NumericalGradientConverter.java
- /* Copyright 2002-2020 CS GROUP
- * Licensed to CS GROUP (CS) under one or more
- * contributor license agreements. See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * CS licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
- package org.orekit.propagation.numerical;
- import java.util.ArrayList;
- import java.util.List;
- import org.hipparchus.Field;
- import org.hipparchus.analysis.differentiation.Gradient;
- import org.hipparchus.analysis.differentiation.GradientField;
- import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
- import org.hipparchus.geometry.euclidean.threed.Vector3D;
- import org.orekit.attitudes.AttitudeProvider;
- import org.orekit.attitudes.FieldAttitude;
- import org.orekit.forces.ForceModel;
- import org.orekit.orbits.FieldCartesianOrbit;
- import org.orekit.orbits.FieldOrbit;
- import org.orekit.propagation.FieldSpacecraftState;
- import org.orekit.propagation.SpacecraftState;
- import org.orekit.propagation.integration.AbstractGradientConverter;
- import org.orekit.utils.FieldAngularCoordinates;
- import org.orekit.utils.FieldPVCoordinates;
- import org.orekit.utils.ParameterDriver;
- import org.orekit.utils.TimeStampedFieldAngularCoordinates;
- import org.orekit.utils.TimeStampedFieldPVCoordinates;
- /** Converter for states and parameters arrays.
- * @author Luc Maisonobe
- * @since 10.2
- */
- class NumericalGradientConverter extends AbstractGradientConverter {
- /** Dimension of the state. */
- private final int freeStateParameters;
- /** States with various number of additional parameters for force models. */
- private final List<FieldSpacecraftState<Gradient>> gStates;
- /** Simple constructor.
- * @param state regular state
- * @param freeStateParameters number of free parameters, either 3 (position) or 6 (position-velocity)
- * @param provider provider to use if attitude needs to be recomputed
- */
- NumericalGradientConverter(final SpacecraftState state, final int freeStateParameters,
- final AttitudeProvider provider) {
- super(freeStateParameters);
- this.freeStateParameters = freeStateParameters;
- // Derivative field
- final Field<Gradient> field = GradientField.getField(freeStateParameters);
- // position always has derivatives
- final Vector3D pos = state.getPVCoordinates().getPosition();
- final FieldVector3D<Gradient> posG = new FieldVector3D<>(Gradient.variable(freeStateParameters, 0, pos.getX()),
- Gradient.variable(freeStateParameters, 1, pos.getY()),
- Gradient.variable(freeStateParameters, 2, pos.getZ()));
- // velocity may have derivatives or not
- final Vector3D vel = state.getPVCoordinates().getVelocity();
- final FieldVector3D<Gradient> velG;
- if (freeStateParameters > 3) {
- velG = new FieldVector3D<>(Gradient.variable(freeStateParameters, 3, vel.getX()),
- Gradient.variable(freeStateParameters, 4, vel.getY()),
- Gradient.variable(freeStateParameters, 5, vel.getZ()));
- } else {
- velG = new FieldVector3D<>(Gradient.constant(freeStateParameters, vel.getX()),
- Gradient.constant(freeStateParameters, vel.getY()),
- Gradient.constant(freeStateParameters, vel.getZ()));
- }
- // acceleration never has derivatives
- final Vector3D acc = state.getPVCoordinates().getAcceleration();
- final FieldVector3D<Gradient> accG = new FieldVector3D<>(Gradient.constant(freeStateParameters, acc.getX()),
- Gradient.constant(freeStateParameters, acc.getY()),
- Gradient.constant(freeStateParameters, acc.getZ()));
- // mass never has derivatives
- final Gradient gM = Gradient.constant(freeStateParameters, state.getMass());
- final Gradient gMu = Gradient.constant(freeStateParameters, state.getMu());
- final FieldOrbit<Gradient> gOrbit =
- new FieldCartesianOrbit<>(new TimeStampedFieldPVCoordinates<>(state.getDate(), posG, velG, accG),
- state.getFrame(), gMu);
- final FieldAttitude<Gradient> gAttitude;
- if (freeStateParameters > 3) {
- // compute attitude partial derivatives with respect to position/velocity
- gAttitude = provider.getAttitude(gOrbit, gOrbit.getDate(), gOrbit.getFrame());
- } else {
- // force model does not depend on attitude, don't bother recomputing it
- gAttitude = new FieldAttitude<>(field, state.getAttitude());
- }
- // initialize the list with the state having 0 force model parameters
- gStates = new ArrayList<>();
- gStates.add(new FieldSpacecraftState<>(gOrbit, gAttitude, gM));
- }
- /** Get the state with the number of parameters consistent with force model.
- * @param forceModel force model
- * @return state with the number of parameters consistent with force model
- */
- public FieldSpacecraftState<Gradient> getState(final ForceModel forceModel) {
- // count the required number of parameters
- int nbParams = 0;
- for (final ParameterDriver driver : forceModel.getParametersDrivers()) {
- if (driver.isSelected()) {
- ++nbParams;
- }
- }
- // fill in intermediate slots
- while (gStates.size() < nbParams + 1) {
- gStates.add(null);
- }
- if (gStates.get(nbParams) == null) {
- // it is the first time we need this number of parameters
- // we need to create the state
- final int freeParameters = freeStateParameters + nbParams;
- final FieldSpacecraftState<Gradient> s0 = gStates.get(0);
- // orbit
- final FieldPVCoordinates<Gradient> pv0 = s0.getPVCoordinates();
- final FieldOrbit<Gradient> gOrbit =
- new FieldCartesianOrbit<>(new TimeStampedFieldPVCoordinates<>(s0.getDate().toAbsoluteDate(),
- extend(pv0.getPosition(), freeParameters),
- extend(pv0.getVelocity(), freeParameters),
- extend(pv0.getAcceleration(), freeParameters)),
- s0.getFrame(),
- extend(s0.getMu(), freeParameters));
- // attitude
- final FieldAngularCoordinates<Gradient> ac0 = s0.getAttitude().getOrientation();
- final FieldAttitude<Gradient> gAttitude =
- new FieldAttitude<>(s0.getAttitude().getReferenceFrame(),
- new TimeStampedFieldAngularCoordinates<>(gOrbit.getDate(),
- extend(ac0.getRotation(), freeParameters),
- extend(ac0.getRotationRate(), freeParameters),
- extend(ac0.getRotationAcceleration(), freeParameters)));
- // mass
- final Gradient gM = extend(s0.getMass(), freeParameters);
- gStates.set(nbParams, new FieldSpacecraftState<>(gOrbit, gAttitude, gM));
- }
- return gStates.get(nbParams);
- }
- /** Get the force model parameters.
- * @param state state as returned by {@link #getState(ForceModel)}
- * @param forceModel force model associated with the parameters
- * @return force model parameters
- */
- public Gradient[] getParameters(final FieldSpacecraftState<Gradient> state,
- final ForceModel forceModel) {
- final int freeParameters = state.getMass().getFreeParameters();
- final ParameterDriver[] drivers = forceModel.getParametersDrivers();
- final Gradient[] parameters = new Gradient[drivers.length];
- int index = freeStateParameters;
- for (int i = 0; i < drivers.length; ++i) {
- parameters[i] = drivers[i].isSelected() ?
- Gradient.variable(freeParameters, index++, drivers[i].getValue()) :
- Gradient.constant(freeParameters, drivers[i].getValue());
- }
- return parameters;
- }
- }