Combines a controller, feedforward, and observer for controlling a mechanism with full state feedback. More...

#include <frc/system/LinearSystemLoop.h>

Public Types
using	StateVector = Vectord<States>

using	InputVector = Vectord<Inputs>

using	OutputVector = Vectord<Outputs>

Public Member Functions
	LinearSystemLoop (LinearSystem< States, Inputs, Outputs > &plant, LinearQuadraticRegulator< States, Inputs > &controller, KalmanFilter< States, Inputs, Outputs > &observer, units::volt_t maxVoltage, units::second_t dt)
	Constructs a state-space loop with the given plant, controller, and observer.

	LinearSystemLoop (LinearSystem< States, Inputs, Outputs > &plant, LinearQuadraticRegulator< States, Inputs > &controller, KalmanFilter< States, Inputs, Outputs > &observer, std::function< InputVector(const InputVector &)> clampFunction, units::second_t dt)
	Constructs a state-space loop with the given plant, controller, and observer.

	LinearSystemLoop (LinearQuadraticRegulator< States, Inputs > &controller, const LinearPlantInversionFeedforward< States, Inputs > &feedforward, KalmanFilter< States, Inputs, Outputs > &observer, units::volt_t maxVoltage)
	Constructs a state-space loop with the given controller, feedforward and observer.

	LinearSystemLoop (LinearQuadraticRegulator< States, Inputs > &controller, const LinearPlantInversionFeedforward< States, Inputs > &feedforward, KalmanFilter< States, Inputs, Outputs > &observer, std::function< InputVector(const InputVector &)> clampFunction)
	Constructs a state-space loop with the given controller, feedforward, observer and clamp function.

	LinearSystemLoop (LinearSystemLoop &&)=default

LinearSystemLoop &	operator= (LinearSystemLoop &&)=default

const StateVector &	Xhat () const
	Returns the observer's state estimate x-hat.

double	Xhat (int i) const
	Returns an element of the observer's state estimate x-hat.

const StateVector &	NextR () const
	Returns the controller's next reference r.

double	NextR (int i) const
	Returns an element of the controller's next reference r.

InputVector	U () const
	Returns the controller's calculated control input u.

double	U (int i) const
	Returns an element of the controller's calculated control input u.

void	SetXhat (const StateVector &xHat)
	Set the initial state estimate x-hat.

void	SetXhat (int i, double value)
	Set an element of the initial state estimate x-hat.

void	SetNextR (const StateVector &nextR)
	Set the next reference r.

const LinearQuadraticRegulator< States, Inputs > &	Controller () const
	Return the controller used internally.

const LinearPlantInversionFeedforward< States, Inputs >	Feedforward () const
	Return the feedforward used internally.

const KalmanFilter< States, Inputs, Outputs > &	Observer () const
	Return the observer used internally.

void	Reset (const StateVector &initialState)
	Zeroes reference r and controller output u.

StateVector	Error () const
	Returns difference between reference r and current state x-hat.

void	Correct (const OutputVector &y)
	Correct the state estimate x-hat using the measurements in y.

void	Predict (units::second_t dt)
	Sets new controller output, projects model forward, and runs observer prediction.

InputVector	ClampInput (const InputVector &u) const
	Clamps input vector between system's minimum and maximum allowable input.

Protected Attributes
LinearQuadraticRegulator< States, Inputs > *	m_controller

LinearPlantInversionFeedforward< States, Inputs >	m_feedforward

KalmanFilter< States, Inputs, Outputs > *	m_observer

std::function< InputVector(const InputVector &)>	m_clampFunc
	Clamping function.

StateVector	m_nextR

Static Protected Attributes
static constexpr int	kStates = States

static constexpr int	kInputs = Inputs

static constexpr int	kOutputs = Outputs

Detailed Description

template<int States, int Inputs, int Outputs>
class frc::LinearSystemLoop< States, Inputs, Outputs >

Combines a controller, feedforward, and observer for controlling a mechanism with full state feedback.

For everything in this file, "inputs" and "outputs" are defined from the perspective of the plant. This means U is an input and Y is an output (because you give the plant U (powers) and it gives you back a Y (sensor values). This is the opposite of what they mean from the perspective of the controller (U is an output because that's what goes to the motors and Y is an input because that's what comes back from the sensors).

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.
Outputs	Number of outputs.

Member Typedef Documentation

◆ InputVector

template<int States, int Inputs, int Outputs>

using frc::LinearSystemLoop< States, Inputs, Outputs >::InputVector = Vectord<Inputs>

◆ OutputVector

template<int States, int Inputs, int Outputs>

using frc::LinearSystemLoop< States, Inputs, Outputs >::OutputVector = Vectord<Outputs>

◆ StateVector

template<int States, int Inputs, int Outputs>

using frc::LinearSystemLoop< States, Inputs, Outputs >::StateVector = Vectord<States>

Constructor & Destructor Documentation

◆ LinearSystemLoop() [1/5]

template<int States, int Inputs, int Outputs>

frc::LinearSystemLoop< States, Inputs, Outputs >::LinearSystemLoop	(	LinearSystem< States, Inputs, Outputs > &	plant,
		LinearQuadraticRegulator< States, Inputs > &	controller,
		KalmanFilter< States, Inputs, Outputs > &	observer,
		units::volt_t	maxVoltage,
		units::second_t	dt )

inline

Constructs a state-space loop with the given plant, controller, and observer.

By default, the initial reference is all zeros. Users should call reset with the initial system state before enabling the loop. This constructor assumes that the input(s) to this system are voltage.

Parameters

plant	State-space plant.
controller	State-space controller.
observer	State-space observer.
maxVoltage	The maximum voltage that can be applied. Commonly 12.
dt	The nominal timestep.

◆ LinearSystemLoop() [2/5]

template<int States, int Inputs, int Outputs>

frc::LinearSystemLoop< States, Inputs, Outputs >::LinearSystemLoop	(	LinearSystem< States, Inputs, Outputs > &	plant,
		LinearQuadraticRegulator< States, Inputs > &	controller,
		KalmanFilter< States, Inputs, Outputs > &	observer,
		std::function< InputVector(const InputVector &)>	clampFunction,
		units::second_t	dt )

inline

Constructs a state-space loop with the given plant, controller, and observer.

By default, the initial reference is all zeros. Users should call reset with the initial system state before enabling the loop. This constructor assumes that the input(s) to this system are voltage.

Parameters

plant	State-space plant.
controller	State-space controller.
observer	State-space observer.
clampFunction	The function used to clamp the input vector.
dt	The nominal timestep.

◆ LinearSystemLoop() [3/5]

template<int States, int Inputs, int Outputs>

frc::LinearSystemLoop< States, Inputs, Outputs >::LinearSystemLoop	(	LinearQuadraticRegulator< States, Inputs > &	controller,
		const LinearPlantInversionFeedforward< States, Inputs > &	feedforward,
		KalmanFilter< States, Inputs, Outputs > &	observer,
		units::volt_t	maxVoltage )

inline

Constructs a state-space loop with the given controller, feedforward and observer.

By default, the initial reference is all zeros. Users should call reset with the initial system state.

Parameters

controller	State-space controller.
feedforward	Plant inversion feedforward.
observer	State-space observer.
maxVoltage	The maximum voltage that can be applied. Assumes that the inputs are voltages.

◆ LinearSystemLoop() [4/5]

template<int States, int Inputs, int Outputs>

frc::LinearSystemLoop< States, Inputs, Outputs >::LinearSystemLoop	(	LinearQuadraticRegulator< States, Inputs > &	controller,
		const LinearPlantInversionFeedforward< States, Inputs > &	feedforward,
		KalmanFilter< States, Inputs, Outputs > &	observer,
		std::function< InputVector(const InputVector &)>	clampFunction )

inline

Constructs a state-space loop with the given controller, feedforward, observer and clamp function.

By default, the initial reference is all zeros. Users should call reset with the initial system state.

Parameters

controller	State-space controller.
feedforward	Plant-inversion feedforward.
observer	State-space observer.
clampFunction	The function used to clamp the input vector.

◆ LinearSystemLoop() [5/5]

template<int States, int Inputs, int Outputs>

frc::LinearSystemLoop< States, Inputs, Outputs >::LinearSystemLoop ( LinearSystemLoop< States, Inputs, Outputs > && )

default

Member Function Documentation

◆ ClampInput()

template<int States, int Inputs, int Outputs>

InputVector frc::LinearSystemLoop< States, Inputs, Outputs >::ClampInput ( const InputVector & u ) const

inline

Clamps input vector between system's minimum and maximum allowable input.

Parameters

u	Input vector to clamp.

Returns: Clamped input vector.

◆ Controller()

template<int States, int Inputs, int Outputs>

const LinearQuadraticRegulator< States, Inputs > & frc::LinearSystemLoop< States, Inputs, Outputs >::Controller ( ) const

inline

Return the controller used internally.

◆ Correct()

template<int States, int Inputs, int Outputs>

void frc::LinearSystemLoop< States, Inputs, Outputs >::Correct ( const OutputVector & y )

inline

Correct the state estimate x-hat using the measurements in y.

Parameters

y	Measurement vector.

◆ Error()

template<int States, int Inputs, int Outputs>

StateVector frc::LinearSystemLoop< States, Inputs, Outputs >::Error ( ) const

inline

Returns difference between reference r and current state x-hat.

◆ Feedforward()

template<int States, int Inputs, int Outputs>

const LinearPlantInversionFeedforward< States, Inputs > frc::LinearSystemLoop< States, Inputs, Outputs >::Feedforward ( ) const

inline

Return the feedforward used internally.

Returns: the feedforward used internally.

◆ NextR() [1/2]

template<int States, int Inputs, int Outputs>

const StateVector & frc::LinearSystemLoop< States, Inputs, Outputs >::NextR ( ) const

inline

Returns the controller's next reference r.

◆ NextR() [2/2]

template<int States, int Inputs, int Outputs>

double frc::LinearSystemLoop< States, Inputs, Outputs >::NextR ( int i ) const

inline

Returns an element of the controller's next reference r.

Parameters

i Row of r.

◆ Observer()

template<int States, int Inputs, int Outputs>

const KalmanFilter< States, Inputs, Outputs > & frc::LinearSystemLoop< States, Inputs, Outputs >::Observer ( ) const

inline

Return the observer used internally.

◆ operator=()

template<int States, int Inputs, int Outputs>

LinearSystemLoop & frc::LinearSystemLoop< States, Inputs, Outputs >::operator= ( LinearSystemLoop< States, Inputs, Outputs > && )

default

◆ Predict()

template<int States, int Inputs, int Outputs>

void frc::LinearSystemLoop< States, Inputs, Outputs >::Predict ( units::second_t dt )

inline

Sets new controller output, projects model forward, and runs observer prediction.

After calling this, the user should send the elements of u to the actuators.

Parameters

dt	Timestep for model update.

◆ Reset()

template<int States, int Inputs, int Outputs>

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

inline

Zeroes reference r and controller output u.

The previous reference of the PlantInversionFeedforward and the initial state estimate of the KalmanFilter are set to the initial state provided.

Parameters

initialState The initial state.

◆ SetNextR()

template<int States, int Inputs, int Outputs>

void frc::LinearSystemLoop< States, Inputs, Outputs >::SetNextR ( const StateVector & nextR )

inline

Set the next reference r.

Parameters

nextR Next reference.

◆ SetXhat() [1/2]

template<int States, int Inputs, int Outputs>

void frc::LinearSystemLoop< States, Inputs, Outputs >::SetXhat ( const StateVector & xHat )

inline

Set the initial state estimate x-hat.

Parameters

xHat	The initial state estimate x-hat.

◆ SetXhat() [2/2]

template<int States, int Inputs, int Outputs>

void frc::LinearSystemLoop< States, Inputs, Outputs >::SetXhat	(	int	i,
		double	value )

inline

Set an element of the initial state estimate x-hat.

Parameters

i	Row of x-hat.
value	Value for element of x-hat.

◆ U() [1/2]

template<int States, int Inputs, int Outputs>

InputVector frc::LinearSystemLoop< States, Inputs, Outputs >::U ( ) const

inline

Returns the controller's calculated control input u.

◆ U() [2/2]

template<int States, int Inputs, int Outputs>

double frc::LinearSystemLoop< States, Inputs, Outputs >::U ( int i ) const

inline

Returns an element of the controller's calculated control input u.

Parameters

i Row of u.

◆ Xhat() [1/2]

template<int States, int Inputs, int Outputs>

const StateVector & frc::LinearSystemLoop< States, Inputs, Outputs >::Xhat ( ) const

inline

Returns the observer's state estimate x-hat.

◆ Xhat() [2/2]

template<int States, int Inputs, int Outputs>

double frc::LinearSystemLoop< States, Inputs, Outputs >::Xhat ( int i ) const

inline

Returns an element of the observer's state estimate x-hat.

Parameters

i	Row of x-hat.

Member Data Documentation

◆ kInputs

template<int States, int Inputs, int Outputs>

int frc::LinearSystemLoop< States, Inputs, Outputs >::kInputs = Inputs

staticconstexprprotected

◆ kOutputs

template<int States, int Inputs, int Outputs>

int frc::LinearSystemLoop< States, Inputs, Outputs >::kOutputs = Outputs

staticconstexprprotected

◆ kStates

template<int States, int Inputs, int Outputs>

int frc::LinearSystemLoop< States, Inputs, Outputs >::kStates = States

staticconstexprprotected

◆ m_clampFunc

template<int States, int Inputs, int Outputs>

std::function<InputVector(const InputVector&)> frc::LinearSystemLoop< States, Inputs, Outputs >::m_clampFunc

protected

Clamping function.

◆ m_controller

template<int States, int Inputs, int Outputs>

LinearQuadraticRegulator<States, Inputs>* frc::LinearSystemLoop< States, Inputs, Outputs >::m_controller

protected

◆ m_feedforward

template<int States, int Inputs, int Outputs>

LinearPlantInversionFeedforward<States, Inputs> frc::LinearSystemLoop< States, Inputs, Outputs >::m_feedforward

protected

◆ m_nextR

template<int States, int Inputs, int Outputs>

StateVector frc::LinearSystemLoop< States, Inputs, Outputs >::m_nextR

protected

◆ m_observer

template<int States, int Inputs, int Outputs>

KalmanFilter<States, Inputs, Outputs>* frc::LinearSystemLoop< States, Inputs, Outputs >::m_observer

protected

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

frc/system/LinearSystemLoop.h

Public Types

Public Member Functions

Protected Attributes

Static Protected Attributes

Detailed Description

Member Typedef Documentation

◆ InputVector

◆ OutputVector

◆ StateVector

Constructor & Destructor Documentation

◆ LinearSystemLoop() [1/5]

◆ LinearSystemLoop() [2/5]

◆ LinearSystemLoop() [3/5]

◆ LinearSystemLoop() [4/5]

◆ LinearSystemLoop() [5/5]

Member Function Documentation

◆ ClampInput()

◆ Controller()

◆ Correct()

◆ Error()

◆ Feedforward()

◆ NextR() [1/2]

◆ NextR() [2/2]

◆ Observer()

◆ operator=()

◆ Predict()

◆ Reset()

◆ SetNextR()

◆ SetXhat() [1/2]

◆ SetXhat() [2/2]

◆ U() [1/2]

◆ U() [2/2]

◆ Xhat() [1/2]

◆ Xhat() [2/2]

Member Data Documentation

◆ kInputs

◆ kOutputs

◆ kStates

◆ m_clampFunc

◆ m_controller

◆ m_feedforward

◆ m_nextR

◆ m_observer