Loaded-Contact Rotational Friction
Loaded-contact friction between two rotating surfaces
Libraries:
Simscape /
Driveline /
Brakes & Detents /
Rotational
Description
The Loaded-Contact Rotational Friction block simulates friction between two rotating surfaces loaded with a normal force.
The block is implemented as a structural component based on the Fundamental Friction Clutch block. From the locked state, the two surfaces unlock if the transmitted torque exceeds the static friction, as defined by the static coefficient of friction and current normal force. For details on how the locking and unlocking are modeled, see the Fundamental Friction Clutch block reference page.
Torque is transmitted for normal forces larger than the Threshold force parameter.
You can also enable faulting. When faulting occurs, the surfaces will remain locked or will be unable to transmit power. Faults can occur at a specified time or due to an external trigger at port T.
Equations
The block simulates friction between two rotating surfaces loaded with a normal force. When the two rotating surfaces are not locked, the transmitted torque is determined with the following equations:
where:
τ is the transmitted torque.
N is the normal force.
μ is the friction coefficient.
reff is the effective radius.
ro is the surface outside radius.
ri is the surface inside radius.
ω is the relative angular velocity.
τvisc is the viscous drag torque.
μvisc is the viscous drag torque coefficient.
Velocity-Dependent Model
You can model the effects of rotational velocity change by selecting a
velocity-dependent model. To choose a velocity-dependent model, in
the Friction settings, set the
Friction model parameter to
Velocity-dependent kinetic friction
coefficient
. For information about a friction
model that depends on both velocity and temperature, see Thermal, Velocity-Dependent Model.
For the velocity-dependent model these related parameters become visible in the Friction settings:
Relative velocity vector
Kinetic friction coefficient vector
Friction coefficient interpolation method
Friction coefficient extrapolation method
Thermal Model
You can model the effects of heat flow and temperature change by
selecting a temperature-dependent model. To choose a
temperature-dependent model, in the Friction
settings, set the Friction model parameter to
Temperature-dependent friction
coefficients
. For information about a friction
model that depends on both velocity and temperature, see Thermal, Velocity-Dependent Model.
For the temperature-dependent model, thermal port H and these settings are visible:
In the Friction settings:
Temperature vector
Static friction coefficient vector
Kinetic friction coefficient vector
Friction coefficient interpolation method
Friction coefficient extrapolation method
In the Thermal Port settings:
Thermal mass
Initial Temperature
Thermal, Velocity-Dependent Model
You can model the effects of rotational velocity change and heat flow
by selecting a velocity-dependent and temperature-dependent model.
To choose a model that depends on both velocity and temperature, in
the Friction settings, set the
Friction model parameter to
Temperature and velocity-dependent friction
coefficients
.
For the velocity-dependent and temperature-dependent model, thermal port H and these related settings and parameters become visible:
In the Friction settings:
Relative velocity vector
Temperature vector
Static friction coefficient vector
Kinetic friction coefficient matrix
Friction coefficient interpolation method
Friction coefficient extrapolation method
In the Thermal Port settings:
Thermal mass
Initial Temperature
Faults
You can enable faulty behavior in response to:
Simulation time — Faulting occurs at a specified time.
Simulation behavior — Faulting occurs in response to an external trigger. This exposes port T.
You can choose either or both of these settings for block faulting. If faulting is triggered, the clutch responds according to the Behavior when faulted setting for the remainder of the simulation. The fault options are:
Cannot transmit power
Cannot unlock
You can set the block to issue a fault report as a warning or error message in the Simulink Diagnostic Viewer with the Reporting when fault occurs parameter.
Limitations and Assumptions
The model does not account for inertia. Add inertia terms externally to the B and F ports as required.
The model computes the torque assuming a uniform distribution of the normal force.
Ports
Input
Conserving
Parameters
Extended Capabilities
Version History
Introduced in R2011a