Package edu.wpi.first.wpilibj.drive

Class DifferentialDrive

java.lang.Object

edu.wpi.first.wpilibj.MotorSafety

edu.wpi.first.wpilibj.drive.RobotDriveBase

edu.wpi.first.wpilibj.drive.DifferentialDrive

All Implemented Interfaces:

Sendable, AutoCloseable

public class DifferentialDrive
extends RobotDriveBase
implements Sendable, AutoCloseable

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:

 |_______|
 | |   | |
   |   |
 |_|___|_|
 |       |
 

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.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	DifferentialDrive.WheelSpeeds	Wheel speeds for a differential drive.

Nested classes/interfaces inherited from class edu.wpi.first.wpilibj.drive.RobotDriveBase

RobotDriveBase.MotorType

Field Summary

Fields inherited from class edu.wpi.first.wpilibj.drive.RobotDriveBase

kDefaultDeadband, kDefaultMaxOutput, m_deadband, m_maxOutput

Constructor Summary

Constructors

Constructor	Description
DifferentialDrive(MotorController leftMotor, MotorController rightMotor)	Construct a DifferentialDrive.
DifferentialDrive(DoubleConsumer leftMotor, DoubleConsumer rightMotor)	Construct a DifferentialDrive.

Method Summary

Modifier and Type	Method	Description
void	arcadeDrive(double xSpeed, double zRotation)	Arcade drive method for differential drive platform.
void	arcadeDrive(double xSpeed, double zRotation, boolean squareInputs)	Arcade drive method for differential drive platform.
static DifferentialDrive.WheelSpeeds	arcadeDriveIK(double xSpeed, double zRotation, boolean squareInputs)	Arcade drive inverse kinematics for differential drive platform.
void	close()
void	curvatureDrive(double xSpeed, double zRotation, boolean allowTurnInPlace)	Curvature drive method for differential drive platform.
static DifferentialDrive.WheelSpeeds	curvatureDriveIK(double xSpeed, double zRotation, boolean allowTurnInPlace)	Curvature drive inverse kinematics for differential drive platform.
String	getDescription()	Returns a description to print when an error occurs.
void	initSendable(SendableBuilder builder)	Initializes this Sendable object.
void	stopMotor()	Called to stop the motor when the timeout expires.
void	tankDrive(double leftSpeed, double rightSpeed)	Tank drive method for differential drive platform.
void	tankDrive(double leftSpeed, double rightSpeed, boolean squareInputs)	Tank drive method for differential drive platform.
static DifferentialDrive.WheelSpeeds	tankDriveIK(double leftSpeed, double rightSpeed, boolean squareInputs)	Tank drive inverse kinematics for differential drive platform.

Methods inherited from class edu.wpi.first.wpilibj.drive.RobotDriveBase

feedWatchdog, normalize, setDeadband, setMaxOutput

Methods inherited from class edu.wpi.first.wpilibj.MotorSafety

check, checkMotors, feed, getExpiration, isAlive, isSafetyEnabled, setExpiration, setSafetyEnabled

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

DifferentialDrive

public DifferentialDrive(MotorController leftMotor, MotorController rightMotor)

Construct a DifferentialDrive.

To pass multiple motors per side, use CAN motor controller followers or PWMMotorController.addFollower(PWMMotorController). If a motor needs to be inverted, do so before passing it in.

Parameters:

leftMotor - Left motor.

rightMotor - Right motor.

DifferentialDrive

public DifferentialDrive(DoubleConsumer leftMotor, DoubleConsumer rightMotor)

Construct a DifferentialDrive.

To pass multiple motors per side, use CAN motor controller followers or PWMMotorController.addFollower(PWMMotorController). If a motor needs to be inverted, do so before passing it in.

Parameters:

leftMotor - Left motor setter.

rightMotor - Right motor setter.

Method Details

close

public void close()

Specified by:

close in interface AutoCloseable

arcadeDrive

public void arcadeDrive(double xSpeed, double zRotation)

Arcade drive method for differential drive platform. The calculated values will be squared to decrease sensitivity at low speeds.

Parameters:

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]. Counterclockwise is positive.

arcadeDrive

public void arcadeDrive(double xSpeed, double zRotation, boolean squareInputs)

Arcade drive method for differential drive platform.

Parameters:

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]. Counterclockwise is positive.

squareInputs - If set, decreases the input sensitivity at low speeds.

curvatureDrive

public void curvatureDrive(double xSpeed, 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 speeds.

Parameters:

xSpeed - The robot's speed 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 leftSpeed, double rightSpeed)

Tank drive method for differential drive platform. The calculated values will be squared to decrease sensitivity at low speeds.

Parameters:

leftSpeed - The robot's left side speed along the X axis [-1.0..1.0]. Forward is positive.

rightSpeed - The robot's right side speed along the X axis [-1.0..1.0]. Forward is positive.

tankDrive

public void tankDrive(double leftSpeed, double rightSpeed, boolean squareInputs)

Tank drive method for differential drive platform.

Parameters:

leftSpeed - The robot left side's speed along the X axis [-1.0..1.0]. Forward is positive.

rightSpeed - The robot right side's speed along the X axis [-1.0..1.0]. Forward is positive.

squareInputs - If set, decreases the input sensitivity at low speeds.

arcadeDriveIK

public static DifferentialDrive.WheelSpeeds arcadeDriveIK(double xSpeed, double zRotation, boolean squareInputs)

Arcade drive inverse kinematics for differential drive platform.

Parameters:

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]. Counterclockwise is positive.

squareInputs - If set, decreases the input sensitivity at low speeds.

Returns:

Wheel speeds [-1.0..1.0].

curvatureDriveIK

public static DifferentialDrive.WheelSpeeds curvatureDriveIK(double xSpeed, 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 speeds.

Parameters:

xSpeed - The robot's speed 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 speeds [-1.0..1.0].

tankDriveIK

public static DifferentialDrive.WheelSpeeds tankDriveIK(double leftSpeed, double rightSpeed, boolean squareInputs)

Tank drive inverse kinematics for differential drive platform.

Parameters:

leftSpeed - The robot left side's speed along the X axis [-1.0..1.0]. Forward is positive.

rightSpeed - The robot right side's speed along the X axis [-1.0..1.0]. Forward is positive.

squareInputs - If set, decreases the input sensitivity at low speeds.

Returns:

Wheel speeds [-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.

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