheel (8 mm) = 141 mm
        # or 5.551 inches. We then take into consideration the width of the tires.
        inchPerDegree = math.pi * 5.551 / 360.0

        # Compare distance travelled from start to distance based on degree turn
        return self._getAverageTurningDistance() >= inchPerDegree * self.degrees

    def _getAverageTurningDistance(self) -> float:
        leftDistance = abs(self.drive.getLeftDistanceInch())
        rightDistance = abs(self.drive.getRightDistanceInch())
        return (leftDistance + rightDistance) / 2.0