DateDetector.java
/* Copyright 2002-2020 CS Group
* Licensed to CS Group (CS) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* CS licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.orekit.propagation.events;
import java.util.ArrayList;
import org.hipparchus.ode.events.Action;
import org.orekit.errors.OrekitIllegalArgumentException;
import org.orekit.errors.OrekitMessages;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.events.handlers.EventHandler;
import org.orekit.propagation.events.handlers.StopOnEvent;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.TimeStamped;
/** Finder for date events.
* <p>This class finds date events (i.e. occurrence of some predefined dates).</p>
* <p>As of version 5.1, it is an enhanced date detector:</p>
* <ul>
* <li>it can be defined without prior date ({@link #DateDetector(double, double, TimeStamped...)})</li>
* <li>several dates can be added ({@link #addEventDate(AbsoluteDate)})</li>
* </ul>
* <p>The gap between the added dates must be more than the maxCheck.</p>
* <p>The default implementation behavior is to {@link Action#STOP stop}
* propagation at the first event date occurrence. This can be changed by calling
* {@link #withHandler(EventHandler)} after construction.</p>
* @see org.orekit.propagation.Propagator#addEventDetector(EventDetector)
* @author Luc Maisonobe
* @author Pascal Parraud
*/
public class DateDetector extends AbstractDetector<DateDetector> implements TimeStamped {
/** Last date for g computation. */
private AbsoluteDate gDate;
/** List of event dates. */
private final ArrayList<EventDate> eventDateList;
/** Current event date. */
private int currentIndex;
/** Build a new instance.
* <p>First event dates are set here, but others can be
* added later with {@link #addEventDate(AbsoluteDate)}.</p>
* @param maxCheck maximum checking interval (s)
* @param threshold convergence threshold (s)
* @param dates list of event dates
* @see #addEventDate(AbsoluteDate)
*/
public DateDetector(final double maxCheck, final double threshold, final TimeStamped... dates) {
this(maxCheck, threshold, DEFAULT_MAX_ITER, new StopOnEvent<DateDetector>(), dates);
}
/** Build a new instance.
* <p>This constructor is dedicated to single date detection.
* {@link #getMaxCheckInterval() max check interval} is set to 1.0e10, so almost
* no other date can be added. Tolerance is set to 1.0e-9.</p>
* @param target target date
* @see #addEventDate(AbsoluteDate)
*/
public DateDetector(final AbsoluteDate target) {
this(1.0e10, 1.e-9, target);
}
/** Private constructor with full parameters.
* <p>
* This constructor is private as users are expected to use the builder
* API with the various {@code withXxx()} methods to set up the instance
* in a readable manner without using a huge amount of parameters.
* </p>
* @param maxCheck maximum checking interval (s)
* @param threshold convergence threshold (s)
* @param maxIter maximum number of iterations in the event time search
* @param handler event handler to call at event occurrences
* @param dates list of event dates
* @since 6.1
*/
private DateDetector(final double maxCheck, final double threshold,
final int maxIter, final EventHandler<? super DateDetector> handler,
final TimeStamped... dates) {
super(maxCheck, threshold, maxIter, handler);
this.currentIndex = -1;
this.gDate = null;
this.eventDateList = new ArrayList<DateDetector.EventDate>(dates.length);
for (final TimeStamped ts : dates) {
addEventDate(ts.getDate());
}
}
/** {@inheritDoc} */
@Override
protected DateDetector create(final double newMaxCheck, final double newThreshold,
final int newMaxIter, final EventHandler<? super DateDetector> newHandler) {
return new DateDetector(newMaxCheck, newThreshold, newMaxIter, newHandler,
eventDateList.toArray(new EventDate[eventDateList.size()]));
}
/** Compute the value of the switching function.
* This function measures the difference between the current and the target date.
* @param s the current state information: date, kinematics, attitude
* @return value of the switching function
*/
public double g(final SpacecraftState s) {
gDate = s.getDate();
if (currentIndex < 0) {
return -1.0;
} else {
final EventDate event = getClosest(gDate);
return event.isgIncrease() ? gDate.durationFrom(event.getDate()) : event.getDate().durationFrom(gDate);
}
}
/** Get the current event date according to the propagator.
* @return event date
*/
public AbsoluteDate getDate() {
return currentIndex < 0 ? null : eventDateList.get(currentIndex).getDate();
}
/** Add an event date.
* <p>The date to add must be:</p>
* <ul>
* <li>less than the smallest already registered event date minus the maxCheck</li>
* <li>or more than the largest already registered event date plus the maxCheck</li>
* </ul>
* @param target target date
* @throws IllegalArgumentException if the date is too close from already defined interval
* @see #DateDetector(double, double, TimeStamped...)
*/
public void addEventDate(final AbsoluteDate target) throws IllegalArgumentException {
final boolean increasing;
if (currentIndex < 0) {
increasing = (gDate == null) ? true : target.durationFrom(gDate) > 0.0;
currentIndex = 0;
eventDateList.add(new EventDate(target, increasing));
} else {
final int lastIndex = eventDateList.size() - 1;
if (eventDateList.get(0).getDate().durationFrom(target) > getMaxCheckInterval()) {
increasing = !eventDateList.get(0).isgIncrease();
eventDateList.add(0, new EventDate(target, increasing));
currentIndex++;
} else if (target.durationFrom(eventDateList.get(lastIndex).getDate()) > getMaxCheckInterval()) {
increasing = !eventDateList.get(lastIndex).isgIncrease();
eventDateList.add(new EventDate(target, increasing));
} else {
throw new OrekitIllegalArgumentException(OrekitMessages.EVENT_DATE_TOO_CLOSE,
target,
eventDateList.get(0).getDate(),
eventDateList.get(lastIndex).getDate(),
getMaxCheckInterval());
}
}
}
/** Get the closest EventDate to the target date.
* @param target target date
* @return current EventDate
*/
private EventDate getClosest(final AbsoluteDate target) {
final double dt = target.durationFrom(eventDateList.get(currentIndex).getDate());
if (dt < 0.0 && currentIndex > 0) {
boolean found = false;
while (currentIndex > 0 && !found) {
if (target.durationFrom(eventDateList.get(currentIndex - 1).getDate()) < eventDateList.get(currentIndex).getDate().durationFrom(target)) {
currentIndex--;
} else {
found = true;
}
}
} else if (dt > 0.0 && currentIndex < eventDateList.size() - 1) {
final int maxIndex = eventDateList.size() - 1;
boolean found = false;
while (currentIndex < maxIndex && !found) {
if (target.durationFrom(eventDateList.get(currentIndex + 1).getDate()) > eventDateList.get(currentIndex).getDate().durationFrom(target)) {
currentIndex++;
} else {
found = true;
}
}
}
return eventDateList.get(currentIndex);
}
/** Event date specification. */
private static class EventDate implements TimeStamped {
/** Event date. */
private final AbsoluteDate eventDate;
/** Flag for g function way around event date. */
private final boolean gIncrease;
/** Simple constructor.
* @param date date
* @param increase if true, g function increases around event date
*/
EventDate(final AbsoluteDate date, final boolean increase) {
this.eventDate = date;
this.gIncrease = increase;
}
/** Getter for event date.
* @return event date
*/
public AbsoluteDate getDate() {
return eventDate;
}
/** Getter for g function way at event date.
* @return g function increasing flag
*/
public boolean isgIncrease() {
return gIncrease;
}
}
}