FieldParameterDrivenDateIntervalDetector.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.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;

  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>
  45.  * @see org.orekit.propagation.Propagator#addEventDetector(EventDetector)
  46.  * @param <T> type of the field elements
  47.  * @author Luc Maisonobe
  48.  * @since 11.1
  49.  */
  50. public class FieldParameterDrivenDateIntervalDetector<T extends CalculusFieldElement<T>> extends FieldAbstractDetector<FieldParameterDrivenDateIntervalDetector<T>, T> {

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

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

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

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

  64.     /** Reference interval start driver. */
  65.     private DateDriver start;

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

  70.     /** Median date driver. */
  71.     private DateDriver median;

  73.     /** Duration driver. */
  74.     private ParameterDriver duration;

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

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

  107.     /** Private constructor with full parameters.
  108.      * <p>
  109.      * This constructor is private as users are expected to use the builder
  110.      * API with the various {@code withXxx()} methods to set up the instance
  111.      * in a readable manner without using a huge amount of parameters.
  112.      * </p>
  113.      * @param maxCheck maximum checking interval (s)
  114.      * @param threshold convergence threshold (s)
  115.      * @param maxIter maximum number of iterations in the event time search
  116.      * @param handler event handler to call at event occurrences
  117.      * @param start reference interval start driver
  118.      * @param stop reference interval stop driver
  119.      * @param median median date driver
  120.      * @param duration duration driver
  121.      */
  122.     private FieldParameterDrivenDateIntervalDetector(final T maxCheck, final T threshold, final int maxIter,
  123.                                                      final FieldEventHandler<? super FieldParameterDrivenDateIntervalDetector<T>, T> handler,
  124.                                                      final DateDriver start, final DateDriver stop,
  125.                                                      final DateDriver median, final ParameterDriver duration) {
  126.         super(maxCheck, threshold, maxIter, 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(observer -> driver.removeObserver(observer));

  154.         driver.addObserver(bindingObserver);

  156.     }

  158.     /** {@inheritDoc} */
  159.     @Override
  160.     protected FieldParameterDrivenDateIntervalDetector<T> create(final T newMaxCheck, final T newThreshold, final int newMaxIter,
  161.                                                                  final FieldEventHandler<? super FieldParameterDrivenDateIntervalDetector<T>, T> newHandler) {
  162.         return new FieldParameterDrivenDateIntervalDetector<>(newMaxCheck, newThreshold, newMaxIter, 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) {
  237.             if (driver.isSelected()) {
  238.                 setDelta(driver.getValue() - previousValue);
  239.             }
  240.         }

  242.         /** {@inheritDoc} */
  243.         @Override
  244.         public void selectionChanged(final boolean previousSelection, final ParameterDriver driver) {
  245.             if ((start.isSelected()  || stop.isSelected()) &&
  246.                 (median.isSelected() || duration.isSelected())) {
  247.                 throw new OrekitException(OrekitMessages.INCONSISTENT_SELECTION,
  248.                                           start.getName(), stop.getName(),
  249.                                           median.getName(), duration.getName());
  250.             }
  251.         }

  253.         /** Change a value.
  254.          * @param delta change of value
  255.          */
  256.         protected abstract void setDelta(double delta);

  258.     }

  260.     /** Observer for start date. */
  261.     private class StartObserver extends BindingObserver {
  262.         /** {@inheritDoc} */
  263.         @Override
  264.         protected void setDelta(final double delta) {
  265.             median.setValue(median.getValue() + 0.5 * delta);
  266.             duration.setValue(duration.getValue() - delta);
  267.         }
  268.     }

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

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

  290.     /** Observer for duration. */
  291.     private class DurationObserver extends BindingObserver {
  292.         /** {@inheritDoc} */
  293.         @Override
  294.         protected void setDelta(final double delta) {
  295.             start.setValue(start.getValue() - 0.5 * delta);
  296.             stop.setValue(stop.getValue() + 0.5 * delta);
  297.         }
  298.     }

  300. }
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