wpi::math::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 <wpi/math/kinematics/DifferentialDriveKinematics.hpp>

Inheritance diagram for wpi::math::DifferentialDriveKinematics:

Public Member Functions
constexpr	DifferentialDriveKinematics (wpi::units::meter_t trackwidth)
	Constructs a differential drive kinematics object.
constexpr ChassisVelocities	ToChassisVelocities (const DifferentialDriveWheelVelocities &wheelVelocities) const override
	Returns a chassis velocity from left and right component velocities using forward kinematics.
constexpr DifferentialDriveWheelVelocities	ToWheelVelocities (const ChassisVelocities &chassisVelocities) const override
	Returns left and right component velocities from a chassis velocity using inverse kinematics.
constexpr Twist2d	ToTwist2d (const wpi::units::meter_t leftDistance, const wpi::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.
constexpr ChassisAccelerations	ToChassisAccelerations (const DifferentialDriveWheelAccelerations &wheelAccelerations) const override
	Performs forward kinematics to return the resulting chassis accelerations from the wheel accelerations.
constexpr DifferentialDriveWheelAccelerations	ToWheelAccelerations (const ChassisAccelerations &chassisAccelerations) const override
	Performs inverse kinematics to return the wheel accelerations from a desired chassis acceleration.
Public Member Functions inherited from wpi::math::Kinematics< DifferentialDriveWheelPositions, DifferentialDriveWheelVelocities, DifferentialDriveWheelAccelerations >
virtual	~Kinematics () noexcept=default

Public Attributes
wpi::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 velocity into left and right velocity components whereas forward kinematics converts left and right component velocities into a linear and angular chassis velocity.

Constructor & Destructor Documentation

DifferentialDriveKinematics()

wpi::math::DifferentialDriveKinematics::DifferentialDriveKinematics ( wpi::units::meter_t trackwidth )

inlineexplicitconstexpr

Constructs a differential drive kinematics object.

Parameters

trackwidth

The trackwidth 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 wpi::math::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 wpi::math::Kinematics< DifferentialDriveWheelPositions, DifferentialDriveWheelVelocities, DifferentialDriveWheelAccelerations >.

ToChassisAccelerations()

ChassisAccelerations wpi::math::DifferentialDriveKinematics::ToChassisAccelerations ( const DifferentialDriveWheelAccelerations & wheelAccelerations ) const

inlineconstexproverridevirtual

Performs forward kinematics to return the resulting chassis accelerations from the wheel accelerations.

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

Parameters

wheelAccelerations

The accelerations of the wheels.

Returns

The chassis accelerations.

Implements wpi::math::Kinematics< DifferentialDriveWheelPositions, DifferentialDriveWheelVelocities, DifferentialDriveWheelAccelerations >.

ToChassisVelocities()

ChassisVelocities wpi::math::DifferentialDriveKinematics::ToChassisVelocities ( const DifferentialDriveWheelVelocities & wheelVelocities ) const

inlineconstexproverridevirtual

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

Parameters

wheelVelocities

The left and right velocities.

Returns

The chassis velocity.

Implements wpi::math::Kinematics< DifferentialDriveWheelPositions, DifferentialDriveWheelVelocities, DifferentialDriveWheelAccelerations >.

ToTwist2d() [1/2]

Twist2d wpi::math::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 wpi::math::Kinematics< DifferentialDriveWheelPositions, DifferentialDriveWheelVelocities, DifferentialDriveWheelAccelerations >.

ToTwist2d() [2/2]

Twist2d wpi::math::DifferentialDriveKinematics::ToTwist2d ( const wpi::units::meter_t leftDistance, const wpi::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.

ToWheelAccelerations()

DifferentialDriveWheelAccelerations wpi::math::DifferentialDriveKinematics::ToWheelAccelerations ( const ChassisAccelerations & chassisAccelerations ) const

inlineconstexproverridevirtual

Performs inverse kinematics to return the wheel accelerations from a desired chassis acceleration.

This method is often used for dynamics calculations – converting desired robot accelerations into individual wheel accelerations.

Parameters

chassisAccelerations

The desired chassis accelerations.

Returns

The wheel accelerations.

Implements wpi::math::Kinematics< DifferentialDriveWheelPositions, DifferentialDriveWheelVelocities, DifferentialDriveWheelAccelerations >.

ToWheelVelocities()

DifferentialDriveWheelVelocities wpi::math::DifferentialDriveKinematics::ToWheelVelocities ( const ChassisVelocities & chassisVelocities ) const

inlineconstexproverridevirtual

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

Parameters

chassisVelocities

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

Returns

The left and right velocities.

Implements wpi::math::Kinematics< DifferentialDriveWheelPositions, DifferentialDriveWheelVelocities, DifferentialDriveWheelAccelerations >.

Member Data Documentation

trackwidth

wpi::units::meter_t wpi::math::DifferentialDriveKinematics::trackwidth

Differential drive trackwidth.

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

• wpi/math/kinematics/DifferentialDriveKinematics.hpp