frc::LinearPlantInversionFeedforward< States, Inputs > Class Template Reference

Constructs a plant inversion model-based feedforward from a LinearSystem. More...

#include <frc/controller/LinearPlantInversionFeedforward.h>

Public Types
using	StateVector = Vectord< States >
using	InputVector = Vectord< Inputs >

Public Member Functions
template<int Outputs>
	LinearPlantInversionFeedforward (const LinearSystem< States, Inputs, Outputs > &plant, units::second_t dt)
	Constructs a feedforward with the given plant. More...
	LinearPlantInversionFeedforward (const Matrixd< States, States > &A, const Matrixd< States, Inputs > &B, units::second_t dt)
	Constructs a feedforward with the given coefficients. More...
const InputVector &	Uff () const
	Returns the previously calculated feedforward as an input vector. More...
double	Uff (int i) const
	Returns an element of the previously calculated feedforward. More...
const StateVector &	R () const
	Returns the current reference vector r. More...
double	R (int i) const
	Returns an element of the reference vector r. More...
void	Reset (const StateVector &initialState)
	Resets the feedforward with a specified initial state vector. More...
void	Reset ()
	Resets the feedforward with a zero initial state vector. More...
InputVector	Calculate (const StateVector &nextR)
	Calculate the feedforward with only the desired future reference. More...
InputVector	Calculate (const StateVector &r, const StateVector &nextR)
	Calculate the feedforward with current and future reference vectors. More...

Detailed Description

template<int States, int Inputs>
class frc::LinearPlantInversionFeedforward< States, Inputs >

Constructs a plant inversion model-based feedforward from a LinearSystem.

The feedforward is calculated as u_ff = B⁺ (r_k+1 - A r_k) , where B⁺ is the pseudoinverse of B.

For more on the underlying math, read https://file.tavsys.net/control/controls-engineering-in-frc.pdf.

Template Parameters

States	Number of states.
Inputs	Number of inputs.

Member Typedef Documentation

InputVector

template<int States, int Inputs>

using frc::LinearPlantInversionFeedforward< States, Inputs >::InputVector = Vectord<Inputs>

StateVector

template<int States, int Inputs>

using frc::LinearPlantInversionFeedforward< States, Inputs >::StateVector = Vectord<States>

Constructor & Destructor Documentation

LinearPlantInversionFeedforward() [1/2]

template<int States, int Inputs>

template<int Outputs>

frc::LinearPlantInversionFeedforward< States, Inputs >::LinearPlantInversionFeedforward ( const LinearSystem< States, Inputs, Outputs > &  plant, units::second_t  dt  )

inline

Constructs a feedforward with the given plant.

Template Parameters

Outputs

Number of outputs.

Parameters

plant	The plant being controlled.
dt	Discretization timestep.

LinearPlantInversionFeedforward() [2/2]

template<int States, int Inputs>

frc::LinearPlantInversionFeedforward< States, Inputs >::LinearPlantInversionFeedforward ( const Matrixd< States, States > &  A, const Matrixd< States, Inputs > &  B, units::second_t  dt  )

inline

Constructs a feedforward with the given coefficients.

Parameters

A	Continuous system matrix of the plant being controlled.
B	Continuous input matrix of the plant being controlled.
dt	Discretization timestep.

Member Function Documentation

Calculate() [1/2]

template<int States, int Inputs>

InputVector frc::LinearPlantInversionFeedforward< States, Inputs >::Calculate ( const StateVector &  nextR )

inline

Calculate the feedforward with only the desired future reference.

This uses the internally stored "current" reference.

If this method is used the initial state of the system is the one set using Reset(const StateVector&). If the initial state is not set it defaults to a zero vector.

Parameters

nextR

The reference state of the future timestep (k + dt).

Returns

The calculated feedforward.

Calculate() [2/2]

template<int States, int Inputs>

InputVector frc::LinearPlantInversionFeedforward< States, Inputs >::Calculate ( const StateVector &  r, const StateVector &  nextR  )

inline

Calculate the feedforward with current and future reference vectors.

Parameters

r	The reference state of the current timestep (k).
nextR	The reference state of the future timestep (k + dt).

Returns

The calculated feedforward.

R() [1/2]

template<int States, int Inputs>

const StateVector & frc::LinearPlantInversionFeedforward< States, Inputs >::R ( ) const

inline

Returns the current reference vector r.

Returns

The current reference vector.

R() [2/2]

template<int States, int Inputs>

double frc::LinearPlantInversionFeedforward< States, Inputs >::R ( int  i ) const

inline

Returns an element of the reference vector r.

Parameters

i

Row of r.

Returns

The row of the current reference vector.

Reset() [1/2]

template<int States, int Inputs>

void frc::LinearPlantInversionFeedforward< States, Inputs >::Reset ( )

inline

Resets the feedforward with a zero initial state vector.

Reset() [2/2]

template<int States, int Inputs>

void frc::LinearPlantInversionFeedforward< States, Inputs >::Reset ( const StateVector &  initialState )

inline

Resets the feedforward with a specified initial state vector.

Parameters

initialState

The initial state vector.

Uff() [1/2]

template<int States, int Inputs>

const InputVector & frc::LinearPlantInversionFeedforward< States, Inputs >::Uff ( ) const

inline

Returns the previously calculated feedforward as an input vector.

Returns

The calculated feedforward.

Uff() [2/2]

template<int States, int Inputs>

double frc::LinearPlantInversionFeedforward< States, Inputs >::Uff ( int  i ) const

inline

Returns an element of the previously calculated feedforward.

Parameters

i	Row of uff.

Returns

The row of the calculated feedforward.

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

• frc/controller/LinearPlantInversionFeedforward.h