diff --git a/control/statesp.py b/control/statesp.py
index 5af916bf0..d23fbd7be 100644
--- a/control/statesp.py
+++ b/control/statesp.py
@@ -59,7 +59,8 @@
from numpy.linalg import solve, eigvals, matrix_rank
from numpy.linalg.linalg import LinAlgError
import scipy as sp
-from scipy.signal import lti, cont2discrete
+from scipy.signal import cont2discrete
+from scipy.signal import StateSpace as signalStateSpace
from warnings import warn
from .lti import LTI, timebase, timebaseEqual, isdtime
from . import config
@@ -200,7 +201,7 @@ def __init__(self, *args, **kw):
raise ValueError("Needs 1 or 4 arguments; received %i." % len(args))
# Process keyword arguments
- remove_useless = kw.get('remove_useless',
+ remove_useless = kw.get('remove_useless',
config.defaults['statesp.remove_useless_states'])
# Convert all matrices to standard form
@@ -798,9 +799,7 @@ def minreal(self, tol=0.0):
else:
return StateSpace(self)
-
- # TODO: add discrete time check
- def returnScipySignalLTI(self):
+ def returnScipySignalLTI(self, strict=True):
"""Return a list of a list of :class:`scipy.signal.lti` objects.
For instance,
@@ -809,15 +808,45 @@ def returnScipySignalLTI(self):
>>> out[3][5]
is a :class:`scipy.signal.lti` object corresponding to the transfer
- function from the 6th input to the 4th output."""
+ function from the 6th input to the 4th output.
+
+ Parameters
+ ----------
+ strict : bool, optional
+ True (default):
+ The timebase `ssobject.dt` cannot be None; it must
+ be continuous (0) or discrete (True or > 0).
+ False:
+ If `ssobject.dt` is None, continuous time
+ :class:`scipy.signal.lti` objects are returned.
+
+ Returns
+ -------
+ out : list of list of :class:`scipy.signal.StateSpace`
+ continuous time (inheriting from :class:`scipy.signal.lti`)
+ or discrete time (inheriting from :class:`scipy.signal.dlti`)
+ SISO objects
+ """
+ if strict and self.dt is None:
+ raise ValueError("with strict=True, dt cannot be None")
+
+ if self.dt:
+ kwdt = {'dt': self.dt}
+ else:
+ # scipy convention for continuous time lti systems: call without
+ # dt keyword argument
+ kwdt = {}
# Preallocate the output.
out = [[[] for _ in range(self.inputs)] for _ in range(self.outputs)]
for i in range(self.outputs):
for j in range(self.inputs):
- out[i][j] = lti(asarray(self.A), asarray(self.B[:, j]),
- asarray(self.C[i, :]), self.D[i, j])
+ out[i][j] = signalStateSpace(asarray(self.A),
+ asarray(self.B[:, j:j + 1]),
+ asarray(self.C[i:i + 1, :]),
+ asarray(self.D[i:i + 1, j:j + 1]),
+ **kwdt)
return out
diff --git a/control/tests/statesp_matrix_test.py b/control/tests/statesp_matrix_test.py
index 34a17f992..e7e91364a 100644
--- a/control/tests/statesp_matrix_test.py
+++ b/control/tests/statesp_matrix_test.py
@@ -5,6 +5,7 @@
import unittest
import numpy as np
+import pytest
from numpy.linalg import solve
from scipy.linalg import eigvals, block_diag
from control import matlab
@@ -673,5 +674,56 @@ def test_sample_system_prewarping(self):
decimal=4)
+class TestLTIConverter:
+ """Test returnScipySignalLTI method"""
+
+ @pytest.fixture
+ def mimoss(self, request):
+ """Test system with various dt values"""
+ n = 5
+ m = 3
+ p = 2
+ bx, bu = np.mgrid[1:n + 1, 1:m + 1]
+ cy, cx = np.mgrid[1:p + 1, 1:n + 1]
+ dy, du = np.mgrid[1:p + 1, 1:m + 1]
+ return StateSpace(np.eye(5) + np.eye(5, 5, 1),
+ bx * bu,
+ cy * cx,
+ dy * du,
+ request.param)
+
+ @pytest.mark.parametrize("mimoss",
+ [None,
+ 0,
+ 0.1,
+ 1,
+ True],
+ indirect=True)
+ def test_returnScipySignalLTI(self, mimoss):
+ """Test returnScipySignalLTI method with strict=False"""
+ sslti = mimoss.returnScipySignalLTI(strict=False)
+ for i in range(mimoss.outputs):
+ for j in range(mimoss.inputs):
+ np.testing.assert_allclose(sslti[i][j].A, mimoss.A)
+ np.testing.assert_allclose(sslti[i][j].B, mimoss.B[:,
+ j:j + 1])
+ np.testing.assert_allclose(sslti[i][j].C, mimoss.C[i:i + 1,
+ :])
+ np.testing.assert_allclose(sslti[i][j].D, mimoss.D[i:i + 1,
+ j:j + 1])
+ if mimoss.dt == 0:
+ assert sslti[i][j].dt is None
+ else:
+ assert sslti[i][j].dt == mimoss.dt
+
+ @pytest.mark.parametrize("mimoss", [None], indirect=True)
+ def test_returnScipySignalLTI_error(self, mimoss):
+ """Test returnScipySignalLTI method with dt=None and strict=True"""
+ with pytest.raises(ValueError):
+ mimoss.returnScipySignalLTI()
+ with pytest.raises(ValueError):
+ mimoss.returnScipySignalLTI(strict=True)
+
+
if __name__ == "__main__":
unittest.main()
diff --git a/control/tests/xferfcn_test.py b/control/tests/xferfcn_test.py
index 02e6c2b37..17e602090 100644
--- a/control/tests/xferfcn_test.py
+++ b/control/tests/xferfcn_test.py
@@ -4,6 +4,8 @@
# RMM, 30 Mar 2011 (based on TestXferFcn from v0.4a)
import unittest
+import pytest
+
import sys as pysys
import numpy as np
from control.statesp import StateSpace, _convertToStateSpace, rss
@@ -934,5 +936,44 @@ def test_sample_system_prewarping(self):
decimal=4)
+class TestLTIConverter:
+ """Test returnScipySignalLTI method"""
+
+ @pytest.fixture
+ def mimotf(self, request):
+ """Test system with various dt values"""
+ return TransferFunction([[[11], [12], [13]],
+ [[21], [22], [23]]],
+ [[[1, -1]] * 3] * 2,
+ request.param)
+
+ @pytest.mark.parametrize("mimotf",
+ [None,
+ 0,
+ 0.1,
+ 1,
+ True],
+ indirect=True)
+ def test_returnScipySignalLTI(self, mimotf):
+ """Test returnScipySignalLTI method with strict=False"""
+ sslti = mimotf.returnScipySignalLTI(strict=False)
+ for i in range(2):
+ for j in range(3):
+ np.testing.assert_allclose(sslti[i][j].num, mimotf.num[i][j])
+ np.testing.assert_allclose(sslti[i][j].den, mimotf.den[i][j])
+ if mimotf.dt == 0:
+ assert sslti[i][j].dt is None
+ else:
+ assert sslti[i][j].dt == mimotf.dt
+
+ @pytest.mark.parametrize("mimotf", [None], indirect=True)
+ def test_returnScipySignalLTI_error(self, mimotf):
+ """Test returnScipySignalLTI method with dt=None and strict=True"""
+ with pytest.raises(ValueError):
+ mimotf.returnScipySignalLTI()
+ with pytest.raises(ValueError):
+ mimotf.returnScipySignalLTI(strict=True)
+
+
if __name__ == "__main__":
unittest.main()
diff --git a/control/xferfcn.py b/control/xferfcn.py
index 1cba50bd7..4077080e3 100644
--- a/control/xferfcn.py
+++ b/control/xferfcn.py
@@ -57,7 +57,8 @@
polyadd, polymul, polyval, roots, sqrt, zeros, squeeze, exp, pi, \
where, delete, real, poly, nonzero
import scipy as sp
-from scipy.signal import lti, tf2zpk, zpk2tf, cont2discrete
+from scipy.signal import tf2zpk, zpk2tf, cont2discrete
+from scipy.signal import TransferFunction as signalTransferFunction
from copy import deepcopy
from warnings import warn
from itertools import chain
@@ -801,7 +802,7 @@ def minreal(self, tol=None):
# end result
return TransferFunction(num, den, self.dt)
- def returnScipySignalLTI(self):
+ def returnScipySignalLTI(self, strict=True):
"""Return a list of a list of :class:`scipy.signal.lti` objects.
For instance,
@@ -809,22 +810,44 @@ def returnScipySignalLTI(self):
>>> out = tfobject.returnScipySignalLTI()
>>> out[3][5]
- is a class:`scipy.signal.lti` object corresponding to the
+ is a :class:`scipy.signal.lti` object corresponding to the
transfer function from the 6th input to the 4th output.
+ Parameters
+ ----------
+ strict : bool, optional
+ True (default):
+ The timebase `tfobject.dt` cannot be None; it must be
+ continuous (0) or discrete (True or > 0).
+ False:
+ if `tfobject.dt` is None, continuous time
+ :class:`scipy.signal.lti`objects are returned
+
+ Returns
+ -------
+ out : list of list of :class:`scipy.signal.TransferFunction`
+ continuous time (inheriting from :class:`scipy.signal.lti`)
+ or discrete time (inheriting from :class:`scipy.signal.dlti`)
+ SISO objects
"""
+ if strict and self.dt is None:
+ raise ValueError("with strict=True, dt cannot be None")
- # TODO: implement for discrete time systems
- if self.dt != 0 and self.dt is not None:
- raise NotImplementedError("Function not \
- implemented in discrete time")
+ if self.dt:
+ kwdt = {'dt': self.dt}
+ else:
+ # scipy convention for continuous time lti systems: call without
+ # dt keyword argument
+ kwdt = {}
# Preallocate the output.
out = [[[] for j in range(self.inputs)] for i in range(self.outputs)]
for i in range(self.outputs):
for j in range(self.inputs):
- out[i][j] = lti(self.num[i][j], self.den[i][j])
+ out[i][j] = signalTransferFunction(self.num[i][j],
+ self.den[i][j],
+ **kwdt)
return out
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