chrono::ChConstraintTwo Class Referenceabstract

## Description

This class implements the functionality for a constraint between a COUPLE of TWO objects of type ChVariables(), and defines two constraint matrices, whose column number automatically matches the number of elements in variables vectors.

Before starting the solver one must provide the proper values in constraints (and update them if necessary), i.e. must set at least the c_i and b_i values, and jacobians.

`#include <ChConstraintTwo.h>`

Inheritance diagram for chrono::ChConstraintTwo:

Collaboration diagram for chrono::ChConstraintTwo:

## Public Member Functions | |

ChConstraintTwo () | |

Default constructor. | |

ChConstraintTwo (const ChConstraintTwo &other) | |

Copy constructor. | |

ChConstraintTwo & | operator= (const ChConstraintTwo &other) |

Assignment operator: copy from other object. | |

virtual ChRowVectorRef | Get_Cq_a ()=0 |

Access jacobian vector. | |

virtual ChRowVectorRef | Get_Cq_b ()=0 |

Access jacobian vector. | |

virtual ChVectorRef | Get_Eq_a ()=0 |

Access auxiliary vector (ex: used by iterative solvers). | |

virtual ChVectorRef | Get_Eq_b ()=0 |

Access auxiliary vector (ex: used by iterative solvers). | |

ChVariables * | GetVariables_a () |

Access the first variable object. | |

ChVariables * | GetVariables_b () |

Access the second variable object. | |

virtual void | SetVariables (ChVariables *mvariables_a, ChVariables *mvariables_b)=0 |

Set references to the constrained objects, each of ChVariables type, automatically creating/resizing jacobians if needed. | |

virtual void | ArchiveOUT (ChArchiveOut &marchive) override |

Method to allow serialization of transient data to archives. | |

virtual void | ArchiveIN (ChArchiveIn &marchive) override |

Method to allow de-serialization of transient data from archives. | |

Public Member Functions inherited from chrono::ChConstraint | |

ChConstraint () | |

Default constructor. | |

ChConstraint (const ChConstraint &other) | |

Copy constructor. | |

virtual ChConstraint * | Clone () const =0 |

"Virtual" copy constructor. | |

ChConstraint & | operator= (const ChConstraint &other) |

Assignment operator: copy from other object. | |

bool | operator== (const ChConstraint &other) const |

Comparison (compares only flags, not the jacobians etc.) | |

bool | IsValid () const |

Tells if the constraint data is currently valid. | |

void | SetValid (bool mon) |

Use this function to set the valid state (child class Children classes must use this function depending on the result of their implementations of RestoreReference();. | |

bool | IsDisabled () const |

Tells if the constraint is currently turned on or off by the user. | |

void | SetDisabled (bool mon) |

User can use this to enable/disable the constraint as desired. | |

bool | IsRedundant () const |

Tells if the constraint is redundant or singular. | |

void | SetRedundant (bool mon) |

Solvers may use the following to mark a constraint as redundant. | |

bool | IsBroken () const |

Tells if the constraint is broken, for excess of pulling/pushing. | |

void | SetBroken (bool mon) |

3rd party software can set the 'broken' status via this method (by default, constraints never break); | |

virtual bool | IsUnilateral () const |

Tells if the constraint is unilateral (typical complementarity constraint). | |

virtual bool | IsLinear () const |

Tells if the constraint is linear (if non linear, returns false). | |

eChConstraintMode | GetMode () const |

Gets the mode of the constraint: free / lock / complementary A typical constraint has 'lock = true' by default. | |

void | SetMode (eChConstraintMode mmode) |

Sets the mode of the constraint: free / lock / complementary. | |

bool | IsActive () const |

Tells if the constraint is currently active, in general, that is tells if it must be included into the system solver or not. More... | |

void | SetActive (bool isactive) |

Set the status of the constraint to active. | |

virtual double | Compute_c_i () |

Compute the residual of the constraint using the LINEAR expression. More... | |

double | Get_c_i () const |

Return the residual 'c_i' of this constraint. // CURRENTLY NOT USED. | |

void | Set_b_i (const double mb) |

Sets the known term b_i in [Cq_i]*q + b_i = 0, where: c_i = [Cq_i]*q + b_i = 0. | |

double | Get_b_i () const |

Return the known term b_i in [Cq_i]*q + b_i = 0, where: c_i= [Cq_i]*q + b_i = 0. | |

void | Set_cfm_i (const double mcfm) |

Sets the constraint force mixing term (default=0). More... | |

double | Get_cfm_i () const |

Returns the constraint force mixing term. | |

void | Set_l_i (double ml_i) |

Sets the 'l_i' value (constraint reaction, see 'l' vector) | |

double | Get_l_i () const |

Return the 'l_i' value (constraint reaction, see 'l' vector) | |

virtual void | Update_auxiliary () |

This function must update jacobians and auxiliary data such as the 'g_i' product. More... | |

double | Get_g_i () const |

Return the 'g_i' product , that is [Cq_i]*[invM_i]*[Cq_i]' (+cfm) | |

void | Set_g_i (double m_g_i) |

Usually you should not use the Set_g_i function, because g_i should be automatically computed during the Update_auxiliary() . | |

virtual double | Compute_Cq_q ()=0 |

This function must computes the product between the row-jacobian of this constraint '[Cq_i]' and the vector of variables, 'q', that is, Cq_q=[Cq_i]*q. More... | |

virtual void | Increment_q (const double deltal)=0 |

This function must increment the vector of variables 'q' with the quantity [invM]*[Cq_i]'deltal,that is q+=[invM][Cq_i]'*deltal This is used for some iterative solvers. More... | |

virtual void | MultiplyAndAdd (double &result, const ChVectorDynamic< double > &vect) const =0 |

Computes the product of the corresponding block in the system matrix by 'vect', and add to 'result'. More... | |

virtual void | MultiplyTandAdd (ChVectorDynamic< double > &result, double l)=0 |

Computes the product of the corresponding transposed block in the system matrix (ie. More... | |

virtual void | Project () |

For iterative solvers: project the value of a possible 'l_i' value of constraint reaction onto admissible orthant/set. More... | |

virtual double | Violation (double mc_i) |

Given the residual of the constraint computed as the linear map mc_i = [Cq]*q + b_i + cfm*l_i , returns the violation of the constraint, considering inequalities, etc. More... | |

virtual void | Build_Cq (ChSparseMatrix &storage, int insrow)=0 |

Puts the jacobian portions into the 'insrow' row of a sparse matrix, where each portion of jacobian is shifted in order to match the offset of the corresponding ChVariable. | |

virtual void | Build_CqT (ChSparseMatrix &storage, int inscol)=0 |

Same as Build_Cq, but puts the transposed jacobian row as a column. | |

void | SetOffset (int moff) |

Set offset in global q vector (set automatically by ChSystemDescriptor) | |

int | GetOffset () const |

Get offset in global q vector. | |

## Protected Attributes | |

ChVariables * | variables_a |

The first constrained object. | |

ChVariables * | variables_b |

The second constrained object. | |

Protected Attributes inherited from chrono::ChConstraint | |

double | c_i |

The 'c_i' residual of the constraint (if satisfied, c must be 0) | |

double | l_i |

The 'l_i' lagrangian multiplier (reaction) | |

double | b_i |

The 'b_i' right term in [Cq_i]*q+b_i=0 , note: c_i= [Cq_i]*q + b_i. | |

double | cfm_i |

The constraint force mixing, if needed (usually is zero) to add some numerical 'compliance' in the constraint, that is the equation becomes: c_i= [Cq_i]*q + b_i + cfm*l_i =0; Example, it could be cfm = [k * h^2](^-1) where k is stiffness. | |

eChConstraintMode | mode |

mode of the constraint: free / lock / complementar | |

double | g_i |

'g_i' product [Cq_i]*[invM_i]*[Cq_i]' (+cfm) | |

int | offset |

offset in global "l" state vector (needed by some solvers) | |

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

- /builds/uwsbel/chrono/src/chrono/solver/ChConstraintTwo.h
- /builds/uwsbel/chrono/src/chrono/solver/ChConstraintTwo.cpp