Disc Brake
Brake disc with pressure cylinder and pads.
Description
The Disc Brake unit is a brake disc, in the form of a cylinder, which exerts pressure on one or more brake pads that contact the shaft rotor. The friction of the pads results in a braking element that counteracts the rotation of the shaft.
Model of a disc brake
This figure shows a front and left side view of a brake disc.
The brake disc converts the pressure in the brake cylinder into a force that is applied across the centre radius of the brake pad. The equation the unit uses to calculate the braking torque depends on the speed of the disc, , so that at ,
However, when , the torque applied by the brake is equal to the external torque applied to the rotor. The maximum value of the braking torque, in the case of , is defined as:
In both cases ,
where
-
- braking torque;
-
- is the applied pressure in the piston;
-
- disc rotation speed;
-
- number of brake pads;
-
- coefficient of static friction between pads and rotor;
-
- kinetic friction coefficient between pads and rotor;
-
- brake piston diameter;
-
- average radius of brake pad force application to the rotor disc;
-
- outer radius of the brake pad;
-
- inner radius of the brake pad.
By default, the unit simulates dry braking. You can model viscous friction by setting the Viscous friction coefficient, , to a non-zero value. The torque on the disc in a viscous friction system is:
Thermal modelling
You can model the effects of heat flow and block temperature changes using the H port, an optional non-directional port. To enable the port, select the check box for Thermal Port in the Friction settings. Enabling the thermal port also allows you to change the values for the following parameters:
-
Friction > Static friction coefficient vector
-
Friction > Coulomb friction coefficient vector
-
Thermal Port > Thermal mass
Ports
Input
#
P
—
cylinder pressure
scalar
Details
An input port related to cylinder pressure.
Data types |
|
Complex numbers support |
No |
Conserving
#
S
—
shaft
`rotational mechanics
Details
A non-directional port associated with a rotating disc shaft.
Program usage name |
|
#
H
—
heat flux
`heat
Details
A non-directional port associated with heat flow.
The heat port allows modelling the heat flow between the unit and the connected network.
Dependencies
To use this port, select the Thermal Port check box.
Program usage name |
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Parameters
Geometry
#
Mean pad radius —
average radius of brake shoe mounting
m
| cm
| ft
| in
| km
| mi
| mm
| um
| yd
Details
Average radius of the brake shoe mount.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Cylinder bore —
piston diameter
m
| cm
| ft
| in
| km
| mi
| mm
| um
| yd
Details
Diameter of the brake piston.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
# Number of brake pads — number of pads
Details
Number of brake pads.
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
Friction
# Thermal Port — thermal model
Details
Select this checkbox to enable heat flow and temperature changes.
Default value |
|
Program usage name |
|
Evaluatable |
No |
# Static friction coefficient — static friction
Details
Static friction coefficient. The value must be greater than the value set for Coulomb friction coefficient.
Dependencies
This parameter is available if the Thermal Port parameter is unchecked.
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
# Coulomb friction coefficient — contact friction
Details
Coulomb friction coefficient at the pad-disc contact surface. The value must be greater than zero.
Dependencies
This parameter is available if the Thermal Port parameter is unchecked.
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Temperature —
temperature
K
| degC
| degF
| degR
| deltaK
| deltadegC
| deltadegF
| deltadegR
Details
An array of temperature values used to construct a one-dimensional interpolation table of temperature and efficiency correspondence. The array values should be monotonically increasing.
Dependencies
This parameter is available if the Thermal Port parameter is checked.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
# Static friction coefficient vector — static friction vector
Details
A vector of values of static friction coefficients such that:
-
The number of elements in the vector must be the same as the number of elements in the specified vector for the Temperature parameter;
-
The values must be greater than the corresponding values specified for the Coulomb friction coefficient vector parameter *Coulomb friction coefficient vector.
Dependencies
This parameter is available if the Thermal Port parameter is checked.
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
# Coulomb friction coefficient vector — contact friction vector
Details
The vector of values of Coulomb friction coefficients on the pad-disc contact surface, such that:
-
The number of elements in the vector must be the same as the number of elements in the specified vector for the Temperature parameter;
-
The values are monotonically increasing;
-
Each value must be greater than zero.
Dependencies
This parameter is available when the Thermal Port parameter is checked.
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Breakaway friction velocity —
contact friction threshold
rpm
| deg/s
| rad/s
Details
The angular velocity at which friction changes its pattern from static to kinetic.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
#
Viscous friction coefficient —
viscous friction coefficient
N*m*s/rad
| ft*lbf*s/rad
Details
The viscous friction model represents the energy loss to cool/lubricate between the pads and the disc. To model such a system, specify a non-zero value for the viscous friction coefficient.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
Thermal Port
#
Thermal mass —
heat capacity
J/K
| kJ/K
Details
The heat energy required to change the temperature of a component by one degree. The greater the heat capacity, the more resistant the component is to temperature change.
Dependencies
This parameter is available when Thermal Port is checked.
Values |
|
Default value |
|
Program usage name |
|
Evaluatable |
Yes |
Initial Targets
Temperature
Priority - temperature priority
High (by default)
| Low
| None
Details
Temperature priority set as High
, Low
or None
.
Dependencies
To use this port, select the check box for Thermal Port.
Value - temperature value
300 K (by default)
| scalar
Details
Temperature value specified as a real scalar.
Dependencies
To use this port, select the Thermal Port checkbox.
Data types |
|