Engee documentation

Disc Brake

Brake disc with pressure cylinder and pads.

disc brake

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.

disc brake en

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

Float64.
Complex numbers support

No

Conserving

# S — shaft
`rotational mechanics

Details

A non-directional port associated with a rotating disc shaft.

Program usage name

shaft_flange

# 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

thermal_port

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.

Units

m | cm | ft | in | km | mi | mm | um | yd
Default value

150.0 mm
Program usage name

mean_radius_pad
Evaluatable

Yes

# Cylinder bore — piston diameter
m | cm | ft | in | km | mi | mm | um | yd

Details

Diameter of the brake piston.

Units

m | cm | ft | in | km | mi | mm | um | yd
Default value

10.0 mm
Program usage name

cylinder_bore
Evaluatable

Yes

# Number of brake pads — number of pads

Details

Number of brake pads.

Default value

2
Program usage name

pad_count
Evaluatable

Yes

Friction

# Thermal Port — thermal model

Details

Select this checkbox to enable heat flow and temperature changes.

Default value

false (switched off)
Program usage name

has_thermal_port
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

0.9
Program usage name

static_friction_coefficient
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

0.7
Program usage name

coulomb_friction_coefficient
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.

Units

K | degC | degF | degR | deltaK | deltadegC | deltadegF | deltadegR
Default value

[280.0, 300.0, 320.0] K
Program usage name

temperature_vector
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

[0.9, 0.8, 0.7]
Program usage name

static_friction_coefficient_vector
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

[0.8, 0.7, 0.6]
Program usage name

coulomb_friction_coefficient_vector
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.

Units

rpm | deg/s | rad/s
Default value

0.1 rad/s
Program usage name

w_breakaway
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.

Units

N*m*s/rad | ft*lbf*s/rad
Default value

0.0 N*m*s/rad
Program usage name

viscous_coefficient
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.

Units

J/K | kJ/K
Default value

50.0 kJ/K
Program usage name

thermal_mass
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

Float64.

See also

  1. Band Brake

Examples