OneWayClutch

Parallel connection of freewheel and clutch

Library

Mechanics/Rotational/Components

Description

This component models a one-way clutch, i.e., a component with two flanges where friction is present between the two flanges and these flanges are pressed together via a normal force. These flanges maybe sliding with respect to each other according to a parallel connection of the blocks Clutch and Freewheel. Note, this special component has to be used instead of a Clutch and Freewheel block connected in parallel, because there would be an unresolvable ambiguity when both are stuck.

The normal force fn has to be provided as input signal f_normalized in a normalized form (0 <= f_normalized <= 1), fn = fn_max*f_normalized, where fn_max has to be provided as parameter. Friction in the clutch is modelled as COULOMB friction.

When the relative angular velocity between flange_b (right) and flange_a (left) is positive, the friction torque is a function of the friction coefficient mue_pos, of the normal force fn, and of a geometry constant cgeo which takes into account the geometry of the device and the assumptions on the friction distribution:

    friction_torque = cgeo * mue0 * fn .

When the relative angular velocity becomes zero, the elements connected by the friction element become stuck, i.e., the relative angle between the flanges remains constant. In this phase the friction torque is calculated from a torque balance due to the requirement, that the relative 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 = peak * cgeo * mue_pos * fn ,

where peak >= 1 is another parameter to be defined by the user.

Parameters

    OneWayClutch_0

  • mue_pos [-] : positive sliding friction coefficient (w_rel&gt;=0) (mue_pos): Scalar.
  • peak [-] : peak &gt;= 1, peak*mue_pos = maximum value of mue for w_rel==0 (peak): Scalar.
  • cgeo [-] : cgeo &gt;= 0, Geometry constant containing friction distribution assumption (cgeo): Scalar.
  • fn_max [N] : fn_max &gt;= 0, Maximum normal force (fn_max): Scalar.

Ports

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

See Also