Ill-conditioned matrix (rcond=2.68289e-18): result may not be accurate.

[shishirsanjeeva]

Hi Guys,
I modelled a rotor and its getting plotted. However, when I run .run_static(), I am getting a warning after using Rotor.from_section(). Could you please let me know the reason for the same and how to avoid following warning?

LinAlgWarning:

Ill-conditioned matrix (rcond=2.68289e-18): result may not be accurate.

[raphaeltimbo]

Hi, @shishirsanjeeva. If you could please provide the code used to generate the rotor, or a .toml file with the saved rotor, I could try to investigate the cause of this warning.

[shishirsanjeeva]

Hi @raphaeltimbo.
Please find the attached code below.

import ross as rs
import numpy as np
import plotly.graph_objects as go
import plotly.io as pio

pio.renderers.default='browser'

steel = rs.Material(name="Steel", rho=7810, E=211e9, G_s=81.2e9)

L =   [0.035, 0.005, 0.07/2, 0.07/2, 0.011/2, 0.011/2, 0.03, 0.1, 0.023/2, 0.023/2,
       0.01, 0.01, 0.03/2, 0.03/2, 0.015, 0.01]
o_dl = [0.008, 0.01, 0.012,0.012, 0.012,0.012, 0.015, 0.02, 0.02, 0.015, 0.01,0.01,
       0.012,0.012, 0.012, 0.01]
o_dr = o_dl = [0.008, 0.01, 0.012,0.012, 0.012,0.012, 0.015, 0.02, 0.02, 0.015, 0.01,0.01,
       0.012,0.012, 0.012, 0.01]
i_d = list(np.zeros((16), dtype=int))

n_list = [3, 13]
m_list = [0.5, 0.8]
Ip_list = [500e-6, 600e-6]
Id_list = [400e-6, 300e-6]
color_list=  ['Navy','Firebrick']
tag_list= ["Disc1", "Disc2"]
disk_elements = [
    rs.DiskElement(
        n=n,
        m=m,
        Id=Id,
        Ip=Ip,
        tag=tag1,
        color=color1
    )
    for n, m, Id, Ip,tag1, color1 in zip(n_list, m_list, Id_list, Ip_list,tag_list, color_list)
]

bearing_stiffness= 50e6                 #N-m
bearing0 = rs.BearingElement(
    n=5, 
    kxx= bearing_stiffness,
    kyy= bearing_stiffness,
    cxx=0,
    tag= "B1"
)
bearing1 = rs.BearingElement(
    n=11, 
    kxx= bearing_stiffness,
    kyy= bearing_stiffness,
    cxx=0,
    tag= "B2"
)
bearings = [bearing0, bearing1]

rotor2 = rs.Rotor.from_section(leng_data=L, 
                               idl_data= i_d, 
                               odl_data=o_dl,
                               odr_data=o_dr,
                               material_data=steel,
                               disk_data=disk_elements,
                               brg_seal_data=bearings,
                               #nel_r= 1,
                               tag=" Rotor2",
                               )

rotor2.plot_rotor()
static = rotor2.run_static()