frc::DifferentialDriveKinematics Class Reference

Helper class that converts a chassis velocity (dx and dtheta components) to left and right wheel velocities for a differential drive. More...

#include <frc/kinematics/DifferentialDriveKinematics.h>

Inheritance diagram for frc::DifferentialDriveKinematics:

Public Member Functions
constexpr	DifferentialDriveKinematics (units::meter_t trackWidth)
	Constructs a differential drive kinematics object.
constexpr ChassisSpeeds	ToChassisSpeeds (const DifferentialDriveWheelSpeeds &wheelSpeeds) const override
	Returns a chassis speed from left and right component velocities using forward kinematics.
constexpr DifferentialDriveWheelSpeeds	ToWheelSpeeds (const ChassisSpeeds &chassisSpeeds) const override
	Returns left and right component velocities from a chassis speed using inverse kinematics.
constexpr Twist2d	ToTwist2d (const units::meter_t leftDistance, const units::meter_t rightDistance) const
	Returns a twist from left and right distance deltas using forward kinematics.
constexpr Twist2d	ToTwist2d (const DifferentialDriveWheelPositions &start, const DifferentialDriveWheelPositions &end) const override
	Performs forward kinematics to return the resulting Twist2d from the given change in wheel positions.
constexpr DifferentialDriveWheelPositions	Interpolate (const DifferentialDriveWheelPositions &start, const DifferentialDriveWheelPositions &end, double t) const override
	Performs interpolation between two values.
Public Member Functions inherited from frc::Kinematics< DifferentialDriveWheelSpeeds, DifferentialDriveWheelPositions >
virtual	~Kinematics () noexcept=default

Public Attributes
units::meter_t	trackWidth
	Differential drive trackwidth.

Detailed Description

Helper class that converts a chassis velocity (dx and dtheta components) to left and right wheel velocities for a differential drive.

Inverse kinematics converts a desired chassis speed into left and right velocity components whereas forward kinematics converts left and right component velocities into a linear and angular chassis speed.

Constructor & Destructor Documentation

DifferentialDriveKinematics()

frc::DifferentialDriveKinematics::DifferentialDriveKinematics ( units::meter_t trackWidth )

inlineexplicitconstexpr

Constructs a differential drive kinematics object.

Parameters

trackWidth

The track width of the drivetrain. Theoretically, this is the distance between the left wheels and right wheels. However, the empirical value may be larger than the physical measured value due to scrubbing effects.

Member Function Documentation

Interpolate()

DifferentialDriveWheelPositions frc::DifferentialDriveKinematics::Interpolate ( const DifferentialDriveWheelPositions & start, const DifferentialDriveWheelPositions & end, double t ) const

inlineconstexproverridevirtual

Performs interpolation between two values.

Parameters

start	The value to start at.
end	The value to end at.
t	How far between the two values to interpolate. This should be bounded to [0, 1].

Returns

The interpolated value.

Implements frc::Kinematics< DifferentialDriveWheelSpeeds, DifferentialDriveWheelPositions >.

ToChassisSpeeds()

ChassisSpeeds frc::DifferentialDriveKinematics::ToChassisSpeeds ( const DifferentialDriveWheelSpeeds & wheelSpeeds ) const

inlineconstexproverridevirtual

Returns a chassis speed from left and right component velocities using forward kinematics.

Parameters

wheelSpeeds

The left and right velocities.

Returns

The chassis speed.

Implements frc::Kinematics< DifferentialDriveWheelSpeeds, DifferentialDriveWheelPositions >.

ToTwist2d() [1/2]

Twist2d frc::DifferentialDriveKinematics::ToTwist2d ( const DifferentialDriveWheelPositions & start, const DifferentialDriveWheelPositions & end ) const

inlineconstexproverridevirtual

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< DifferentialDriveWheelSpeeds, DifferentialDriveWheelPositions >.

ToTwist2d() [2/2]

Twist2d frc::DifferentialDriveKinematics::ToTwist2d ( const units::meter_t leftDistance, const units::meter_t rightDistance ) const

inlineconstexpr

Returns a twist from left and right distance deltas using forward kinematics.

Parameters

leftDistance	The distance measured by the left encoder.
rightDistance	The distance measured by the right encoder.

Returns

The resulting Twist2d.

ToWheelSpeeds()

DifferentialDriveWheelSpeeds frc::DifferentialDriveKinematics::ToWheelSpeeds ( const ChassisSpeeds & chassisSpeeds ) const

inlineconstexproverridevirtual

Returns left and right component velocities from a chassis speed using inverse kinematics.

Parameters

chassisSpeeds

The linear and angular (dx and dtheta) components that represent the chassis' speed.

Returns

The left and right velocities.

Implements frc::Kinematics< DifferentialDriveWheelSpeeds, DifferentialDriveWheelPositions >.

Member Data Documentation

trackWidth

units::meter_t frc::DifferentialDriveKinematics::trackWidth

Differential drive trackwidth.

---

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

• frc/kinematics/DifferentialDriveKinematics.h