Helper class that converts a chassis velocity (dx, dy, and dtheta components) into individual wheel speeds. More...

#include <frc/kinematics/MecanumDriveKinematics.h>

Inheritance diagram for frc::MecanumDriveKinematics:

Public Member Functions
	MecanumDriveKinematics (Translation2d frontLeftWheel, Translation2d frontRightWheel, Translation2d rearLeftWheel, Translation2d rearRightWheel)
	Constructs a mecanum drive kinematics object. More...

	MecanumDriveKinematics (const MecanumDriveKinematics &)=default

MecanumDriveWheelSpeeds	ToWheelSpeeds (const ChassisSpeeds &chassisSpeeds, const Translation2d &centerOfRotation) const
	Performs inverse kinematics to return the wheel speeds from a desired chassis velocity. More...

MecanumDriveWheelSpeeds	ToWheelSpeeds (const ChassisSpeeds &chassisSpeeds) const override
	Performs inverse kinematics to return the wheel speeds from a desired chassis velocity. More...

ChassisSpeeds	ToChassisSpeeds (const MecanumDriveWheelSpeeds &wheelSpeeds) const override
	Performs forward kinematics to return the resulting chassis state from the given wheel speeds. More...

Twist2d	ToTwist2d (const MecanumDriveWheelPositions &start, const MecanumDriveWheelPositions &end) const override
	Performs forward kinematics to return the resulting Twist2d from the given change in wheel positions. More...

Twist2d	ToTwist2d (const MecanumDriveWheelPositions &wheelDeltas) const
	Performs forward kinematics to return the resulting Twist2d from the given wheel position deltas. More...

const Translation2d &	GetFrontLeft () const
	Returns the front-left wheel translation. More...

const Translation2d &	GetFrontRight () const
	Returns the front-right wheel translation. More...

const Translation2d &	GetRearLeft () const
	Returns the rear-left wheel translation. More...

const Translation2d &	GetRearRight () const
	Returns the rear-right wheel translation. More...

virtual ChassisSpeeds	ToChassisSpeeds (const MecanumDriveWheelSpeeds &wheelSpeeds) const=0
	Performs forward kinematics to return the resulting chassis speed from the wheel speeds. More...

virtual MecanumDriveWheelSpeeds	ToWheelSpeeds (const ChassisSpeeds &chassisSpeeds) const=0
	Performs inverse kinematics to return the wheel speeds from a desired chassis velocity. More...

virtual Twist2d	ToTwist2d (const MecanumDriveWheelPositions &start, const MecanumDriveWheelPositions &end) const=0
	Performs forward kinematics to return the resulting Twist2d from the given change in wheel positions. More...

Detailed Description

Helper class that converts a chassis velocity (dx, dy, and dtheta components) into individual wheel speeds.

The inverse kinematics (converting from a desired chassis velocity to individual wheel speeds) uses the relative locations of the wheels with respect to the center of rotation. The center of rotation for inverse kinematics is also variable. This means that you can set your set your center of rotation in a corner of the robot to perform special evasion maneuvers.

Forward kinematics (converting an array of wheel speeds into the overall chassis motion) is performs the exact opposite of what inverse kinematics does. Since this is an overdetermined system (more equations than variables), we use a least-squares approximation.

The inverse kinematics: [wheelSpeeds] = [wheelLocations] * [chassisSpeeds] We take the Moore-Penrose pseudoinverse of [wheelLocations] and then multiply by [wheelSpeeds] to get our chassis speeds.

Forward kinematics is also used for odometry – determining the position of the robot on the field using encoders and a gyro.

Constructor & Destructor Documentation

◆ MecanumDriveKinematics() [1/2]

frc::MecanumDriveKinematics::MecanumDriveKinematics	(	Translation2d	frontLeftWheel,
		Translation2d	frontRightWheel,
		Translation2d	rearLeftWheel,
		Translation2d	rearRightWheel
	)

inlineexplicit

Constructs a mecanum drive kinematics object.

Parameters

frontLeftWheel	The location of the front-left wheel relative to the physical center of the robot.
frontRightWheel	The location of the front-right wheel relative to the physical center of the robot.
rearLeftWheel	The location of the rear-left wheel relative to the physical center of the robot.
rearRightWheel	The location of the rear-right wheel relative to the physical center of the robot.

◆ MecanumDriveKinematics() [2/2]

frc::MecanumDriveKinematics::MecanumDriveKinematics ( const MecanumDriveKinematics & )

default

Member Function Documentation

◆ GetFrontLeft()

const Translation2d & frc::MecanumDriveKinematics::GetFrontLeft ( ) const

inline

Returns the front-left wheel translation.

Returns: The front-left wheel translation.

◆ GetFrontRight()

const Translation2d & frc::MecanumDriveKinematics::GetFrontRight ( ) const

inline

Returns the front-right wheel translation.

Returns: The front-right wheel translation.

◆ GetRearLeft()

const Translation2d & frc::MecanumDriveKinematics::GetRearLeft ( ) const

inline

Returns the rear-left wheel translation.

Returns: The rear-left wheel translation.

◆ GetRearRight()

const Translation2d & frc::MecanumDriveKinematics::GetRearRight ( ) const

inline

Returns the rear-right wheel translation.

Returns: The rear-right wheel translation.

◆ ToChassisSpeeds()

ChassisSpeeds frc::MecanumDriveKinematics::ToChassisSpeeds ( const MecanumDriveWheelSpeeds & wheelSpeeds ) const

overridevirtual

Performs forward kinematics to return the resulting chassis state from the given wheel speeds.

This method is often used for odometry – determining the robot's position on the field using data from the real-world speed of each wheel on the robot.

Parameters

wheelSpeeds The current mecanum drive wheel speeds.

Returns: The resulting chassis speed.

Implements frc::Kinematics< MecanumDriveWheelSpeeds, MecanumDriveWheelPositions >.

◆ ToTwist2d() [1/2]

Twist2d frc::MecanumDriveKinematics::ToTwist2d	(	const MecanumDriveWheelPositions &	start,
		const MecanumDriveWheelPositions &	end
	)		const

overridevirtual

Performs forward kinematics to return the resulting Twist2d from the given change in wheel positions.

This method is often used for odometry – determining the robot's position on the field using changes in the distance driven by each wheel on the robot.

Parameters

start	The starting distances driven by the wheels.
end	The ending distances driven by the wheels.

Returns: The resulting Twist2d in the robot's movement.

Implements frc::Kinematics< MecanumDriveWheelSpeeds, MecanumDriveWheelPositions >.

◆ ToTwist2d() [2/2]

Twist2d frc::MecanumDriveKinematics::ToTwist2d ( const MecanumDriveWheelPositions & wheelDeltas ) const

Performs forward kinematics to return the resulting Twist2d from the given wheel position deltas.

This method is often used for odometry – determining the robot's position on the field using data from the distance driven by each wheel on the robot.

Parameters

wheelDeltas The change in distance driven by each wheel.

Returns: The resulting chassis speed.

◆ ToWheelSpeeds() [1/2]

MecanumDriveWheelSpeeds frc::MecanumDriveKinematics::ToWheelSpeeds ( const ChassisSpeeds & chassisSpeeds ) const

inlineoverridevirtual

Performs inverse kinematics to return the wheel speeds from a desired chassis velocity.

This method is often used to convert joystick values into wheel speeds.

Parameters

chassisSpeeds The desired chassis speed.

Returns: The wheel speeds.

Implements frc::Kinematics< MecanumDriveWheelSpeeds, MecanumDriveWheelPositions >.

◆ ToWheelSpeeds() [2/2]

MecanumDriveWheelSpeeds frc::MecanumDriveKinematics::ToWheelSpeeds	(	const ChassisSpeeds &	chassisSpeeds,
		const Translation2d &	centerOfRotation
	)		const

Performs inverse kinematics to return the wheel speeds from a desired chassis velocity.

This method is often used to convert joystick values into wheel speeds.

This function also supports variable centers of rotation. During normal operations, the center of rotation is usually the same as the physical center of the robot; therefore, the argument is defaulted to that use case. However, if you wish to change the center of rotation for evasive maneuvers, vision alignment, or for any other use case, you can do so.

Parameters

chassisSpeeds	The desired chassis speed.
centerOfRotation	The center of rotation. For example, if you set the center of rotation at one corner of the robot and provide a chassis speed that only has a dtheta component, the robot will rotate around that corner.

Returns: The wheel speeds. Use caution because they are not normalized. Sometimes, a user input may cause one of the wheel speeds to go above the attainable max velocity. Use the MecanumDriveWheelSpeeds::Normalize() function to rectify this issue. In addition, you can leverage the power of C++17 to directly assign the wheel speeds to variables:

auto [fl, fr, bl, br] = kinematics.ToWheelSpeeds(chassisSpeeds);

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

frc/kinematics/MecanumDriveKinematics.h

Public Member Functions

Detailed Description

Constructor & Destructor Documentation

◆ MecanumDriveKinematics() [1/2]

◆ MecanumDriveKinematics() [2/2]

Member Function Documentation

◆ GetFrontLeft()

◆ GetFrontRight()

◆ GetRearLeft()

◆ GetRearRight()

◆ ToChassisSpeeds()

◆ ToTwist2d() [1/2]

◆ ToTwist2d() [2/2]

◆ ToWheelSpeeds() [1/2]

◆ ToWheelSpeeds() [2/2]