FieldParameterDrivenDateIntervalDetector.java

  1. /* Copyright 2002-2025 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.List;
  20. import java.util.stream.Collectors;

  22. import org.hipparchus.CalculusFieldElement;
  23. import org.hipparchus.Field;
  24. import org.hipparchus.util.FastMath;
  25. import org.orekit.errors.OrekitException;
  26. import org.orekit.errors.OrekitMessages;
  27. import org.orekit.propagation.FieldSpacecraftState;
  28. import org.orekit.propagation.events.handlers.FieldEventHandler;
  29. import org.orekit.propagation.events.handlers.FieldStopOnEvent;
  30. import org.orekit.time.AbsoluteDate;
  31. import org.orekit.utils.DateDriver;
  32. import org.orekit.utils.ParameterDriver;
  33. import org.orekit.utils.ParameterObserver;
  34. import org.orekit.utils.TimeSpanMap;
  35. import org.orekit.utils.TimeSpanMap.Span;

  37. /** Detector for date intervals that may be offset thanks to parameter drivers.
  38.  * <p>
  39.  * Two dual views can be used for date intervals: either start date/stop date or
  40.  * median date/duration. {@link #getStartDriver() start}/{@link #getStopDriver() stop}
  41.  * drivers and {@link #getMedianDriver() median}/{@link #getDurationDriver() duration}
  42.  * drivers work in pair. Both drivers in one pair can be selected and their changes will
  43.  * be propagated to the other pair, but attempting to select drivers in both
  44.  * pairs at the same time will trigger an exception. Changing the value of a driver
  45.  * that is not selected should be avoided as it leads to inconsistencies between the pairs.
  46.  * </p>
  47.  * @see org.orekit.propagation.Propagator#addEventDetector(EventDetector)
  48.  * @param <T> type of the field elements
  49.  * @author Luc Maisonobe
  50.  * @since 11.1
  51.  */
  52. public class FieldParameterDrivenDateIntervalDetector<T extends CalculusFieldElement<T>>
  53.     extends FieldAbstractDetector<FieldParameterDrivenDateIntervalDetector<T>, T> {

  55.     /** Default suffix for start driver. */
  56.     public static final String START_SUFFIX = "_START";

  58.     /** Default suffix for stop driver. */
  59.     public static final String STOP_SUFFIX = "_STOP";

  61.     /** Default suffix for median driver. */
  62.     public static final String MEDIAN_SUFFIX = "_MEDIAN";

  64.     /** Default suffix for duration driver. */
  65.     public static final String DURATION_SUFFIX = "_DURATION";

  67.     /** Reference interval start driver. */
  68.     private DateDriver start;

  70.     /** Reference interval stop driver. */
  71.     private DateDriver stop;

  73.     /** Median date driver. */
  74.     private DateDriver median;

  76.     /** Duration driver. */
  77.     private ParameterDriver duration;

  79.     /** Build a new instance.
  80.      * @param field field to which the elements belong
  81.      * @param prefix prefix to use for parameter drivers names
  82.      * @param refMedian reference interval median date
  83.      * @param refDuration reference duration
  84.      */
  85.     public FieldParameterDrivenDateIntervalDetector(final Field<T> field, final String prefix,
  86.                                                     final AbsoluteDate refMedian, final double refDuration) {
  87.         this(field, prefix,
  88.              refMedian.shiftedBy(-0.5 * refDuration),
  89.              refMedian.shiftedBy(+0.5 * refDuration));
  90.     }

  92.     /** Build a new instance.
  93.      * @param field field to which the elements belong
  94.      * @param prefix prefix to use for parameter drivers names
  95.      * @param refStart reference interval start date
  96.      * @param refStop reference interval stop date
  97.      */
  98.     public FieldParameterDrivenDateIntervalDetector(final Field<T> field, final String prefix,
  99.                                                     final AbsoluteDate refStart, final AbsoluteDate refStop) {
  100.         this(new FieldEventDetectionSettings<>(field, EventDetectionSettings.getDefaultEventDetectionSettings()),
  101.              new FieldStopOnEvent<>(),
  102.              new DateDriver(refStart, prefix + START_SUFFIX, true),
  103.              new DateDriver(refStop, prefix + STOP_SUFFIX, false),
  104.              new DateDriver(refStart.shiftedBy(0.5 * refStop.durationFrom(refStart)), prefix + MEDIAN_SUFFIX, true),
  105.              new ParameterDriver(prefix + DURATION_SUFFIX, refStop.durationFrom(refStart), 1.0, 0.0, Double.POSITIVE_INFINITY));
  106.     }

  108.     /** Protected constructor with full parameters.
  109.      * <p>
  110.      * This constructor is not public as users are expected to use the builder
  111.      * API with the various {@code withXxx()} methods to set up the instance
  112.      * in a readable manner without using a huge amount of parameters.
  113.      * </p>
  114.      * @param detectionSettings event detection settings
  115.      * @param handler event handler to call at event occurrences
  116.      * @param start reference interval start driver
  117.      * @param stop reference interval stop driver
  118.      * @param median median date driver
  119.      * @param duration duration driver
  120.      * @since 13.0
  121.      */
  122.     protected FieldParameterDrivenDateIntervalDetector(final FieldEventDetectionSettings<T> detectionSettings,
  123.                                                        final FieldEventHandler<T> handler,
  124.                                                        final DateDriver start, final DateDriver stop,
  125.                                                        final DateDriver median, final ParameterDriver duration) {
  126.         super(detectionSettings, handler);
  127.         this.start    = start;
  128.         this.stop     = stop;
  129.         this.median   = median;
  130.         this.duration = duration;

  132.         // set up delegation between drivers
  133.         replaceBindingObserver(start,    new StartObserver());
  134.         replaceBindingObserver(stop,     new StopObserver());
  135.         replaceBindingObserver(median,   new MedianObserver());
  136.         replaceBindingObserver(duration, new DurationObserver());

  138.     }

  140.     /** Replace binding observers.
  141.      * @param driver driver for whose binding observers should be replaced
  142.      * @param bindingObserver new binding observer
  143.      */
  144.     private void replaceBindingObserver(final ParameterDriver driver, final BindingObserver bindingObserver) {

  146.         // remove the previous binding observers
  147.         final List<ParameterObserver> original = driver.
  148.                                                  getObservers().
  149.                                                  stream().
  150.                                                  filter(observer -> observer instanceof FieldParameterDrivenDateIntervalDetector.BindingObserver).
  151.                                                  collect(Collectors.toList());
  152.         original.forEach(driver::removeObserver);

  154.         driver.addObserver(bindingObserver);

  156.     }

  158.     /** {@inheritDoc} */
  159.     @Override
  160.     protected FieldParameterDrivenDateIntervalDetector<T> create(final FieldEventDetectionSettings<T> detectionSettings,
  161.                                                                  final FieldEventHandler<T> newHandler) {
  162.         return new FieldParameterDrivenDateIntervalDetector<>(detectionSettings, newHandler,
  163.                                                               start, stop, median, duration);
  164.     }

  166.     /** Get the driver for start date.
  167.      * <p>
  168.      * Note that the start date is automatically adjusted if either
  169.      * {@link #getMedianDriver() median date} or {@link #getDurationDriver() duration}
  170.      * are {@link ParameterDriver#isSelected() selected} and changed.
  171.      * </p>
  172.      * @return driver for start date
  173.      */
  174.     public DateDriver getStartDriver() {
  175.         return start;
  176.     }

  178.     /** Get the driver for stop date.
  179.      * <p>
  180.      * Note that the stop date is automatically adjusted if either
  181.      * {@link #getMedianDriver() median date} or {@link #getDurationDriver() duration}
  182.      * are {@link ParameterDriver#isSelected() selected} changed.
  183.      * </p>
  184.      * @return driver for stop date
  185.      */
  186.     public DateDriver getStopDriver() {
  187.         return stop;
  188.     }

  190.     /** Get the driver for median date.
  191.      * <p>
  192.      * Note that the median date is automatically adjusted if either
  193.      * {@link #getStartDriver()} start date or {@link #getStopDriver() stop date}
  194.      * are {@link ParameterDriver#isSelected() selected} changed.
  195.      * </p>
  196.      * @return driver for median date
  197.      */
  198.     public DateDriver getMedianDriver() {
  199.         return median;
  200.     }

  202.     /** Get the driver for duration.
  203.      * <p>
  204.      * Note that the duration is automatically adjusted if either
  205.      * {@link #getStartDriver()} start date or {@link #getStopDriver() stop date}
  206.      * are {@link ParameterDriver#isSelected() selected} changed.
  207.      * </p>
  208.      * @return driver for duration
  209.      */
  210.     public ParameterDriver getDurationDriver() {
  211.         return duration;
  212.     }

  214.     /** Compute the value of the switching function.
  215.      * <p>
  216.      * The function is positive for dates within the interval defined
  217.      * by applying the parameter drivers shifts to reference dates,
  218.      * and negative for dates outside of this interval. Note that
  219.      * if Δt_start - Δt_stop is less than ref_stop.durationFrom(ref_start),
  220.      * then the interval degenerates to empty and the function never
  221.      * reaches positive values.
  222.      * </p>
  223.      * @param s the current state information: date, kinematics, attitude
  224.      * @return value of the switching function
  225.      */
  226.     public T g(final FieldSpacecraftState<T> s) {
  227.         return FastMath.min(s.getDate().durationFrom(start.getDate()),
  228.                             s.getDate().durationFrom(stop.getDate()).negate());
  229.     }

  231.     /** Base observer. */
  232.     private abstract class BindingObserver implements ParameterObserver {

  234.         /** {@inheritDoc} */
  235.         @Override
  236.         public void valueChanged(final double previousValue, final ParameterDriver driver, final AbsoluteDate date) {
  237.             if (driver.isSelected()) {
  238.                 setDelta(driver.getValue(date) - previousValue, date);
  239.             }
  240.         }

  242.         /** {@inheritDoc} */
  243.         @Override
  244.         public void valueSpanMapChanged(final TimeSpanMap<Double> previousValue, final ParameterDriver driver) {
  245.             if (driver.isSelected()) {
  246.                 for (Span<Double> span = driver.getValueSpanMap().getFirstSpan(); span != null; span = span.next()) {
  247.                     setDelta(span.getData() - previousValue.get(span.getStart()), span.getStart());
  248.                 }
  249.             }
  250.         }

  252.         /** {@inheritDoc} */
  253.         @Override
  254.         public void selectionChanged(final boolean previousSelection, final ParameterDriver driver) {
  255.             if ((start.isSelected()  || stop.isSelected()) &&
  256.                 (median.isSelected() || duration.isSelected())) {
  257.                 throw new OrekitException(OrekitMessages.INCONSISTENT_SELECTION,
  258.                                           start.getName(), stop.getName(),
  259.                                           median.getName(), duration.getName());
  260.             }
  261.         }

  263.         /** Change a value.
  264.          * @param date date for which the value wants to be change
  265.          * @param delta change of value
  266.          */
  267.         protected abstract void setDelta(double delta, AbsoluteDate date);

  269.     }

  271.     /** Observer for start date. */
  272.     private class StartObserver extends BindingObserver {
  273.         /** {@inheritDoc} */
  274.         @Override
  275.         protected void setDelta(final double delta, final AbsoluteDate date) {
  276.             median.setValue(median.getValue(date) + 0.5 * delta, date);
  277.             duration.setValue(duration.getValue(date) - delta, date);
  278.         }
  279.     }

  281.     /** Observer for stop date. */
  282.     private class StopObserver extends BindingObserver {
  283.         /** {@inheritDoc} */
  284.         @Override
  285.         protected void setDelta(final double delta, final AbsoluteDate date) {
  286.             median.setValue(median.getValue(date) + 0.5 * delta, date);
  287.             duration.setValue(duration.getValue(date) + delta, date);
  288.         }
  289.     }

  291.     /** Observer for median date. */
  292.     private class MedianObserver extends BindingObserver {
  293.         /** {@inheritDoc} */
  294.         @Override
  295.         protected void setDelta(final double delta, final AbsoluteDate date) {
  296.             start.setValue(start.getValue(date) + delta, date);
  297.             stop.setValue(stop.getValue(date) + delta, date);
  298.         }
  299.     }

  301.     /** Observer for duration. */
  302.     private class DurationObserver extends BindingObserver {
  303.         /** {@inheritDoc} */
  304.         @Override
  305.         protected void setDelta(final double delta, final AbsoluteDate date) {
  306.             start.setValue(start.getValue(date) - 0.5 * delta, date);
  307.             stop.setValue(stop.getValue(date) + 0.5 * delta, date);
  308.         }
  309.     }

  311. }
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