SurgSim::Physics::MlcpPhysicsProblem Struct Reference

A description of a physical mixed LCP system to be solved. More...

#include <MlcpPhysicsProblem.h>

Inheritance diagram for SurgSim::Physics::MlcpPhysicsProblem:

Public Member Functions
	~MlcpPhysicsProblem () override
	Destructor.
void	updateConstraint (const Eigen::SparseVector< double, Eigen::RowMajor, ptrdiff_t > &newSubH, const Vector &newCHt, size_t indexSubC, size_t indexNewSubH)
	Applies a new constraint to a specific Representation. More...
void	setZero (size_t numDof, size_t numConstraintDof, size_t numConstraints) override
	Resize an MlcpPhysicsProblem and set to zero. More...
Public Member Functions inherited from SurgSim::Math::MlcpProblem
virtual	~MlcpProblem ()
	Destructor.
size_t	getSize () const
	Gets the size of the system. More...
bool	isConsistent () const
	Checks if the sizes of various elements of the system are consistent with each other. More...

Static Public Member Functions
static MlcpPhysicsProblem	Zero (size_t numDof, size_t numConstraintDof, size_t numConstraints)
	Initialize an MlcpPhysicsProblem with zero values. More...
Static Public Member Functions inherited from SurgSim::Math::MlcpProblem
static MlcpProblem	Zero (size_t numDof, size_t numConstraintDof, size_t numConstraints)
	Initialize an MlcpProblem with zero values. More...

Public Attributes
Eigen::SparseMatrix< double, Eigen::RowMajor, ptrdiff_t >	H
	The matrix \(\mathbf{H}\), which is a matrix of size \(c\times n\) that converts from the \(n\) degrees of freedom in the system (i.e., the sum of all the DOF over all the representations in the scene), to the \(c\) degrees of freedom summed over all the constraints being applied to the system. More...
Matrix	CHt
	The matrix \(\mathbf{C\;H^T}\), which is a matrix of size \(n\times c\) that is used to convert the vector of \(c\) constraint forces to the \(n\) displacements of each degree of freedom of the system. More...
Public Attributes inherited from SurgSim::Math::MlcpProblem
Matrix	A
	Matrix \(\mathbf{A}\) used to describe the mixed LCP problem.
Vector	b
	Vector \(b\) used to describe the mixed LCP problem.
Vector	mu
	A vector of friction coefficients used to describe the mixed LCP problem. More...
std::vector< MlcpConstraintType >	constraintTypes
	A vector of constraint types used to describe the mixed LCP problem. More...

Additional Inherited Members
Public Types inherited from SurgSim::Math::MlcpProblem
typedef Eigen::Matrix< double, Eigen::Dynamic, Eigen::Dynamic >	Matrix
typedef Eigen::Matrix< double, Eigen::Dynamic, 1 >	Vector

Detailed Description

A description of a physical mixed LCP system to be solved.

This extends the pure mathematical MLCP problem by storing the intermediate matrices H and CHt that are necessary to physically interpret the solution.

Note that the matrix \(\mathbf{A}\) used in the MlcpProblem is computed in the physical problem as \(\mathbf{H\;C\;H^T}\), where \(\mathbf{C}\) is the compliance matrix. For contact constraints, \(b\) is the initial signed displacements between the colliding representations, \(b_i \lt 0\) when the representations interpenetrate, \(x\) is the forces to apply at each contact to prevent penetration, and \(c\) is the signed displacements after the forces are applied.

Note

The solution to the MLCP will only address the constraints that were provided, and application of \(x\) to the representations in the scene may cause new collisions for constraints that were not originally incorporated in the MLCP.

See also

SurgSim::Math::MlcpProblem

Member Function Documentation

setZero()

void SurgSim::Physics::MlcpPhysicsProblem::setZero ( size_t  numDof, size_t  numConstraintDof, size_t  numConstraints  )

overridevirtual

Resize an MlcpPhysicsProblem and set to zero.

Parameters

numDof	the total degrees of freedom.
numConstraintDof	the total constrained degrees of freedom.
numConstraints	the number of constraints.

Reimplemented from SurgSim::Math::MlcpProblem.

updateConstraint()

void SurgSim::Physics::MlcpPhysicsProblem::updateConstraint	(	const Eigen::SparseVector< double, Eigen::RowMajor, ptrdiff_t > &	newSubH,
		const Vector &	newCHt,
		size_t	indexSubC,
		size_t	indexNewSubH
	)

Applies a new constraint to a specific Representation.

Parameters

newSubH	New constraint to be added to H
newCHt	Compliance matrix (system matrix inverse) times newSubH
indexSubC	Index of the Representation's compliance matrix
indexNewSubH	Index of the new constraint within H

Zero()

MlcpPhysicsProblem SurgSim::Physics::MlcpPhysicsProblem::Zero ( size_t  numDof, size_t  numConstraintDof, size_t  numConstraints  )

static

Initialize an MlcpPhysicsProblem with zero values.

Parameters

numDof	the total degrees of freedom for the MlcpPhysicsProblem to be constructed.
numConstraintDof	the total constrained degrees of freedom for the MlcpPhysicsProblem to be constructed.
numConstraints	the number of constraints for the MlcpPhysicsProblem to be constructed.

Returns

An MlcpPhysicsProblem appropriately sized and initialized to zero.

Member Data Documentation

CHt

Matrix SurgSim::Physics::MlcpPhysicsProblem::CHt

The matrix \(\mathbf{C\;H^T}\), which is a matrix of size \(n\times c\) that is used to convert the vector of \(c\) constraint forces to the \(n\) displacements of each degree of freedom of the system.

H

Eigen::SparseMatrix<double, Eigen::RowMajor, ptrdiff_t> SurgSim::Physics::MlcpPhysicsProblem::H

The matrix \(\mathbf{H}\), which is a matrix of size \(c\times n\) that converts from the \(n\) degrees of freedom in the system (i.e., the sum of all the DOF over all the representations in the scene), to the \(c\) degrees of freedom summed over all the constraints being applied to the system.

It is used to convert the vector of \(n\) displacements of each degree of freedom of the system to the vector of \(c\) displacements of each degree of freedom of the constraints. Given a set of constraints \(\mathbf{G}(t, \mathbf{x})\), then \(\mathbf{H} = \frac{d \mathbf{G}}{d \mathbf{x}}\) (i.e., the constraints' tangential space).

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

• SurgSim/Physics/MlcpPhysicsProblem.h
• SurgSim/Physics/MlcpPhysicsProblem.cpp