Band Brake
A friction brake with a flexible band wound on a rotating drum.
blockType: Engee1DMechanical.Brakes.Band
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Path in the library: |
Description
Block Band Brake It is a friction brake with a flexible band that wraps around the periphery of a rotating drum to create a braking effect. The positive driving force causes the belt to tighten around the rotating drum and brings the friction surfaces into contact. The viscous and contact friction between the surfaces of the drum and the flexible belt slows down the rotating drum.
You can simulate the effects of heat flow and unit temperature changes using the H port, an additional port for heat preservation.
Belt brakes provide high braking torque at the cost of reduced braking accuracy in applications such as winch drums, chainsaws, go-karts, and mini bikes.
The equations
The block uses simple parameterization with simple brake geometry and friction parameters.
The braking torque, depending on the force of the external brake actuator that tightens the belt, is:
where:
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— braking torque;
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— the reaction force of the support in which the tape is attached;
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— the force of the external brake drive;
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— the radius of the drum;
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— coefficient of viscous friction;
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— coefficient of contact friction;
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— the angle of the girth.
Forces and satisfy the relation:
Replacing the dependency in the braking torque formula eliminates the force so that:
To avoid breaks in the event of a sudden change in the direction of friction, when the relative velocity changes its sign, the model determines the final external braking force. as the following hyperbolic function:
where:
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— belt tension input signal;
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— the threshold of angular velocity.
The thermal model
You can simulate the effects of heat flow and temperature changes by adding an additional heat port. To use this port, check the box for the parameter Thermal Port.
Limitations and assumptions
The model does not take into account the flow rate consumed by the drive.
Variables
Use the parameter group Initial Targets to set the priority and initial target values for the block parameter variables before modeling. For more information, see Configuring physical blocks using target values.
Ports
Input
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F
—
belt tension force
scalar
Details
The input signal associated with the external tension force applied to the belt.
| Data types |
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| Complex numbers support |
I don’t |
Conserving
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S
—
drum shaft
rotational mechanics
Details
A non-directional port connected to the shaft of a rotating drum.
| Program usage name |
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H
—
heat flow
heat
Details
A non-directional port connected to the heat flow.
The thermal port allows you to simulate the heat flow between the unit and the connected network.
Dependencies
To use this port, select the check box for the parameter Thermal Port.
| Program usage name |
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Parameters
Geometry
#
Drum radius —
radius of the contact surface
m | um | mm | cm | km | in | ft | yd | mi | nmi
Details
The radius of the contact surface of the drum. The value must be greater than zero.
| Units |
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| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
#
Wrap angle —
girth angle
rad | deg | rev | mrad | arcsec | arcmin | gon
Details
The angle of girth between the flexible band and the rotating drum. The value must be greater than zero.
| Units |
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| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
Friction
#
Viscous friction coefficient —
viscous friction
N*m*s/rad | mN*m*s/rad | kN*m*s/rad | kgf*m*s/rad | lbf*ft*s/rad
Details
Coefficient of viscous friction on the contact surface of the belt with the drum. The value must be greater than or equal to zero.
| Units |
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| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
# Thermal Port — The thermal model
Details
Check this box to use the model for heat flow and temperature changes.
Dependencies
If this option is checked, the thermal port H and its associated parameters will be displayed.
| Default value |
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| Program usage name |
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| Evaluatable |
No |
# Contact friction coefficient — Coulomb friction
Details
The coefficient of Coulomb friction on the contact surface of the belt with the drum. The value must be greater than zero.
Dependencies
To use this option, uncheck the box for the option Thermal Port.
| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
#
Temperature —
temperature
K | degC | degF | degR | deltaK | deltadegC | deltadegF | deltadegR
Details
An array of temperatures used to build a 1-D interpolation table of temperature and efficiency correspondence. The values of the array should increase monotonously.
Dependencies
To use this option, check the box for the option Thermal Port.
| Units |
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| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
# Contact friction coefficient vector — Coulomb friction
Details
The Coulomb friction coefficient on the contact surface of the belt with the drum, set as a vector with the following constraints (conditions):
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The number of elements in the vector must be the same as the number of elements in the specified vector for the parameter Temperature;
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The values are monotonously increasing;
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Each value must be greater than zero.
Dependencies
To use this option, check the box for the option Thermal Port.
| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
#
Angular velocity threshold —
the rotational speed required for almost stationary contact friction
rad/s | deg/s | rad/min | deg/min | rpm | rps
Details
The angular velocity at which the coefficient of contact friction practically reaches its stationary value. The value must be greater than zero.
| Units |
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| Default value |
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| Program usage name |
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| Evaluatable |
Yes |
Thermal Port
#
Thermal mass —
resistance to temperature changes
J/K | kJ/K
Details
The thermal energy required to change the temperature of a component by one degree. The greater the thermal mass, the more resistant the component is to temperature changes.
Dependencies
To use this option, check the box for the option Thermal Port.
| Units |
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| Default value |
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| Program usage name |
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| Evaluatable |
Yes |