#include <CCable.h>

Inheritance diagram for CCable:

Collaboration diagram for CCable:

Public Member Functions
	CCable (const string &simObjectName, ISimObjectCreator *const creator)
	Reads parameters, registers states, input/output ports and shared resources. More...

void	OdeFcn (const double T, const double const X, double const XDot, const bool bIsMajorTimeStep)
	free allocated memory More...

void	InitialConditionSetup (const double T, const double const currentIC, double const updatedIC, ISimObjectCreator *const creator)
	Sets initial conditions based on the value of input ports. More...

void	FinalSetup (const double T, const double const X, ISimObjectCreator const creator)

const double *	ForceA (const double T, const double *const X)
	retrieves pointer to environment object

const double *	ForceB (const double T, const double *const X)
	output port. See PortDefs.h. Returns force at point A

void	computeEndForces (const double T, const double *const X)
	output port. See PortDefs.h. Returns force at point B

	CCable (std::string sSimObjectName, ISimObjectCreator *pCreator)
	The constructor sets the pointer to the output object and the parser object.

	~CCable ()
	The destructor deletes dynamically allocated memory.

void	OdeFcn (const double dT, const double const adX, double const adXDot, const bool bIsMajorTimeStep)

void	InitialConditionSetup (const double dT, const double const adCurrentIC, double const adUpdatedIC, ISimObjectCreator *const pCreator)
	functionality for setting initialconditions based on input port results.

void	FinalSetup (const double dT, const double const adX, ISimObjectCreator const pCreator)

void	CalcOutput (const double dT, const double *const adX)

const double *	OutForceA (const double dT, const double *const adX)

const double *	OutForceB (const double dT, const double *const adX)

const double *	OutPosA (const double dT, const double *const adX)

const double *	OutPosB (const double dT, const double *const adX)

Protected Member Functions
void	computeSegmentForces (const double T, const double X, const double pA, const double pB, const double vA, const double vB, double FA, double *FB)
	computes free nodes and both end forces More...

void	computeVirtualPoint (const double const target, const double const point, const double const targetVel, const double const pointVel, double virtualPoint, double virtualPointVel, double residual, double dResidual)
	Computes position and velocity of the virtual point. More...

void	testPositiveParam (double value, ISimObjectCreator *creator, string valueName)

void	computeElementTension (const double prev, const double curr, double *force)
	test if a parameter is positive, and reports error if not.

void	UpdateLength (double dNewLength, double dDeltaT)

void	UpdateStiffness (const double const adForceA, const double const adForceB)
	Updates the stiffness of the cable to ensure that this is not too large.

void	UpdateInertia ()
	Updates the inertia of the cable according to the changing length.

Protected Attributes
double	m_cableLength
	compute structural tension for a single element

double	m_cableWeight
	total cable length [m]

double	m_Emodulus
	cable weight [kg/m]

double	m_tensileCrossSectionArea
	Young's modulus of load bearing material [Pa].

double	m_displacementCrossSectionArea
	cross section area of load bearing material [m^2]

double	m_diameter
	displaced fluid volume per meter cable [m^2]

double	m_hydrodynamicDiameter
	cable diameter [m]

double	m_submergedWeight
	effective hydrodynamic diameter [m]

double	m_internalDamping
	weight of cable underwater [kg/m]

int	m_numElements
	structural axial damping. [N*s/m]

double	m_elementMass
	number of elements in the cable [#]

double	m_elementMassInverse
	mass of each element [kg]

double	m_segmentMass
	inverse mass of each element [kg^-1]

double	m_segmentSubmergedMass
	mass of each segment [kg]

double	m_segmentLength
	submerged weight of each element [kg]

double	m_segmentStiffness
	length of spring between elements [m]

int *	m_elementPositionIndex
	spring stiffness [N/m]

int *	m_elementVelocityIndex
	The relative index of the position state in the state array for each element [#].

ISignalPort *	m_PositionA
	The relative index of the velocity state in the state array for each element [#].

ISignalPort *	m_PositionB
	input port. Position of point A [m]

ISignalPort *	m_VelocityA
	input port. Position of point B [m]

ISignalPort *	m_VelocityB
	input port. Velocity of point A [m/s]

ISignalPort *	m_retractedLengthPortA
	input port. Velocity of point B [m/s]

ISignalPort *	m_retractedLengthPortB
	amount of retracted cable at endpoint A [m]

ISignalPort *	m_retractedSpeedPortA
	amount of retracted cable at endpoint B [m]

ISignalPort *	m_retractedSpeedPortB
	retraction rate at endpoint A [m/s]

double	m_endForceA [3]
	retraction rate at endpoint B [m/s]

double	m_endForceB [3]
	reactive force at endpoint A [N]

double	m_nodeForceA [3]
	reactive force at endpoint A [N]

double	m_nodeForceB [3]
	force on first free node at endpoint A [N]

double	m_retractedLengthA
	force on first free node at endpoint A [N]

double	m_retractedLengthB
	amount of retracted cable at endpoint A [m]

int	m_retractedNodesA
	amount of retracted cable at endpoint B [m]

int	m_retractedNodesB
	number of nodes currently on winch A

double	m_virtualPointA [3]
	number of nodes currently on winch B

double	m_virtualPointB [3]
	when cable is winched, the closest free node is attracted towards a ghost point "beyond" the actual endpoint [m]

double	m_virtualPointVelocityA [3]
	when cable is winched, the closest free node is attracted towards a ghost point "beyond" the actual endpoint [m]

double	m_virtualPointVelocityB [3]
	when cable is winched, the closest free node is attracted towards a ghost point "beyond" the actual endpoint [m/s]

double	m_residualA
	when cable is winched, the closest free node is attracted towards a ghost point "beyond" the actual endpoint [m/s]

double	m_residualB
	free length of closest free node [m]

ICommonComputation *	m_computeEndForces
	free length of closest free node [m]

const double *	m_posA
	computation node for endpoint reaction forces

const double *	m_posB
	Position of point A [m].

const double *	m_velA
	Position of point B [m].

const double *	m_velB
	Velocity of point A [m].

CEnvironment *	m_environment
	Velocity of point B [m].

ISignalPort *	m_pInLength
	The cable length input port.

ISignalPort *	m_pInVelA
	The velocity A input port.

ISignalPort *	m_pInVelB
	The velocity B input port.

ISignalPort *	m_pInPosA
	The position A input port.

ISignalPort *	m_pInPosB
	The position B input port.

int	m_IStates
	The index to the internal states of the cable.

ICommonComputation *	m_pCommonCalc
	Calculations necessary for more than one output port.

int	m_iNumElements
	The number of elements to divide the cable into.

int	m_iNumNodes
	The number of nodes of the cable.

double	m_dInertiaA
	The inertia of the end A.

double	m_dInertiaB
	The inertia of the end B.

double	m_adForceA [3]
	The force on the end A.

double	m_adForceB [3]
	The force on the end B.

double *	m_adLengths
	The lengths of the cable elements.

std::string	m_sCableName
	The identification name of the cable;.

CInternalCableWithBottomContact *	m_pInternalCable

SCableSpec	m_CableSpec
	The cable specification.

IBasicBottom **	m_ppBottom

ICurrentVel **	m_ppCurrentVel

Detailed Description

This class simulates a cable object consisting of one or more elements. Each element is of type CCableElDynStiff. Each element has methods to make it possible to use larger time steps in the integration. This is done by decreasing the stiffness of the element until the eigenfrequency of the element is low enough for the integration to be performed with the defined maximum step size.

Each element is regarded as a straight segment, responsible for calculating the forces acting on each of its ends, as well as the mass associated with each end node. The forces and mass from each element is added to the corresponding nodes of the cable, and the acceleration of each node is calculated in the OdeFcn.

The cable is influenced by:

Internal stiffness
Internal damping
Hydrodynamic normal and tangential forces
Buoyancy and gravity
Added mass

The calculation of these forces are more thoroughly explained in CCableElDynStiff.

Properties

Property	Default	Comment
NumElements	2	The number of cable elements.
Length	100	Not used, as it is now read from an input port.
Density	-	The density of the cable (kg/m^3).
NumericalDamping	0	Added numerical damping on each node. The damping force is calculated as \(\vec F_i = -k m_i \vec v_i\), where \(\vec F_i\) is the added damping force, \(k\) is the numerical damping factor, \(m_i\) is the node inertia and \(\vec v_i\) is the velocity of the node.
Diameter	-	The diameter of the cable.
E	-	The Young's modulus (elasticity) of the cable.
DampingRatio	1	The relative axial damping of the cable. 0 is no damping, 1 is critical damping.
FluidRho	1025	The density of the ambient fluid.
MaxStepLength	0.01	Controls the stiffness of the cable to allow integration with step lengths up to this value.
MaxTension	-	The maximum tension. If above this value, the tension is set to this this value.
MaxAcceleration	1000	The maximum acceleration. If above this value, the acceleration is set to this this value.
StepSafetyFactor	50	A safety factor between the MaxStepLength and the one used for calculating the stiffness of the cable.
MeanTension	0	Possibility to add a mean tension to correct for decreased stiffness of the cable.
AdaptationPeriod	0	If above zero, this tells the cable to correct its initial length to avoid length errors because of decreased stiffness.
MaterialName	Trawl/Wire2	The material to use for visualizing the cable.
NumFaces	5	The number of planes to visualize the cable surface.
DrawScale	2	The scale of the visual appearance of the cable. This is used to make it more visible.

Input ports

Tag	Size	Comment
Length	1	The length of the cable.
PosA	3	The position of end A.
PosB	3	The position of end B.
VelA	3	The velocity of end A.
VelB	3	The velocity of end B.
VelWater	3	The velocity of the water.

Output ports

Tag	Size	Comment
ForceA	3	The force from end A of the cable.
ForceB	3	The force from end B of the cable.
PosA	3	The position of end A.
PosB	3	The position of end B.

Revision history:

24.07.2007 KJR: Initial version.
24.11.2010 KJR: Added some class documentation.

Constructor & Destructor Documentation

◆ CCable()

CCable::CCable	(	const string &	simObjectName,
		ISimObjectCreator *const	creator
	)

This constructor performs all initial setup for a point mass simobject. Reading in parameters, setting up communication interface i.e. output ports, input ports, and states, plus additional 'one time only' resource setup.

Parameters

[in]	simObjectName	-> The name of the simobject. Used primarily by superclass constructor
[in]	creator	-> Retrieve parameters. Register states, ports and shared resources

Member Function Documentation

◆ computeSegmentForces()

void CCable::computeSegmentForces	(	const double	T,
		const double *	X,
		const double *	pA,
		const double *	pB,
		const double *	vA,
		const double *	vB,
		double *	FA,
		double *	FB
	)

protected

Computes all forces acting on an element

Computes structural and environmental forces acting on an element i.e. the cable length between two cable nodes, and distributes the total force on the two nodes.

Parameters

[in]	T	-> current simulation time
[in]	X	-> current simulation state
[in]	pA	-> position of element A
[in]	pB	-> position of element B
[in]	vA	-> velocity of element A
[in]	vB	-> velocity of element B
[out]	FA	-> force on element A
[out]	FB	-> force on element B

◆ computeVirtualPoint()

void CCable::computeVirtualPoint	(	const double *const	target,
		const double *const	point,
		const double *const	targetVel,
		const double *const	pointVel,
		double *	virtualPoint,
		double *	virtualPointVel,
		double	residual,
		double	dResidual
	)

protected

Winch functionality is implemented by pulling the closest free node towards a virtual point rather than the actual endpoint.

Parameters

[in]	target	-> actual endpoint position
[in]	point	-> position of free node
[in]	targetVel	-> actual endpoint velocity
[in]	pointVel	-> velocity of free node
[in]	residual	-> free element length
[in]	dResidual	-> rate of change in free element length
[out]	virtualPoint	-> position of virtual point
[out]	virtualPointVel	-> velocity of virtual point

◆ InitialConditionSetup()

void CCable::InitialConditionSetup	(	const double	T,
		const double *const	currentIC,
		double *const	updatedIC,
		ISimObjectCreator *const	creator
	)

Sets initial conditions based on the value of input ports. Element positions of free nodes are equally distributed between endpoint positions. Element Velocity are linearly interpolated between endpoint velocity

Parameters

[in]	T	-> The time at the beginning of the simulation. Usually but not necessarily zero
[in]	currentIC	-> Array of initial conditions. If the value is QNAN, the value is not set yet and can be set by the SimObject, otherwise the value is set, and can not be changed. Trying to change an already set value will trigger an error
[in]	creator	-> Report back to creator if output port are not ready
[out]	updatedIC	-> Array of ONAN. Any initial condition that are ready to be set, should be written to this array.

◆ OdeFcn()

void CCable::OdeFcn	(	const double	T,
		const double *const	X,
		double *const	XDot,
		const bool	bIsMajorTimeStep
	)

Computes object derivatives as a function of time, states and input ports

Returns state derivatives. Velocity as derivative of position, external-force/mass and gravity as derivative of velocity. Adjusts position of not-free nodes.

Parameters

[in]	T	-> current simulation time
[in]	X	-> current simulation state
[out]	XDot	-> state derivatives
[in]	bIsMajorTimeStep	-> Is this a major time step?

The documentation for this class was generated from the following files:

reloadrepos/fhsim_base/src/cable/Cable.h
reloadrepos/fhsim_extras/src/cable/CCable.h

Public Member Functions

Protected Member Functions

Protected Attributes

Detailed Description

Constructor & Destructor Documentation

◆ CCable()

Member Function Documentation

◆ computeSegmentForces()

◆ computeVirtualPoint()

◆ InitialConditionSetup()

◆ OdeFcn()