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 <wpi/drive/DifferentialDrive.hpp>

Inheritance diagram for wpi::DifferentialDrive:

Classes
struct	WheelVelocities
	Wheel velocities for a differential drive. More...

Public Member Functions
WPI_IGNORE_DEPRECATED	DifferentialDrive (MotorController &leftMotor, MotorController &rightMotor)
	Construct a DifferentialDrive.
WPI_UNIGNORE_DEPRECATED	DifferentialDrive (std::function< void(double)> leftMotor, std::function< void(double)> rightMotor)
	Construct a DifferentialDrive.
	~DifferentialDrive () override=default
	DifferentialDrive (DifferentialDrive &&)=default
DifferentialDrive &	operator= (DifferentialDrive &&)=default
void	ArcadeDrive (double xVelocity, double zRotation, bool squareInputs=true)
	Arcade drive method for differential drive platform.
void	CurvatureDrive (double xVelocity, double zRotation, bool allowTurnInPlace)
	Curvature drive method for differential drive platform.
void	TankDrive (double leftVelocity, double rightVelocity, bool squareInputs=true)
	Tank drive method for differential drive platform.
void	StopMotor () override
	Called to stop the motor when the timeout expires.
std::string	GetDescription () const override
	Returns a description to print when an error occurs.
void	InitSendable (wpi::util::SendableBuilder &builder) override
	Initializes this Sendable object.
Public Member Functions inherited from wpi::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).
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.
void	FeedWatchdog ()
	Feed the motor safety object.
Public Member Functions inherited from wpi::MotorSafety
	MotorSafety ()
virtual	~MotorSafety ()
	MotorSafety (MotorSafety &&rhs)
MotorSafety &	operator= (MotorSafety &&rhs)
void	Feed ()
	Feed the motor safety object.
void	SetExpiration (wpi::units::second_t expirationTime)
	Set the expiration time for the corresponding motor safety object.
wpi::units::second_t	GetExpiration () const
	Retrieve the timeout value for the corresponding motor safety object.
bool	IsAlive () const
	Determine if the motor is still operating or has timed out.
void	SetSafetyEnabled (bool enabled)
	Enable/disable motor safety for this device.
bool	IsSafetyEnabled () const
	Return the state of the motor safety enabled flag.
void	Check ()
	Check if this motor has exceeded its timeout.
Public Member Functions inherited from wpi::util::Sendable
virtual constexpr	~Sendable ()=default
Public Member Functions inherited from wpi::util::SendableHelper< DifferentialDrive >
constexpr	SendableHelper (const SendableHelper &rhs)=default
constexpr SendableHelper &	operator= (const SendableHelper &rhs)=default

Static Public Member Functions
static WheelVelocities	ArcadeDriveIK (double xVelocity, double zRotation, bool squareInputs=true)
	Arcade drive inverse kinematics for differential drive platform.
static WheelVelocities	CurvatureDriveIK (double xVelocity, double zRotation, bool allowTurnInPlace)
	Curvature drive inverse kinematics for differential drive platform.
static WheelVelocities	TankDriveIK (double leftVelocity, double rightVelocity, bool squareInputs=true)
	Tank drive inverse kinematics for differential drive platform.
Static Public Member Functions inherited from wpi::MotorSafety
static void	CheckMotors ()
	Check the motors to see if any have timed out.

Additional Inherited Members
Public Types inherited from wpi::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::util::SendableHelper< DifferentialDrive >
constexpr	~SendableHelper ()
Static Protected Member Functions inherited from wpi::RobotDriveBase
static void	Desaturate (std::span< double > wheelVelocities)
	Renormalize all wheel velocities if the magnitude of any wheel is greater than 1.0.
Protected Attributes inherited from wpi::RobotDriveBase
double	m_deadband = kDefaultDeadband
	Input deadband.
double	m_maxOutput = kDefaultMaxOutput
	Maximum output.
Static Protected Attributes inherited from wpi::RobotDriveBase
static constexpr double	kDefaultDeadband = 0.02
	Default input deadband.
static constexpr double	kDefaultMaxOutput = 1.0
	Default maximum output.

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 setter per side. For four and six motor drivetrains, use CAN motor controller followers or PWMMotorController::AddFollower().

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() [1/3]

WPI_IGNORE_DEPRECATED wpi::DifferentialDrive::DifferentialDrive	(	MotorController &	leftMotor,
		MotorController &	rightMotor )

Construct a DifferentialDrive.

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

Parameters

leftMotor	Left motor.
rightMotor	Right motor.

◆ DifferentialDrive() [2/3]

WPI_UNIGNORE_DEPRECATED wpi::DifferentialDrive::DifferentialDrive	(	std::function< void(double)>	leftMotor,
		std::function< void(double)>	rightMotor )

Construct a DifferentialDrive.

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

Parameters

leftMotor	Left motor setter.
rightMotor	Right motor setter.

◆ ~DifferentialDrive()

wpi::DifferentialDrive::~DifferentialDrive ( )

overridedefault

◆ DifferentialDrive() [3/3]

wpi::DifferentialDrive::DifferentialDrive ( DifferentialDrive && )

default

Member Function Documentation

◆ ArcadeDrive()

void wpi::DifferentialDrive::ArcadeDrive	(	double	xVelocity,
		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

xVelocity	The velocity 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 velocities.

◆ ArcadeDriveIK()

WheelVelocities wpi::DifferentialDrive::ArcadeDriveIK	(	double	xVelocity,
		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

xVelocity	The velocity 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 velocities.

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

◆ CurvatureDrive()

void wpi::DifferentialDrive::CurvatureDrive	(	double	xVelocity,
		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 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.

◆ CurvatureDriveIK()

WheelVelocities wpi::DifferentialDrive::CurvatureDriveIK	(	double	xVelocity,
		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 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]. 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 velocities [-1.0..1.0].

◆ GetDescription()

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

overridevirtual

Returns a description to print when an error occurs.

Returns: Description to print when an error occurs.

Implements wpi::RobotDriveBase.

◆ InitSendable()

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

overridevirtual

Initializes this Sendable object.

Parameters

builder sendable builder

Implements wpi::util::Sendable.

◆ operator=()

DifferentialDrive & wpi::DifferentialDrive::operator= ( DifferentialDrive && )

default

◆ StopMotor()

void wpi::DifferentialDrive::StopMotor ( )

overridevirtual

Called to stop the motor when the timeout expires.

Implements wpi::RobotDriveBase.

◆ TankDrive()

void wpi::DifferentialDrive::TankDrive	(	double	leftVelocity,
		double	rightVelocity,
		bool	squareInputs = true )

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.

◆ TankDriveIK()

WheelVelocities wpi::DifferentialDrive::TankDriveIK	(	double	leftVelocity,
		double	rightVelocity,
		bool	squareInputs = true )

static

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].

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

wpi/drive/DifferentialDrive.hpp

Classes

Public Member Functions

Static Public Member Functions

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ DifferentialDrive() [1/3]

◆ DifferentialDrive() [2/3]

◆ ~DifferentialDrive()

◆ DifferentialDrive() [3/3]

Member Function Documentation

◆ ArcadeDrive()

◆ ArcadeDriveIK()

◆ CurvatureDrive()

◆ CurvatureDriveIK()

◆ GetDescription()

◆ InitSendable()

◆ operator=()

◆ StopMotor()

◆ TankDrive()

◆ TankDriveIK()