ross.stochastic.ST_Rotor

class ross.stochastic.ST_Rotor(shaft_elements, disk_elements=None, bearing_elements=None, point_mass_elements=None, min_w=None, max_w=None, rated_w=None, tag=None)

A random rotor object.

This class will create several rotors according to random elements passed to the arguments. The number of rotors to be created depends on the amount of random elements instantiated and theirs respective sizes.

Parameters:

shaft_elementslist

List with the shaft elements

disk_elementslist

List with the disk elements

bearing_elementslist

List with the bearing elements

point_mass_elements: list

List with the point mass elements

tagstr

A tag for the rotor

Attributes:

RV_sizeint

Number of random rotor instances.

ndofint

Number of degrees of freedom for random rotor instances.

Returns:

Random rotors objects

Examples

# Rotor with 2 shaft elements, 1 random disk element and 2 bearings >>> import numpy as np >>> import ross as rs >>> import ross.stochastic as srs >>> steel = rs.materials.steel >>> le = 0.25 >>> i_d = 0 >>> o_d = 0.05 >>> tim0 = rs.ShaftElement(le, i_d, o_d, material=steel) >>> tim1 = rs.ShaftElement(le, i_d, o_d, material=steel) >>> shaft_elm = [tim0, tim1]

# Building random disk element >>> size = 5 >>> i_d = np.random.uniform(0.05, 0.06, size) >>> o_d = np.random.uniform(0.35, 0.39, size) >>> disk0 = srs.ST_DiskElement.from_geometry(n=1, … material=steel, … width=0.07, … i_d=i_d, … o_d=o_d, … is_random=[“i_d”, “o_d”], … ) >>> stf = 1e6 >>> bearing0 = rs.BearingElement(0, kxx=stf, cxx=0) >>> bearing1 = rs.BearingElement(2, kxx=stf, cxx=0) >>> rand_rotor = srs.ST_Rotor(shaft_elm, [disk0], [bearing0, bearing1]) >>> len(list(iter(rand_rotor))) 5

Methods

__init__(shaft_elements, disk_elements=None, bearing_elements=None, point_mass_elements=None, min_w=None, max_w=None, rated_w=None, tag=None)

run_campbell(speed_range, frequencies=6, frequency_type='wd')

Stochastic Campbell diagram for multiples rotor systems.

This function will calculate the damped or undamped natural frequencies for a speed range for every rotor instance.

Parameters:

speed_rangearray

Array with the desired range of frequencies.

frequenciesint, optional

Number of frequencies that will be calculated. Default is 6.

frequency_typestr, optional

Choose between displaying results related to the undamped natural frequencies (“wn”) or damped natural frequencies (“wd”). The default is “wd”.

Returns:

results.speed_rangearray

Array with the frequency range

results.wdarray

Array with the damped or undamped natural frequencies corresponding to each speed of the speed_range array for each rotor instance.

results.log_decarray

Array with the log dec corresponding to each speed of the speed_range array for each rotor instance.

run_freq_response(inp, out, speed_range=None, modes=None)

Stochastic frequency response for multiples rotor systems.

This method returns the frequency response for every rotor instance, given a range of frequencies, the degrees of freedom to be excited and observed and the modes that will be used.

Parameters:

inpint

Input DoF.

outint

Output DoF.

speed_rangearray, optional

Array with the desired range of frequencies. Default is 0 to 1.5 x highest damped natural frequency.

modeslist, optional

Modes that will be used to calculate the frequency response (all modes will be used if a list is not given).

Returns:

results.speed_rangearray

Array with the frequencies.

results.magnitudearray

Amplitude response for each rotor system.

results.phasearray

Phase response for each rotor system.

run_time_response(speed, force, time_range, ic=None)

Stochastic time response for multiples rotor systems.

This function will take a rotor object and plot its time response given a force and a time. This method displays the amplitude vs time or the rotor orbits. The force and ic parameters can be passed as random variables.

Parameters:

speed: float

Rotor speed

force2-dimensional array, 3-dimensional array

Force array (needs to have the same number of rows as time array). Each column corresponds to a dof and each row to a time step. Inputing a 3-dimensional array, the method considers the force as a random variable. The 3rd dimension must have the same size than ST_Rotor.RV_size

time_range1-dimensional array

Time array.

ic1-dimensional array, 2-dimensional array, optional

The initial conditions on the state vector (zero by default). Inputing a 2-dimensional array, the method considers the initial condition as a random variable.

Returns:

results.time_rangearray

Array containing the time array.

results.youtarray

System response.

results.xout

Time evolution of the state vector for each rotor system.

run_unbalance_response(node, unbalance_magnitude, unbalance_phase, frequency_range=None, modes=None)

Stochastic unbalance response for multiples rotor systems.

This method returns the unbalanced response for every rotor instance, given magnitide and phase of the unbalance, the node where it’s applied and a frequency range.

Magnitude and phase parameters can be passed as random variables.

Parameters:

nodelist, int

Node where the unbalance is applied.

unbalance_magnitudelist, float, pint.Quantity

Unbalance magnitude (kg.m). If node is int, input a list to make make it random. If node is list, input a list of lists to make it random. If there’re multiple unbalances and not all of the magnitudes are supposed to be stochastic, input a list with repeated values to the unbalance magnitude considered deterministic.

unbalance_phaselist, float, pint.Quantity

Unbalance phase (rad). If node is int, input a list to make make it random. If node is list, input a list of lists to make it random. If there’re multiple unbalances and not all of the phases are supposed to be stochastic, input a list with repeated values to the unbalance phase considered deterministic.

frequency_rangelist, float, optional

Array with the desired range of frequencies. Default is 0 to 1.5 x highest damped natural frequency.

modeslist, optional

Modes that will be used to calculate the frequency response (all modes will be used if a list is not given).

Returns:

results.force_resparray

Array with the force response for each node for each frequency

results.speed_rangearray

Array with the frequencies.

results.magnitudearray

Magnitude of the frequency response for node for each frequency.

results.phasearray

Phase of the frequency response for node for each frequencye.

use_random_var(f, is_random, *args)

Generate a list of random objects from random attributes.

This function creates a list of objects with random values for selected attributes from ross.Rotor class or its methods.

Parameters:

fcallable

Function to be instantiated randomly with its respective *args.

is_randomlist

List of the object attributes to become stochastic.

*argsdict

Dictionary instanciating the ross.Rotor class. The attributes that are supposed to be stochastic should be set as lists of random variables.

Returns:

f_listgenerator

Generator of random objects.