1 /* Copyright 2022-2024 Romain Serra
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
18 package org.orekit.propagation.events;
19
20 import org.hipparchus.CalculusFieldElement;
21 import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
22 import org.hipparchus.ode.events.Action;
23 import org.orekit.propagation.FieldSpacecraftState;
24 import org.orekit.propagation.events.handlers.FieldEventHandler;
25 import org.orekit.propagation.events.handlers.FieldStopOnEvent;
26 import org.orekit.utils.FieldPVCoordinatesProvider;
27
28 /**
29 * Detector of specific value for the distance relative to another trajectory (using the Euclidean norm).
30 * <p>
31 * The default implementation behavior is to {@link Action#STOP stop} propagation.
32 * This can be changed by calling {@link #withHandler(org.orekit.propagation.events.handlers.FieldEventHandler)} after construction.
33 * </p>
34 * <p>
35 * As this detector needs two objects (moving relative to each other), it embeds one
36 * {@link org.orekit.utils.FieldPVCoordinatesProvider coordinates provider} for the secondary object and is registered as an event detector in
37 * the propagator of the primary object. The secondary object {@link org.orekit.utils.FieldPVCoordinatesProvider coordinates provider} will
38 * therefore be driven by this detector (and hence by the propagator in which this detector is registered).
39 * </p>
40 * <p>
41 * For efficiency reason during the event search loop, it is recommended to have the secondary provider be an analytical
42 * propagator or an ephemeris. A numerical propagator as a secondary propagator works but is expected to be
43 * computationally costly.
44 * </p>
45 *
46 * @see org.orekit.propagation.FieldPropagator#addEventDetector(FieldEventDetector)
47 * @author Romain Serra
48 * @since 12.1
49 */
50 public class FieldRelativeDistanceDetector<T extends CalculusFieldElement<T>>
51 extends FieldAbstractDetector<FieldRelativeDistanceDetector<T>, T> {
52
53 /**
54 * PVCoordinates provider of the other object used to define relative distance.
55 */
56 private final FieldPVCoordinatesProvider<T> secondaryPVProvider;
57
58 /** Relative distance value triggering detection. */
59 private final T distanceThreshold;
60
61 /**
62 * Constructor with default values.
63 * <p>
64 * By default, the implemented behavior is to {@link Action#STOP stop} propagation at detection.
65 * </p>
66 *
67 * @param secondaryPVProvider PVCoordinates provider of the other object defining relative distance.
68 * @param distanceThreshold Relative distance threshold for event detection
69 */
70 public FieldRelativeDistanceDetector(final FieldPVCoordinatesProvider<T> secondaryPVProvider,
71 final T distanceThreshold) {
72 this(FieldAdaptableInterval.of(DEFAULT_MAXCHECK), distanceThreshold.getField().getZero().newInstance(DEFAULT_THRESHOLD),
73 DEFAULT_MAX_ITER, new FieldStopOnEvent<>(), secondaryPVProvider, distanceThreshold);
74 }
75
76 /**
77 * Constructor.
78 * <p>
79 * This constructor is to be used if the user wants to change the default behavior of the detector.
80 * </p>
81 *
82 * @param maxCheck Maximum checking interval.
83 * @param threshold Convergence threshold (s).
84 * @param maxIter Maximum number of iterations in the event time search.
85 * @param handler Event handler to call at event occurrences.
86 * @param secondaryPVProvider PVCoordinates provider of the other object defining relative distance.
87 * @param distanceThreshold Relative distance threshold for event detection
88 * @see FieldEventHandler
89 */
90 protected FieldRelativeDistanceDetector(final FieldAdaptableInterval<T> maxCheck, final T threshold, final int maxIter,
91 final FieldEventHandler<T> handler, final FieldPVCoordinatesProvider<T> secondaryPVProvider,
92 final T distanceThreshold) {
93 super(maxCheck, threshold, maxIter, handler);
94 this.secondaryPVProvider = secondaryPVProvider;
95 this.distanceThreshold = distanceThreshold;
96 }
97
98 /**
99 * The {@code g} is positive when the relative distance is larger or equal than the threshold,
100 * non-positive otherwise.
101 *
102 * @param s the current state information: date, kinematics, attitude
103 * @return value of the switching function
104 */
105 @Override
106 public T g(final FieldSpacecraftState<T> s) {
107 final FieldVector3D<T> secondaryPosition = getSecondaryPVProvider().getPosition(s.getDate(), s.getFrame());
108 final T relativeDistance = s.getPosition().subtract(secondaryPosition).getNorm();
109 return relativeDistance.subtract(distanceThreshold);
110 }
111
112 /** {@inheritDoc} */
113 @Override
114 protected FieldRelativeDistanceDetector<T> create(final FieldAdaptableInterval<T> newMaxCheck, final T newThreshold,
115 final int newMaxIter, final FieldEventHandler<T> newHandler) {
116 return new FieldRelativeDistanceDetector<>(newMaxCheck, newThreshold, newMaxIter, newHandler, secondaryPVProvider,
117 distanceThreshold);
118 }
119
120 /**
121 * Get the secondary position-velocity provider stored in this instance.
122 *
123 * @return the secondary position-velocity provider stored in this instance
124 */
125 public FieldPVCoordinatesProvider<T> getSecondaryPVProvider() {
126 return secondaryPVProvider;
127 }
128
129 /**
130 * Get the relative distance threshold.
131 *
132 * @return threshold triggering detection
133 */
134 public T getDistanceThreshold() {
135 return distanceThreshold;
136 }
137 }