CartesianFuel.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
* 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.control.indirect.adjoint.cost;
import org.hipparchus.CalculusFieldElement;
import org.hipparchus.Field;
import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.orekit.propagation.FieldSpacecraftState;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.events.EventDetectionSettings;
import org.orekit.propagation.events.EventDetector;
import org.orekit.propagation.events.FieldEventDetectionSettings;
import org.orekit.propagation.events.FieldEventDetector;
import org.orekit.propagation.events.handlers.EventHandler;
import org.orekit.propagation.events.handlers.FieldEventHandler;
import org.orekit.propagation.events.handlers.FieldResetDerivativesOnEvent;
import org.orekit.propagation.events.handlers.ResetDerivativesOnEvent;
import java.util.stream.Stream;
/**
* Class for fuel cost with Cartesian coordinates.
* It is the integral over time of the Euclidean norm of the thrust vector.
*
* @author Romain Serra
* @see CartesianCost
* @since 13.0
*/
public class CartesianFuel extends AbstractCartesianCost {
/** Maximum value of thrust force Euclidean norm. */
private final double maximumThrustMagnitude;
/** Detection settings for singularity detection. */
private final EventDetectionSettings eventDetectionSettings;
/**
* Constructor with default detection settings.
* @param name name
* @param massFlowRateFactor mass flow rate factor
* @param maximumThrustMagnitude maximum thrust magnitude
*/
public CartesianFuel(final String name, final double massFlowRateFactor, final double maximumThrustMagnitude) {
this(name, massFlowRateFactor, maximumThrustMagnitude, EventDetectionSettings.getDefaultEventDetectionSettings());
}
/**
* Constructor.
* @param name name
* @param massFlowRateFactor mass flow rate factor
* @param maximumThrustMagnitude maximum thrust magnitude
* @param eventDetectionSettings singularity event detection settings
*/
public CartesianFuel(final String name, final double massFlowRateFactor, final double maximumThrustMagnitude,
final EventDetectionSettings eventDetectionSettings) {
super(name, massFlowRateFactor);
this.maximumThrustMagnitude = maximumThrustMagnitude;
this.eventDetectionSettings = eventDetectionSettings;
}
/**
* Getter for event detection settings.
* @return detection settings.
*/
public EventDetectionSettings getEventDetectionSettings() {
return eventDetectionSettings;
}
/**
* Evaluate switching function (whose sign determines the bang-bang control profile).
* @param adjointVariables adjoint vector
* @param mass mass
* @return value of switch function
*/
private double evaluateSwitchFunction(final double[] adjointVariables, final double mass) {
return getAdjointVelocityNorm(adjointVariables) / mass - adjointVariables[6] * getMassFlowRateFactor() - 1.;
}
/**
* Evaluate switching function (whose sign determines the bang-bang control profile).
* @param adjointVariables adjoint vector
* @param mass mass
* @param <T> field type
* @return value of switch function
*/
private <T extends CalculusFieldElement<T>> T evaluateFieldSwitchFunction(final T[] adjointVariables, final T mass) {
return getFieldAdjointVelocityNorm(adjointVariables).divide(mass).subtract(adjointVariables[6].multiply(getMassFlowRateFactor())).subtract(1.);
}
/**
* Computes the direction of thrust.
* @param adjointVariables adjoint vector
* @return thrust direction
*/
private Vector3D getThrustDirection(final double[] adjointVariables) {
return new Vector3D(adjointVariables[3], adjointVariables[4], adjointVariables[5]).normalize();
}
/**
* Computes the direction of thrust.
* @param adjointVariables adjoint vector
* @param <T> field type
* @return thrust direction
*/
private <T extends CalculusFieldElement<T>> FieldVector3D<T> getFieldThrustDirection(final T[] adjointVariables) {
return new FieldVector3D<>(adjointVariables[3], adjointVariables[4], adjointVariables[5]).normalize();
}
/** {@inheritDoc} */
@Override
public Vector3D getThrustAccelerationVector(final double[] adjointVariables, final double mass) {
final double switchFunction = evaluateSwitchFunction(adjointVariables, mass);
if (switchFunction > 0.) {
return getThrustDirection(adjointVariables).scalarMultiply(maximumThrustMagnitude / mass);
} else {
return Vector3D.ZERO;
}
}
/** {@inheritDoc} */
@Override
public <T extends CalculusFieldElement<T>> FieldVector3D<T> getFieldThrustAccelerationVector(final T[] adjointVariables,
final T mass) {
final T switchFunction = evaluateFieldSwitchFunction(adjointVariables, mass);
if (switchFunction.getReal() > 0.) {
return getFieldThrustDirection(adjointVariables).scalarMultiply(mass.reciprocal().multiply(maximumThrustMagnitude));
} else {
return FieldVector3D.getZero(mass.getField());
}
}
/** {@inheritDoc} */
@Override
public void updateAdjointDerivatives(final double[] adjointVariables, final double mass,
final double[] adjointDerivatives) {
final double switchFunction = evaluateSwitchFunction(adjointVariables, mass);
if (switchFunction > 0.) {
adjointDerivatives[6] += getAdjointVelocityNorm(adjointVariables) * maximumThrustMagnitude / (mass * mass);
}
}
/** {@inheritDoc} */
@Override
public <T extends CalculusFieldElement<T>> void updateFieldAdjointDerivatives(final T[] adjointVariables,
final T mass,
final T[] adjointDerivatives) {
final T switchFunction = evaluateFieldSwitchFunction(adjointVariables, mass);
if (switchFunction.getReal() > 0.) {
adjointDerivatives[6] = adjointDerivatives[6].add(getFieldAdjointVelocityNorm(adjointVariables).multiply(maximumThrustMagnitude).divide(mass.square()));
}
}
/** {@inheritDoc} */
@Override
public double getHamiltonianContribution(final double[] adjointVariables, final double mass) {
final Vector3D thrustForce = getThrustAccelerationVector(adjointVariables, mass).scalarMultiply(mass);
return -thrustForce.getNorm();
}
/** {@inheritDoc} */
@Override
public <T extends CalculusFieldElement<T>> T getFieldHamiltonianContribution(final T[] adjointVariables, final T mass) {
final FieldVector3D<T> thrustForce = getFieldThrustAccelerationVector(adjointVariables, mass).scalarMultiply(mass);
return thrustForce.getNorm().negate();
}
/** {@inheritDoc} */
@Override
public Stream<EventDetector> getEventDetectors() {
return Stream.of(new SwitchDetector(getEventDetectionSettings()));
}
/** {@inheritDoc} */
@Override
public <T extends CalculusFieldElement<T>> Stream<FieldEventDetector<T>> getFieldEventDetectors(final Field<T> field) {
return Stream.of(new FieldSwitchDetector<>(new FieldEventDetectionSettings<>(field, getEventDetectionSettings())));
}
/**
* Event detector for bang-bang switches.
*/
private class SwitchDetector implements EventDetector {
/** Event detection settings. */
private final EventDetectionSettings eventDetectionSettings;
/**
* Constructor.
* @param eventDetectionSettings detection settings
*/
SwitchDetector(final EventDetectionSettings eventDetectionSettings) {
this.eventDetectionSettings = eventDetectionSettings;
}
/** {@inheritDoc} */
@Override
public double g(final SpacecraftState state) {
final double[] adjoint = state.getAdditionalState(getAdjointName());
return evaluateSwitchFunction(adjoint, state.getMass());
}
@Override
public EventDetectionSettings getDetectionSettings() {
return eventDetectionSettings;
}
@Override
public EventHandler getHandler() {
return new ResetDerivativesOnEvent();
}
}
/**
* Field event detector for bang-bang switches.
*/
private class FieldSwitchDetector<T extends CalculusFieldElement<T>> implements FieldEventDetector<T> {
/** Event detection settings. */
private final FieldEventDetectionSettings<T> eventDetectionSettings;
/**
* Constructor.
* @param eventDetectionSettings detection settings
*/
FieldSwitchDetector(final FieldEventDetectionSettings<T> eventDetectionSettings) {
this.eventDetectionSettings = eventDetectionSettings;
}
/** {@inheritDoc} */
@Override
public T g(final FieldSpacecraftState<T> state) {
final T[] adjoint = state.getAdditionalState(getAdjointName());
return evaluateFieldSwitchFunction(adjoint, state.getMass());
}
@Override
public FieldEventDetectionSettings<T> getDetectionSettings() {
return eventDetectionSettings;
}
@Override
public FieldEventHandler<T> getHandler() {
return new FieldResetDerivativesOnEvent<>();
}
}
}