Class DifferentialDrive

java.lang.Object
org.wpilib.hardware.motor.MotorSafety
org.wpilib.drive.RobotDriveBase
org.wpilib.drive.DifferentialDrive
All Implemented Interfaces:
TelemetryLoggable
public class DifferentialDrive extends RobotDriveBase implements TelemetryLoggable
A class for driving differential drive/skid-steer drive platforms such as the Kit of Parts drive base, "tank drive", or West Coast Drive.

These drive bases typically have drop-center / skid-steer with two or more wheels per side (e.g., 6WD or 8WD). This class takes a setter per side. For four and six motor drivetrains, use CAN motor controller followers or PWMMotorController.addFollower(PWMMotorController).

A differential drive robot has left and right wheels separated by an arbitrary width.

Drive base diagram: 

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Each drive function provides different inverse kinematic relations for a differential drive robot.

This library uses the NWU axes convention (North-West-Up as external reference in the world frame). The positive X axis points ahead, the positive Y axis points to the left, and the positive Z axis points up. Rotations follow the right-hand rule, so counterclockwise rotation around the Z axis is positive.

Inputs smaller then 0.02 will be set to 0, and larger values will be scaled so that the full range is still used. This deadband value can be changed with RobotDriveBase.setDeadband(double).

MotorSafety is enabled by default. The tankDrive, arcadeDrive, or curvatureDrive methods should be called periodically to avoid Motor Safety timeouts.

  • Constructor Details

  • Method Details

    • arcadeDrive

      public void arcadeDrive(double xVelocity, double zRotation)
      Arcade drive method for differential drive platform. The calculated values will be squared to decrease sensitivity at low velocities.
      Parameters:
      xVelocity - The robot's velocity along the X axis [-1.0..1.0]. Forward is positive.
      zRotation - The robot's rotation rate around the Z axis [-1.0..1.0]. Counterclockwise is positive.

    • arcadeDrive

      public void arcadeDrive(double xVelocity, double zRotation, boolean squareInputs)
      Arcade drive method for differential drive platform.
      Parameters:
      xVelocity - The robot's velocity along the X axis [-1.0..1.0]. Forward is positive.
      zRotation - The robot's rotation rate around the Z axis [-1.0..1.0]. Counterclockwise is positive.
      squareInputs - If set, decreases the input sensitivity at low velocities.

    • curvatureDrive

      public void curvatureDrive(double xVelocity, double zRotation, boolean allowTurnInPlace)
      Curvature drive method for differential drive platform.

      The rotation argument controls the curvature of the robot's path rather than its rate of heading change. This makes the robot more controllable at high velocities.

      Parameters:
      xVelocity - The robot's velocity along the X axis [-1.0..1.0]. Forward is positive.
      zRotation - The normalized curvature [-1.0..1.0]. Counterclockwise is positive.
      allowTurnInPlace - If set, overrides constant-curvature turning for turn-in-place maneuvers. zRotation will control turning rate instead of curvature.

    • tankDrive

      public void tankDrive(double leftVelocity, double rightVelocity)
      Tank drive method for differential drive platform. The calculated values will be squared to decrease sensitivity at low velocities.
      Parameters:
      leftVelocity - The robot's left side velocity along the X axis [-1.0..1.0]. Forward is positive.
      rightVelocity - The robot's right side velocity along the X axis [-1.0..1.0]. Forward is positive.

    • tankDrive

      public void tankDrive(double leftVelocity, double rightVelocity, boolean squareInputs)
      Tank drive method for differential drive platform.
      Parameters:
      leftVelocity - The robot left side's velocity along the X axis [-1.0..1.0]. Forward is positive.
      rightVelocity - The robot right side's velocity along the X axis [-1.0..1.0]. Forward is positive.
      squareInputs - If set, decreases the input sensitivity at low velocities.

    • arcadeDriveIK

      public static DifferentialDrive.WheelVelocities arcadeDriveIK(double xVelocity, double zRotation, boolean squareInputs)
      Arcade drive inverse kinematics for differential drive platform.
      Parameters:
      xVelocity - The robot's velocity along the X axis [-1.0..1.0]. Forward is positive.
      zRotation - The robot's rotation rate around the Z axis [-1.0..1.0]. Counterclockwise is positive.
      squareInputs - If set, decreases the input sensitivity at low velocities.
      Returns:
      Wheel velocities [-1.0..1.0].

    • curvatureDriveIK

      public static DifferentialDrive.WheelVelocities curvatureDriveIK(double xVelocity, double zRotation, boolean allowTurnInPlace)
      Curvature drive inverse kinematics for differential drive platform.

      The rotation argument controls the curvature of the robot's path rather than its rate of heading change. This makes the robot more controllable at high velocities.

      Parameters:
      xVelocity - The robot's velocity along the X axis [-1.0..1.0]. Forward is positive.
      zRotation - The normalized curvature [-1.0..1.0]. Counterclockwise is positive.
      allowTurnInPlace - If set, overrides constant-curvature turning for turn-in-place maneuvers. zRotation will control rotation rate around the Z axis instead of curvature.
      Returns:
      Wheel velocities [-1.0..1.0].

    • tankDriveIK

      public static DifferentialDrive.WheelVelocities tankDriveIK(double leftVelocity, double rightVelocity, boolean squareInputs)
      Tank drive inverse kinematics for differential drive platform.
      Parameters:
      leftVelocity - The robot left side's velocity along the X axis [-1.0..1.0]. Forward is positive.
      rightVelocity - The robot right side's velocity along the X axis [-1.0..1.0]. Forward is positive.
      squareInputs - If set, decreases the input sensitivity at low velocities.
      Returns:
      Wheel velocities [-1.0..1.0].

    • stopMotor

      public void stopMotor()
      Description copied from class: MotorSafety
      Called to stop the motor when the timeout expires.
      Specified by:
      stopMotor in class RobotDriveBase

    • getDescription

      public String getDescription()
      Description copied from class: MotorSafety
      Returns a description to print when an error occurs.
      Specified by:
      getDescription in class RobotDriveBase
      Returns:
      Description to print when an error occurs.

    • logTo

      public void logTo(TelemetryTable table)
      Description copied from interface: TelemetryLoggable
      Logs the object to a TelemetryTable.
      Specified by:
      logTo in interface TelemetryLoggable
      Parameters:
      table - telemetry table

    • getTelemetryType

      public String getTelemetryType()
      Description copied from interface: TelemetryLoggable
      Gets the telemetry table type. Default is no specified table type (null). A mismatch in type during logging results in a reported warning, so this should always return the same value.
      Specified by:
      getTelemetryType in interface TelemetryLoggable
      Returns:
      Table type