AbstractCartesianAdjointEquationTerm.java
/* Copyright 2022-2024 Romain Serra
* 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
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*/
package org.orekit.control.indirect.adjoint;
import org.hipparchus.CalculusFieldElement;
import org.hipparchus.analysis.differentiation.FieldGradient;
import org.hipparchus.analysis.differentiation.FieldGradientField;
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.hipparchus.util.MathArrays;
import org.orekit.frames.Frame;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.FieldAbsoluteDate;
/**
* Abstract class to define terms in the adjoint equations and Hamiltonian for Cartesian coordinates.
* @author Romain Serra
* @see CartesianAdjointDerivativesProvider
* @see FieldCartesianAdjointDerivativesProvider
* @since 12.2
*/
public abstract class AbstractCartesianAdjointEquationTerm implements CartesianAdjointEquationTerm {
/** Dimension of gradient. */
private static final int GRADIENT_DIMENSION = 6;
/** {@inheritDoc} */
@Override
public double[] getRatesContribution(final AbsoluteDate date, final double[] stateVariables,
final double[] adjointVariables, final Frame frame) {
final GradientField field = GradientField.getField(GRADIENT_DIMENSION);
final FieldAbsoluteDate<Gradient> fieldDate = new FieldAbsoluteDate<>(field, date);
final Gradient[] stateAsGradients = buildGradientCartesianVector(stateVariables);
final FieldVector3D<Gradient> acceleration = getFieldAcceleration(fieldDate, stateAsGradients, frame);
final double[] accelerationXgradient = acceleration.getX().getGradient();
final double[] accelerationYgradient = acceleration.getY().getGradient();
final double[] accelerationZgradient = acceleration.getZ().getGradient();
final double[] contribution = new double[adjointVariables.length];
for (int i = 0; i < 6; i++) {
contribution[i] = -(accelerationXgradient[i] * adjointVariables[3] + accelerationYgradient[i] * adjointVariables[4] + accelerationZgradient[i] * adjointVariables[5]);
}
return contribution;
}
/** {@inheritDoc} */
@Override
public double getHamiltonianContribution(final AbsoluteDate date, final double[] stateVariables,
final double[] adjointVariables, final Frame frame) {
final Vector3D acceleration = getAcceleration(date, stateVariables, frame);
return acceleration.getX() * adjointVariables[3] + acceleration.getY() * adjointVariables[4] + acceleration.getZ() * adjointVariables[5];
}
/**
* Compute the acceleration vector.
*
* @param date date
* @param stateVariables state variables
* @param frame propagation frame
* @return acceleration vector
*/
protected abstract Vector3D getAcceleration(AbsoluteDate date, double[] stateVariables,
Frame frame);
/** {@inheritDoc} */
@Override
public <T extends CalculusFieldElement<T>> T[] getFieldRatesContribution(final FieldAbsoluteDate<T> date,
final T[] stateVariables,
final T[] adjointVariables,
final Frame frame) {
final FieldGradientField<T> field = FieldGradientField.getField(date.getField(), GRADIENT_DIMENSION);
final FieldAbsoluteDate<FieldGradient<T>> fieldDate = new FieldAbsoluteDate<>(field, date.toAbsoluteDate());
final FieldGradient<T>[] gradients = buildFieldGradientCartesianVector(stateVariables);
final FieldVector3D<FieldGradient<T>> acceleration = getFieldAcceleration(fieldDate, gradients, frame);
final T[] contribution = MathArrays.buildArray(date.getField(), adjointVariables.length);
final T[] accelerationXgradient = acceleration.getX().getGradient();
final T[] accelerationYgradient = acceleration.getY().getGradient();
final T[] accelerationZgradient = acceleration.getZ().getGradient();
for (int i = 0; i < 6; i++) {
contribution[i] = (accelerationXgradient[i].multiply(adjointVariables[3])
.add(accelerationYgradient[i].multiply(adjointVariables[4])).add(accelerationZgradient[i].multiply(adjointVariables[5]))).negate();
}
return contribution;
}
/** {@inheritDoc} */
@Override
public <T extends CalculusFieldElement<T>> T getFieldHamiltonianContribution(final FieldAbsoluteDate<T> date,
final T[] stateVariables,
final T[] adjointVariables,
final Frame frame) {
final FieldVector3D<T> acceleration = getFieldAcceleration(date, stateVariables, frame);
return acceleration.dotProduct(new FieldVector3D<>(adjointVariables[3], adjointVariables[4], adjointVariables[5]));
}
/**
* Compute the acceleration vector.
*
* @param <T> field type
* @param date date
* @param stateVariables state variables
* @param frame propagation frame
* @return acceleration vector
*/
protected abstract <T extends CalculusFieldElement<T>> FieldVector3D<T> getFieldAcceleration(FieldAbsoluteDate<T> date,
T[] stateVariables,
Frame frame);
/**
* Build a Cartesian vector whose components are independent variables for automatic differentiation at order 1.
* @param stateVariables Cartesian variables
* @return vector of independent variables
*/
protected static Gradient[] buildGradientCartesianVector(final double[] stateVariables) {
final GradientField field = GradientField.getField(GRADIENT_DIMENSION);
final Gradient[] gradients = MathArrays.buildArray(field, GRADIENT_DIMENSION);
gradients[0] = Gradient.variable(GRADIENT_DIMENSION, 0, stateVariables[0]);
gradients[1] = Gradient.variable(GRADIENT_DIMENSION, 1, stateVariables[1]);
gradients[2] = Gradient.variable(GRADIENT_DIMENSION, 2, stateVariables[2]);
gradients[3] = Gradient.variable(GRADIENT_DIMENSION, 3, stateVariables[3]);
gradients[4] = Gradient.variable(GRADIENT_DIMENSION, 4, stateVariables[4]);
gradients[5] = Gradient.variable(GRADIENT_DIMENSION, 5, stateVariables[5]);
return gradients;
}
/**
* Build a Cartesian vector whose components are independent variables for automatic differentiation at order 1.
* @param stateVariables Cartesian variables
* @param <T> field type
* @return vector of independent variables
*/
protected static <T extends CalculusFieldElement<T>> FieldGradient<T>[] buildFieldGradientCartesianVector(final T[] stateVariables) {
final FieldGradientField<T> field = FieldGradientField.getField(stateVariables[0].getField(), GRADIENT_DIMENSION);
final FieldGradient<T>[] gradients = MathArrays.buildArray(field, GRADIENT_DIMENSION);
gradients[0] = FieldGradient.variable(GRADIENT_DIMENSION, 0, stateVariables[0]);
gradients[1] = FieldGradient.variable(GRADIENT_DIMENSION, 1, stateVariables[1]);
gradients[2] = FieldGradient.variable(GRADIENT_DIMENSION, 2, stateVariables[2]);
gradients[3] = FieldGradient.variable(GRADIENT_DIMENSION, 3, stateVariables[3]);
gradients[4] = FieldGradient.variable(GRADIENT_DIMENSION, 4, stateVariables[4]);
gradients[5] = FieldGradient.variable(GRADIENT_DIMENSION, 5, stateVariables[5]);
return gradients;
}
}