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Added discrete time simulation capability
 * Moved timebase functions to lti.py * Implemented time response using scipy.signal.dsim * First cut at unit tests (needs more work)
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‎ChangeLog‎

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2012-10-07 Richard Murray <murray@altura.local>
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* src/timeresp.py (forced_response): added discrete time simulator,
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using dlsim from scipy.signal
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2012-10-07 Richard Murray <murray@altura.local>
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* doc/conf.py: fixed release number (0.6a instead of 0.6c)
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* src/__init__.py: moved timebase functions from dtime to lti
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* src/lti.py: moved isdtime, isctime, timebase, and timebaseEqual
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from dtime.py to lti.py. Moved initialization of dt to
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Lti.__init__().
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* src/statesp.py (StateSpace.__init__): Moved dt
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initialization to Lti object initialization
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* src/xferfcn.py (TransferFunction.__init__): Moved dt
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initialization to Lti object initialization
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2012-10-06 Richard Murray <murray@altura.local>
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* tests/discrete_test.py: added additional tests for dt = True cases

‎doc/conf.py‎

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# The short X.Y version.
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version = '0.6'
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# The full version, including alpha/beta/rc tags.
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release = '0.6c'
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release = '0.6a'
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# The language for content autogenerated by Sphinx. Refer to documentation
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# for a list of supported languages.

‎src/__init__.py‎

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#! Should probably only import the exact functions we use...
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from bdalg import series, parallel, negate, feedback
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from delay import pade
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from dtime import timebase, isdtime, isctime
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from freqplot import bode_plot, nyquist_plot, gangof4_plot
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from freqplot import bode, nyquist, gangof4
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from lti import timebaseEqual
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from lti import timebase, timebaseEqual, isdtime, isctime
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from margins import stability_margins, phase_crossover_frequencies
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from mateqn import lyap, dlyap, care, dare
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from modelsimp import hsvd, modred, balred, era, markov

‎src/dtime.py‎

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‎src/lti.py‎

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Routines in this module:
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Lti.__init__
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isdtime()
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isctime()
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timebase()
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timebaseEqual()
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"""
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class Lti:
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"""Lti is a parent class to linear time invariant control (LTI) objects.
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Lti is the parent to the StateSpace and TransferFunction child classes. It
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contains the number of inputs and outputs, but this can be expanded in the
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future.
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Lti is the parent to the StateSpace and TransferFunction child
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classes. It contains the number of inputs and outputs, and the
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timebase (dt) for the system.
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The timebase for the system, dt, is used to specify whether the
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system is operating in continuous or discrete time. It can have
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the following values:
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* dt = None No timebase specified
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* dt = 0 Continuous time system
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* dt > 0 Discrete time system with sampling time dt
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* dt = True Discrete time system with unspecified sampling time
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When to Lti systems are combined, there timebases much match. A system
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with timebase None can be combined with a system having a specified
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timebase, and the result will have the timebase of the latter system.
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The StateSpace and TransferFunction child classes contain several common
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"virtual" functions. These are:
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"""
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def __init__(self, inputs=1, outputs=1):
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def __init__(self, inputs=1, outputs=1, dt=None):
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"""Assign the LTI object's numbers of inputs and ouputs."""
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# Data members common to StateSpace and TransferFunction.
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self.inputs = inputs
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self.outputs = outputs
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self.dt = dt
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# Return the timebase of a system
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def timebase(sys):
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# TODO: add docstring
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# If we get passed a constant, timebase is None
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if isinstance(sys, (int, float, long, complex)):
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return None
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# Check for a transfer fucntion or state space object
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if isinstance(sys, Lti):
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if sys.dt > 0 or sys.dt == True:
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return 'dtime';
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elif sys.dt == 0:
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return 'ctime';
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elif sys.dt == None:
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return None
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# Got pased something we don't recognize or bad timebase
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return False;
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# Check to see if two timebases are equal
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def timebaseEqual(dt1, dt2):
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return True
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else:
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return dt1 == dt2
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# Check to see if a system is a discrete time system
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def isdtime(sys, strict=False):
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# TODO: add docstring
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# Check to see if this is a constant
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if isinstance(sys, (int, float, long, complex)):
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# OK as long as strict checking is off
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return True if not strict else False
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# Check for a transfer fucntion or state space object
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if isinstance(sys, Lti):
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# Look for dt > 0 or dt == None (if not strict)
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# Note that dt = True will be checked by dt > 0
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return sys.dt > 0 or (not strict and sys.dt == None)
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# Got possed something we don't recognize
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return False
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# Check to see if a system is a continuous time system
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def isctime(sys, strict=False):
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# TODO: add docstring
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# Check to see if this is a constant
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if isinstance(sys, (int, float, long, complex)):
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# OK as long as strict checking is off
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return True if not strict else False
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# Check for a transfer fucntion or state space object
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if isinstance(sys, Lti):
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# Look for dt == 0 or dt == None (if not strict)
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return sys.dt == 0 or (not strict and sys.dt == None)
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# Got possed something we don't recognize
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return False

‎src/statesp.py‎

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matrices[i] = matrix(matrices[i])
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[A, B, C, D] = matrices
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Lti.__init__(self, B.shape[1], C.shape[0], dt)
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self.A = A
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self.B = B
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self.C = C
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self.D = D
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self.dt = dt
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self.states = A.shape[0]
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Lti.__init__(self, B.shape[1], C.shape[0])
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# Check that the matrix sizes are consistent.
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if self.states != A.shape[1]:

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