Band Brake
Frictional brake with flexible band wrapped around rotating drum with triggered faults
Libraries:
Simscape /
Driveline /
Brakes & Detents /
Rotational
Description
The Band Brake block represents a frictional brake with a flexible band that wraps around the periphery of a rotating drum to produce a braking action. A positive actuating force causes the band to tighten around the rotating drum and it places the friction surfaces in contact. Viscous and contact friction between the surfaces of the drum and the flexible band causes the rotating drum to decelerate.
You can model the effects of heat flow and temperature change for the block by using port H, an optional thermal conserving port.
You can also enable faulting. When faulting occurs, the belt will exert a user-specified force. Faults can occur at a specified time or due to an external trigger at port T.
Band brakes provide high braking torque at the cost of reduced braking precision in applications that include winch drums, chainsaws, go-karts, and mini-bikes.
Equations
The model employs a simple parameterization with readily accessible brake geometry and friction parameters.
The braking torque as a function of the external brake actuation force that tightens the belt is
Where:
T is the braking torque.
FTB is the force acting on the tense branch of the band.
FA is the external brake actuation force.
rD is the drum radius.
μvisc is the viscous friction coefficient.
μ is the contact friction coefficient.
ϕ is the wrap angle.
Forces FTB and FA satisfy the relationship
Replacing the relationship in the braking torque formula eliminates force FTB such that
To avoid discontinuity at zero relative velocity, the model defines the actuation force, FS, as a hyperbolic function
Where:
Fin is the force input signal.
ωthreshold is the angular velocity threshold.
Faults
When faults are enabled, a belt force is applied in response to one or both of these triggers:
Simulation time — Faulting occurs at a specified time.
Simulation behavior — Faulting occurs in response to an external trigger. This exposes port T.
If a fault trigger occurs, the input force is replaced by the Belt force
when faulted value for the remainder of the simulation. A value of
0
implies that no braking will occur. A relatively large
value implies that the brake is stuck.
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.
Thermal Model
You can model the effects of heat flow and temperature change by exposing the
optional thermal port. To expose the port, in the Friction
settings, set the Thermal Port parameter to
Model
. Exposing the thermal port also exposes these
related settings:
Friction > Temperature
Friction > Contact friction coefficient vector
Thermal Port > Thermal mass
Variables > Temperature
Variables
Use the Variables settings to set the priority and initial target values for the block variables before simulating. For more information, see Set Priority and Initial Target for Block Variables.
Variable settings are visible only when, in the Friction settings, the
Thermal port parameter is set to
Model
.
Limitations and Assumptions
The model does not account for actuator flow consumption.
Ports
Input
Conserving
Parameters
Extended Capabilities
Version History
Introduced in R2012b