Package edu.wpi.first.wpilibj.simulation

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

java.lang.Object

edu.wpi.first.wpilibj.simulation.LinearSystemSim<States,Inputs,Outputs>

Type Parameters:

States - Number of states of the system.

Inputs - Number of inputs to the system.

Outputs - Number of outputs of the system.

Direct Known Subclasses:

DCMotorSim, ElevatorSim, FlywheelSim, SingleJointedArmSim

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

This class helps simulate linear systems. To use this class, do the following in the IterativeRobotBase.simulationPeriodic() method.

Call setInput(double...) with the inputs to the system (usually voltage).

Call update(double) to update the simulation.

Set simulated sensor readings with the simulated positions in getOutput()

Field Summary

Fields

Modifier and Type	Field	Description
protected Matrix<Outputs,N1>	m_measurementStdDevs	The standard deviations of measurements, used for adding noise to the measurements.
protected LinearSystem<States,Inputs,Outputs>	m_plant	The plant that represents the linear system.
protected Matrix<Inputs,N1>	m_u	Input vector.
protected Matrix<States,N1>	m_x	State vector.
protected Matrix<Outputs,N1>	m_y	Output vector.

Constructor Summary

Constructors

Constructor	Description
LinearSystemSim(LinearSystem<States,Inputs,Outputs> system)	Creates a simulated generic linear system.
LinearSystemSim(LinearSystem<States,Inputs,Outputs> system, Matrix<Outputs,N1> measurementStdDevs)	Creates a simulated generic linear system with measurement noise.

Method Summary

Modifier and Type	Method	Description
protected Matrix<Inputs,N1>	clampInput(Matrix<Inputs,N1> u)	Clamp the input vector such that no element exceeds the given voltage.
double	getCurrentDrawAmps()	Returns the current drawn by this simulated system.
Matrix<Inputs,N1>	getInput()	Returns the current input of the plant.
double	getInput(int row)	Returns an element of the current input of the plant.
Matrix<Outputs,N1>	getOutput()	Returns the current output of the plant.
double	getOutput(int row)	Returns an element of the current output of the plant.
void	setInput(double... u)	Sets the system inputs.
void	setInput(int row, double value)	Sets the system inputs.
void	setInput(Matrix<Inputs,N1> u)	Sets the system inputs (usually voltages).
void	setState(Matrix<States,N1> state)	Sets the system state.
void	update(double dtSeconds)	Updates the simulation.
protected Matrix<States,N1>	updateX(Matrix<States,N1> currentXhat, Matrix<Inputs,N1> u, double dtSeconds)	Updates the state estimate of the system.

Methods inherited from class java.lang.Object

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

Field Details

m_plant

protected final LinearSystem<States extends Num,Inputs extends Num,Outputs extends Num> m_plant

The plant that represents the linear system.

m_x

protected Matrix<States extends Num,N1> m_x

State vector.

m_u

protected Matrix<Inputs extends Num,N1> m_u

Input vector.

m_y

protected Matrix<Outputs extends Num,N1> m_y

Output vector.

m_measurementStdDevs

protected final Matrix<Outputs extends Num,N1> m_measurementStdDevs

The standard deviations of measurements, used for adding noise to the measurements.

Constructor Details

LinearSystemSim

public LinearSystemSim(LinearSystem<States,Inputs,Outputs> system)

Creates a simulated generic linear system.

Parameters:

system - The system to simulate.

LinearSystemSim

public LinearSystemSim(LinearSystem<States,Inputs,Outputs> system, Matrix<Outputs,N1> measurementStdDevs)

Creates a simulated generic linear system with measurement noise.

Parameters:

system - The system being controlled.

measurementStdDevs - Standard deviations of measurements. Can be null if no noise is desired.

Method Details

update

public void update(double dtSeconds)

Updates the simulation.

Parameters:

dtSeconds - The time between updates.

getOutput

public Matrix<Outputs,N1> getOutput()

Returns the current output of the plant.

Returns:

The current output of the plant.

getOutput

public double getOutput(int row)

Returns an element of the current output of the plant.

Parameters:

row - The row to return.

Returns:

An element of the current output of the plant.

setInput

public void setInput(Matrix<Inputs,N1> u)

Sets the system inputs (usually voltages).

Parameters:

u - The system inputs.

setInput

public void setInput(int row, double value)

Sets the system inputs.

Parameters:

row - The row in the input matrix to set.

value - The value to set the row to.

setInput

public void setInput(double... u)

Sets the system inputs.

Parameters:

u - An array of doubles that represent the inputs of the system.

getInput

public Matrix<Inputs,N1> getInput()

Returns the current input of the plant.

Returns:

The current input of the plant.

getInput

public double getInput(int row)

Returns an element of the current input of the plant.

Parameters:

row - The row to return.

Returns:

An element of the current input of the plant.

setState

public void setState(Matrix<States,N1> state)

Sets the system state.

Parameters:

state - The new state.

getCurrentDrawAmps

public double getCurrentDrawAmps()

Returns the current drawn by this simulated system. Override this method to add a custom current calculation.

Returns:

The current drawn by this simulated mechanism.

updateX

protected Matrix<States,N1> updateX(Matrix<States,N1> currentXhat, Matrix<Inputs,N1> u, double dtSeconds)

Updates the state estimate of the system.

Parameters:

currentXhat - The current state estimate.

u - The system inputs (usually voltage).

dtSeconds - The time difference between controller updates.

Returns:

The new state.

clampInput

protected Matrix<Inputs,N1> clampInput(Matrix<Inputs,N1> u)

Clamp the input vector such that no element exceeds the given voltage. If any does, the relative magnitudes of the input will be maintained.

Parameters:

u - The input vector.

Returns:

The normalized input.