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From: <all...@us...> - 2011-02-13 13:21:35
|
Revision: 133
http://python-control.svn.sourceforge.net/python-control/?rev=133&view=rev
Author: allanmcinnes
Date: 2011-02-13 13:21:29 +0000 (Sun, 13 Feb 2011)
Log Message:
-----------
Split out common code from M-circle and N-circle utility functions. Make variable naming through nichols_grid and utility functions more consistent, and provide more explanation of what's going on.
Modified Paths:
--------------
trunk/src/freqplot.py
Modified: trunk/src/freqplot.py
===================================================================
--- trunk/src/freqplot.py 2011-02-13 03:35:38 UTC (rev 132)
+++ trunk/src/freqplot.py 2011-02-13 13:21:29 UTC (rev 133)
@@ -247,55 +247,69 @@
-------------
None
"""
- gmin_default = -40.0 # dB
- gain_step = 20.0 # dB
+ mag_min_default = -40.0 # dB
+ mag_step = 20.0 # dB
+ # Chart defaults
+ phase_min, phase_max, mag_min, mag_max = -360.0, 0.0, mag_min_default, 40.0
+
+ # Set actual chart bounds based on current plot
if plt.gcf().gca().has_data():
- pmin, pmax, gmin, gmax = plt.axis()
+ phase_min, phase_max, mag_min, mag_max = plt.axis()
+
+ # M-circle magnitudes.
+ # The "fixed" set are always generated, since this guarantees a recognizable
+ # Nichols chart grid.
+ mags_fixed = np.array([-40.0, -20.0, -12.0, -6.0, -3.0, -1.0, -0.5, 0.0,
+ 0.25, 0.5, 1.0, 3.0, 6.0, 12.0])
+
+ if mag_min < mag_min_default:
+ # Outside the "fixed" set of magnitudes, the generated M-circles
+ # are extended in steps of 'mag_step' dB to cover anything made
+ # visible by the range of the existing plot
+ mags_adjust = np.arange(mag_step*np.floor(mag_min/mag_step),
+ mag_min_default, mag_step)
+ mags = np.concatenate((mags_adjust, mags_fixed))
else:
- pmin, pmax = -360.0, 0.0
- gmin, gmax = gmin_default, 40.0
-
- # Determine the bounds of the chart
- mags_low_end = np.min([gmin_default, gain_step*np.floor(gmin/gain_step)])
- phases_low_end = 360.0*np.ceil(pmin/360.0)
- phases_high_end = 360.0*(1.0 + np.ceil(pmax/360.0))
-
- # M-circle magnitudes - we adjust the lower end of the range to match
- # any existing data
- mags_fixed = np.array([-20.0, -12.0, -6.0, -3.0, -1.0, -0.5, 0.0,
- 0.25, 0.5, 1.0, 3.0, 6.0, 12.0])
- mags_adjustable = np.arange(mags_low_end, np.min(mags_fixed), gain_step)
- mags = np.concatenate((mags_adjustable, mags_fixed))
+ mags = mags_fixed
# N-circle phases (should be in the range -360 to 0)
phases = np.array([-0.25, -10.0, -20.0, -30.0, -45.0, -60.0, -90.0,
-120.0, -150.0, -180.0, -210.0, -240.0, -270.0,
-310.0, -325.0, -340.0, -350.0, -359.75])
+
# Find the M-contours
- mcs = m_circles(mags, pmin=np.min(phases), pmax=np.max(phases))
- mag_m = 20*sp.log10(np.abs(mcs))
- phase_m = sp.mod(sp.degrees(sp.angle(mcs)), -360.0) # Unwrap
+ m = m_circles(mags, phase_min=np.min(phases), phase_max=np.max(phases))
+ m_mag = 20*sp.log10(np.abs(m))
+ m_phase = sp.mod(sp.degrees(sp.angle(m)), -360.0) # Unwrap
# Find the N-contours
- ncs = n_circles(phases, gmin=np.min(mags), gmax=np.max(mags))
- mag_n = 20*sp.log10(np.abs(ncs))
- phase_n = sp.mod(sp.degrees(sp.angle(ncs)), -360.0) # Unwrap
+ n = n_circles(phases, mag_min=np.min(mags), mag_max=np.max(mags))
+ n_mag = 20*sp.log10(np.abs(n))
+ n_phase = sp.mod(sp.degrees(sp.angle(n)), -360.0) # Unwrap
- # Plot the contours
- for phase_offset in np.arange(phases_low_end, phases_high_end, 360.0):
- plt.plot(phase_m + phase_offset, mag_m, color='gray',
+ # Plot the contours behind other plot elements.
+ # The "phase offset" is used to produce copies of the chart that cover
+ # the entire range of the plotted data, starting from a base chart computed
+ # over the range -360 < phase < 0 (see above). Given the range
+ # the base chart is computed over, the phase offset should be 0
+ # for -360 < phase_min < 0.
+ phase_offset_min = 360.0*np.ceil(phase_min/360.0)
+ phase_offset_max = 360.0*np.ceil(phase_max/360.0) + 360.0
+ phase_offsets = np.arange(phase_offset_min, phase_offset_max, 360.0)
+ for phase_offset in phase_offsets:
+ plt.plot(m_phase + phase_offset, m_mag, color='gray',
linestyle='dashed', zorder=0)
- plt.plot(phase_n + phase_offset, mag_n, color='gray',
+ plt.plot(n_phase + phase_offset, n_mag, color='gray',
linestyle='dashed', zorder=0)
# Add magnitude labels
- for x, y, m in zip(phase_m[:][-1], mag_m[:][-1], mags):
+ for x, y, m in zip(m_phase[:][-1], m_mag[:][-1], mags):
align = 'right' if m < 0.0 else 'left'
plt.text(x, y, str(m) + ' dB', size='small', ha=align)
# Make sure axes conform to any pre-existing plot.
- plt.axis([pmin, pmax, gmin, gmax])
+ plt.axis([phase_min, phase_max, mag_min, mag_max])
# Gang of Four
#! TODO: think about how (and whether) to handle lists of systems
@@ -402,54 +416,84 @@
return omega
+# Compute contours of a closed-loop transfer function
+def closed_loop_contours(Hmag, Hphase):
+ """Contours of the function H = G/(1+G).
+
+ Usage
+ =====
+ contours = closed_loop_contours(mags, phases)
+
+ Parameters
+ ----------
+ mags : array-like
+ Meshgrid array of magnitudes of the contours
+ phases : array-like
+ Meshgrid array of phases in radians of the contours
+
+ Return values
+ -------------
+ contours : complex array
+ Array of complex numbers corresponding to the contours.
+ """
+ # Compute the contours in H-space
+ H = Hmag*sp.exp(1.j*Hphase)
+
+ # Invert H = G/(1+G) to get an expression for the contours in G-space
+ return H/(1.0 - H)
+
# M-circle
-def m_circles(mags, pmin=-359.75, pmax=-0.25):
+def m_circles(mags, phase_min=-359.75, phase_max=-0.25):
"""Constant-magnitude contours of the function H = G/(1+G).
Usage
=====
- contour = m_circle(mags)
+ contours = m_circles(mags)
Parameters
----------
mags : array-like
Array of magnitudes in dB of the M-circles
+ phase_min : degrees
+ Minimum phase in degrees of the N-circles
+ phase_max : degrees
+ Maximum phase in degrees of the N-circles
Return values
-------------
- contour : complex array
- Array of complex numbers corresponding to the contour.
+ contours : complex array
+ Array of complex numbers corresponding to the contours.
"""
- # Compute the contours in H-space
- phases = sp.radians(sp.linspace(pmin, pmax, 500))
+ # Convert magnitudes and phase range into a grid suitable for
+ # building contours
+ phases = sp.radians(sp.linspace(phase_min, phase_max, 500))
Hmag, Hphase = sp.meshgrid(10.0**(mags/20.0), phases)
- H = Hmag*sp.exp(1.j*Hphase)
-
- # Invert H = G/(1+G) to get an expression for the contour in G-space
- return H/(1.0 - H)
+ return closed_loop_contours(Hmag, Hphase)
# N-circle
-def n_circles(phases, gmin=-40.0, gmax=12.0):
+def n_circles(phases, mag_min=-40.0, mag_max=12.0):
"""Constant-phase contours of the function H = G/(1+G).
Usage
=====
- contour = n_circle(angles)
+ contour = n_circles(angles)
Parameters
----------
phases : array-like
- Array of phases in degrees of the N-circle
+ Array of phases in degrees of the N-circles
+ mag_min : dB
+ Minimum magnitude in dB of the N-circles
+ mag_max : dB
+ Maximum magnitude in dB of the N-circles
Return values
-------------
- contour : complex array
+ contours : complex array
Array of complex numbers corresponding to the contours.
"""
- # Compute the contours in H-space
- mags = sp.linspace(10**(gmin/20.0), 10**(gmax/20.0), 2000)
+ # Convert phases and magnitude range into a grid suitable for
+ # building contours
+ mags = sp.linspace(10**(mag_min/20.0), 10**(mag_max/20.0), 2000)
Hphase, Hmag = sp.meshgrid(sp.radians(phases), mags)
- H = Hmag*sp.exp(1.j*Hphase)
-
- # Invert H = G/(1+G) to get an expression for the contours in G-space
- return H/(1.0 - H)
+ return closed_loop_contours(Hmag, Hphase)
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|
|
From: <all...@us...> - 2011-02-14 07:49:12
|
Revision: 135
http://python-control.svn.sourceforge.net/python-control/?rev=135&view=rev
Author: allanmcinnes
Date: 2011-02-14 07:49:05 +0000 (Mon, 14 Feb 2011)
Log Message:
-----------
Add the ability to define custom Nichols charts by passing magnitude and/or phase arrays to nichols_grid. Also some tweaks to the chart grid generation and axis configuration, and further clean-up of documentation and naming.
Modified Paths:
--------------
trunk/src/freqplot.py
Modified: trunk/src/freqplot.py
===================================================================
--- trunk/src/freqplot.py 2011-02-13 16:49:58 UTC (rev 134)
+++ trunk/src/freqplot.py 2011-02-14 07:49:05 UTC (rev 135)
@@ -181,7 +181,7 @@
# Nichols plot
# Contributed by Allan McInnes <All...@ca...>
#! TODO: need unit test code
-def nichols(syslist, omega=None):
+def nichols(syslist, omega=None, grid=True):
"""Nichols plot for a system
Usage
@@ -196,6 +196,8 @@
List of linear input/output systems (single system is OK)
omega : freq_range
Range of frequencies (list or bounds) in rad/sec
+ grid : boolean
+ True if the plot should include a Nichols-chart grid
Return values
-------------
@@ -228,88 +230,114 @@
# Mark the -180 point
plt.plot([-180], [0], 'r+')
+
+ # Add grid
+ if grid:
+ nichols_grid()
# Nichols grid
-def nichols_grid():
+def nichols_grid(**kwargs):
"""Nichols chart grid
Usage
=====
nichols_grid()
- Plots a Nichols chart grid on the current axis.
+ Plots a Nichols chart grid on the current axis, or creates a new chart
+ if no plot already exists.
Parameters
----------
- None
+ cl_mags : array-like (dB)
+ Array of closed-loop magnitudes defining the iso-gain lines on a
+ custom Nichols chart.
+ cl_phases : array-like (degrees)
+ Array of closed-loop phases defining the iso-phase lines on a custom
+ Nichols chart. Must be in the range -360 < cl_phases < 0
Return values
-------------
None
"""
- mag_min_default = -40.0 # dB
- mag_step = 20.0 # dB
+ # Default chart size
+ ol_phase_min = -359.99
+ ol_phase_max = 0.0
+ ol_mag_min = -40.0
+ ol_mag_max = default_ol_mag_max = 50.0
+
+ # Find bounds of the current dataset, if there is one.
+ if plt.gcf().gca().has_data():
+ ol_phase_min, ol_phase_max, ol_mag_min, ol_mag_max = plt.axis()
- # Chart defaults
- phase_min, phase_max, mag_min, mag_max = -360.0, 0.0, mag_min_default, 40.0
-
- # Set actual chart bounds based on current plot
- if plt.gcf().gca().has_data():
- phase_min, phase_max, mag_min, mag_max = plt.axis()
-
# M-circle magnitudes.
- # The "fixed" set are always generated, since this guarantees a recognizable
- # Nichols chart grid.
- mags_fixed = np.array([-40.0, -20.0, -12.0, -6.0, -3.0, -1.0, -0.5, 0.0,
- 0.25, 0.5, 1.0, 3.0, 6.0, 12.0])
-
- if mag_min < mag_min_default:
- # Outside the "fixed" set of magnitudes, the generated M-circles
- # are extended in steps of 'mag_step' dB to cover anything made
- # visible by the range of the existing plot
- mags_adjust = np.arange(mag_step*np.floor(mag_min/mag_step),
- mag_min_default, mag_step)
- mags = np.concatenate((mags_adjust, mags_fixed))
+ if kwargs.has_key('cl_mags'):
+ # Custom chart
+ cl_mags = kwargs['cl_mags']
else:
- mags = mags_fixed
+ # Default chart magnitudes
+ # The key set of magnitudes are always generated, since this
+ # guarantees a recognizable Nichols chart grid.
+ key_cl_mags = np.array([-40.0, -20.0, -12.0, -6.0, -3.0, -1.0, -0.5, 0.0,
+ 0.25, 0.5, 1.0, 3.0, 6.0, 12.0])
+ # Extend the range of magnitudes if necessary. The extended arange
+ # will end up empty if no extension is required. Assumes that closed-loop
+ # magnitudes are approximately aligned with open-loop magnitudes beyond
+ # the value of np.min(key_cl_mags)
+ cl_mag_step = -20.0 # dB
+ extended_cl_mags = np.arange(np.min(key_cl_mags),
+ ol_mag_min + cl_mag_step, cl_mag_step)
+ cl_mags = np.concatenate((extended_cl_mags, key_cl_mags))
# N-circle phases (should be in the range -360 to 0)
- phases = np.array([-0.25, -10.0, -20.0, -30.0, -45.0, -60.0, -90.0,
- -120.0, -150.0, -180.0, -210.0, -240.0, -270.0,
- -310.0, -325.0, -340.0, -350.0, -359.75])
+ if kwargs.has_key('cl_phases'):
+ # Custom chart
+ cl_phases = kwargs['cl_phases']
+ assert ((-360.0 < np.min(cl_phases)) and (np.max(cl_phases) < 0.0))
+ else:
+ # Choose a reasonable set of default phases (denser if the open-loop
+ # data is restricted to a relatively small range of phases).
+ key_cl_phases = np.array([-0.25, -45.0, -90.0, -180.0, -270.0, -325.0, -359.75])
+ if np.abs(ol_phase_max - ol_phase_min) < 90.0:
+ other_cl_phases = np.arange(-10.0, -360.0, -10.0)
+ else:
+ other_cl_phases = np.arange(-10.0, -360.0, -20.0)
+ cl_phases = np.concatenate((key_cl_phases, other_cl_phases))
# Find the M-contours
- m = m_circles(mags, phase_min=np.min(phases), phase_max=np.max(phases))
+ m = m_circles(cl_mags, phase_min=np.min(cl_phases), phase_max=np.max(cl_phases))
m_mag = 20*sp.log10(np.abs(m))
m_phase = sp.mod(sp.degrees(sp.angle(m)), -360.0) # Unwrap
# Find the N-contours
- n = n_circles(phases, mag_min=np.min(mags), mag_max=np.max(mags))
+ n = n_circles(cl_phases, mag_min=np.min(cl_mags), mag_max=np.max(cl_mags))
n_mag = 20*sp.log10(np.abs(n))
n_phase = sp.mod(sp.degrees(sp.angle(n)), -360.0) # Unwrap
# Plot the contours behind other plot elements.
# The "phase offset" is used to produce copies of the chart that cover
# the entire range of the plotted data, starting from a base chart computed
- # over the range -360 < phase < 0 (see above). Given the range
+ # over the range -360 < phase < 0. Given the range
# the base chart is computed over, the phase offset should be 0
- # for -360 < phase_min < 0.
- phase_offset_min = 360.0*np.ceil(phase_min/360.0)
- phase_offset_max = 360.0*np.ceil(phase_max/360.0) + 360.0
+ # for -360 < ol_phase_min < 0.
+ phase_offset_min = 360.0*np.ceil(ol_phase_min/360.0)
+ phase_offset_max = 360.0*np.ceil(ol_phase_max/360.0) + 360.0
phase_offsets = np.arange(phase_offset_min, phase_offset_max, 360.0)
+
for phase_offset in phase_offsets:
+ # Draw M and N contours
plt.plot(m_phase + phase_offset, m_mag, color='gray',
linestyle='dashed', zorder=0)
plt.plot(n_phase + phase_offset, n_mag, color='gray',
linestyle='dashed', zorder=0)
- # Add magnitude labels
- for x, y, m in zip(m_phase[:][-1], m_mag[:][-1], mags):
- align = 'right' if m < 0.0 else 'left'
- plt.text(x, y, str(m) + ' dB', size='small', ha=align)
+ # Add magnitude labels
+ for x, y, m in zip(m_phase[:][-1] + phase_offset, m_mag[:][-1], cl_mags):
+ align = 'right' if m < 0.0 else 'left'
+ plt.text(x, y, str(m) + ' dB', size='small', ha=align)
- # Make sure axes conform to any pre-existing plot.
- plt.axis([phase_min, phase_max, mag_min, mag_max])
+ # Fit axes to generated chart
+ plt.axis([phase_offset_min - 360.0, phase_offset_max - 360.0,
+ np.min(cl_mags), np.max([ol_mag_max, default_ol_mag_max])])
# Gang of Four
#! TODO: think about how (and whether) to handle lists of systems
@@ -417,38 +445,44 @@
return omega
# Compute contours of a closed-loop transfer function
-def closed_loop_contours(Hmag, Hphase):
- """Contours of the function H = G/(1+G).
+def closed_loop_contours(Gcl_mags, Gcl_phases):
+ """Contours of the function Gcl = Gol/(1+Gol), where
+ Gol is an open-loop transfer function, and Gcl is a corresponding
+ closed-loop transfer function.
Usage
=====
- contours = closed_loop_contours(mags, phases)
+ contours = closed_loop_contours(Gcl_mags, Gcl_phases)
Parameters
----------
- mags : array-like
- Meshgrid array of magnitudes of the contours
- phases : array-like
- Meshgrid array of phases in radians of the contours
+ Gcl_mags : array-like
+ Array of magnitudes of the contours
+ Gcl_phases : array-like
+ Array of phases in radians of the contours
Return values
-------------
contours : complex array
Array of complex numbers corresponding to the contours.
"""
- # Compute the contours in H-space
- H = Hmag*sp.exp(1.j*Hphase)
+ # Compute the contours in Gcl-space. Since we're given closed-loop
+ # magnitudes and phases, this is just a case of converting them into
+ # a complex number.
+ Gcl = Gcl_mags*sp.exp(1.j*Gcl_phases)
- # Invert H = G/(1+G) to get an expression for the contours in G-space
- return H/(1.0 - H)
+ # Invert Gcl = Gol/(1+Gol) to map the contours into the open-loop space
+ return Gcl/(1.0 - Gcl)
# M-circle
def m_circles(mags, phase_min=-359.75, phase_max=-0.25):
- """Constant-magnitude contours of the function H = G/(1+G).
+ """Constant-magnitude contours of the function Gcl = Gol/(1+Gol), where
+ Gol is an open-loop transfer function, and Gcl is a corresponding
+ closed-loop transfer function.
Usage
=====
- contours = m_circles(mags)
+ contours = m_circles(mags, phase_min, phase_max)
Parameters
----------
@@ -467,16 +501,18 @@
# Convert magnitudes and phase range into a grid suitable for
# building contours
phases = sp.radians(sp.linspace(phase_min, phase_max, 500))
- Hmag, Hphase = sp.meshgrid(10.0**(mags/20.0), phases)
- return closed_loop_contours(Hmag, Hphase)
+ Gcl_mags, Gcl_phases = sp.meshgrid(10.0**(mags/20.0), phases)
+ return closed_loop_contours(Gcl_mags, Gcl_phases)
# N-circle
def n_circles(phases, mag_min=-40.0, mag_max=12.0):
- """Constant-phase contours of the function H = G/(1+G).
+ """Constant-phase contours of the function Gcl = Gol/(1+Gol), where
+ Gol is an open-loop transfer function, and Gcl is a corresponding
+ closed-loop transfer function.
Usage
=====
- contour = n_circles(angles)
+ contours = n_circles(phases, mag_min, mag_max)
Parameters
----------
@@ -495,5 +531,5 @@
# Convert phases and magnitude range into a grid suitable for
# building contours
mags = sp.linspace(10**(mag_min/20.0), 10**(mag_max/20.0), 2000)
- Hphase, Hmag = sp.meshgrid(sp.radians(phases), mags)
- return closed_loop_contours(Hmag, Hphase)
+ Gcl_phases, Gcl_mags = sp.meshgrid(sp.radians(phases), mags)
+ return closed_loop_contours(Gcl_mags, Gcl_phases)
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|
|
From: <all...@us...> - 2011-02-19 03:02:13
|
Revision: 136
http://python-control.svn.sourceforge.net/python-control/?rev=136&view=rev
Author: allanmcinnes
Date: 2011-02-19 03:02:07 +0000 (Sat, 19 Feb 2011)
Log Message:
-----------
Add a Nyquist grid (aka Hall chart) showing M-circles and N-circles on the complex plane. Tweak Nichols grid to eliminate unnecessary use of kwargs.
Modified Paths:
--------------
trunk/src/freqplot.py
Modified: trunk/src/freqplot.py
===================================================================
--- trunk/src/freqplot.py 2011-02-14 07:49:05 UTC (rev 135)
+++ trunk/src/freqplot.py 2011-02-19 03:02:07 UTC (rev 136)
@@ -178,6 +178,83 @@
# Mark the -1 point
plt.plot([-1], [0], 'r+')
+# Nyquist grid
+#! TODO: Consider making linestyle configurable
+def nyquist_grid(cl_mags=None, cl_phases=None):
+ """Nyquist plot grid of M-circles and N-circles (aka "Hall chart")
+
+ Usage
+ =====
+ nyquist_grid()
+
+ Plots a grid of M-circles and N-circles on the current axis, or
+ creates a default grid if no plot already exists.
+
+ Parameters
+ ----------
+ cl_mags : array-like (dB)
+ Array of closed-loop magnitudes defining a custom set of
+ M-circle iso-gain lines.
+ cl_phases : array-like (degrees)
+ Array of closed-loop phases defining a custom set of
+ N-circle iso-phase lines. Must be in the range -180.0 < cl_phases < 180.0
+
+ Return values
+ -------------
+ None
+ """
+ # Default chart size
+ re_min = -4.0
+ re_max = 3.0
+ im_min = -2.0
+ im_max = 2.0
+
+ # Find bounds of the current dataset, if there is one.
+ if plt.gcf().gca().has_data():
+ re_min, re_max, im_min, im_max = plt.axis()
+
+ # M-circle magnitudes.
+ if cl_mags is None:
+ cl_mags = np.array([-20.0, -10.0, -6.0, -4.0, -2.0, 0.0,
+ 2.0, 4.0, 6.0, 10.0, 20.0])
+
+ # N-circle phases (should be in the range -180.0 to 180.0)
+ if cl_phases is None:
+ cl_phases = np.array([-90.0, -60.0, -45.0, -30.0, -15.0,
+ 15.0, 30.0, 45.0, 60.0, 90.0])
+ else:
+ assert ((-180.0 < np.min(cl_phases)) and (np.max(cl_phases) < 180.0))
+
+ # Find the M-contours and N-contours
+ m = m_circles(cl_mags, phase_min=0.0, phase_max=359.99)
+ n = n_circles(cl_phases, mag_min=-40.0, mag_max=40.0)
+
+ # Draw contours
+ plt.plot(np.real(m), np.imag(m), color='gray', linestyle='dotted', zorder=0)
+ plt.plot(np.real(n), np.imag(n), color='gray', linestyle='dotted', zorder=0)
+
+ # Add magnitude labels
+ for i in range(0, len(cl_mags)):
+ if not cl_mags[i] == 0.0:
+ mag = 10.0**(cl_mags[i]/20.0)
+ x = -mag**2.0/(mag**2.0 - 1.0) # Center of the M-circle
+ y = np.abs(mag/(mag**2.0 - 1.0)) # Maximum point
+ else:
+ x, y = -0.5, im_max
+ plt.text(x, y, str(cl_mags[i]) + ' dB', size='small', color='gray')
+
+ # Add phase labels
+ for i in range(0, len(cl_phases)):
+ y = np.sign(cl_phases[i])*np.max(np.abs(np.imag(n)[:,i]))
+ p = str(cl_phases[i])
+ plt.text(-0.5, y, p + '$^\circ$', size='small', color='gray')
+
+ # Fit axes to original plot
+ plt.axis([re_min, re_max, im_min, im_max])
+
+# Make an alias
+hall_grid = nyquist_grid
+
# Nichols plot
# Contributed by Allan McInnes <All...@ca...>
#! TODO: need unit test code
@@ -209,7 +286,7 @@
syslist = (syslist,)
# Select a default range if none is provided
- if (omega == None):
+ if omega is None:
omega = default_frequency_range(syslist)
for sys in syslist:
@@ -236,7 +313,8 @@
nichols_grid()
# Nichols grid
-def nichols_grid(**kwargs):
+#! TODO: Consider making linestyle configurable
+def nichols_grid(cl_mags=None, cl_phases=None):
"""Nichols chart grid
Usage
@@ -270,10 +348,7 @@
ol_phase_min, ol_phase_max, ol_mag_min, ol_mag_max = plt.axis()
# M-circle magnitudes.
- if kwargs.has_key('cl_mags'):
- # Custom chart
- cl_mags = kwargs['cl_mags']
- else:
+ if cl_mags is None:
# Default chart magnitudes
# The key set of magnitudes are always generated, since this
# guarantees a recognizable Nichols chart grid.
@@ -289,11 +364,7 @@
cl_mags = np.concatenate((extended_cl_mags, key_cl_mags))
# N-circle phases (should be in the range -360 to 0)
- if kwargs.has_key('cl_phases'):
- # Custom chart
- cl_phases = kwargs['cl_phases']
- assert ((-360.0 < np.min(cl_phases)) and (np.max(cl_phases) < 0.0))
- else:
+ if cl_phases is None:
# Choose a reasonable set of default phases (denser if the open-loop
# data is restricted to a relatively small range of phases).
key_cl_phases = np.array([-0.25, -45.0, -90.0, -180.0, -270.0, -325.0, -359.75])
@@ -302,6 +373,8 @@
else:
other_cl_phases = np.arange(-10.0, -360.0, -20.0)
cl_phases = np.concatenate((key_cl_phases, other_cl_phases))
+ else:
+ assert ((-360.0 < np.min(cl_phases)) and (np.max(cl_phases) < 0.0))
# Find the M-contours
m = m_circles(cl_mags, phase_min=np.min(cl_phases), phase_max=np.max(cl_phases))
@@ -326,14 +399,14 @@
for phase_offset in phase_offsets:
# Draw M and N contours
plt.plot(m_phase + phase_offset, m_mag, color='gray',
- linestyle='dashed', zorder=0)
+ linestyle='dotted', zorder=0)
plt.plot(n_phase + phase_offset, n_mag, color='gray',
- linestyle='dashed', zorder=0)
+ linestyle='dotted', zorder=0)
# Add magnitude labels
for x, y, m in zip(m_phase[:][-1] + phase_offset, m_mag[:][-1], cl_mags):
align = 'right' if m < 0.0 else 'left'
- plt.text(x, y, str(m) + ' dB', size='small', ha=align)
+ plt.text(x, y, str(m) + ' dB', size='small', ha=align, color='gray')
# Fit axes to generated chart
plt.axis([phase_offset_min - 360.0, phase_offset_max - 360.0,
@@ -500,7 +573,7 @@
"""
# Convert magnitudes and phase range into a grid suitable for
# building contours
- phases = sp.radians(sp.linspace(phase_min, phase_max, 500))
+ phases = sp.radians(sp.linspace(phase_min, phase_max, 2000))
Gcl_mags, Gcl_phases = sp.meshgrid(10.0**(mags/20.0), phases)
return closed_loop_contours(Gcl_mags, Gcl_phases)
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|
|
From: <all...@us...> - 2011-02-19 03:15:24
|
Revision: 137
http://python-control.svn.sourceforge.net/python-control/?rev=137&view=rev
Author: allanmcinnes
Date: 2011-02-19 03:15:18 +0000 (Sat, 19 Feb 2011)
Log Message:
-----------
Bugfix freqplot.default_frequency_range(), which failed to deal properly with single systems. Also add an option to control the number of points. Set default to a larger number of points than the logspace default, so that we're more likely to get a smooth curve on bode, nyquist, and nichols plots.
Modified Paths:
--------------
trunk/src/freqplot.py
Modified: trunk/src/freqplot.py
===================================================================
--- trunk/src/freqplot.py 2011-02-19 03:02:07 UTC (rev 136)
+++ trunk/src/freqplot.py 2011-02-19 03:15:18 UTC (rev 137)
@@ -192,10 +192,10 @@
Parameters
----------
- cl_mags : array-like (dB)
+ cl_mags : array-like (dB), optional
Array of closed-loop magnitudes defining a custom set of
M-circle iso-gain lines.
- cl_phases : array-like (degrees)
+ cl_phases : array-like (degrees), optional
Array of closed-loop phases defining a custom set of
N-circle iso-phase lines. Must be in the range -180.0 < cl_phases < 180.0
@@ -273,8 +273,8 @@
List of linear input/output systems (single system is OK)
omega : freq_range
Range of frequencies (list or bounds) in rad/sec
- grid : boolean
- True if the plot should include a Nichols-chart grid
+ grid : boolean, optional
+ True if the plot should include a Nichols-chart grid. Default is True.
Return values
-------------
@@ -326,10 +326,10 @@
Parameters
----------
- cl_mags : array-like (dB)
+ cl_mags : array-like (dB), optional
Array of closed-loop magnitudes defining the iso-gain lines on a
custom Nichols chart.
- cl_phases : array-like (degrees)
+ cl_phases : array-like (degrees), optional
Array of closed-loop phases defining the iso-phase lines on a custom
Nichols chart. Must be in the range -360 < cl_phases < 0
@@ -468,7 +468,7 @@
#
# Compute reasonable defaults for axes
-def default_frequency_range(syslist):
+def default_frequency_range(syslist, num=1000):
"""Compute a reasonable default frequency range for frequency
domain plots.
@@ -483,6 +483,8 @@
----------
syslist : linsys
List of linear input/output systems (single system is OK)
+ num : integer, optional
+ Number of samples to generate. Default is 50.
Return values
-------------
@@ -495,6 +497,10 @@
# integer. It excludes poles and zeros at the origin. If no features
# are found, it turns logspace(-1, 1)
+ # If argument was a singleton, turn it into a list
+ if (not getattr(syslist, '__iter__', False)):
+ syslist = (syslist,)
+
# Find the list of all poles and zeros in the systems
features = np.array(())
for sys in syslist:
@@ -513,7 +519,7 @@
# Set the range to be an order of magnitude beyond any features
omega = sp.logspace(np.floor(np.min(features))-1,
- np.ceil(np.max(features))+1)
+ np.ceil(np.max(features))+1, num)
return omega
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|
|
From: <mur...@us...> - 2012-01-08 02:56:30
|
Revision: 179
http://python-control.svn.sourceforge.net/python-control/?rev=179&view=rev
Author: murrayrm
Date: 2012-01-08 02:56:24 +0000 (Sun, 08 Jan 2012)
Log Message:
-----------
small doc fix
Modified Paths:
--------------
trunk/src/freqplot.py
Modified: trunk/src/freqplot.py
===================================================================
--- trunk/src/freqplot.py 2012-01-08 02:55:55 UTC (rev 178)
+++ trunk/src/freqplot.py 2012-01-08 02:56:24 UTC (rev 179)
@@ -319,8 +319,8 @@
syslist : list of Lti
List of linear input/output systems (single system is OK)
- Return
- ------
+ Returns
+ -------
omega : array
Range of frequencies in rad/sec
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|
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