A class for driving differential drive/skid-steer drive platforms such as the Kit of Parts drive base, "tank drive", or West Coast Drive. More...

#include <frc/drive/DifferentialDrive.h>

Inheritance diagram for frc::DifferentialDrive:

Classes
struct	WheelSpeeds
	Wheel speeds for a differential drive. More...

Public Member Functions
	DifferentialDrive (MotorController &leftMotor, MotorController &rightMotor)
	Construct a DifferentialDrive. More...

	~DifferentialDrive () override=default

	DifferentialDrive (DifferentialDrive &&)=default

DifferentialDrive &	operator= (DifferentialDrive &&)=default

void	ArcadeDrive (double xSpeed, double zRotation, bool squareInputs=true)
	Arcade drive method for differential drive platform. More...

void	CurvatureDrive (double xSpeed, double zRotation, bool allowTurnInPlace)
	Curvature drive method for differential drive platform. More...

void	TankDrive (double leftSpeed, double rightSpeed, bool squareInputs=true)
	Tank drive method for differential drive platform. More...

void	StopMotor () override

std::string	GetDescription () const override
	The return value from this method is printed out when an error occurs. More...

void	InitSendable (wpi::SendableBuilder &builder) override
	Initializes this Sendable object. More...

Public Member Functions inherited from frc::RobotDriveBase
	RobotDriveBase ()

	~RobotDriveBase () override=default

	RobotDriveBase (RobotDriveBase &&)=default

RobotDriveBase &	operator= (RobotDriveBase &&)=default

void	SetDeadband (double deadband)
	Sets the deadband applied to the drive inputs (e.g., joystick values). More...

void	SetMaxOutput (double maxOutput)
	Configure the scaling factor for using RobotDrive with motor controllers in a mode other than PercentVbus or to limit the maximum output. More...

void	FeedWatchdog ()
	Feed the motor safety object. More...

void	StopMotor () override=0

std::string	GetDescription () const override=0
	The return value from this method is printed out when an error occurs. More...

Public Member Functions inherited from frc::MotorSafety
	MotorSafety ()

virtual	~MotorSafety ()

	MotorSafety (MotorSafety &&rhs)

MotorSafety &	operator= (MotorSafety &&rhs)

void	Feed ()
	Feed the motor safety object. More...

void	SetExpiration (units::second_t expirationTime)
	Set the expiration time for the corresponding motor safety object. More...

units::second_t	GetExpiration () const
	Retrieve the timeout value for the corresponding motor safety object. More...

bool	IsAlive () const
	Determine if the motor is still operating or has timed out. More...

void	SetSafetyEnabled (bool enabled)
	Enable/disable motor safety for this device. More...

bool	IsSafetyEnabled () const
	Return the state of the motor safety enabled flag. More...

void	Check ()
	Check if this motor has exceeded its timeout. More...

virtual void	StopMotor ()=0

virtual std::string	GetDescription () const =0
	The return value from this method is printed out when an error occurs. More...

Public Member Functions inherited from wpi::Sendable
virtual	~Sendable ()=default

virtual void	InitSendable (SendableBuilder &builder)=0
	Initializes this Sendable object. More...

Public Member Functions inherited from wpi::SendableHelper< DifferentialDrive >
	SendableHelper (const SendableHelper &rhs)=default

	SendableHelper (SendableHelper &&rhs)

SendableHelper &	operator= (const SendableHelper &rhs)=default

SendableHelper &	operator= (SendableHelper &&rhs)

Static Public Member Functions
static WheelSpeeds	ArcadeDriveIK (double xSpeed, double zRotation, bool squareInputs=true)
	Arcade drive inverse kinematics for differential drive platform. More...

static WheelSpeeds	CurvatureDriveIK (double xSpeed, double zRotation, bool allowTurnInPlace)
	Curvature drive inverse kinematics for differential drive platform. More...

static WheelSpeeds	TankDriveIK (double leftSpeed, double rightSpeed, bool squareInputs=true)
	Tank drive inverse kinematics for differential drive platform. More...

Static Public Member Functions inherited from frc::MotorSafety
static void	CheckMotors ()
	Check the motors to see if any have timed out. More...

Additional Inherited Members
Public Types inherited from frc::RobotDriveBase
enum	MotorType { kFrontLeft = 0 , kFrontRight = 1 , kRearLeft = 2 , kRearRight = 3 , kLeft = 0 , kRight = 1 , kBack = 2 }
	The location of a motor on the robot for the purpose of driving. More...

Protected Member Functions inherited from wpi::SendableHelper< DifferentialDrive >
	SendableHelper ()=default

	~SendableHelper ()

Static Protected Member Functions inherited from frc::RobotDriveBase
static void	Desaturate (std::span< double > wheelSpeeds)
	Renormalize all wheel speeds if the magnitude of any wheel is greater than 1.0. More...

Protected Attributes inherited from frc::RobotDriveBase
double	m_deadband = 0.02

double	m_maxOutput = 1.0

Detailed Description

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 MotorController per side. For four and six motor drivetrains, construct and pass in MotorControllerGroup instances as follows.

Four motor drivetrain:

class Robot {
 public:
  frc::PWMVictorSPX m_frontLeft{1};
  frc::PWMVictorSPX m_rearLeft{2};
  frc::MotorControllerGroup m_left{m_frontLeft, m_rearLeft};
 
  frc::PWMVictorSPX m_frontRight{3};
  frc::PWMVictorSPX m_rearRight{4};
  frc::MotorControllerGroup m_right{m_frontRight, m_rearRight};
 
  frc::DifferentialDrive m_drive{m_left, m_right};
};

Six motor drivetrain:

class Robot {
 public:
  frc::PWMVictorSPX m_frontLeft{1};
  frc::PWMVictorSPX m_midLeft{2};
  frc::PWMVictorSPX m_rearLeft{3};
  frc::MotorControllerGroup m_left{m_frontLeft, m_midLeft, m_rearLeft};
 
  frc::PWMVictorSPX m_frontRight{4};
  frc::PWMVictorSPX m_midRight{5};
  frc::PWMVictorSPX m_rearRight{6};
  frc::MotorControllerGroup m_right{m_frontRight, m_midRight, m_rearRight};
 
  frc::DifferentialDrive m_drive{m_left, m_right};
};

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 SetDeadband().

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

Constructor & Destructor Documentation

◆ DifferentialDrive() [1/2]

frc::DifferentialDrive::DifferentialDrive	(	MotorController &	leftMotor,
		MotorController &	rightMotor
	)

Construct a DifferentialDrive.

To pass multiple motors per side, use a MotorControllerGroup. If a motor needs to be inverted, do so before passing it in.

◆ ~DifferentialDrive()

frc::DifferentialDrive::~DifferentialDrive ( )

overridedefault

◆ DifferentialDrive() [2/2]

frc::DifferentialDrive::DifferentialDrive ( DifferentialDrive && )

default

Member Function Documentation

◆ ArcadeDrive()

void frc::DifferentialDrive::ArcadeDrive	(	double	xSpeed,
		double	zRotation,
		bool	squareInputs = `true`
	)

Arcade drive method for differential drive platform.

Note: Some drivers may prefer inverted rotation controls. This can be done by negating the value passed for rotation.

Parameters

xSpeed	The speed at which the robot should drive along the X axis [-1.0..1.0]. Forward is positive.
zRotation	The rotation rate of the robot around the Z axis [-1.0..1.0]. Counterclockwise is positive.
squareInputs	If set, decreases the input sensitivity at low speeds.

◆ ArcadeDriveIK()

static WheelSpeeds frc::DifferentialDrive::ArcadeDriveIK	(	double	xSpeed,
		double	zRotation,
		bool	squareInputs = `true`
	)

static

Arcade drive inverse kinematics for differential drive platform.

Note: Some drivers may prefer inverted rotation controls. This can be done by negating the value passed for rotation.

Parameters

xSpeed	The speed at which the robot should drive along the X axis [-1.0..1.0]. Forward is positive.
zRotation	The rotation rate of the robot around the Z axis [-1.0..1.0]. Clockwise is positive.
squareInputs	If set, decreases the input sensitivity at low speeds.

Returns: Wheel speeds [-1.0..1.0].

◆ CurvatureDrive()

void frc::DifferentialDrive::CurvatureDrive	(	double	xSpeed,
		double	zRotation,
		bool	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.

◆ CurvatureDriveIK()

static WheelSpeeds frc::DifferentialDrive::CurvatureDriveIK	(	double	xSpeed,
		double	zRotation,
		bool	allowTurnInPlace
	)

static

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]. Clockwise is positive.
allowTurnInPlace	If set, overrides constant-curvature turning for turn-in-place maneuvers. zRotation will control turning rate instead of curvature.

Returns: Wheel speeds [-1.0..1.0].

◆ GetDescription()

std::string frc::DifferentialDrive::GetDescription ( ) const

overridevirtual

The return value from this method is printed out when an error occurs.

This method must not throw!

Implements frc::RobotDriveBase.

◆ InitSendable()

void frc::DifferentialDrive::InitSendable ( wpi::SendableBuilder & builder )

overridevirtual

Initializes this Sendable object.

Parameters

builder sendable builder

Implements wpi::Sendable.

◆ operator=()

DifferentialDrive & frc::DifferentialDrive::operator= ( DifferentialDrive && )

default

◆ StopMotor()

void frc::DifferentialDrive::StopMotor ( )

overridevirtual

Implements frc::RobotDriveBase.

◆ TankDrive()

void frc::DifferentialDrive::TankDrive	(	double	leftSpeed,
		double	rightSpeed,
		bool	squareInputs = `true`
	)

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.

◆ TankDriveIK()

static WheelSpeeds frc::DifferentialDrive::TankDriveIK	(	double	leftSpeed,
		double	rightSpeed,
		bool	squareInputs = `true`
	)

static

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].

The documentation for this class was generated from the following file:

frc/drive/DifferentialDrive.h

Classes

Public Member Functions

Static Public Member Functions

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ DifferentialDrive() [1/2]

◆ ~DifferentialDrive()

◆ DifferentialDrive() [2/2]

Member Function Documentation

◆ ArcadeDrive()

◆ ArcadeDriveIK()

◆ CurvatureDrive()

◆ CurvatureDriveIK()

◆ GetDescription()

◆ InitSendable()

◆ operator=()

◆ StopMotor()

◆ TankDrive()

◆ TankDriveIK()