ParameterDrivenDateIntervalDetector.java

  1. /* Copyright 2002-2024 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.util.FastMath;
  23. import org.orekit.errors.OrekitException;
  24. import org.orekit.errors.OrekitMessages;
  25. import org.orekit.propagation.SpacecraftState;
  26. import org.orekit.propagation.events.handlers.EventHandler;
  27. import org.orekit.propagation.events.handlers.StopOnDecreasing;
  28. import org.orekit.time.AbsoluteDate;
  29. import org.orekit.utils.DateDriver;
  30. import org.orekit.utils.ParameterDriver;
  31. import org.orekit.utils.ParameterObserver;
  32. import org.orekit.utils.TimeSpanMap;
  33. import org.orekit.utils.TimeSpanMap.Span;

  35. /** Detector for date intervals that may be offset thanks to parameter drivers.
  36.  * <p>
  37.  * Two dual views can be used for date intervals: either start date/stop date or
  38.  * median date/duration. {@link #getStartDriver() start}/{@link #getStopDriver() stop}
  39.  * drivers and {@link #getMedianDriver() median}/{@link #getDurationDriver() duration}
  40.  * drivers work in pair. Both drivers in one pair can be selected and their changes will
  41.  * be propagated to the other pair, but attempting to select drivers in both
  42.  * pairs at the same time will trigger an exception. Changing the value of a driver
  43.  * that is not selected should be avoided as it leads to inconsistencies between the pairs.
  44.  * </p>. Warning, startDate driver, stopDate driver, duration driver and medianDate driver
  45.  * must all have the same number of values to estimate (same number of span in valueSpanMap), that is is to
  46.  * say that the {@link org.orekit.utils.ParameterDriver#addSpans(AbsoluteDate, AbsoluteDate, double)}
  47.  * should be called with same arguments.
  48.  * @see org.orekit.propagation.Propagator#addEventDetector(EventDetector)
  49.  * @author Luc Maisonobe
  50.  * @since 11.1
  51.  */
  52. public class ParameterDrivenDateIntervalDetector extends AbstractDetector<ParameterDrivenDateIntervalDetector> {

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

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

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

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

  66.     /** Detection threshold. */
  67.     private static final double THRESHOLD = 1.0e-10;

  69.     /** Reference interval start driver. */
  70.     private DateDriver start;

  72.     /** Reference interval stop driver. */
  73.     private DateDriver stop;

  75.     /** Median date driver. */
  76.     private DateDriver median;

  78.     /** Duration driver. */
  79.     private ParameterDriver duration;

  81.     /** Build a new instance.
  82.      * @param prefix prefix to use for parameter drivers names
  83.      * @param refMedian reference interval median date
  84.      * @param refDuration reference duration
  85.      */
  86.     public ParameterDrivenDateIntervalDetector(final String prefix,
  87.                                                final AbsoluteDate refMedian, final double refDuration) {
  88.         this(prefix,
  89.              refMedian.shiftedBy(-0.5 * refDuration),
  90.              refMedian.shiftedBy(+0.5 * refDuration));
  91.     }

  93.     /** Build a new instance.
  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 ParameterDrivenDateIntervalDetector(final String prefix,
  99.                                                final AbsoluteDate refStart, final AbsoluteDate refStop) {
  100.         this(s -> FastMath.max(0.5 * refStop.durationFrom(refStart), THRESHOLD),
  101.              THRESHOLD, DEFAULT_MAX_ITER,
  102.              new StopOnDecreasing(),
  103.              new DateDriver(refStart, prefix + START_SUFFIX, true),
  104.              new DateDriver(refStop, prefix + STOP_SUFFIX, false),
  105.              new DateDriver(refStart.shiftedBy(0.5 * refStop.durationFrom(refStart)), prefix + MEDIAN_SUFFIX, true),
  106.              new ParameterDriver(prefix + DURATION_SUFFIX, refStop.durationFrom(refStart), 1.0, 0.0, Double.POSITIVE_INFINITY));
  107.     }

  109.     /** Protected constructor with full parameters.
  110.      * <p>
  111.      * This constructor is not public as users are expected to use the builder
  112.      * API with the various {@code withXxx()} methods to set up the instance
  113.      * in a readable manner without using a huge amount of parameters.
  114.      * </p>
  115.      * @param maxCheck maximum checking interval
  116.      * @param threshold convergence threshold (s)
  117.      * @param maxIter maximum number of iterations in the event time search
  118.      * @param handler event handler to call at event occurrences
  119.      * @param start reference interval start driver
  120.      * @param stop reference interval stop driver
  121.      * @param median median date driver
  122.      * @param duration duration driver
  123.      */
  124.     protected ParameterDrivenDateIntervalDetector(final AdaptableInterval maxCheck, final double threshold, final int maxIter,
  125.                                                   final EventHandler handler,
  126.                                                   final DateDriver start, final DateDriver stop,
  127.                                                   final DateDriver median, final ParameterDriver duration) {
  128.         super(new EventDetectionSettings(maxCheck, threshold, maxIter), handler);
  129.         this.start    = start;
  130.         this.stop     = stop;
  131.         this.median   = median;
  132.         this.duration = duration;

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

  140.     }

  142.     /** Replace binding observers.
  143.      * @param driver driver for whose binding observers should be replaced
  144.      * @param bindingObserver new binding observer
  145.      */
  146.     private void replaceBindingObserver(final ParameterDriver driver, final BindingObserver bindingObserver) {

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

  156.         driver.addObserver(bindingObserver);

  158.     }

  160.     /** {@inheritDoc} */
  161.     @Override
  162.     protected ParameterDrivenDateIntervalDetector create(final AdaptableInterval newMaxCheck, final double newThreshold, final int newMaxIter,
  163.                                                          final EventHandler newHandler) {
  164.         return new ParameterDrivenDateIntervalDetector(newMaxCheck, newThreshold, newMaxIter, newHandler,
  165.                                                        start, stop, median, duration);
  166.     }

  168.     /** Get the driver for start date.
  169.      * <p>
  170.      * Note that the start date is automatically adjusted if either
  171.      * {@link #getMedianDriver() median date} or {@link #getDurationDriver() duration}
  172.      * are {@link ParameterDriver#isSelected() selected} and changed.
  173.      * </p>
  174.      * @return driver for start date
  175.      */
  176.     public DateDriver getStartDriver() {
  177.         return start;
  178.     }

  180.     /** Get the driver for stop date.
  181.      * <p>
  182.      * Note that the stop date is automatically adjusted if either
  183.      * {@link #getMedianDriver() median date} or {@link #getDurationDriver() duration}
  184.      * are {@link ParameterDriver#isSelected() selected} changed.
  185.      * </p>
  186.      * @return driver for stop date
  187.      */
  188.     public DateDriver getStopDriver() {
  189.         return stop;
  190.     }

  192.     /** Get the driver for median date.
  193.      * <p>
  194.      * Note that the median date is automatically adjusted if either
  195.      * {@link #getStartDriver()} start date or {@link #getStopDriver() stop date}
  196.      * are {@link ParameterDriver#isSelected() selected} changed.
  197.      * </p>
  198.      * @return driver for median date
  199.      */
  200.     public DateDriver getMedianDriver() {
  201.         return median;
  202.     }

  204.     /** Get the driver for duration.
  205.      * <p>
  206.      * Note that the duration is automatically adjusted if either
  207.      * {@link #getStartDriver()} start date or {@link #getStopDriver() stop date}
  208.      * are {@link ParameterDriver#isSelected() selected} changed.
  209.      * </p>
  210.      * @return driver for duration
  211.      */
  212.     public ParameterDriver getDurationDriver() {
  213.         return duration;
  214.     }

  216.     /** Compute the value of the switching function.
  217.      * <p>
  218.      * The function is positive for dates within the interval defined
  219.      * by applying the parameter drivers shifts to reference dates,
  220.      * and negative for dates outside of this interval. Note that
  221.      * if Δt_start - Δt_stop is less than ref_stop.durationFrom(ref_start),
  222.      * then the interval degenerates to empty and the function never
  223.      * reaches positive values.
  224.      * </p>
  225.      * @param s the current state information: date, kinematics, attitude
  226.      * @return value of the switching function
  227.      */
  228.     public double g(final SpacecraftState s) {
  229.         return FastMath.min(s.getDate().durationFrom(start.getDate()),
  230.                             stop.getDate().durationFrom(s.getDate()));
  231.     }

  233.     /** Base observer. */
  234.     private abstract class BindingObserver implements ParameterObserver {

  236.         /** {@inheritDoc} */
  237.         @Override
  238.         public void valueChanged(final double previousValue, final ParameterDriver driver, final AbsoluteDate date) {
  239.             if (driver.isSelected()) {
  240.                 setDelta(driver.getValue(date) - previousValue, date);
  241.             }
  242.         }
  243.         /** {@inheritDoc} */
  244.         @Override
  245.         public void valueSpanMapChanged(final TimeSpanMap<Double> previousValue, final ParameterDriver driver) {
  246.             if (driver.isSelected()) {
  247.                 for (Span<Double> span = driver.getValueSpanMap().getFirstSpan(); span != null; span = span.next()) {
  248.                     setDelta(span.getData() - previousValue.get(span.getStart()), span.getStart());
  249.                 }
  250.             }
  251.         }
  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 delta change of value
  265.          * @param date date at which the delta wants to be set
  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.             // date driver has no validity period, only 1 value is estimated
  277.             // over the all interval so there is no problem for calling getValue with null argument
  278.             // or any date, it would give the same result as there is only 1 span on the valueSpanMap
  279.             // of the driver
  280.             median.setValue(median.getValue(date) + 0.5 * delta, date);
  281.             duration.setValue(duration.getValue(date) - delta, date);
  282.         }
  283.     }

  285.     /** Observer for stop date. */
  286.     private class StopObserver extends BindingObserver {
  287.         /** {@inheritDoc} */
  288.         @Override
  289.         protected void setDelta(final double delta, final AbsoluteDate date) {
  290.             // date driver has no validity period, only 1 value is estimated
  291.             // over the all interval so there is no problem for calling getValue with null argument
  292.             // or any date, it would give the same result as there is only 1 span on the valueSpanMap
  293.             // of the driver
  294.             median.setValue(median.getValue(date) + 0.5 * delta, date);
  295.             duration.setValue(duration.getValue(date) + delta, date);
  296.         }
  297.     }

  299.     /** Observer for median date. */
  300.     private class MedianObserver extends BindingObserver {
  301.         /** {@inheritDoc} */
  302.         @Override
  303.         protected void setDelta(final double delta, final AbsoluteDate date) {
  304.             // date driver has no validity period, only 1 value is estimated
  305.             // over the all interval so there is no problem for calling getValue with null argument
  306.             // or any date, it would give the same result as there is only 1 span on the valueSpanMap
  307.             // of the driver
  308.             start.setValue(start.getValue(date) + delta, date);
  309.             stop.setValue(stop.getValue(date) + delta, date);
  310.         }
  311.     }

  313.     /** Observer for duration. */
  314.     private class DurationObserver extends BindingObserver {
  315.         /** {@inheritDoc} */
  316.         @Override
  317.         protected void setDelta(final double delta, final AbsoluteDate date) {
  318.             // date driver has no validity period, only 1 value is estimated
  319.             // over the all interval so there is no problem for calling getValue with null argument
  320.             // or any date, it would give the same result as there is only 1 span on the valueSpanMap
  321.             // of the driver
  322.             start.setValue(start.getValue(date) - 0.5 * delta, date);
  323.             stop.setValue(stop.getValue(date) + 0.5 * delta, date);
  324.         }
  325.     }

  327. }
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