Package edu.wpi.first.wpilibj.drive

Class MecanumDrive

java.lang.Object
edu.wpi.first.wpilibj.MotorSafety
edu.wpi.first.wpilibj.drive.RobotDriveBase
edu.wpi.first.wpilibj.drive.MecanumDrive
All Implemented Interfaces:
Sendable, AutoCloseable
public class MecanumDrive
extends RobotDriveBase
implements Sendable, AutoCloseable
A class for driving Mecanum drive platforms.

Mecanum drives are rectangular with one wheel on each corner. Each wheel has rollers toed in 45 degrees toward the front or back. When looking at the wheels from the top, the roller axles should form an X across the robot. Each drive() function provides different inverse kinematic relations for a Mecanum drive robot.

Drive base diagram: 

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 /_|___|_\\
 /       \\

Each drive() function provides different inverse kinematic relations for a Mecanum drive robot. Motor outputs for the right side are negated, so motor direction inversion by the user is usually unnecessary.

This library uses the NED axes convention (North-East-Down as external reference in the world frame): http://www.nuclearprojects.com/ins/images/axis_big.png.

The positive X axis points ahead, the positive Y axis points right, and the positive Z axis points down. Rotations follow the right-hand rule, so clockwise 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).

RobotDrive porting guide:
In MecanumDrive, the right side motor controllers are automatically inverted, while in RobotDrive, no motor controllers are automatically inverted.
driveCartesian(double, double, double, double) is equivalent to RobotDrive's mecanumDrive_Cartesian(double, double, double, double) if a deadband of 0 is used, and the ySpeed and gyroAngle values are inverted compared to RobotDrive (eg driveCartesian(xSpeed, -ySpeed, zRotation, -gyroAngle).
drivePolar(double, double, double) is equivalent to RobotDrive's mecanumDrive_Polar(double, double, double)} if a deadband of 0 is used.

  • Constructor Details

    • MecanumDrive

      public MecanumDrive​(SpeedController frontLeftMotor, SpeedController rearLeftMotor, SpeedController frontRightMotor, SpeedController rearRightMotor)
      Construct a MecanumDrive.

      If a motor needs to be inverted, do so before passing it in.

      Parameters:
      frontLeftMotor - The motor on the front-left corner.
      rearLeftMotor - The motor on the rear-left corner.
      frontRightMotor - The motor on the front-right corner.
      rearRightMotor - The motor on the rear-right corner.

  • Method Details

    • close

      public void close()
      Specified by:
      close in interface AutoCloseable

    • driveCartesian

      public void driveCartesian​(double ySpeed, double xSpeed, double zRotation)
      Drive method for Mecanum platform.

      Angles are measured clockwise from the positive X axis. The robot's speed is independent from its angle or rotation rate.

      Parameters:
      ySpeed - The robot's speed along the Y axis [-1.0..1.0]. Right is positive.
      xSpeed - The robot's speed 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]. Clockwise is positive.

    • driveCartesian

      public void driveCartesian​(double ySpeed, double xSpeed, double zRotation, double gyroAngle)
      Drive method for Mecanum platform.

      Angles are measured clockwise from the positive X axis. The robot's speed is independent from its angle or rotation rate.

      Parameters:
      ySpeed - The robot's speed along the Y axis [-1.0..1.0]. Right is positive.
      xSpeed - The robot's speed 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]. Clockwise is positive.
      gyroAngle - The current angle reading from the gyro in degrees around the Z axis. Use this to implement field-oriented controls.

    • drivePolar

      public void drivePolar​(double magnitude, double angle, double zRotation)
      Drive method for Mecanum platform.

      Angles are measured counter-clockwise from straight ahead. The speed at which the robot drives (translation) is independent from its angle or rotation rate.

      Parameters:
      magnitude - The robot's speed at a given angle [-1.0..1.0]. Forward is positive.
      angle - The angle around the Z axis at which the robot drives in degrees [-180..180].
      zRotation - The robot's rotation rate around the Z axis [-1.0..1.0]. Clockwise is positive.

    • driveCartesianIK

      public static MecanumDrive.WheelSpeeds driveCartesianIK​(double ySpeed, double xSpeed, double zRotation, double gyroAngle)
      Cartesian inverse kinematics for Mecanum platform.

      Angles are measured clockwise from the positive X axis. The robot's speed is independent from its angle or rotation rate.

      Parameters:
      ySpeed - The robot's speed along the Y axis [-1.0..1.0]. Right is positive.
      xSpeed - The robot's speed 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]. Clockwise is positive.
      gyroAngle - The current angle reading from the gyro in degrees around the Z axis. Use this to implement field-oriented controls.
      Returns:
      Wheel speeds.

    • stopMotor

      public void stopMotor()
      Specified by:
      stopMotor in class RobotDriveBase

    • getDescription

      public String getDescription()
      Specified by:
      getDescription in class RobotDriveBase

    • initSendable

      public void initSendable​(SendableBuilder builder)
      Description copied from interface: Sendable
      Initializes this Sendable object.
      Specified by:
      initSendable in interface Sendable
      Parameters:
      builder - sendable builder