org.orekit.propagation.events
Class AdaptedEventDetector

java.lang.Object
  org.orekit.propagation.events.AdaptedEventDetector

All Implemented Interfaces:

Serializable, EventHandler

public class AdaptedEventDetector
extends Object
implements EventHandler, Serializable

Adapt an EventDetector to commons-math EventHandler interface.
The implemented classes should A list of AdditionalStateInfo is needed, so that the state vector can be translated to/from additional states in a simple and generic manner by SpacecraftState. Conditionally thread-safe if all attributes are thread-safe.

Author:

Fabien Maussion

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.commons.math3.ode.events.EventHandler

EventHandler.Action

Field Summary

Fields inherited from interface org.apache.commons.math3.ode.events.EventHandler

DECREASING, INCREASING, INCREASING_DECREASING

Constructor Summary

AdaptedEventDetector(EventDetector detector, Map<String,AdditionalStateInfo> info, OrbitType orbitType, PositionAngle angleType, AttitudeProvider attProviderForces, AttitudeProvider attProviderEvents, AbsoluteDate referenceDate, double mu, Frame integrationFrame)
Build a wrapped event detector.

Method Summary

EventHandler.Action	eventOccurred(double t, double[] y, boolean increasing, boolean forward) Handle an event and choose what to do next.
double	g(double t, double[] y) Compute the value of the switching function.
int	getSlopeSelection() Get the parameter in charge of the selection of detected events by the slope of the g-function.
void	init(double t0, double[] y0, double t) Initialize event handler at the start of an ODE integration.
void	resetState(double t, double[] y) Reset the state prior to continue the integration.
boolean	shouldBeRemoved() This method is called after the step handler has returned and before the next step is started, but only when EventHandler.eventOccurred(double, double[], boolean, boolean) has been called.

Methods inherited from class java.lang.Object

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

Constructor Detail

AdaptedEventDetector

public AdaptedEventDetector(EventDetector detector,
                            Map<String,AdditionalStateInfo> info,
                            OrbitType orbitType,
                            PositionAngle angleType,
                            AttitudeProvider attProviderForces,
                            AttitudeProvider attProviderEvents,
                            AbsoluteDate referenceDate,
                            double mu,
                            Frame integrationFrame)

Build a wrapped event detector.

Parameters:

detector - event detector to wrap

info - information on additional states (position in the state vector is deduced from it)

orbitType - orbit type

angleType - position angle type

attProviderForces - attitude provider for forces computation

attProviderEvents - attitude provider for events computation

referenceDate - reference date from which t is counted

mu - central body attraction coefficient (m³/s²)

integrationFrame - frame in which integration is performed

Method Detail

init

public void init(double t0,
                 double[] y0,
                 double t)

Initialize event handler at the start of an ODE integration.

This method is called once at the start of the integration. It may be used by the event handler to initialize some internal data if needed.

Specified by:

init in interface EventHandler

Parameters:

t0 - start value of the independent time variable

y0 - array containing the start value of the state vector

t - target time for the integration

g

public double g(double t,
                double[] y)

Compute the value of the switching function.

The discrete events are generated when the sign of this switching function changes. The integrator will take care to change the stepsize in such a way these events occur exactly at step boundaries. The switching function must be continuous in its roots neighborhood (but not necessarily smooth), as the integrator will need to find its roots to locate precisely the events.

Specified by:

g in interface EventHandler

Parameters:

t - current value of the independent time variable

y - array containing the current value of the state vector

Returns:

value of the g switching function

eventOccurred

public EventHandler.Action eventOccurred(double t,
                                         double[] y,
                                         boolean increasing,
                                         boolean forward)

Handle an event and choose what to do next.

This method is called when the integrator has accepted a step ending exactly on a sign change of the function, just before the step handler itself is called (see below for scheduling). It allows the user to update his internal data to acknowledge the fact the event has been handled (for example setting a flag in the differential equations to switch the derivatives computation in case of discontinuity), or to direct the integrator to either stop or continue integration, possibly with a reset state or derivatives.

• if EventHandler.Action.STOP is returned, the step handler will be called with the isLast flag of the handleStep method set to true and the integration will be stopped,
• if EventHandler.Action.RESET_STATE is returned, the resetState method will be called once the step handler has finished its task, and the integrator will also recompute the derivatives,
• if EventHandler.Action.RESET_DERIVATIVES is returned, the integrator will recompute the derivatives,
• if EventHandler.Action.CONTINUE is returned, no specific action will be taken (apart from having called this method) and integration will continue.

The scheduling between this method and the StepHandler method handleStep(interpolator, isLast) is to call this method first and handleStep afterwards. This scheduling allows the integrator to pass true as the isLast parameter to the step handler to make it aware the step will be the last one if this method returns EventHandler.Action.STOP. As the interpolator may be used to navigate back throughout the last step (as StepNormalizer does for example), user code called by this method and user code called by step handlers may experience apparently out of order values of the independent time variable. As an example, if the same user object implements both this EventHandler interface and the FixedStepHandler interface, a forward integration may call its eventOccurred method with t = 10 first and call its handleStep method with t = 9 afterwards. Such out of order calls are limited to the size of the integration step for variable step handlers and to the size of the fixed step for fixed step handlers.

Specified by:

eventOccurred in interface EventHandler

Parameters:

t - current value of the independent time variable

y - array containing the current value of the state vector

increasing - if true, the value of the switching function increases when times increases around event (note that increase is measured with respect to physical time, not with respect to integration which may go backward in time)

forward - if true, the integration variable (time) increases during integration

Returns:

indication of what the integrator should do next, this value must be one of EventHandler.Action.STOP, EventHandler.Action.RESET_STATE, EventHandler.Action.RESET_DERIVATIVES, EventHandler.Action.CONTINUE

shouldBeRemoved

public boolean shouldBeRemoved()

This method is called after the step handler has returned and before the next step is started, but only when EventHandler.eventOccurred(double, double[], boolean, boolean) has been called.

Specified by:

shouldBeRemoved in interface EventHandler

Returns:

true if the current detector should be removed

resetState

public void resetState(double t,
                       double[] y)

Reset the state prior to continue the integration.

This method is called after the step handler has returned and before the next step is started, but only when EventHandler.eventOccurred(double, double[], boolean, boolean) has itself returned the EventHandler.Action.RESET_STATE indicator. It allows the user to reset the state vector for the next step, without perturbing the step handler of the finishing step. If the EventHandler.eventOccurred(double, double[], boolean, boolean) never returns the EventHandler.Action.RESET_STATE indicator, this function will never be called, and it is safe to leave its body empty.

Specified by:

resetState in interface EventHandler

Parameters:

t - current value of the independent time variable

y - array containing the current value of the state vector the new state should be put in the same array

getSlopeSelection

public int getSlopeSelection()

Get the parameter in charge of the selection of detected events by the slope of the g-function.

Specified by:

getSlopeSelection in interface EventHandler

Returns:

EventHandler.INCREASING (0): events related to the increasing g-function;
EventHandler.DECREASING (1): events related to the decreasing g-function;
EventHandler.INCREASING_DECREASING (2): events related to both increasing and decreasing g-function.