agi.foundation.propagators

(agi.foundation.orbitpropagation-2023r1.jar)

Class PropagationEulerianAxes

java.lang.Object

agi.foundation.infrastructure.DefinitionalObject

agi.foundation.propagators.advanced.PropagationStateElement

agi.foundation.propagators.PropagationEulerianAxes

All Implemented Interfaces:

ICloneWithContext, IEnumerateDependencies, IEquatableDefinition, IFreezable

public class PropagationEulerianAxes
extends PropagationStateElement

A PropagationStateElement representing the attitude (and angular velocity) of a rigid body with its angular acceleration represented by Euler's equations of motion. Body-fixed coordinates are used for the initial attitude, angular velocity, and moment of inertia matrix.

While this class is initialized using UnitQuaternion as an attitude parameterization, the rotation vector is used internally to propagate the attitude. Thus, the NumericalPropagationStateHistory created by propagating this state produces a DateMotionCollection<RotationVectorAngularVelocity> after GetDateMotionCollection<RotationVectorAngularVelocity> is called. This collection can be transformed into a DateMotionCollection<UnitQuaternion, Cartesian> using the static methods available in RotationVectorAngularVelocity. Finally, the DateMotionCollection<UnitQuaternion, Cartesian> can be used to initialize a RotationalMotionInterpolator or AxesInterpolator to provide smooth interpolation of the attitude results.

Constructor Summary

Constructors

Modifier	Constructor and Description
	PropagationEulerianAxes() Initializes a new instance.
protected	PropagationEulerianAxes(PropagationEulerianAxes existingInstance, CopyContext context) Initializes a new instance as a copy of an existing instance.
	PropagationEulerianAxes(String id, ReferenceFrame propagationFrame, UnitQuaternion initialAttitudeQuaternion, Cartesian initialAngularVelocity, Matrix3By3Symmetric inertiaMatrix) Initializes a new instance.

Method Summary

Modifier and Type	Method and Description
protected boolean	checkForSameDefinition(PropagationEulerianAxes other) Checks to determine if another instance has the same definition as this instance and returns true if it does.
protected boolean	checkForSameDefinition(PropagationStateElement other) Checks to determine if another instance has the same definition as this instance and returns true if it does.
Object	clone(CopyContext context) Clones this object using the specified context.
protected int	computeCurrentDefinitionHashCode() Computes a hash code based on the current properties of this object.
void	enumerateDependencies(DependencyEnumerator enumerator) Enumerates the dependencies of this object by calling DependencyEnumerator#enumerate(T) for each object that this object directly depends upon.
protected void	freezeAggregatedObjects() Called by DefinitionalObject.freeze() to also freeze any objects that are considered to be a part of this object.
List<TorqueModel>	getAppliedTorques() Gets a list of the torques applied on the IntegrationAxes (get).
PropagationStateElementConverter	getConverter(EvaluatorGroup group, Motion1<int[]> stateInputIndices) Gets an instance of an output type which can convert the output of propagation back into the native type of this state element.
PropagationStateElementEvaluator	getDerivatives(EvaluatorGroup group) This is used by the NumericalPropagatorDefinition to obtain an instance of a state element evaluator that can compute the derivatives of this element of the state during propagation.
int	getDimension() Gets the number of parameters (per Order (get)) within this element.
Matrix3By3Symmetric	getInertiaMatrix() Gets the 3x3 inertia matrix of the body on which the torques are applied.
Cartesian	getInitialAngularVelocity() Gets the initial angular velocity expressed in body-fixed axes.
UnitQuaternion	getInitialAttitudeQuaternion() Gets the initial attitude quaternion that rotates from the IntegrationFrame (get / set) to the body-fixed reference frame.
Axes	getIntegrationAxes() Gets a Axes which is parameterized on the attitude and angular velocity in the state during integration.
ReferenceFrame	getIntegrationFrame() Gets the inertial ReferenceFrame in which the attitude is defined.
int	getOrder() Gets the order of the differential equation corresponding to this element.
PropagationStateParameter	getStateParameter() Gets a parameter which represents the state during propagation.
IUpdatePriorToStep	getStateUpdater(EvaluatorGroup group) Transforms the rotation vector that is used internally to propagate the attitude to avoid the singularity at rotation vector magnitudes near 2*pi radians.
void	setInertiaMatrix(Matrix3By3Symmetric value) Sets the 3x3 inertia matrix of the body on which the torques are applied.
void	setInitialAngularVelocity(Cartesian value) Sets the initial angular velocity expressed in body-fixed axes.
void	setInitialAttitudeQuaternion(UnitQuaternion value) Sets the initial attitude quaternion that rotates from the IntegrationFrame (get / set) to the body-fixed reference frame.
void	setIntegrationFrame(ReferenceFrame value) Sets the inertial ReferenceFrame in which the attitude is defined.
void	setStateParameter(PropagationStateParameter value) Sets a parameter which represents the state during propagation.

Methods inherited from class agi.foundation.propagators.advanced.PropagationStateElement

checkForSameDefinition, getIdentification, getIncludeHighestDerivativeInOutput, setIdentification, setIncludeHighestDerivativeInOutput

Methods inherited from class agi.foundation.infrastructure.DefinitionalObject

areSameDefinition, areSameDefinition, areSameDefinition, areSameDefinition, areSameDefinition, collectionItemsAreSameDefinition, collectionItemsAreSameDefinition, collectionItemsAreSameDefinition, dictionaryItemsAreSameDefinition, freeze, getCollectionHashCode, getCollectionHashCode, getCollectionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDictionaryHashCode, getIsFrozen, isSameDefinition, throwIfFrozen

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

PropagationEulerianAxes

public PropagationEulerianAxes()

Initializes a new instance. By default, Earth's inertial frame will be used as the propagation frame, the identity quaternion will be used as the initial attitude, the zero vector will be used as the initial angular velocity, and the identity matrix will be used as the inertia matrix.

PropagationEulerianAxes

public PropagationEulerianAxes(String id,
                               ReferenceFrame propagationFrame,
                               @Nonnull
                               UnitQuaternion initialAttitudeQuaternion,
                               @Nonnull
                               Cartesian initialAngularVelocity,
                               @Nonnull
                               Matrix3By3Symmetric inertiaMatrix)

Initializes a new instance.

Parameters:

id - A unique string identifying this attitude in the output.

propagationFrame - The inertial frame in which to propagate.

initialAttitudeQuaternion - The body-fixed attitude at the starting epoch of propagation with respect to the axes of the propagationFrame.

initialAngularVelocity - The body-fixed angular velocity at the starting epoch of propagation.

inertiaMatrix - The 3x3 body-fixed, positive definite inertia matrix of the rigid body.

PropagationEulerianAxes

protected PropagationEulerianAxes(@Nonnull
                                  PropagationEulerianAxes existingInstance,
                                  @Nonnull
                                  CopyContext context)

Initializes a new instance as a copy of an existing instance.

See ICloneWithContext.clone(CopyContext) for more information about how to implement this constructor in a derived class.

Parameters:

existingInstance - The existing instance to copy.

context - A CopyContext that controls the depth of the copy.

Throws:

ArgumentNullException - Thrown when existingInstance or context is null.

Method Detail

clone

public Object clone(CopyContext context)

Clones this object using the specified context.

This method should be implemented to call a copy constructor on the class of the object being cloned. The copy constructor should take the CopyContext as a parameter in addition to the existing instance to copy. The copy constructor should first call CopyContext.addObjectMapping(T, T) to identify the newly constructed instance as a copy of the existing instance. It should then copy all fields, using CopyContext.updateReference(T) to copy any reference fields.

A typical implementation of ICloneWithContext:

public static class MyClass implements ICloneWithContext {
    public MyClass(MyClass existingInstance, CopyContext context) {
        context.addObjectMapping(existingInstance, this);
        someReference = context.updateReference(existingInstance.someReference);
    }

    @Override
    public final Object clone(CopyContext context) {
        return new MyClass(this, context);
    }

    private Object someReference;
}

In general, all fields that are reference types should be copied with a call to CopyContext.updateReference(T). There are a couple of exceptions:

1. Fields that are aggregate parts of the object should always be copied. A referenced object is an aggregate if properties or methods on the object being copied can modify the externally-visible value of the referenced object.
2. If the semantics of the referenced object require that it have a single parent, owner, context, etc., and the object being copied is that parent, owner, or context, then the referenced object should always be copied.

If one of these exceptions applies, the CopyContext should be given an opportunity to update the reference before the reference is copied explicitly. Use CopyContext.updateReference(T) to update the reference. If CopyContext.updateReference(T) returns the original object, indicating that the context does not have a replacement registered, then copy the object manually by invoking a Clone method, a copy constructor, or by manually constructing a new instance and copying the values.

alwaysCopy = context.updateReference(existingInstance.alwaysCopy);
if (existingInstance.alwaysCopy != null && alwaysCopy == existingInstance.alwaysCopy) {
    alwaysCopy = (AlwaysCopy) existingInstance.alwaysCopy.clone(context);
}

If you are implementing an evaluator (a class that implements IEvaluator), the IEvaluator.updateEvaluatorReferences(agi.foundation.infrastructure.CopyContext) method shares some responsibilities with the copy context constructor. Code duplication can be avoided by doing the following:

1. For references to other evaluators ONLY, simply assign the reference in the constructor instead of calling CopyContext.updateReference(T). You should still call CopyContext.updateReference(T) on any references to non-evaluators.
2. Call IEvaluator.updateEvaluatorReferences(agi.foundation.infrastructure.CopyContext) as the last line in the constructor and pass it the same CopyContext passed to the constructor.
3. Implement IEvaluator.updateEvaluatorReferences(agi.foundation.infrastructure.CopyContext) as normal. See the reference documentation for IEvaluator.updateEvaluatorReferences(agi.foundation.infrastructure.CopyContext) for more information on implementing that method.

public MyClass(MyClass existingInstance, CopyContext context) {
    super(existingInstance, context);
    someReference = context.updateReference(existingInstance.someReference);
    evaluatorReference = existingInstance.evaluatorReference;
    updateEvaluatorReferences(context);
}

@Override
public void updateEvaluatorReferences(CopyContext context) {
    evaluatorReference = context.updateReference(evaluatorReference);
}

@Override
public Object clone(CopyContext context) {
    return new MyClass(this, context);
}

private Object someReference;
private IEvaluator evaluatorReference;

Specified by:

clone in interface ICloneWithContext

Specified by:

clone in class DefinitionalObject

Parameters:

context - The context to use to perform the copy.

Returns:

A new instance which is a copy of this object.

checkForSameDefinition

protected final boolean checkForSameDefinition(PropagationStateElement other)

Checks to determine if another instance has the same definition as this instance and returns true if it does. Derived classes MUST override this method and check all new fields introduced by the derived class for definitional equivalence. It is NOT necessary to check base class fields because the base class will already have done that. When overriding this method, you should NOT call the base implementation because it will return false for all derived-class instances. Derived classes should check the type of other to preserve the symmetric nature of IEquatableDefinition.isSameDefinition(java.lang.Object).

Specified by:

checkForSameDefinition in class PropagationStateElement

Parameters:

other - The other instance to compare to this one.

Returns:

true if the two objects are defined equivalently; otherwise false.

checkForSameDefinition

protected boolean checkForSameDefinition(PropagationEulerianAxes other)

Checks to determine if another instance has the same definition as this instance and returns true if it does. Derived classes MUST override this method and check all new fields introduced by the derived class for definitional equivalence. It is NOT necessary to check base class fields because the base class will already have done that. When overriding this method, you should NOT call the base implementation because it will return false for all derived-class instances. Derived classes should check the type of other to preserve the symmetric nature of IEquatableDefinition.isSameDefinition(java.lang.Object).

Parameters:

other - The other instance to compare to this one.

Returns:

true if the two objects are defined equivalently; otherwise false.

computeCurrentDefinitionHashCode

protected int computeCurrentDefinitionHashCode()

Computes a hash code based on the current properties of this object. Derived classes MUST override this method and compute a hash code that combines: a unique hash code seed, the base implementation result, and the hash codes of all new fields introduced by the derived class which are used in the PropagationEulerianAxes.checkForSameDefinition(agi.foundation.propagators.advanced.PropagationStateElement) method.

Overrides:

computeCurrentDefinitionHashCode in class PropagationStateElement

Returns:

The computed hash code.

enumerateDependencies

public void enumerateDependencies(DependencyEnumerator enumerator)

Enumerates the dependencies of this object by calling DependencyEnumerator#enumerate(T) for each object that this object directly depends upon. Derived classes which contain additional dependencies MUST override this method, call the base implementation, and enumerate dependencies introduced by the derived class.

Specified by:

enumerateDependencies in interface IEnumerateDependencies

Overrides:

enumerateDependencies in class DefinitionalObject

Parameters:

enumerator - The enumerator that is informed of the dependencies of this object.

freezeAggregatedObjects

protected void freezeAggregatedObjects()

Called by DefinitionalObject.freeze() to also freeze any objects that are considered to be a part of this object. Derived classes which contain additional aggregated objects MUST override this method, call the base implementation, and freeze aggregated objects introduced by the derived class. The objects that need to be frozen in this method are frequently created in this object's constructor and are not settable via properties.

Overrides:

freezeAggregatedObjects in class DefinitionalObject

getDimension

public int getDimension()

Gets the number of parameters (per Order (get)) within this element.

Specified by:

getDimension in class PropagationStateElement

getOrder

public int getOrder()

Gets the order of the differential equation corresponding to this element.

Specified by:

getOrder in class PropagationStateElement

getInitialAttitudeQuaternion

@Nonnull
public final UnitQuaternion getInitialAttitudeQuaternion()

Gets the initial attitude quaternion that rotates from the IntegrationFrame (get / set) to the body-fixed reference frame.

setInitialAttitudeQuaternion

public final void setInitialAttitudeQuaternion(@Nonnull
                                               UnitQuaternion value)

Sets the initial attitude quaternion that rotates from the IntegrationFrame (get / set) to the body-fixed reference frame.

getInitialAngularVelocity

@Nonnull
public final Cartesian getInitialAngularVelocity()

Gets the initial angular velocity expressed in body-fixed axes.

setInitialAngularVelocity

public final void setInitialAngularVelocity(@Nonnull
                                            Cartesian value)

Sets the initial angular velocity expressed in body-fixed axes.

getIntegrationAxes

public final Axes getIntegrationAxes()

Gets a Axes which is parameterized on the attitude and angular velocity in the state during integration. This axes is only valid while the NumericalPropagator is running. For more general use, a AxesInterpolator or a RotationalMotionInterpolator should be created from the NumericalPropagationStateHistory produced by the propagator.

getStateParameter

public PropagationStateParameter getStateParameter()

Gets a parameter which represents the state during propagation. In general, users should never need to explicitly set this property. It should only be set when multiple NumericalPropagator objects are running in the same EvaluatorGroup, such as when elements of a state require additional instances of a NumericalPropagator inside their implementation in order to produce their values. In such cases, it may be necessary to distinguish between the state of the exterior propagator and the state of the interior propagator. In these cases, it is up to the user to ensure that both the state and all of its elements are configured with the same parameter. Otherwise, the state will throw an exception when creating its propagator.

Specified by:

getStateParameter in class PropagationStateElement

setStateParameter

public void setStateParameter(PropagationStateParameter value)

Sets a parameter which represents the state during propagation. In general, users should never need to explicitly set this property. It should only be set when multiple NumericalPropagator objects are running in the same EvaluatorGroup, such as when elements of a state require additional instances of a NumericalPropagator inside their implementation in order to produce their values. In such cases, it may be necessary to distinguish between the state of the exterior propagator and the state of the interior propagator. In these cases, it is up to the user to ensure that both the state and all of its elements are configured with the same parameter. Otherwise, the state will throw an exception when creating its propagator.

Specified by:

setStateParameter in class PropagationStateElement

getAppliedTorques

public final List<TorqueModel> getAppliedTorques()

Gets a list of the torques applied on the IntegrationAxes (get). These torques will be converted to the body-fixed frame before they are evaluated.

getInertiaMatrix

@Nonnull
public final Matrix3By3Symmetric getInertiaMatrix()

Gets the 3x3 inertia matrix of the body on which the torques are applied. This must be defined in the same body-fixed frame that the angular velocity is defined.

setInertiaMatrix

public final void setInertiaMatrix(@Nonnull
                                   Matrix3By3Symmetric value)

Sets the 3x3 inertia matrix of the body on which the torques are applied. This must be defined in the same body-fixed frame that the angular velocity is defined.

getIntegrationFrame

public final ReferenceFrame getIntegrationFrame()

Gets the inertial ReferenceFrame in which the attitude is defined. By default, the integration frame is set to the InertialFrame (get / set) of the Earth.

setIntegrationFrame

public final void setIntegrationFrame(ReferenceFrame value)

Sets the inertial ReferenceFrame in which the attitude is defined. By default, the integration frame is set to the InertialFrame (get / set) of the Earth.

getConverter

public PropagationStateElementConverter getConverter(EvaluatorGroup group,
                                                     @Nonnull
                                                     Motion1<int[]> stateInputIndices)

Gets an instance of an output type which can convert the output of propagation back into the native type of this state element. This method is also responsible for configuring the state parameter and the state input indices on any parameterized geometry types used by this element. Each parameterized geometry type will have a static configuration method which will allow it to configure itself in a particular EvaluatorGroup.

Specified by:

getConverter in class PropagationStateElement

Parameters:

group - The evaluator group in which to configure the parameters.

stateInputIndices - The set of indices corresponding to the location of each value or derivative of this state element in the overall state.

Returns:

The output instance associated with this state element.

getDerivatives

public PropagationStateElementEvaluator getDerivatives(EvaluatorGroup group)

This is used by the NumericalPropagatorDefinition to obtain an instance of a state element evaluator that can compute the derivatives of this element of the state during propagation. It cannot be used outside of a NumericalPropagator as the geometry for the propagation state will be unavailable.

Specified by:

getDerivatives in class PropagationStateElement

Parameters:

group - The group in which to create the evaluator and its dependents.

Returns:

The evaluator that can compute the derivatives of this element of the state.

getStateUpdater

@Nonnull
public IUpdatePriorToStep getStateUpdater(EvaluatorGroup group)

Transforms the rotation vector that is used internally to propagate the attitude to avoid the singularity at rotation vector magnitudes near 2*pi radians. If R is the rotation vector and r is its current magnitude, the transformation is (r-2*pi)*R/r -> R and only occurs if r > pi. This transformation ensures that the rotation vector never approaches its singularity.

Overrides:

getStateUpdater in class PropagationStateElement

Parameters:

group - The EvaluatorGroup the state updater will be part of.

Returns:

An IUpdatePriorToStep that transforms the rotation vector if its magnitude is greater than pi.