Projected Gauss Seidel impulse solver. More...

Inheritance diagram for SimTK::PGSImpulseSolver:

Public Member Functions
	PGSImpulseSolver (Real roll2slipTransitionSpeed)

bool	solve (int phase, const Array_< MultiplierIndex > &participating, const Matrix &A, const Vector &D, const Array_< MultiplierIndex > &expanding, Vector &piExpand, Vector &verrStart, Vector &verrApplied, Vector &pi, Array_< UncondRT > &unconditional, Array_< UniContactRT > &uniContact, Array_< UniSpeedRT > &uniSpeed, Array_< BoundedRT > &bounded, Array_< ConstraintLtdFrictionRT > &consLtdFriction, Array_< StateLtdFrictionRT > &stateLtdFriction) const override
	Solve with conditional constraints. More...

bool	solveBilateral (const Array_< MultiplierIndex > &participating, const Matrix &A, const Vector &D, const Vector &rhs, Vector &pi) const override
	Solve with only unconditional constraints. More...

Public Member Functions inherited from SimTK::ImpulseSolver
	ImpulseSolver (Real roll2slipTransitionSpeed, Real convergenceTol, int maxIters)

virtual	~ImpulseSolver ()

void	setMaxRollingSpeed (Real roll2slipTransitionSpeed)

Real	getMaxRollingSpeed () const

void	setConvergenceTol (Real tol)

Real	getConvergenceTol () const

void	setMaxIterations (int maxIts)

int	getMaxIterations () const

void	clearStats () const

void	clearStats (int phase) const

Additional Inherited Members
Public Types inherited from SimTK::ImpulseSolver
enum	ContactType { TypeNA =-1, Observing =0, Known =1, Participating =2 }

enum	UniCond { UniNA =-1, UniOff =0, UniActive =1, UniKnown =2 }

enum	FricCond { FricNA =-1, FricOff =0, Sliding =1, Impending =2, Rolling =3 }

enum	BndCond { BndNA =-1, SlipLow =0, ImpendLow =1, Engaged =2, ImpendHigh =3, SlipHigh =4 }

Static Public Member Functions inherited from SimTK::ImpulseSolver
static const char *	getContactTypeName (ContactType ct)

static const char *	getUniCondName (UniCond uc)

static const char *	getFricCondName (FricCond fc)

static const char *	getBndCondName (BndCond bc)

static void	dumpUniContacts (const String &msg, const Array_< UniContactRT > &uniContacts)

Static Public Attributes inherited from SimTK::ImpulseSolver
static const int	MaxNumPhases = 3

Protected Attributes inherited from SimTK::ImpulseSolver
Real	m_maxRollingTangVel

Real	m_convergenceTol

int	m_maxIters

long long	m_nSolves [MaxNumPhases]

long long	m_nIters [MaxNumPhases]

long long	m_nFail [MaxNumPhases]

long long	m_nBilateralSolves

long long	m_nBilateralIters

long long	m_nBilateralFail

Detailed Description

Projected Gauss Seidel impulse solver.

Finds a solution to

    [A+D] (piExpand+piUnknown) = v
    subject to
    piExpand <= 0 (given)

    piUnknown_z <= 0         unilateral contact must push, not pull
    ||(piUnknown_x,piUnknown_y)|| <= -mu*pi_z   unilateral friction cone
    where pi=piExpand+piUnknown.

    piUnknown_speed <= 0           one-way ratchets
    lb <= piUnknown_bounded <= ub  torque-limited motor

    ||piUnknown_F|| <= mu*||piUnknown_N||  friction in bilateral constraint
    ||piUnknown_F|| <= mu*N                friction with known normal force N

When piUnknown_z[k] hits its upper limit of 0, we must have v_z[k] >= 0 (contact surfaces separating). We don't explicitly enforce that here; it depends on all diag(A)[z[k]] > 0. That means that if v_z[k]<0 we could improve the solution by making piUnknown_z[k] negative, so it wouldn't have hit the limit.

Constructor & Destructor Documentation

◆ PGSImpulseSolver()

SimTK::PGSImpulseSolver::PGSImpulseSolver ( Real roll2slipTransitionSpeed )

inlineexplicit

Member Function Documentation

◆ solve()

bool SimTK::PGSImpulseSolver::solve	(	int	phase,
		const Array_< MultiplierIndex > &	participating,
		const Matrix &	A,
		const Vector &	D,
		const Array_< MultiplierIndex > &	expanding,
		Vector &	piExpand,
		Vector &	verrStart,
		Vector &	verrApplied,
		Vector &	pi,
		Array_< UncondRT > &	unconditional,
		Array_< UniContactRT > &	uniContact,
		Array_< UniSpeedRT > &	uniSpeed,
		Array_< BoundedRT > &	bounded,
		Array_< ConstraintLtdFrictionRT > &	consLtdFriction,
		Array_< StateLtdFrictionRT > &	stateLtdFriction
	)		const

overridevirtual

Solve with conditional constraints.

In the common underdetermined case (redundant contact) we will return the first solution encountered but it is unlikely to be the best possible solution.

Implements SimTK::ImpulseSolver.

◆ solveBilateral()

bool SimTK::PGSImpulseSolver::solveBilateral	(	const Array_< MultiplierIndex > &	participating,
		const Matrix &	A,
		const Vector &	D,
		const Vector &	rhs,
		Vector &	pi
	)		const

overridevirtual

Solve with only unconditional constraints.

In the underdetermined case we return one of the possible solutions but it will not in general be the least squares one. In the overdetermined, inconsistent case we will iterate for a long time and may converge on the least-error solution but cannot guarantee that.