ross.MagneticBearingElement#

class ross.MagneticBearingElement(n, g0, i0, ag, nw, alpha, kp_pid, kd_pid, k_amp, k_sense, tag=None, n_link=None, scale_factor=1, **kwargs)#

Magnetic bearing.

This class creates a magnetic bearing element. Converts electromagnetic parameters and PID gains to stiffness and damping coefficients.

Parameters

nint: The node in which the magnetic bearing will be located in the rotor.
g0float: Air gap in m^2.
i0float: Bias current in Ampere
agfloat: Pole area in m^2.
nwfloat or int: Number of windings
alphafloat or int: Pole angle in radians.
kp_pidfloat or int: Proportional gain of the PID controller.
kd_pidfloat or int: Derivative gain of the PID controller.
k_ampfloat or int: Gain of the amplifier model.
k_sensefloat or int: Gain of the sensor model.
tagstr, optional: A tag to name the element Default is None.
n_linkint, optional: Node to which the bearing will connect. If None the bearing is connected to ground. Default is None.
scale_factorfloat, optional: The scale factor is used to scale the bearing drawing. Default is 1.
———-
See the following reference for the electromagnetic parameters g0, i0, ag, nw, alpha:
Book: Magnetic Bearings. Theory, Design, and Application to Rotating Machinery
Authors: Gerhard Schweitzer and Eric H. Maslen
Page: 69-80

Examples

>>> n = 0
>>> g0 = 1e-3
>>> i0 = 1.0
>>> ag = 1e-4
>>> nw = 200
>>> alpha = 0.392
>>> kp_pid = 1.0
>>> kd_pid = 1.0
>>> k_amp = 1.0
>>> k_sense = 1.0
>>> tag = "magneticbearing"
>>> mbearing = MagneticBearingElement(n=n, g0=g0, i0=i0, ag=ag, nw=nw,alpha=alpha,
...                                   kp_pid=kp_pid, kd_pid=kd_pid, k_amp=k_amp,
...                                   k_sense=k_sense)
>>> mbearing.kxx
[-4640.623377181318]

Methods

C(frequency)#

Damping matrix for an instance of a bearing element.

This method returns the damping matrix for an instance of a bearing element.

Parameters

frequencyfloat: The excitation frequency (rad/s).

Returns

Cnp.ndarray: A 2x2 matrix of floats containing the cxx, cxy, cyx, and cyy values (N*s/m).

Examples

>>> bearing = bearing_example()
>>> bearing.C(0)
array([[200.,   0.],
       [  0., 150.]])

G()#

Gyroscopic matrix for an instance of a bearing element.

This method returns the mass matrix for an instance of a bearing element.

Returns

Gnp.ndarray: A 2x2 matrix of floats.

Examples

>>> bearing = bearing_example()
>>> bearing.G()
array([[0., 0.],
       [0., 0.]])

K(frequency)#

Stiffness matrix for an instance of a bearing element.

This method returns the stiffness matrix for an instance of a bearing element.

Parameters

frequencyfloat: The excitation frequency (rad/s).

Returns

Knp.ndarray: A 2x2 matrix of floats containing the kxx, kxy, kyx, and kyy values.

Examples

>>> bearing = bearing_example()
>>> bearing.K(0)
array([[1000000.,       0.],
       [      0.,  800000.]])

M(frequency)#

Mass matrix for an instance of a bearing element.

This method returns the mass matrix for an instance of a bearing element.

Returns

Mnp.ndarray: Mass matrix (kg).

Examples

>>> bearing = bearing_example()
>>> bearing.M(0)
array([[0., 0.],
       [0., 0.]])

__init__(n, g0, i0, ag, nw, alpha, kp_pid, kd_pid, k_amp, k_sense, tag=None, n_link=None, scale_factor=1, **kwargs)#

dof_local_index()#

Get the local index for a element specific degree of freedom.

Returns

local_index: namedtupple: A named tuple containing the local index.

Examples

>>> # Example using BearingElement
>>> from ross.bearing_seal_element import bearing_example
>>> bearing = bearing_example()
>>> bearing.dof_local_index()
LocalIndex(x_0=0, y_0=1)

dof_mapping()#

Degrees of freedom mapping.

Returns a dictionary with a mapping between degree of freedom and its index.

Returns

dof_mappingdict: A dictionary containing the degrees of freedom and their indexes.

Examples

The numbering of the degrees of freedom for each node.

Being the following their ordering for a node:

x_0 - horizontal translation y_0 - vertical translation

>>> bearing = bearing_example()
>>> bearing.dof_mapping()
{'x_0': 0, 'y_0': 1}

classmethod from_table(n, file, sheet_name=0, tag=None, n_link=None, scale_factor=1, color='#355d7a')#

Instantiate a bearing using inputs from an Excel table.

A header with the names of the columns is required. These names should match the names expected by the routine (usually the names of the parameters, but also similar ones). The program will read every row bellow the header until they end or it reaches a NaN.

Parameters

nint: The node in which the bearing will be located in the rotor.
filestr: Path to the file containing the bearing parameters.
sheet_nameint or str, optional: Position of the sheet in the file (starting from 0) or its name. If none is passed, it is assumed to be the first sheet in the file.
tagstr, optional: A tag to name the element. Default is None.
n_linkint, optional: Node to which the bearing will connect. If None the bearing is connected to ground. Default is None.
scale_factorfloat, optional: The scale factor is used to scale the bearing drawing. Default is 1.
colorstr, optional: A color to be used when the element is represented. Default is ‘#355d7a’ (Cardinal).

Returns

bearingrs.BearingElement: A bearing object.

Examples

>>> import os
>>> file_path = os.path.dirname(os.path.realpath(__file__)) + '/tests/data/bearing_seal_si.xls'
>>> BearingElement.from_table(0, file_path, n_link=1) 
BearingElement(n=0, n_link=1,
 kxx=[1.379...

classmethod load(file)#

plot(coefficients=None, frequency_units='rad/s', stiffness_units='N/m', damping_units='N*s/m', mass_units='kg', fig=None, **kwargs)#

Plot coefficient vs frequency.

Parameters

coefficientslist, str: List or str with the coefficients to plot.
frequency_unitsstr, optional: Frequency units. Default is rad/s.
stiffness_unitsstr, optional: Stiffness units. Default is N/m.
damping_unitsstr, optional: Damping units. Default is N*s/m.
mass_unitsstr, optional: Mass units. Default is kg.
**kwargsoptional: Additional key word arguments can be passed to change the plot layout only (e.g. width=1000, height=800, …). *See Plotly Python Figure Reference for more information.

Returns

figPlotly graph_objects.Figure(): The figure object with the plot.

classmethod read_toml_data(data)#

Read and parse data stored in a .toml file.

The data passed to this method needs to be according to the format saved in the .toml file by the .save() method.

Parameters

datadict: Dictionary obtained from toml.load().

Returns

The element object.

Examples

>>> # Example using BearingElement
>>> from tempfile import tempdir
>>> from pathlib import Path
>>> from ross.bearing_seal_element import bearing_example
>>> from ross.bearing_seal_element import BearingElement
>>> # create path for a temporary file
>>> file = Path(tempdir) / 'bearing1.toml'
>>> bearing1 = bearing_example()
>>> bearing1.save(file)
>>> bearing1_loaded = BearingElement.load(file)
>>> bearing1 == bearing1_loaded
True

save(file)#

Save the element in a .toml file.

This function will save the element to a .toml file. The file will have all the argument’s names and values that are needed to reinstantiate the element.

Parameters

filestr, pathlib.Path: The name of the file the element will be saved in.

Examples

>>> # Example using DiskElement
>>> from tempfile import tempdir
>>> from pathlib import Path
>>> from ross.disk_element import disk_example
>>> # create path for a temporary file
>>> file = Path(tempdir) / 'disk.toml'
>>> disk = disk_example()
>>> disk.save(file)

summary()#

Present a summary for the element.

A pandas series with the element properties as variables.

Returns

A pandas series.

Examples

>>> # Example using DiskElement
>>> from ross.disk_element import disk_example
>>> disk = disk_example()
>>> disk.summary() 
n                             0
n_l                           0
n_r                           0...

classmethod table_to_toml(n, file)#

Convert bearing parameters to toml.

Convert a table with parameters of a bearing element to a dictionary ready to save to a toml file that can be later loaded by ross.

Parameters

nint: The node in which the bearing will be located in the rotor.
filestr: Path to the file containing the bearing parameters.

Returns

datadict: A dict that is ready to save to toml and readable by ross.

Examples

>>> import os
>>> file_path = os.path.dirname(os.path.realpath(__file__)) + '/tests/data/bearing_seal_si.xls'
>>> BearingElement.table_to_toml(0, file_path) 
{'n': 0, 'kxx': array([...

ROSS

ross.MagneticBearingElement

ross.MagneticBearingElement#