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fixed prewarp not working in c2d and sample_system, margin docstring improvements #669

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Merged
bnavigator merged 4 commits into from
Nov 8, 2021
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fixed prewarp not working in c2d and sample_system, margin docstring improvements #669

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ca8e670
misc bugfixes: fixed prewarp not working in c2d and sample_system, in…
sawyerbfuller Nov 5, 2021
bc5079b
reverted mistaken margin argument rearrangement and clarified definit…
sawyerbfuller Nov 5, 2021
cfb6e86
clarified docstring in stability-margins
sawyerbfuller Nov 5, 2021
4c66fb1
test prewarp in c2d and sample_system
sawyerbfuller Nov 8, 2021
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misc bugfixes: fixed prewarp not working in c2d and sample_system, in… 
…correct order of return arguments in margin, typos and changed to ControlMIMONotImplemented error where needed.
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@sawyerbfuller
sawyerbfuller committed Nov 5, 2021
commit ca8e67025c1b429ef8fb57541eb449059eddd8a5
6 changes: 4 additions & 2 deletions control/dtime.py
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Expand Up @@ -89,7 +89,8 @@ def sample_system(sysc, Ts, method='zoh', alpha=None, prewarp_frequency=None):
if not isctime(sysc):
raise ValueError("First argument must be continuous time system")

return sysc.sample(Ts, method, alpha, prewarp_frequency)
return sysc.sample(Ts,
method=method, alpha=alpha, prewarp_frequency=prewarp_frequency)
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def c2d(sysc, Ts, method='zoh', prewarp_frequency=None):
Expand Down Expand Up @@ -126,6 +127,7 @@ def c2d(sysc, Ts, method='zoh', prewarp_frequency=None):
"""

# Call the sample_system() function to do the work
sysd = sample_system(sysc, Ts, method, prewarp_frequency)
sysd = sample_system(sysc, Ts,
method=method, prewarp_frequency=prewarp_frequency)
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return sysd
8 changes: 4 additions & 4 deletions control/margins.py
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Expand Up @@ -283,7 +283,7 @@ def stability_margins(sysdata, returnall=False, epsw=0.0, method='best'):
-------
gm : float or array_like
Gain margin
pm : float or array_loke
pm : float or array_like
Phase margin
sm : float or array_like
Stability margin, the minimum distance from the Nyquist plot to -1
Expand Down Expand Up @@ -522,10 +522,10 @@ def margin(*args):
Gain margin
pm : float
Phase margin (in degrees)
wpc : float or array_like
Phase crossover frequency (where phase crosses -180 degrees)
wgc : float or array_like
Gain crossover frequency (where gain crosses 1)
wpc : float or array_like
Phase crossover frequency (where phase crosses -180 degrees)
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Outdated

Margins are calculated for a SISO open-loop system.

Expand All @@ -548,4 +548,4 @@ def margin(*args):
raise ValueError("Margin needs 1 or 3 arguments; received %i."
% len(args))

return margin[0], margin[1], margin[3], margin[4]
return margin[0], margin[1], margin[4], margin[3]
20 changes: 10 additions & 10 deletions control/tests/margin_test.py
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Expand Up @@ -102,15 +102,15 @@ def test_margin_sys(tsys):
sys, refout, refoutall = tsys
"""Test margin() function with system input"""
out = margin(sys)
assert_allclose(out, np.array(refout)[[0, 1, 3, 4]], atol=1.5e-3)
assert_allclose(out, np.array(refout)[[0, 1, 4, 3]], atol=1.5e-3)

def test_margin_3input(tsys):
sys, refout, refoutall = tsys
"""Test margin() function with mag, phase, omega input"""
omega = np.logspace(-2, 2, 2000)
mag, phase, omega_ = sys.frequency_response(omega)
out = margin((mag, phase*180/np.pi, omega_))
assert_allclose(out, np.array(refout)[[0, 1, 3, 4]], atol=1.5e-3)
assert_allclose(out, np.array(refout)[[0, 1, 4, 3]], atol=1.5e-3)


@pytest.mark.parametrize(
Expand Down Expand Up @@ -276,23 +276,23 @@ def tsys_zmore(request, tsys_zmoresystems):
@pytest.mark.parametrize(
'tsys_zmore',
[dict(sysname='typem1', K=2.0, atol=1.5e-3,
result=(float('Inf'), -120.0007, float('NaN'), 0.5774)),
result=(float('Inf'), -120.0007, 0.5774, float('NaN'))),
dict(sysname='type0', K=0.8, atol=1.5e-3,
result=(10.0014, float('inf'), 1.7322, float('nan'))),
result=(10.0014, float('inf'), float('nan'), 1.7322)),
dict(sysname='type0', K=2.0, atol=1e-2,
result=(4.000, 67.6058, 1.7322, 0.7663)),
result=(4.000, 67.6058, 0.7663, 1.7322)),
dict(sysname='type1', K=1.0, atol=1e-4,
result=(float('Inf'), 144.9032, float('NaN'), 0.3162)),
result=(float('Inf'), 144.9032, 0.3162, float('NaN'))),
dict(sysname='type2', K=1.0, atol=1e-4,
result=(float('Inf'), 44.4594, float('NaN'), 0.7907)),
result=(float('Inf'), 44.4594, 0.7907, float('NaN'))),
dict(sysname='type3', K=1.0, atol=1.5e-3,
result=(0.0626, 37.1748, 0.1119, 0.7951)),
result=(0.0626, 37.1748, 0.7951, 0.1119)),
dict(sysname='example21', K=1.0, atol=1e-2,
result=(0.0100, -14.5640, 0, 0.0022)),
dict(sysname='example21', K=1000.0, atol=1e-2,
result=(0.1793, 22.5215, 0.0243, 0.0630)),
result=(0.1793, 22.5215, 0.0630, 0.0243)),
dict(sysname='example21', K=5000.0, atol=1.5e-3,
result=(4.5596, 21.2101, 0.4385, 0.1868)),
result=(4.5596, 21.2101, 0.1868, 0.4385)),
],
indirect=True)
def test_zmore_margin(tsys_zmore):
Expand Down
6 changes: 3 additions & 3 deletions control/tests/matlab_test.py
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Expand Up @@ -361,7 +361,7 @@ def testMargin(self, siso):
gm, pm, wg, wp = margin(siso.ss2)
gm, pm, wg, wp = margin(siso.ss2 * siso.ss2 * 2)
np.testing.assert_array_almost_equal(
[gm, pm, wg, wp], [1.5451, 75.9933, 1.2720, 0.6559], decimal=3)
[gm, pm, wg, wp], [1.5451, 75.9933, 0.6559, 1.2720], decimal=3)

def testDcgain(self, siso):
"""Test dcgain() for SISO system"""
Expand Down Expand Up @@ -785,8 +785,8 @@ def testCombi01(self):
# print("%f %f %f %f" % (gm, pm, wg, wp))
np.testing.assert_allclose(gm, 3.32065569155)
np.testing.assert_allclose(pm, 46.9740430224)
np.testing.assert_allclose(wg, 0.176469728448)
np.testing.assert_allclose(wp, 0.0616288455466)
np.testing.assert_allclose(wg, 0.0616288455466)
np.testing.assert_allclose(wp, 0.176469728448)

def test_tf_string_args(self):
"""Make sure s and z are defined properly"""
Expand Down
12 changes: 7 additions & 5 deletions control/xferfcn.py
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Expand Up @@ -64,6 +64,7 @@
from itertools import chain
from re import sub
from .lti import LTI, common_timebase, isdtime, _process_frequency_response
from .exception import ControlMIMONotImplemented
from . import config

__all__ = ['TransferFunction', 'tf', 'ss2tf', 'tfdata']
Expand Down Expand Up @@ -793,9 +794,9 @@ def feedback(self, other=1, sign=-1):
if (self.ninputs > 1 or self.noutputs > 1 or
other.ninputs > 1 or other.noutputs > 1):
# TODO: MIMO feedback
raise NotImplementedError(
"TransferFunction.feedback is currently only implemented "
"for SISO functions.")
raise ControlMIMONotImplemented(
"TransferFunction.feedback is currently not implemented for "
"MIMO systems.")
dt = common_timebase(self.dt, other.dt)

num1 = self.num[0][0]
Expand Down Expand Up @@ -1117,7 +1118,7 @@ def sample(self, Ts, method='zoh', alpha=None, prewarp_frequency=None):
if not self.isctime():
raise ValueError("System must be continuous time system")
if not self.issiso():
raise NotImplementedError("MIMO implementation not available")
raise ControlMIMONotImplemented("Not implemented for MIMO systems")
if method == "matched":
return _c2d_matched(self, Ts)
sys = (self.num[0][0], self.den[0][0])
Expand Down Expand Up @@ -1373,7 +1374,8 @@ def _convert_to_transfer_function(sys, **kw):
except ImportError:
# If slycot is not available, use signal.lti (SISO only)
if sys.ninputs != 1 or sys.noutputs != 1:
raise TypeError("No support for MIMO without slycot.")
raise ControlMIMONotImplemented("Not implemented for " +
"MIMO systems without slycot.")

# Do the conversion using sp.signal.ss2tf
# Note that this returns a 2D array for the numerator
Expand Down