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Rotational Friction

Purpose

Ideal rotational stick/slip friction

Library

Mechanical / Rotational / Components

Description

pict

The Rotational Friction models any combination of static, Coulomb and viscous friction between two flanges in a rotational system. While the component is stuck, it exerts whatever force is necessary in order to maintain zero relative speed between the flanges, up to the limit of the breakaway torque τbrk  . When the breakaway torque is exceeded, the flanges begin sliding against each other, and the component exerts a torque that consists of the Coulomb friction torque τC   and a speed-dependent viscous friction torque cv ⋅ω  .

The figure below shows the speed/torque characteristic and the state chart of the component. Note that the friction torque is opposed to the movement, hence the negative sign.

pict

Parameters

Breakaway friction torque
The maximum magnitude of the stiction torque τbrk  , in Netwon meters Nm  . Must be greater than or equal to zero.
Coulomb friction torque
The magnitude of the (constant) Coulomb friction torque τC  , in Netwon meters Nm  . Must be greater than or equal to zero and less than or equal to the breakaway friction torque.
Viscous friction coefficient
The proportionality coefficient cv   that determines the speed dependent viscous friction torque, in Nms
rad  .

Probe Signals

Torque
The transmitted torque τ   flowing from the unmarked to the marked flange, in Newton meters (Nm).
Speed
The angular speed ω   of the marked flange with respect to the unmarked flange, in rad
-s-  .
State
The internal state of the component: -1 sliding backward, 0 stuck, +1 sliding forward.