BearingFriction

Coulomb friction with Stribeck effect in bearings

Library

Mechanics/Rotational/Components

Description

This block models COULOMB friction with STRIBECK effect in bearings, i.e., a component where a frictional torque is acting between two rigidly connected flanges (left, right) and a housing (bottom). This frictional torque depends on the angular velocity of the flanges and the friction parameters Tau_Coulomb, Tau_Stribeck, fexp, and Tau_prop.

When the relative angular velocity w of the flanges with respect to the housing is not zero, the friction torque is computed as:

    friction_torque = Tau_Coulomb + Tau_Stribeck * exp(-fexp * w) + Tau_prop * w .

When the relative angular velocity w of the flanges becomes zero, the elements connected by the friction element become stuck, i.e., the absolute angular position of the flanges remains constant. In this phase the friction torque is calculated from a torque balance due to the requirement, that the absolute acceleration shall be zero. The elements begin to slide when the friction torque exceeds a threshold value, called the maximum static friction (stiction) torque, computed as:

    stiction_torque = Tau_Coulomb + Tau_Stribeck .

Parameters

    BearingFriction_0

  • Tau_prop [N.m/(rad/s)] : Angular velocity dependent friction (Tau_prop): Scalar.
  • Tau_Coulomb [N.m] : Constant fricton: Coulomb torque (Tau_Coulomb): Scalar.
  • Tau_Stribeck [N.m] : Stribeck effect (Tau_Stribeck): Scalar.
  • fexp [1/(rad/s)] : Exponential decay of Stribeck effect (fexp): Scalar.
  • mode_start [-] : Initial sliding mode (-1=Backward,0=Sticking,1=Forward,2=Free) (mode_start): Scalar.

Ports

  • Port 1 at left position: implicit input fixedport numbered 1.
  • Port 1 at right position: implicit output fixedport numbered 1.
  • Port 1 at bottom position: implicit output fixedport numbered 2.

See Also