Rotational Friction
Purpose
Ideal rotational stick/slip friction
Library
Mechanical / Rotational / Components
Description
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 torque is necessary in order to maintain zero relative speed between the flanges, up to the limit of the breakaway torque \(\tau_\mathrm{brk}\). 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 \(\tau_\mathrm{C}\) and a speed-dependent viscous friction torque \(c_\mathrm{v} \cdot \omega\).
Fig. 286 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.
Fig. 286 Rotational friction speed/torque characteristic and state chart
Parameters
- Breakaway friction torque
The maximum magnitude of the stiction torque \(\tau_\mathrm{brk}\), in newton-meters \((\mathrm{Nm})\). Must be greater than or equal to zero.
- Coulomb friction torque
The magnitude of the (constant) Coulomb friction torque \(\tau_\mathrm{C}\), in newton-meters \((\mathrm{Nm})\). Must be greater than or equal to zero and less than or equal to the breakaway friction torque.
- Viscous friction coefficient
The proportionality coefficient \(c_\mathrm{v}\) that determines the speed dependent viscous friction torque, in \((\frac{\mathrm{rad}}{\mathrm{s}})\).
Probe Signals
- Torque
The transmitted torque \(\tau\) flowing from the unmarked to the marked flange, in newton-meters \((\mathrm{Nm})\).
- Speed
The angular speed \(\omega\) of the marked flange with respect to the unmarked flange, in \((\frac{\mathrm{rad}}{\mathrm{s}})\).
- State
The internal state of the component:
-1sliding backward,0stuck,+1sliding forward.