TransferFunction Class Reference

Detailed Description

Represents a linear-time-invariant (LTI) system in transfer function form, e.g.

complex rational functions corresponding to the Laplace transform or z-transform of the impulse response (https://en.wikipedia.org/wiki/Transfer_function).

For example, to create the transfer function H(s) = 1/(s + 1), you can write:

auto s = TransferFunction::s();
TransferFunction H(1.0 / (s + 1.0));

To create the transfer function H(z) = 1/(z - 0.5), you can write:

auto z = TransferFunction::z();
double time_step = 0.1;
TransferFunction H(1.0 / (z - 0.5), time_step);

Note that TransferFunction is not a LeafSystem. To use it in the Systems framework, you must convert it to state-space form, represented by LinearSystem.

#include <drake/systems/primitives/transfer_function.h>

Public Member Functions
	TransferFunction ()
	Constructs a zero-input, zero-output (continuous-time) transfer function.
	TransferFunction (MatrixX< symbolic::RationalFunction > H, double time_step=0.0)
	Constructs a transfer function from the symbolic form.
	TransferFunction (symbolic::RationalFunction H, double time_step=0.0)
	Convenience overload for single-input, single-output (SISO) systems.
	~TransferFunction ()=default
	TODO(russt): Construct a TransferFunction from a LinearSystem once we have more symbolic support for complex numbers (#20159).
const MatrixX< symbolic::RationalFunction > &	H () const
	Returns the transfer function matrix.
double	time_step () const
	Returns the time step.
Does not allow copy, move, or assignment
	TransferFunction (const TransferFunction &)=delete
TransferFunction &	operator= (const TransferFunction &)=delete
	TransferFunction (TransferFunction &&)=delete
TransferFunction &	operator= (TransferFunction &&)=delete

Static Public Member Functions
static symbolic::RationalFunction	s ()
	Returns a symbolic::RationalFunction s which can be used to build a continuous-time transfer function symbolically.
static symbolic::Variable	s_var ()
	Returns the singleton symbolic::Variable denoting the complex frequency (σ+jω) used in the Laplace transform for continuous-time transfer functions.
static symbolic::RationalFunction	z ()
	Returns a symbolic::RationalFunction s which can be used to build a discrete-time transfer function symbolically.
static symbolic::Variable	z_var ()
	Returns the singleton symbolic::Variable denoting the complex frequency (σ+jω) used in the Z transform for discrete-time transfer functions.

Constructor & Destructor Documentation

TransferFunction() [1/5]

TransferFunction ( const TransferFunction & )

delete

TransferFunction() [2/5]

TransferFunction ( TransferFunction && )

delete

TransferFunction() [3/5]

TransferFunction

(

)

Constructs a zero-input, zero-output (continuous-time) transfer function.

TransferFunction() [4/5]

TransferFunction ( MatrixX< symbolic::RationalFunction > H, double time_step = 0.0 )

explicit

Constructs a transfer function from the symbolic form.

If time_step is zero, then the model is of a continuous-time system, and H must only be a function of s(). If time_step > 0, then the model is of a discrete-time system, and H must only be a function of z().

Exceptions

std::exception	if time_step is negative.
std::exception	if H has variables other than s() or z(), as described above.

TransferFunction() [5/5]

TransferFunction ( symbolic::RationalFunction H, double time_step = 0.0 )

explicit

Convenience overload for single-input, single-output (SISO) systems.

~TransferFunction()

~TransferFunction ( )

default

TODO(russt): Construct a TransferFunction from a LinearSystem once we have more symbolic support for complex numbers (#20159).

Member Function Documentation

H()

const MatrixX< symbolic::RationalFunction > & H

(

)

const

Returns the transfer function matrix.

operator=() [1/2]

TransferFunction & operator= ( const TransferFunction & )

delete

operator=() [2/2]

TransferFunction & operator= ( TransferFunction && )

delete

s()

symbolic::RationalFunction s ( )

static

Returns a symbolic::RationalFunction s which can be used to build a continuous-time transfer function symbolically.

s_var()

symbolic::Variable s_var ( )

static

Returns the singleton symbolic::Variable denoting the complex frequency (σ+jω) used in the Laplace transform for continuous-time transfer functions.

time_step()

double time_step

(

)

const

Returns the time step.

z()

symbolic::RationalFunction z ( )

static

Returns a symbolic::RationalFunction s which can be used to build a discrete-time transfer function symbolically.

z_var()

symbolic::Variable z_var ( )

static

Returns the singleton symbolic::Variable denoting the complex frequency (σ+jω) used in the Z transform for discrete-time transfer functions.

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

• drake/systems/primitives/transfer_function.h