Force: Joint Friction

Format

<Force_JointFriction
  id                         = "integer"  
  [ mu_static                = "real" ]
  [ mu_dynamic               = "real" ]
  [ max_stiction_deform      = "real" ]  
  [ stiction_trans_vel       = "real"]  
  [ inputs                   = "4-bit integer" ]     
  [ torque_preload           = "real" ]
  [ friction_arm             = "real" ]
  [ bending_reaction_arm     = "real" ]
  [ pin_radius               = "real" ]
/>

<Force_JointFriction
  id                         = "integer"
  [ mu_static                = "real" ]
  [ mu_dynamic               = "real" ]
  [ max_stiction_deform      = "real" ]
  [ stiction_trans_vel       = "real"]
  [ inputs                   = "4-bit integer" ] 
  [ torque_preload           = "real" ]
  [ ball_radius              = "real" ]
/>

<Force_JointFriction
  id                         = "integer"
  [ mu_static                = "real" ]
  [ mu_dynamic               = "real" ]
  [ max_stiction_deform      = "real" ]
  [ stiction_trans_vel       = "real" ]
  [ inputs                   = "4-bit integer " ]  
  [ force_preload            = "real" ]
  [ reaction_arm             = "real" ]
  [ initial_overlap          = "real" ]
/>

<Force_JointFriction
  id                         = "integer"
  [ mu_static                = "real" ]
  [ mu_dynamic               = "real" ]
  [ max_stiction_deform      = "real" ]
  [ stiction_trans_vel       = "real" ]
  [ inputs                   = "4-bit integer" ]
  [ force_preload            = "real" ]
  [ torque_preload           = "real" ]
  [ pin_radius               = "real" ]
  [ initial_overlap          = "real" ]
/>

<Force_JointFriction
  id                         = "integer"
  [ mu_static                = "real" ]
  [ mu_dynamic               = "real" ]
  [ max_stiction_deform      = "real"]
  [ stiction_trans_vel       = "real"]
  [ inputs                   = "4-bit integer" ]
  [ torque_preload           = "real" ]
  [ friction_arm             = "real" ]
  [ bending_reaction_arm     = "real" ]
  [ pin_radius               = "real" ]
/>

Attributes

id

Element identification number, (integer > 0). This number is unique among all Force_JointFriction elements.

mu_static

Specifies the static friction coefficient, (μ_s), in the joint.

MU_STATIC > 0.

mu_dynamic

Specifies the dynamic friction coefficient, (μ_d), in the joint.

MU_DYNAMIC > 0.

max_stiction_deform

Specifies the maximum deformation that can occur in a joint for static friction or stiction regime.

stiction_trans_vel

Real value of the absolute velocity below, which the friction transitions from dynamic friction to static friction.

inputs

A 4-bit integer value that specifies the input forces to the friction model. By default, all the preload and joint reaction forces are included. Valid values are 0 or 1 for each bit.

There are four choices to be made:

• 1^st bit: Preload
• 2^nd bit: Reaction_Force
• 3^rd bit: Bending_Moment
• 4^th bit: Torsional_Moment

Setting a 0 or 1 for each bit of the input's value controls individual inputs.

Thus:

• 1111 - All four inputs are included
• 0000 - None of the four inputs are included
• 1000 - Only include Preload
• 1101 - Include Preload, Reaction_Force and Torsional_Moment, but not Bending_Moment
• 1001 - Include Preload and Torsional_Moment, but not Reaction_Force and Bending_Moment

Options available per joint type are as defined below:

• Translational - Preload, Reaction_Force, Bending_Moment, Torsional_Moment
• Cylindrical, Revolute, Universal, Hooke - Preload, Reaction_Force, Bending_Moment
• Spherical - Preload, Reaction_Force

force_preload

Specifies the preload friction force for Translational and Cylindrical joints.

torque_preload

Specifies the preload friction torque for Revolute, Cylindrical, Universal and Spherical joints.

friction_arm

Specifies the moment arm used to compute axial friction torque in revolute, universal joints.

reaction_arm

Specifies the moment arm of the reaction torque about the Translation joint axial axes.

bending_reaction_arm

Specifies the moment arm to compute the bending moment in Revolute, Hooke and Universal joints.

pin_radius

Specifies the radius of the pin for Revolute, Cylindrical, Hooke and Universal joints.

ball_radius

Specifies the radius of the Spherical joint.

initial_overlap

Specifies the initial overlap of the sliding parts in Translation and Cylindrical joints.

overlap_delta

Specifies friction characteristics in the sliding joint.

INCREASE - Overlap increases as the I Marker translates in the positive direction of the z-axis of the J Marker.

DECREASE - Overlap decreases in the positive direction of the J marker.