*SetJointFrictionLugre() - joint pair

Sets the friction properties for a joint pair with friction.

*Applicable for the MotionSolve SolverMode only.

Syntax

*SetJointFrictionLugre(varname, bristle_stiffness_l, 
                                          damping_effects_l, viscous_effects_l, 
                                          bristle_stiffness_r, 
                                          damping_effects_r, viscous_effects_r)

Arguments

varname: The variable name of the joint.; Data type: varname
bristle_stiffness_l: Specifies the LuGre bristle stiffness to be used. See Comments below.; Default: 100; Data type: real
damping_effects_l: Specifies the LuGre damping coefficient for the stiction regime. See Comments below.; Default: 0.316; Data type: real
viscous_effects_l: Specifies the coefficient for the viscous damping force that occurs when relative sliding actually begins. See Comments below.; Default: 0.0004; Data type: real

The parameters for the right side joint are appended with "_r" in the *SetJointFrictionLugre() statement above. These parameters hold the same meaning as their left side counterparts, but are applicable to the right side joint.

Example

*BeginMDL( the_model, "Model" )
 *StandardInclude(FILE)
 *PointPair( p_0, "Pivot" )
 *PointPair( p_1, "Point 1" )
 *BodyPair( b_pendu, "Pendulum", p_1, , , , )
 *RevJointPair( j_0, "Pivot", b_pendu, B_Ground, p_0, VECTOR, V_Global_Y )
 *SetBodyInertia( b_pendu, LEFT, 1.0, 100.0, 100.0, 100.0, 0.0, 0.0, 0.0 )
 *Set( b_pendu.usecm, true )
 *SetPoint( p_1, LEFT, -100, -100.0, -75 )
 *SetPoint( p_0, LEFT, , -100 )
 *SetJointFriction( j_0, , true, 0.35, 0.28, ACTIVE_STATIC, 0.16, , , PRELOAD, REACTION_FORCE, BENDING_MOMENT, , , , , , , 1000, 9, 25, 55, 
 , true )
 *SetJointFrictionLugre( j_0, 100, 0.316, 0.0004, 200, 0.5, 0.0008 )
*EndMDL()

Context

Comments

This statement is used to set the LuGre parameters for the friction model of a joint pair in "Non-Compliant" mode. This statement is valid for the MotionSolve SolverMode and if friction is enabled for the joint using the *SetJointFriction() statement.

LuGre parameters cannot be made symmetric through the *SetJointFrictionLugre() statement. To set the LuGre parameters as symmetric, use the sym option on the *SetJointFriction() statement.

bristle_stiffness: Specifies the bristle stiffness in the LuGre model. It models the stiffness resisting micro-deformation in the friction element.
damping_effects: Defines the damping coefficient for the pre-displacement (or stiction) regime. Its main role is to damp out bristle vibrations in the pre-displacement regime.
viscous_effects: Represents viscous damping. This is primarily responsible for the increase in friction force with the increase in the slip velocity.