DateDetector.java

  1. /* Copyright 2002-2022 CS GROUP
  2.  * Licensed to CS GROUP (CS) under one or more
  3.  * contributor license agreements.  See the NOTICE file distributed with
  4.  * this work for additional information regarding copyright ownership.
  5.  * CS licenses this file to You under the Apache License, Version 2.0
  6.  * (the "License"); you may not use this file except in compliance with
  7.  * the License.  You may obtain a copy of the License at
  8.  *
  9.  *   http://www.apache.org/licenses/LICENSE-2.0
  10.  *
  11.  * Unless required by applicable law or agreed to in writing, software
  12.  * distributed under the License is distributed on an "AS IS" BASIS,
  13.  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14.  * See the License for the specific language governing permissions and
  15.  * limitations under the License.
  16.  */
  17. package org.orekit.propagation.events;

  19. import java.util.ArrayList;
  20. import java.util.Collections;
  21. import java.util.List;

  23. import org.hipparchus.ode.events.Action;
  24. import org.orekit.errors.OrekitIllegalArgumentException;
  25. import org.orekit.errors.OrekitMessages;
  26. import org.orekit.propagation.SpacecraftState;
  27. import org.orekit.propagation.events.handlers.EventHandler;
  28. import org.orekit.propagation.events.handlers.StopOnEvent;
  29. import org.orekit.time.AbsoluteDate;
  30. import org.orekit.time.TimeStamped;

  32. /** Finder for date events.
  33.  * <p>This class finds date events (i.e. occurrence of some predefined dates).</p>
  34.  * <p>As of version 5.1, it is an enhanced date detector:</p>
  35.  * <ul>
  36.  *   <li>it can be defined without prior date ({@link #DateDetector(double, double, TimeStamped...)})</li>
  37.  *   <li>several dates can be added ({@link #addEventDate(AbsoluteDate)})</li>
  38.  * </ul>
  39.  * <p>The gap between the added dates must be more than the maxCheck.</p>
  40.  * <p>The default implementation behavior is to {@link Action#STOP stop}
  41.  * propagation at the first event date occurrence. This can be changed by calling
  42.  * {@link #withHandler(EventHandler)} after construction.</p>
  43.  * @see org.orekit.propagation.Propagator#addEventDetector(EventDetector)
  44.  * @author Luc Maisonobe
  45.  * @author Pascal Parraud
  46.  */
  47. public class DateDetector extends AbstractDetector<DateDetector> implements TimeStamped {

  49.     /** Last date for g computation. */
  50.     private AbsoluteDate gDate;

  52.     /** List of event dates. */
  53.     private final ArrayList<EventDate> eventDateList;

  55.     /** Current event date. */
  56.     private int currentIndex;

  58.     /** Build a new instance.
  59.      * <p>First event dates are set here, but others can be
  60.      * added later with {@link #addEventDate(AbsoluteDate)}.</p>
  61.      * @param maxCheck maximum checking interval (s)
  62.      * @param threshold convergence threshold (s)
  63.      * @param dates list of event dates
  64.      * @see #addEventDate(AbsoluteDate)
  65.      */
  66.     public DateDetector(final double maxCheck, final double threshold, final TimeStamped... dates) {
  67.         this(maxCheck, threshold, DEFAULT_MAX_ITER, new StopOnEvent<DateDetector>(), dates);
  68.     }

  70.     /** Build a new instance.
  71.      * <p>This constructor is dedicated to single date detection.
  72.      * {@link #getMaxCheckInterval() max check interval} is set to 1.0e10, so almost
  73.      * no other date can be added. Tolerance is set to 1.0e-9.</p>
  74.      * @param target target date
  75.      * @see #addEventDate(AbsoluteDate)
  76.      */
  77.     public DateDetector(final AbsoluteDate target) {
  78.         this(1.0e10, 1.e-9, target);
  79.     }

  81.     /** Private constructor with full parameters.
  82.      * <p>
  83.      * This constructor is private as users are expected to use the builder
  84.      * API with the various {@code withXxx()} methods to set up the instance
  85.      * in a readable manner without using a huge amount of parameters.
  86.      * </p>
  87.      * @param maxCheck maximum checking interval (s)
  88.      * @param threshold convergence threshold (s)
  89.      * @param maxIter maximum number of iterations in the event time search
  90.      * @param handler event handler to call at event occurrences
  91.      * @param dates list of event dates
  92.      * @since 6.1
  93.      */
  94.     private DateDetector(final double maxCheck, final double threshold,
  95.                          final int maxIter, final EventHandler<? super DateDetector> handler,
  96.                          final TimeStamped... dates) {
  97.         super(maxCheck, threshold, maxIter, handler);
  98.         this.currentIndex  = -1;
  99.         this.gDate         = null;
  100.         this.eventDateList = new ArrayList<DateDetector.EventDate>(dates.length);
  101.         for (final TimeStamped ts : dates) {
  102.             addEventDate(ts.getDate());
  103.         }
  104.     }

  106.     /** {@inheritDoc} */
  107.     @Override
  108.     protected DateDetector create(final double newMaxCheck, final double newThreshold,
  109.                                   final int newMaxIter, final EventHandler<? super DateDetector> newHandler) {
  110.         return new DateDetector(newMaxCheck, newThreshold, newMaxIter, newHandler,
  111.                                 eventDateList.toArray(new EventDate[eventDateList.size()]));
  112.     }

  114.     /** Get all event dates currently managed, in chronological order.
  115.      * @return all event dates currently managed, in chronological order
  116.      * @since 11.1
  117.      */
  118.     public List<TimeStamped> getDates() {
  119.         return Collections.unmodifiableList(eventDateList);
  120.     }

  122.     /** Compute the value of the switching function.
  123.      * This function measures the difference between the current and the target date.
  124.      * @param s the current state information: date, kinematics, attitude
  125.      * @return value of the switching function
  126.      */
  127.     public double g(final SpacecraftState s) {
  128.         gDate = s.getDate();
  129.         if (currentIndex < 0) {
  130.             return -1.0;
  131.         } else {
  132.             final EventDate event = getClosest(gDate);
  133.             return event.isgIncrease() ? gDate.durationFrom(event.getDate()) : event.getDate().durationFrom(gDate);
  134.         }
  135.     }

  137.     /** Get the current event date according to the propagator.
  138.      * @return event date
  139.      */
  140.     public AbsoluteDate getDate() {
  141.         return currentIndex < 0 ? null : eventDateList.get(currentIndex).getDate();
  142.     }

  144.     /** Add an event date.
  145.      * <p>The date to add must be:</p>
  146.      * <ul>
  147.      *   <li>less than the smallest already registered event date minus the maxCheck</li>
  148.      *   <li>or more than the largest already registered event date plus the maxCheck</li>
  149.      * </ul>
  150.      * @param target target date
  151.      * @throws IllegalArgumentException if the date is too close from already defined interval
  152.      * @see #DateDetector(double, double, TimeStamped...)
  153.      */
  154.     public void addEventDate(final AbsoluteDate target) throws IllegalArgumentException {
  155.         final boolean increasing;
  156.         if (currentIndex < 0) {
  157.             increasing = (gDate == null) ? true : target.durationFrom(gDate) > 0.0;
  158.             currentIndex = 0;
  159.             eventDateList.add(new EventDate(target, increasing));
  160.         } else {
  161.             final int lastIndex = eventDateList.size() - 1;
  162.             final AbsoluteDate firstDate = eventDateList.get(0).getDate();
  163.             final AbsoluteDate lastDate = eventDateList.get(lastIndex).getDate();
  164.             if (firstDate.durationFrom(target) > getMaxCheckInterval()) {
  165.                 increasing = !eventDateList.get(0).isgIncrease();
  166.                 eventDateList.add(0, new EventDate(target, increasing));
  167.                 currentIndex++;
  168.             } else if (target.durationFrom(lastDate) > getMaxCheckInterval()) {
  169.                 increasing = !eventDateList.get(lastIndex).isgIncrease();
  170.                 eventDateList.add(new EventDate(target, increasing));
  171.             } else {
  172.                 throw new OrekitIllegalArgumentException(OrekitMessages.EVENT_DATE_TOO_CLOSE,
  173.                                                          target,
  174.                                                          firstDate,
  175.                                                          lastDate,
  176.                                                          getMaxCheckInterval(),
  177.                                                          firstDate.durationFrom(target),
  178.                                                          target.durationFrom(lastDate));
  179.             }
  180.         }
  181.     }

  183.     /** Get the closest EventDate to the target date.
  184.      * @param target target date
  185.      * @return current EventDate
  186.      */
  187.     private EventDate getClosest(final AbsoluteDate target) {
  188.         final double dt = target.durationFrom(eventDateList.get(currentIndex).getDate());
  189.         if (dt < 0.0 && currentIndex > 0) {
  190.             boolean found = false;
  191.             while (currentIndex > 0 && !found) {
  192.                 if (target.durationFrom(eventDateList.get(currentIndex - 1).getDate()) < eventDateList.get(currentIndex).getDate().durationFrom(target)) {
  193.                     currentIndex--;
  194.                 } else {
  195.                     found = true;
  196.                 }
  197.             }
  198.         } else if (dt > 0.0 && currentIndex < eventDateList.size() - 1) {
  199.             final int maxIndex = eventDateList.size() - 1;
  200.             boolean found = false;
  201.             while (currentIndex < maxIndex && !found) {
  202.                 if (target.durationFrom(eventDateList.get(currentIndex + 1).getDate()) > eventDateList.get(currentIndex).getDate().durationFrom(target)) {
  203.                     currentIndex++;
  204.                 } else {
  205.                     found = true;
  206.                 }
  207.             }
  208.         }
  209.         return eventDateList.get(currentIndex);
  210.     }

  212.     /** Event date specification. */
  213.     private static class EventDate implements TimeStamped {

  215.         /** Event date. */
  216.         private final AbsoluteDate eventDate;

  218.         /** Flag for g function way around event date. */
  219.         private final boolean gIncrease;

  221.         /** Simple constructor.
  222.          * @param date date
  223.          * @param increase if true, g function increases around event date
  224.          */
  225.         EventDate(final AbsoluteDate date, final boolean increase) {
  226.             this.eventDate = date;
  227.             this.gIncrease = increase;
  228.         }

  230.         /** Getter for event date.
  231.          * @return event date
  232.          */
  233.         public AbsoluteDate getDate() {
  234.             return eventDate;
  235.         }

  237.         /** Getter for g function way at event date.
  238.          * @return g function increasing flag
  239.          */
  240.         public boolean isgIncrease() {
  241.             return gIncrease;
  242.         }

  244.     }

  246. }
Created with JaCoCo 0.8.7.202105040129