org.jcpsim.ode
Class DifferentialEquations

java.lang.Object
  org.jcpsim.ode.DifferentialEquations

Direct Known Subclasses:

ArterialLine.ArterialLineModel, Function.TestModel, Pendulum.PendulumModel, SimpleRespirator.RCModel, VentilationOfRcLung.RCModel

public class DifferentialEquations
extends java.lang.Object

Superclass for all differential equations

Nested Class Summary

static class

DifferentialEquations.Method

Field Summary

DifferentialEquation[]	de
double	dtused
int	n
Tasks[]	st
int	taskN

Constructor Summary

DifferentialEquations(double t, double dt, DifferentialEquations.Method method)

Method Summary

DifferentialEquation	add(DifferentialEquation eq)
java.util.List<DifferentialEquation>	add(java.util.List<DifferentialEquation> list)
Tasks	addTasks(Tasks st)
void	after()
void	before()
double	getDt() Gets proposed value for next time step.
double	getDtmax() Gets biggest allowed time step (default: initial dt).
double	getDtmin() Gets lowest allowed time step (default: initial dt * 0.000001).
double	getDttiny() Gets time distance before curve break (default: initial dt * 0.0001).
double	getDtused() Gets value used for last time step.
double	getEps() Gets error tolerance level (default: 0.000001).
double	getNextStepsize() Can be overridden.
double	getT() Gets the actual simulation time.
boolean	remove(DifferentialEquation eq)
boolean	removeTasks(Tasks st)
void	setDt(double x) Sets proposed value for next time step.
void	setDtmax(double x) Sets biggest allowed time step (default: initial dt).
void	setDtmin(double x) Sets lowest allowed time step (default: initial dt * 0.000001).
void	setDttiny(double x) Sets time distance before curve break (default: initial dt * 0.0001).
void	setEps(double x) Sets error tolerance level (default: 0.000001).
void	setInitialValues() Sets all state variables to their initial value at start time.
void	setMethod(DifferentialEquations.Method m) Sets the integration method.
void	setNextStepsize(double dt)
void	setT(double t)
void	setValues(double t) Is called just before (#link dxdt).
void	step_Euler() The simplest integration method (should only be used for testing purposes).
void	step_RungeKutta4() Implements the fourth-order Runge-Kutta algorithm.
void	step_RungeKutta45() performs one integration step with variable stepsize computes: dtused = value just used for last step dt = proposed value for next step
void	step()
void	stepDelta(double delta)
void	stepUntil(double until) Should be called often enough to achieve smooth animations (ca. 10 Hz).

Methods inherited from class java.lang.Object

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

Field Detail

dtused

public double dtused

n

public int n

de

public DifferentialEquation[] de

taskN

public int taskN

st

public Tasks[] st

Constructor Detail

DifferentialEquations

public DifferentialEquations(double t,
                             double dt,
                             DifferentialEquations.Method method)

Parameters:

t - start time

dt - initial (and maximum) stepsize (delta t)

method - integration method

Method Detail

setMethod

public void setMethod(DifferentialEquations.Method m)

Sets the integration method.

getT

public double getT()

Gets the actual simulation time.

setT

public void setT(double t)

setDt

public void setDt(double x)

Sets proposed value for next time step.

getDt

public double getDt()

Gets proposed value for next time step.

getDtused

public double getDtused()

Gets value used for last time step.

setDtmax

public void setDtmax(double x)

Sets biggest allowed time step (default: initial dt).

getDtmax

public double getDtmax()

Gets biggest allowed time step (default: initial dt).

setDtmin

public void setDtmin(double x)

Sets lowest allowed time step (default: initial dt * 0.000001).

getDtmin

public double getDtmin()

Gets lowest allowed time step (default: initial dt * 0.000001).

setDttiny

public void setDttiny(double x)

Sets time distance before curve break (default: initial dt * 0.0001). Variable stepsize algorithms will try to step just a tiny distance before the next break in the curves (as set by DifferentialEquation.dxdt(double))

getDttiny

public double getDttiny()

Gets time distance before curve break (default: initial dt * 0.0001). Variable stepsize algorithms will try to step just a tiny distance before the next break in the curves (as set by DifferentialEquation.dxdt(double))

setEps

public void setEps(double x)

Sets error tolerance level (default: 0.000001).

getEps

public double getEps()

Gets error tolerance level (default: 0.000001).

before

public void before()

after

public void after()

add

public DifferentialEquation add(DifferentialEquation eq)

add

public java.util.List<DifferentialEquation> add(java.util.List<DifferentialEquation> list)

remove

public boolean remove(DifferentialEquation eq)

addTasks

public Tasks addTasks(Tasks st)

removeTasks

public boolean removeTasks(Tasks st)

setInitialValues

public void setInitialValues()

Sets all state variables to their initial value at start time.

setValues

public void setValues(double t)

Is called just before (#link dxdt). Useful is more than one Numerical model has to be solved. May be overridden.

Parameters:

t - the actual time

getNextStepsize

public double getNextStepsize()

Can be overridden.

Returns:

if this is greater than 0: time to next break

Integration algorithms with variable stepsize (like step_RungeKutta45()) will set their stepsize so that no step will jump over the break in the curves.

setNextStepsize

public void setNextStepsize(double dt)

step

public void step()

stepUntil

public void stepUntil(double until)

Should be called often enough to achieve smooth animations (ca. 10 Hz). TODO: Step exactly to 'until' time *and* consider 'nextStepSize' ! TODO: stepIntervall(double t)

stepDelta

public void stepDelta(double delta)

step_Euler

public void step_Euler()

The simplest integration method (should only be used for testing purposes). Performs one integration step of all differential equations with fixed stepsize dt

step_RungeKutta4

public void step_RungeKutta4()

Implements the fourth-order Runge-Kutta algorithm.

step_RungeKutta45

public void step_RungeKutta45()

performs one integration step with variable stepsize
computes:
dtused = value just used for last step
dt = proposed value for next step