Package edu.wpi.first.math.system

Class LinearSystem<States extends Num,Inputs extends Num,Outputs extends Num>

java.lang.Object

edu.wpi.first.math.system.LinearSystem<States,Inputs,Outputs>

Type Parameters:

States - Number of states.

Inputs - Number of inputs.

Outputs - Number of outputs.

public class LinearSystem<States extends Num,Inputs extends Num,Outputs extends Num>
extends Object

A plant defined using state-space notation.

A plant is a mathematical model of a system's dynamics.

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

Constructor Summary

Constructors

Constructor	Description
LinearSystem(Matrix<States,States> A, Matrix<States,Inputs> B, Matrix<Outputs,States> C, Matrix<Outputs,Inputs> D)	Construct a new LinearSystem from the four system matrices.

Method Summary

Modifier and Type	Method	Description
Matrix<States,N1>	calculateX(Matrix<States,N1> x, Matrix<Inputs,N1> clampedU, double dtSeconds)	Computes the new x given the old x and the control input.
Matrix<Outputs,N1>	calculateY(Matrix<States,N1> x, Matrix<Inputs,N1> clampedU)	Computes the new y given the control input.
Matrix<States,States>	getA()	Returns the system matrix A.
double	getA(int row, int col)	Returns an element of the system matrix A.
Matrix<States,Inputs>	getB()	Returns the input matrix B.
double	getB(int row, int col)	Returns an element of the input matrix B.
Matrix<Outputs,States>	getC()	Returns the output matrix C.
double	getC(int row, int col)	Returns an element of the output matrix C.
Matrix<Outputs,Inputs>	getD()	Returns the feedthrough matrix D.
double	getD(int row, int col)	Returns an element of the feedthrough matrix D.
LinearSystem<States,Inputs,? extends Num>	slice(int... outputIndices)	Returns the LinearSystem with the outputs listed in outputIndices.
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Details

LinearSystem

public LinearSystem(Matrix<States,States> A,
 Matrix<States,Inputs> B,
 Matrix<Outputs,States> C,
 Matrix<Outputs,Inputs> D)

Construct a new LinearSystem from the four system matrices.

Parameters:

A - The system matrix A.

B - The input matrix B.

C - The output matrix C.

D - The feedthrough matrix D.

Throws:

IllegalArgumentException - if any matrix element isn't finite.

Method Details

getA

public Matrix<States,States> getA()

Returns the system matrix A.

Returns:

the system matrix A.

getA

public double getA(int row,
 int col)

Returns an element of the system matrix A.

Parameters:

row - Row of A.

col - Column of A.

Returns:

the system matrix A at (i, j).

getB

public Matrix<States,Inputs> getB()

Returns the input matrix B.

Returns:

the input matrix B.

getB

public double getB(int row,
 int col)

Returns an element of the input matrix B.

Parameters:

row - Row of B.

col - Column of B.

Returns:

The value of the input matrix B at (i, j).

getC

public Matrix<Outputs,States> getC()

Returns the output matrix C.

Returns:

Output matrix C.

getC

public double getC(int row,
 int col)

Returns an element of the output matrix C.

Parameters:

row - Row of C.

col - Column of C.

Returns:

the double value of C at the given position.

getD

public Matrix<Outputs,Inputs> getD()

Returns the feedthrough matrix D.

Returns:

the feedthrough matrix D.

getD

public double getD(int row,
 int col)

Returns an element of the feedthrough matrix D.

Parameters:

row - Row of D.

col - Column of D.

Returns:

The feedthrough matrix D at (i, j).

calculateX

public Matrix<States,N1> calculateX(Matrix<States,N1> x,
 Matrix<Inputs,N1> clampedU,
 double dtSeconds)

Computes the new x given the old x and the control input.

This is used by state observers directly to run updates based on state estimate.

Parameters:

x - The current state.

clampedU - The control input.

dtSeconds - Timestep for model update.

Returns:

the updated x.

calculateY

public Matrix<Outputs,N1> calculateY(Matrix<States,N1> x,
 Matrix<Inputs,N1> clampedU)

Computes the new y given the control input.

This is used by state observers directly to run updates based on state estimate.

Parameters:

x - The current state.

clampedU - The control input.

Returns:

the updated output matrix Y.

slice

public LinearSystem<States,Inputs,? extends Num> slice(int... outputIndices)

Returns the LinearSystem with the outputs listed in outputIndices.

This is used by state observers such as the Kalman Filter.

Parameters:

outputIndices - the list of output indices to include in the sliced system.

Returns:

the sliced LinearSystem with outputs set to row vectors of LinearSystem.

Throws:

IllegalArgumentException - if any outputIndices are outside the range of system outputs.

IllegalArgumentException - if number of outputIndices exceeds the number of system outputs.

IllegalArgumentException - if duplication exists in outputIndices.

toString

public String toString()

Overrides:

toString in class Object