Represents the speed of a robot chassis. More...

#include <frc/kinematics/ChassisSpeeds.h>

Public Member Functions
constexpr Twist2d	ToTwist2d (units::second_t dt) const
	Creates a Twist2d from ChassisSpeeds.

constexpr ChassisSpeeds	operator+ (const ChassisSpeeds &other) const
	Adds two ChassisSpeeds and returns the sum.

constexpr ChassisSpeeds	operator- (const ChassisSpeeds &other) const
	Subtracts the other ChassisSpeeds from the current ChassisSpeeds and returns the difference.

constexpr ChassisSpeeds	operator- () const
	Returns the inverse of the current ChassisSpeeds.

constexpr ChassisSpeeds	operator* (double scalar) const
	Multiplies the ChassisSpeeds by a scalar and returns the new ChassisSpeeds.

constexpr ChassisSpeeds	operator/ (double scalar) const
	Divides the ChassisSpeeds by a scalar and returns the new ChassisSpeeds.

constexpr bool	operator== (const ChassisSpeeds &other) const =default
	Compares the ChassisSpeeds with another ChassisSpeed.

Static Public Member Functions
static constexpr ChassisSpeeds	Discretize (units::meters_per_second_t vx, units::meters_per_second_t vy, units::radians_per_second_t omega, units::second_t dt)
	Discretizes a continuous-time chassis speed.

static constexpr ChassisSpeeds	Discretize (const ChassisSpeeds &continuousSpeeds, units::second_t dt)
	Discretizes a continuous-time chassis speed.

static constexpr ChassisSpeeds	FromFieldRelativeSpeeds (units::meters_per_second_t vx, units::meters_per_second_t vy, units::radians_per_second_t omega, const Rotation2d &robotAngle)
	Converts a user provided field-relative set of speeds into a robot-relative ChassisSpeeds object.

static constexpr ChassisSpeeds	FromFieldRelativeSpeeds (const ChassisSpeeds &fieldRelativeSpeeds, const Rotation2d &robotAngle)
	Converts a user provided field-relative ChassisSpeeds object into a robot-relative ChassisSpeeds object.

static constexpr ChassisSpeeds	FromRobotRelativeSpeeds (units::meters_per_second_t vx, units::meters_per_second_t vy, units::radians_per_second_t omega, const Rotation2d &robotAngle)
	Converts a user provided robot-relative set of speeds into a field-relative ChassisSpeeds object.

static constexpr ChassisSpeeds	FromRobotRelativeSpeeds (const ChassisSpeeds &robotRelativeSpeeds, const Rotation2d &robotAngle)
	Converts a user provided robot-relative ChassisSpeeds object into a field-relative ChassisSpeeds object.

Public Attributes
units::meters_per_second_t	vx = 0_mps
	Velocity along the x-axis.

units::meters_per_second_t	vy = 0_mps
	Velocity along the y-axis.

units::radians_per_second_t	omega = 0_rad_per_s
	Represents the angular velocity of the robot frame.

Detailed Description

Represents the speed of a robot chassis.

Although this struct contains similar members compared to a Twist2d, they do NOT represent the same thing. Whereas a Twist2d represents a change in pose w.r.t to the robot frame of reference, a ChassisSpeeds struct represents a robot's velocity.

A strictly non-holonomic drivetrain, such as a differential drive, should never have a dy component because it can never move sideways. Holonomic drivetrains such as swerve and mecanum will often have all three components.

Member Function Documentation

◆ Discretize() [1/2]

static constexpr ChassisSpeeds frc::ChassisSpeeds::Discretize	(	const ChassisSpeeds &	continuousSpeeds,
		units::second_t	dt )

inlinestaticconstexpr

Discretizes a continuous-time chassis speed.

This function converts a continuous-time chassis speed into a discrete-time one such that when the discrete-time chassis speed is applied for one timestep, the robot moves as if the velocity components are independent (i.e., the robot moves v_x * dt along the x-axis, v_y * dt along the y-axis, and omega * dt around the z-axis).

This is useful for compensating for translational skew when translating and rotating a holonomic (swerve or mecanum) drivetrain. However, scaling down the ChassisSpeeds after discretizing (e.g., when desaturating swerve module speeds) rotates the direction of net motion in the opposite direction of rotational velocity, introducing a different translational skew which is not accounted for by discretization.

Parameters

continuousSpeeds	The continuous speeds.
dt	The duration of the timestep the speeds should be applied for.

Returns: Discretized ChassisSpeeds.

◆ Discretize() [2/2]

static constexpr ChassisSpeeds frc::ChassisSpeeds::Discretize	(	units::meters_per_second_t	vx,
		units::meters_per_second_t	vy,
		units::radians_per_second_t	omega,
		units::second_t	dt )

inlinestaticconstexpr

Discretizes a continuous-time chassis speed.

This function converts a continuous-time chassis speed into a discrete-time one such that when the discrete-time chassis speed is applied for one timestep, the robot moves as if the velocity components are independent (i.e., the robot moves v_x * dt along the x-axis, v_y * dt along the y-axis, and omega * dt around the z-axis).

This is useful for compensating for translational skew when translating and rotating a holonomic (swerve or mecanum) drivetrain. However, scaling down the ChassisSpeeds after discretizing (e.g., when desaturating swerve module speeds) rotates the direction of net motion in the opposite direction of rotational velocity, introducing a different translational skew which is not accounted for by discretization.

Parameters

vx	Forward velocity.
vy	Sideways velocity.
omega	Angular velocity.
dt	The duration of the timestep the speeds should be applied for.

Returns: Discretized ChassisSpeeds.

◆ FromFieldRelativeSpeeds() [1/2]

static constexpr ChassisSpeeds frc::ChassisSpeeds::FromFieldRelativeSpeeds	(	const ChassisSpeeds &	fieldRelativeSpeeds,
		const Rotation2d &	robotAngle )

inlinestaticconstexpr

Converts a user provided field-relative ChassisSpeeds object into a robot-relative ChassisSpeeds object.

Parameters

fieldRelativeSpeeds	The ChassisSpeeds object representing the speeds in the field frame of reference. Positive x is away from your alliance wall. Positive y is to your left when standing behind the alliance wall.
robotAngle	The angle of the robot as measured by a gyroscope. The robot's angle is considered to be zero when it is facing directly away from your alliance station wall. Remember that this should be CCW positive.

Returns: ChassisSpeeds object representing the speeds in the robot's frame of reference.

◆ FromFieldRelativeSpeeds() [2/2]

static constexpr ChassisSpeeds frc::ChassisSpeeds::FromFieldRelativeSpeeds	(	units::meters_per_second_t	vx,
		units::meters_per_second_t	vy,
		units::radians_per_second_t	omega,
		const Rotation2d &	robotAngle )

inlinestaticconstexpr

Converts a user provided field-relative set of speeds into a robot-relative ChassisSpeeds object.

Parameters

vx	The component of speed in the x direction relative to the field. Positive x is away from your alliance wall.
vy	The component of speed in the y direction relative to the field. Positive y is to your left when standing behind the alliance wall.
omega	The angular rate of the robot.
robotAngle	The angle of the robot as measured by a gyroscope. The robot's angle is considered to be zero when it is facing directly away from your alliance station wall. Remember that this should be CCW positive.

Returns: ChassisSpeeds object representing the speeds in the robot's frame of reference.

◆ FromRobotRelativeSpeeds() [1/2]

static constexpr ChassisSpeeds frc::ChassisSpeeds::FromRobotRelativeSpeeds	(	const ChassisSpeeds &	robotRelativeSpeeds,
		const Rotation2d &	robotAngle )

inlinestaticconstexpr

Converts a user provided robot-relative ChassisSpeeds object into a field-relative ChassisSpeeds object.

Parameters

robotRelativeSpeeds	The ChassisSpeeds object representing the speeds in the robot frame of reference. Positive x is the towards robot's front. Positive y is towards the robot's left.
robotAngle	The angle of the robot as measured by a gyroscope. The robot's angle is considered to be zero when it is facing directly away from your alliance station wall. Remember that this should be CCW positive.

Returns: ChassisSpeeds object representing the speeds in the field's frame of reference.

◆ FromRobotRelativeSpeeds() [2/2]

static constexpr ChassisSpeeds frc::ChassisSpeeds::FromRobotRelativeSpeeds	(	units::meters_per_second_t	vx,
		units::meters_per_second_t	vy,
		units::radians_per_second_t	omega,
		const Rotation2d &	robotAngle )

inlinestaticconstexpr

Converts a user provided robot-relative set of speeds into a field-relative ChassisSpeeds object.

Parameters

vx	The component of speed in the x direction relative to the robot. Positive x is towards the robot's front.
vy	The component of speed in the y direction relative to the robot. Positive y is towards the robot's left.
omega	The angular rate of the robot.
robotAngle	The angle of the robot as measured by a gyroscope. The robot's angle is considered to be zero when it is facing directly away from your alliance station wall. Remember that this should be CCW positive.

Returns: ChassisSpeeds object representing the speeds in the field's frame of reference.

◆ operator*()

ChassisSpeeds frc::ChassisSpeeds::operator* ( double scalar ) const

inlineconstexpr

Multiplies the ChassisSpeeds by a scalar and returns the new ChassisSpeeds.

For example, ChassisSpeeds{2.0, 2.5, 1.0} * 2 = ChassisSpeeds{4.0, 5.0, 1.0}

Parameters

scalar The scalar to multiply by.

Returns: The scaled ChassisSpeeds.

◆ operator+()

ChassisSpeeds frc::ChassisSpeeds::operator+ ( const ChassisSpeeds & other ) const

inlineconstexpr

Adds two ChassisSpeeds and returns the sum.

For example, ChassisSpeeds{1.0, 0.5, 1.5} + ChassisSpeeds{2.0, 1.5, 0.5} = ChassisSpeeds{3.0, 2.0, 2.0}

Parameters

other The ChassisSpeeds to add.

Returns: The sum of the ChassisSpeeds.

◆ operator-() [1/2]

ChassisSpeeds frc::ChassisSpeeds::operator- ( ) const

inlineconstexpr

Returns the inverse of the current ChassisSpeeds.

This is equivalent to negating all components of the ChassisSpeeds.

Returns: The inverse of the current ChassisSpeeds.

◆ operator-() [2/2]

ChassisSpeeds frc::ChassisSpeeds::operator- ( const ChassisSpeeds & other ) const

inlineconstexpr

Subtracts the other ChassisSpeeds from the current ChassisSpeeds and returns the difference.

For example, ChassisSpeeds{5.0, 4.0, 2.0} - ChassisSpeeds{1.0, 2.0, 1.0} = ChassisSpeeds{4.0, 2.0, 1.0}

Parameters

other The ChassisSpeeds to subtract.

Returns: The difference between the two ChassisSpeeds.

◆ operator/()

ChassisSpeeds frc::ChassisSpeeds::operator/ ( double scalar ) const

inlineconstexpr

Divides the ChassisSpeeds by a scalar and returns the new ChassisSpeeds.

For example, ChassisSpeeds{2.0, 2.5, 1.0} / 2 = ChassisSpeeds{1.0, 1.25, 0.5}

Parameters

scalar The scalar to divide by.

Returns: The scaled ChassisSpeeds.

◆ operator==()

bool frc::ChassisSpeeds::operator== ( const ChassisSpeeds & other ) const

constexprdefault

Compares the ChassisSpeeds with another ChassisSpeed.

Parameters

other The other ChassisSpeeds.

Returns: The result of the comparison. Is true if they are the same.

◆ ToTwist2d()

Twist2d frc::ChassisSpeeds::ToTwist2d ( units::second_t dt ) const

inlineconstexpr

Creates a Twist2d from ChassisSpeeds.

Parameters

dt	The duration of the timestep.

Returns: Twist2d.

Member Data Documentation

◆ omega

units::radians_per_second_t frc::ChassisSpeeds::omega = 0_rad_per_s

Represents the angular velocity of the robot frame.

(CCW is +)

◆ vx

units::meters_per_second_t frc::ChassisSpeeds::vx = 0_mps

Velocity along the x-axis.

(Fwd is +)

◆ vy

units::meters_per_second_t frc::ChassisSpeeds::vy = 0_mps

Velocity along the y-axis.

(Left is +)

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

frc/kinematics/ChassisSpeeds.h

Public Member Functions

Static Public Member Functions

Public Attributes

Detailed Description

Member Function Documentation

◆ Discretize() [1/2]

◆ Discretize() [2/2]

◆ FromFieldRelativeSpeeds() [1/2]

◆ FromFieldRelativeSpeeds() [2/2]

◆ FromRobotRelativeSpeeds() [1/2]

◆ FromRobotRelativeSpeeds() [2/2]

◆ operator*()

◆ operator+()

◆ operator-() [1/2]

◆ operator-() [2/2]

◆ operator/()

◆ operator==()

◆ ToTwist2d()

Member Data Documentation

◆ omega

◆ vx

◆ vy