A helper class that computes feedforward voltages for a simple permanent-magnet DC motor. More...

#include <frc/controller/SimpleMotorFeedforward.h>

Public Types
using	Velocity

using	Acceleration

using	kv_unit = units::compound_unit<units::volts, units::inverse<Velocity>>

using	ka_unit

Public Member Functions
constexpr	SimpleMotorFeedforward (units::volt_t kS, units::unit_t< kv_unit > kV, units::unit_t< ka_unit > kA=units::unit_t< ka_unit >(0), units::second_t dt=20_ms)
	Creates a new SimpleMotorFeedforward with the specified gains.

constexpr units::volt_t	Calculate (units::unit_t< Velocity > velocity, units::unit_t< Acceleration > acceleration) const
	Calculates the feedforward from the gains and setpoints assuming continuous control.

constexpr units::volt_t	Calculate (units::unit_t< Velocity > velocity) const
	Calculates the feedforward from the gains and velocity setpoint assuming discrete control.

constexpr units::volt_t	Calculate (units::unit_t< Velocity > currentVelocity, units::unit_t< Velocity > nextVelocity) const
	Calculates the feedforward from the gains and setpoints assuming discrete control.

constexpr units::unit_t< Velocity >	MaxAchievableVelocity (units::volt_t maxVoltage, units::unit_t< Acceleration > acceleration) const
	Calculates the maximum achievable velocity given a maximum voltage supply and an acceleration.

constexpr units::unit_t< Velocity >	MinAchievableVelocity (units::volt_t maxVoltage, units::unit_t< Acceleration > acceleration) const
	Calculates the minimum achievable velocity given a maximum voltage supply and an acceleration.

constexpr units::unit_t< Acceleration >	MaxAchievableAcceleration (units::volt_t maxVoltage, units::unit_t< Velocity > velocity) const
	Calculates the maximum achievable acceleration given a maximum voltage supply and a velocity.

constexpr units::unit_t< Acceleration >	MinAchievableAcceleration (units::volt_t maxVoltage, units::unit_t< Velocity > velocity) const
	Calculates the minimum achievable acceleration given a maximum voltage supply and a velocity.

constexpr void	SetKs (units::volt_t kS)
	Sets the static gain.

constexpr void	SetKv (units::unit_t< kv_unit > kV)
	Sets the velocity gain.

constexpr void	SetKa (units::unit_t< ka_unit > kA)
	Sets the acceleration gain.

constexpr units::volt_t	GetKs () const
	Returns the static gain.

constexpr units::unit_t< kv_unit >	GetKv () const
	Returns the velocity gain.

constexpr units::unit_t< ka_unit >	GetKa () const
	Returns the acceleration gain.

constexpr units::second_t	GetDt () const
	Returns the period.

Detailed Description

template<class Distance>
requires units::length_unit<Distance> || units::angle_unit<Distance>
class frc::SimpleMotorFeedforward< Distance >

A helper class that computes feedforward voltages for a simple permanent-magnet DC motor.

Member Typedef Documentation

◆ Acceleration

template<class Distance >

using frc::SimpleMotorFeedforward< Distance >::Acceleration

Initial value:

units::compound_unit<Velocity, units::inverse<units::seconds>>

units::compound_unit

typename units::detail::compound_impl< U, Us... >::type compound_unit

Represents a unit type made up from other units.

Definition base.h:1438

◆ ka_unit

template<class Distance >

using frc::SimpleMotorFeedforward< Distance >::ka_unit

Initial value:

units::compound_unit<units::volts, units::inverse<Acceleration>>

◆ kv_unit

template<class Distance >

using frc::SimpleMotorFeedforward< Distance >::kv_unit = units::compound_unit<units::volts, units::inverse<Velocity>>

◆ Velocity

template<class Distance >

using frc::SimpleMotorFeedforward< Distance >::Velocity

Initial value:

units::compound_unit<Distance, units::inverse<units::seconds>>

Constructor & Destructor Documentation

◆ SimpleMotorFeedforward()

template<class Distance >

frc::SimpleMotorFeedforward< Distance >::SimpleMotorFeedforward	(	units::volt_t	kS,
		units::unit_t< kv_unit >	kV,
		units::unit_t< ka_unit >	kA = units::unit_t<ka_unit>(0),
		units::second_t	dt = 20_ms )

inlineconstexpr

Creates a new SimpleMotorFeedforward with the specified gains.

Parameters

kS	The static gain, in volts.
kV	The velocity gain, in volt seconds per distance.
kA	The acceleration gain, in volt seconds² per distance.
dt	The period in seconds.

Throws:: IllegalArgumentException for kv < zero.

Throws:: IllegalArgumentException for ka < zero.

Throws:: IllegalArgumentException for period ≤ zero.

Member Function Documentation

◆ Calculate() [1/3]

template<class Distance >

units::volt_t frc::SimpleMotorFeedforward< Distance >::Calculate	(	units::unit_t< Velocity >	currentVelocity,
		units::unit_t< Velocity >	nextVelocity ) const

inlineconstexpr

Calculates the feedforward from the gains and setpoints assuming discrete control.

Note this method is inaccurate when the velocity crosses 0.

Parameters

currentVelocity	The current velocity setpoint.
nextVelocity	The next velocity setpoint.

Returns: The computed feedforward, in volts.

◆ Calculate() [2/3]

template<class Distance >

units::volt_t frc::SimpleMotorFeedforward< Distance >::Calculate ( units::unit_t< Velocity > velocity ) const

inlineconstexpr

Calculates the feedforward from the gains and velocity setpoint assuming discrete control.

Use this method when the velocity setpoint does not change.

Parameters

velocity The velocity setpoint.

Returns: The computed feedforward, in volts.

◆ Calculate() [3/3]

template<class Distance >

units::volt_t frc::SimpleMotorFeedforward< Distance >::Calculate	(	units::unit_t< Velocity >	velocity,
		units::unit_t< Acceleration >	acceleration ) const

inlineconstexpr

Calculates the feedforward from the gains and setpoints assuming continuous control.

Parameters

velocity	The velocity setpoint.
acceleration	The acceleration setpoint.

Returns: The computed feedforward, in volts.

Deprecated: Use the current/next velocity overload instead.

◆ GetDt()

template<class Distance >

units::second_t frc::SimpleMotorFeedforward< Distance >::GetDt ( ) const

inlineconstexpr

Returns the period.

Returns: The period.

◆ GetKa()

template<class Distance >

units::unit_t< ka_unit > frc::SimpleMotorFeedforward< Distance >::GetKa ( ) const

inlineconstexpr

Returns the acceleration gain.

Returns: The acceleration gain.

◆ GetKs()

template<class Distance >

units::volt_t frc::SimpleMotorFeedforward< Distance >::GetKs ( ) const

inlineconstexpr

Returns the static gain.

Returns: The static gain.

◆ GetKv()

template<class Distance >

units::unit_t< kv_unit > frc::SimpleMotorFeedforward< Distance >::GetKv ( ) const

inlineconstexpr

Returns the velocity gain.

Returns: The velocity gain.

◆ MaxAchievableAcceleration()

template<class Distance >

units::unit_t< Acceleration > frc::SimpleMotorFeedforward< Distance >::MaxAchievableAcceleration	(	units::volt_t	maxVoltage,
		units::unit_t< Velocity >	velocity ) const

inlineconstexpr

Calculates the maximum achievable acceleration given a maximum voltage supply and a velocity.

Useful for ensuring that velocity and acceleration constraints for a trapezoidal profile are simultaneously achievable - enter the velocity constraint, and this will give you a simultaneously-achievable acceleration constraint.

Parameters

maxVoltage	The maximum voltage that can be supplied to the motor.
velocity	The velocity of the motor.

Returns: The maximum possible acceleration at the given velocity.

◆ MaxAchievableVelocity()

template<class Distance >

units::unit_t< Velocity > frc::SimpleMotorFeedforward< Distance >::MaxAchievableVelocity	(	units::volt_t	maxVoltage,
		units::unit_t< Acceleration >	acceleration ) const

inlineconstexpr

Calculates the maximum achievable velocity given a maximum voltage supply and an acceleration.

Useful for ensuring that velocity and acceleration constraints for a trapezoidal profile are simultaneously achievable - enter the acceleration constraint, and this will give you a simultaneously-achievable velocity constraint.

Parameters

maxVoltage	The maximum voltage that can be supplied to the motor.
acceleration	The acceleration of the motor.

Returns: The maximum possible velocity at the given acceleration.

◆ MinAchievableAcceleration()

template<class Distance >

units::unit_t< Acceleration > frc::SimpleMotorFeedforward< Distance >::MinAchievableAcceleration	(	units::volt_t	maxVoltage,
		units::unit_t< Velocity >	velocity ) const

inlineconstexpr

Calculates the minimum achievable acceleration given a maximum voltage supply and a velocity.

Useful for ensuring that velocity and acceleration constraints for a trapezoidal profile are simultaneously achievable - enter the velocity constraint, and this will give you a simultaneously-achievable acceleration constraint.

Parameters

maxVoltage	The maximum voltage that can be supplied to the motor.
velocity	The velocity of the motor.

Returns: The minimum possible acceleration at the given velocity.

◆ MinAchievableVelocity()

template<class Distance >

units::unit_t< Velocity > frc::SimpleMotorFeedforward< Distance >::MinAchievableVelocity	(	units::volt_t	maxVoltage,
		units::unit_t< Acceleration >	acceleration ) const

inlineconstexpr

Calculates the minimum achievable velocity given a maximum voltage supply and an acceleration.

Useful for ensuring that velocity and acceleration constraints for a trapezoidal profile are simultaneously achievable - enter the acceleration constraint, and this will give you a simultaneously-achievable velocity constraint.

Parameters

maxVoltage	The maximum voltage that can be supplied to the motor.
acceleration	The acceleration of the motor.

Returns: The minimum possible velocity at the given acceleration.

◆ SetKa()

template<class Distance >

void frc::SimpleMotorFeedforward< Distance >::SetKa ( units::unit_t< ka_unit > kA )

inlineconstexpr

Sets the acceleration gain.

Parameters

kA	The acceleration gain.

◆ SetKs()

template<class Distance >

void frc::SimpleMotorFeedforward< Distance >::SetKs ( units::volt_t kS )

inlineconstexpr

Sets the static gain.

Parameters

kS	The static gain.

◆ SetKv()

template<class Distance >

void frc::SimpleMotorFeedforward< Distance >::SetKv ( units::unit_t< kv_unit > kV )

inlineconstexpr

Sets the velocity gain.

Parameters

kV	The velocity gain.

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

frc/controller/SimpleMotorFeedforward.h

Public Types

Public Member Functions

Detailed Description

Member Typedef Documentation

◆ Acceleration

◆ ka_unit

◆ kv_unit

◆ Velocity

Constructor & Destructor Documentation

◆ SimpleMotorFeedforward()

Member Function Documentation

◆ Calculate() [1/3]

◆ Calculate() [2/3]

◆ Calculate() [3/3]

◆ GetDt()

◆ GetKa()

◆ GetKs()

◆ GetKv()

◆ MaxAchievableAcceleration()

◆ MaxAchievableVelocity()

◆ MinAchievableAcceleration()

◆ MinAchievableVelocity()

◆ SetKa()

◆ SetKs()

◆ SetKv()