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fix damp command natural frequency printout for discrete poles on real axis #894

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Merged
merged 3 commits into from
May 28, 2023
Merged

fix damp command natural frequency printout for discrete poles on real axis #894

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47cbe72
fix damp command natural frequency printout for discrete poles on rea…
sawyerbfuller May 22, 2023
cec6b5c
docstring make explicit that doprint is optional
sawyerbfuller May 22, 2023
6cfd466
output more readable
sawyerbfuller May 23, 2023
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72 changes: 31 additions & 41 deletions control/lti.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2,22 +2,14 @@

The lti module contains the LTI parent class to the child classes StateSpace
and TransferFunction. It is designed for use in the python-control library.

Routines in this module:

LTI.__init__
isdtime()
isctime()
timebase()
common_timebase()
"""

import numpy as np

from numpy import absolute, real, angle, abs
from numpy import real, angle, abs
from warnings import warn
from . import config
from .namedio import NamedIOSystem, isdtime
from .namedio import NamedIOSystem

__all__ = ['poles', 'zeros', 'damp', 'evalfr', 'frequency_response',
'freqresp', 'dcgain', 'bandwidth', 'pole', 'zero']
Expand Down Expand Up @@ -110,21 +102,21 @@ def damp(self):
Returns
-------
wn : array
Natural frequencies for each system pole
Natural frequency for each system pole
zeta : array
Damping ratio for each system pole
poles : array
Array of system poles
System pole locations
'''
poles = self.poles()

if self.isdtime(strict=True):
splane_poles = np.log(poles.astype(complex))/self.dt
else:
splane_poles = poles
wn = absolute(splane_poles)
Z = -real(splane_poles)/wn
return wn, Z, poles
wn = abs(splane_poles)
zeta = -real(splane_poles)/wn
return wn, zeta, poles

def frequency_response(self, omega, squeeze=None):
"""Evaluate the linear time-invariant system at an array of angular
Expand Down Expand Up @@ -346,25 +338,23 @@ def zero(sys):

def damp(sys, doprint=True):
"""
Compute natural frequency, damping ratio, and poles of a system

The function takes 1 or 2 parameters
Compute natural frequencies, damping ratios, and poles of a system

Parameters
----------
sys: LTI (StateSpace or TransferFunction)
sys : LTI (StateSpace or TransferFunction)
A linear system object
doprint:
if true, print table with values
doprint : bool (optional)
if True, print table with values

Returns
-------
wn: array
Natural frequencies of the poles
damping: array
Damping values
poles: array
Pole locations
wn : array
Natural frequency for each system pole
zeta : array
Damping ratio for each system pole
poles : array
System pole locations

See Also
--------
Expand All @@ -374,37 +364,37 @@ def damp(sys, doprint=True):
-----
If the system is continuous,
wn = abs(poles)
Z = -real(poles)/poles.
zeta = -real(poles)/poles

If the system is discrete, the discrete poles are mapped to their
equivalent location in the s-plane via

s = log10(poles)/dt
s = log(poles)/dt

and

wn = abs(s)
Z = -real(s)/wn.
zeta = -real(s)/wn.

Examples
--------
>>> G = ct.tf([1], [1, 4])
>>> wn, damping, poles = ct.damp(G)
_____Eigenvalue______ Damping___ Frequency_
-4 1 4
>>> wn, zeta, poles = ct.damp(G)
Eigenvalue (pole) Damping Frequency
-4 1 4

"""
wn, damping, poles = sys.damp()
wn, zeta, poles = sys.damp()
if doprint:
print('_____Eigenvalue______ Damping___ Frequency_')
for p, d, w in zip(poles, damping, wn):
print(' Eigenvalue (pole) Damping Frequency')
for p, z, w in zip(poles, zeta, wn):
if abs(p.imag) < 1e-12:
print("%10.4g %10.4g %10.4g" %
(p.real, 1.0, -p.real))
print(" %10.4g %10.4g %10.4g" %
(p.real, 1.0, w))
else:
print("%10.4g%+10.4gj %10.4g %10.4g" %
(p.real, p.imag, d, w))
return wn, damping, poles
print("%10.4g%+10.4gj %10.4g %10.4g" %
(p.real, p.imag, z, w))
return wn, zeta, poles


def evalfr(sys, x, squeeze=None):
Expand Down