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murrayrmmurrayrm
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initial release of I/O systems module (#301)
This PR introduces a new module for representing (nonlinear) input/output systems and support for simulation, linearization, and composition. The following features are supported: * Input/output systems can be created using the LinearIOSystem and NonlinearIOSystem classes, and I/O systems can be simulated in continuous and discrete time using the input_output_response() function, which is equivalent to the forced_response() function for LTI system. * Input/output systems can be composed using the existing series, parallel, and feedback functions, as well as using the * and + operators. In addition, the InterconnectedSystem class can be used to interconnect a collection of I/O subsystems, with functionality similar to the connect function in MATLAB. * Input/output systems and input/output signals can be named and Interconnections between I/O systems can be specified using system and signal names. * Input/output systems can be linearized about an equilibrium point using the linearize() function, which returns a LinearIOSystem object. The LinearIOSystem is derived from the StateSpace class, allowing all operations on linear systems to be applied to the linearized system. The find_eqpt() function can be used to find an equilibrium point for an input/output system. Documentation and examples are included to illustrate the use of the iosys module.
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‎control/__init__.py‎

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@@ -68,6 +68,7 @@
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from .robust import *
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from .config import *
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from .sisotool import *
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from .iosys import *
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# Exceptions
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from .exception import *

‎control/bdalg.py‎

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@@ -224,6 +224,11 @@ def feedback(sys1, sys2=1, sign=-1):
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scalars, then TransferFunction.feedback is used.
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"""
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# Allow anything with a feedback function to call that function
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try:
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return sys1.feedback(sys2, sign)
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except AttributeError:
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pass
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# Check for correct input types.
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if not isinstance(sys1, (int, float, complex, np.number,

‎control/iosys.py‎

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‎control/lti.py‎

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@@ -178,6 +178,28 @@ def timebaseEqual(sys1, sys2):
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else:
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return sys1.dt == sys2.dt
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# Find a common timebase between two or more systems
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def _find_timebase(sys1, *sysn):
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"""Find the common timebase between systems, otherwise return False"""
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# Create a list of systems to check
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syslist = [sys1]
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syslist.append(*sysn)
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# Look for a common timebase
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dt = None
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for sys in syslist:
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# Make sure time bases are consistent
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if (dt is None and sys.dt is not None) or \
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(dt is True and isdiscrete(sys)):
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# Timebase was not specified; set to match this system
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dt = sys.dt
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elif dt != sys.dt:
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return False
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return dt
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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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"""
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if isinstance(sys, LTI):
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return sys.isdtime(strict)
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# Check to see if object has a dt object
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if hasattr(sys, 'dt'):
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# If no timebase is given, answer depends on strict flag
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if sys.dt == None:
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return True if not strict else False
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# Look for dt > 0 (also works if dt = True)
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return sys.dt > 0
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# Got passed something we don't recognize
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return False
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if isinstance(sys, LTI):
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return sys.isctime(strict)
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# Check to see if object has a dt object
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if hasattr(sys, 'dt'):
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# If no timebase is given, answer depends on strict flag
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if sys.dt is None:
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return True if not strict else False
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return sys.dt == 0
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# Got passed something we don't recognize
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return False
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‎control/statesp.py‎

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@@ -115,7 +115,7 @@ class StateSpace(LTI):
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sampling time.
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"""
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def __init__(self, *args):
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def __init__(self, *args, **kw):
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"""
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StateSpace(A, B, C, D[, dt])
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@@ -152,6 +152,9 @@ def __init__(self, *args):
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else:
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raise ValueError("Needs 1 or 4 arguments; received %i." % len(args))
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# Process keyword arguments
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remove_useless = kw.get('remove_useless', True)
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A, B, C, D = [_matrix(M) for M in (A, B, C, D)]
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# TODO: use super here?
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raise ValueError("C and D must have the same number of rows.")
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# Check for states that don't do anything, and remove them.
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self._remove_useless_states()
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if remove_useless: self._remove_useless_states()
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def _remove_useless_states(self):
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"""Check for states that don't do anything, and remove them.

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