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Bode margins plot#199

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Merged
murrayrm merged 5 commits intopython-control:masterfromicam0:bode_margins_plot
Dec 28, 2018
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53 changes: 50 additions & 3 deletionscontrol/freqplot.py
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -47,6 +47,7 @@
import math
from .ctrlutil import unwrap
from .bdalg import feedback
from .margins import stability_margins

__all__ = ['bode_plot', 'nyquist_plot', 'gangof4_plot',
'bode', 'nyquist', 'gangof4']
Expand All@@ -60,7 +61,7 @@

# Bode plot
def bode_plot(syslist, omega=None, dB=None, Hz=None, deg=None,
Plot=True, omega_limits=None, omega_num=None, *args, **kwargs):
Plot=True, omega_limits=None, omega_num=None,margins=None, *args, **kwargs):
"""
Bode plot for a system

Expand All@@ -85,6 +86,8 @@ def bode_plot(syslist, omega=None, dB=None, Hz=None, deg=None,
If Hz=True the limits are in Hz otherwise in rad/s.
omega_num: int
number of samples
margins : boolean
if True, plot gain and phase margin
\*args, \**kwargs:
Additional options to matplotlib (color, linestyle, etc)

Expand DownExpand Up@@ -209,7 +212,7 @@ def bode_plot(syslist, omega=None, dB=None, Hz=None, deg=None,
color=pltline[0].get_color())

# Add a grid to the plot + labeling
ax_mag.grid(True, which='both')
ax_mag.grid(False if margins elseTrue, which='both')
ax_mag.set_ylabel("Magnitude (dB)" if dB else "Magnitude")

# Phase plot
Expand All@@ -219,6 +222,50 @@ def bode_plot(syslist, omega=None, dB=None, Hz=None, deg=None,
phase_plot = phase
ax_phase.semilogx(omega_plot, phase_plot, *args, **kwargs)

# Show the phase and gain margins in the plot
if margins:
margin = stability_margins(sys)
gm, pm, Wcg, Wcp = margin[0], margin[1], margin[3], margin[4]
if pm >= 0.:
phase_limit = -180.
else:
phase_limit = 180.

ax_mag.axhline(y=0 if dB else 1, color='k', linestyle=':')
ax_phase.axhline(y=phase_limit if deg else math.radians(phase_limit), color='k', linestyle=':')
mag_ylim = ax_mag.get_ylim()
phase_ylim = ax_phase.get_ylim()

if pm != float('inf') and Wcp != float('nan'):
if dB:
ax_mag.semilogx([Wcp, Wcp], [0.,-1e5],color='k', linestyle=':')
else:
ax_mag.loglog([Wcp,Wcp], [1.,1e-8],color='k',linestyle=':')

if deg:
ax_phase.semilogx([Wcp, Wcp], [1e5, phase_limit+pm],color='k', linestyle=':')
ax_phase.semilogx([Wcp, Wcp], [phase_limit + pm, phase_limit],color='k')
else:
ax_phase.semilogx([Wcp, Wcp], [1e5, math.radians(phase_limit)+math.radians(pm)],color='k', linestyle=':')
ax_phase.semilogx([Wcp, Wcp], [math.radians(phase_limit) +math.radians(pm), math.radians(phase_limit)],color='k')

if gm != float('inf') and Wcg != float('nan'):
if dB:
ax_mag.semilogx([Wcg, Wcg], [-20.*np.log10(gm), -1e5],color='k', linestyle=':')
ax_mag.semilogx([Wcg, Wcg], [0,-20*np.log10(gm)],color='k')
else:
ax_mag.loglog([Wcg, Wcg], [1./gm,1e-8],color='k', linestyle=':')
ax_mag.loglog([Wcg, Wcg], [1.,1./gm],color='k')

if deg:
ax_phase.semilogx([Wcg, Wcg], [1e-8, phase_limit],color='k', linestyle=':')
else:
ax_phase.semilogx([Wcg, Wcg], [1e-8, math.radians(phase_limit)],color='k', linestyle=':')

ax_mag.set_ylim(mag_ylim)
ax_phase.set_ylim(phase_ylim)
plt.suptitle('Gm = %.2f %s(at %.2f rad/s), Pm = %.2f %s (at %.2f rad/s)'%(20*np.log10(gm) if dB else gm,'dB ' if dB else '\b',Wcg,pm if deg else math.radians(pm),'deg' if deg else 'rad',Wcp))

if nyquistfrq_plot:
ax_phase.axvline(nyquistfrq_plot, color=pltline[0].get_color())

Expand All@@ -237,7 +284,7 @@ def genZeroCenteredSeries(val_min, val_max, period):
ylim = ax_phase.get_ylim()
ax_phase.set_yticks(genZeroCenteredSeries(ylim[0], ylim[1], math.pi / 4.))
ax_phase.set_yticks(genZeroCenteredSeries(ylim[0], ylim[1], math.pi / 12.), minor=True)
ax_phase.grid(True, which='both')
ax_phase.grid(False if margins elseTrue, which='both')
# ax_mag.grid(which='minor', alpha=0.3)
# ax_mag.grid(which='major', alpha=0.9)
# ax_phase.grid(which='minor', alpha=0.3)
Expand Down
29 changes: 29 additions & 0 deletionscontrol/tests/freqresp_test.py
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -13,6 +13,7 @@
from control.xferfcn import TransferFunction
from control.matlab import ss, tf, bode, rss
from control.exception import slycot_check
from control.tests.margin_test import assert_array_almost_equal
import matplotlib.pyplot as plt

class TestFreqresp(unittest.TestCase):
Expand DownExpand Up@@ -108,6 +109,34 @@ def test_mimo(self):
#plt.figure(4)
#bode(sysMIMO,self.omega)

def test_bode_margin(self):
num = [1000]
den = [1, 25, 100, 0]
sys = ctrl.tf(num, den)
ctrl.bode_plot(sys, margins=True,dB=False,deg = True)
fig = plt.gcf()
allaxes = fig.get_axes()

mag_to_infinity = (np.array([6.07828691, 6.07828691]),
np.array([1.00000000e+00, 1.00000000e-08]))
assert_array_almost_equal(mag_to_infinity, allaxes[0].lines[2].get_data())

gm_to_infinty = (np.array([10., 10.]), np.array([4.00000000e-01, 1.00000000e-08]))
assert_array_almost_equal(gm_to_infinty, allaxes[0].lines[3].get_data())

one_to_gm = (np.array([10., 10.]), np.array([1., 0.4]))
assert_array_almost_equal(one_to_gm, allaxes[0].lines[4].get_data())

pm_to_infinity = (np.array([6.07828691, 6.07828691]),
np.array([100000., -157.46405841]))
assert_array_almost_equal(pm_to_infinity, allaxes[1].lines[2].get_data())

pm_to_phase = (np.array([6.07828691, 6.07828691]), np.array([-157.46405841, -180.]))
assert_array_almost_equal(pm_to_phase, allaxes[1].lines[3].get_data())

phase_to_infinity = (np.array([10., 10.]), np.array([1.00000000e-08, -1.80000000e+02]))
assert_array_almost_equal(phase_to_infinity, allaxes[1].lines[4].get_data())

def test_discrete(self):
# Test discrete time frequency response

Expand Down
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