Class LagrangianR

Defined in Program listing for file kernel/src/modelingTools/LagrangianR.hpp

class LagrangianR : public Relation

Lagrangian Non Linear Relation (generic interface)

This class is an interface for specific Lagrangian Relations used for Lagrangian dynamical systems.

  • \( y = h(t,q,\dot q,\ldots) \) describes the constraint (the relation)

  • The Jacobian of the constraints with respect to the coodinates \( q \) i.e. \( \nabla^T_q h(t,q,\dot q,\ldots) \) , is accessed with jachq().

This Jacobian is mainly used for Newton linearization and to compute the time-derivative of the constraint,

\( y = h(q,\ldots) \) that is \( \dot y (t) = \nabla^T_q h(t,q,\dot q,\ldots) (q) \dot q +\ldots \)

This object can also store more general linearized part of the gap function. If \( y=h(q) \) models a gap function, then the time derivative can be generically written as

\( \dot y (t) = H(q,\ldots) \dot q +\ldots. \) The matrix \( H(q,\ldots) \) can also be accessed using jachq().

  • The Jacobian of the constraints with respect to the generalized velocities \( \dot q \)

i.e. \( \nabla^\top_{\dot q} h(t,q,\dot q,\ldots) \) is accessed using jachqDot().

  • The time-derivative of Jacobian of the constraints with respect to the generalized coordinates \( q \)

i.e. \( \frac{d}{dt} \nabla^\top_{q} h(t,q,\dot q,\ldots). \) , is accessed using dotJachq().

This value is useful to compute the second-order time—derivative of the constraints with respect to time.

All these operators can be defined with user-defined plugins.

Subclassed by LagrangianCompliantLinearTIR, LagrangianCompliantR, LagrangianLinearTIR, LagrangianRheonomousR, LagrangianScleronomousR

Public Functions

virtual ~LagrangianR() noexcept = default


inline virtual void initialize(Interaction &inter) override

initialize the relation (check sizes, memory allocation …)


inter – the interaction using this relation

inline SP::SimpleMatrix jachq() const

get a pointer on matrix Jach[index]


a pointer on a SimpleMatrix

inline void setJachqPtr(SP::SimpleMatrix newPtr)

set Jach[index] to pointer newPtr (pointer link)


newPtr – the new matrix

virtual void display() const override

main relation members display