Simbody  3.6
SimTK::PGSImpulseSolver Class Reference

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)

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

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

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.

Implements SimTK::ImpulseSolver.

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