updated MIMO not implemented w/ unit test, per @sawyerbfuller

murrayrm · murrayrm · commit 31793e6d4a75 · 2023-11-07T22:23:24.000-08:00
diff --git a/control/statesp.py b/control/statesp.py
@@ -60,10 +60,10 @@
 from scipy.signal import StateSpace as signalStateSpace
 from warnings import warn
 
-from .exception import ControlSlycot, slycot_check
+from .exception import ControlSlycot, slycot_check, ControlMIMONotImplemented
 from .frdata import FrequencyResponseData
 from .lti import LTI, _process_frequency_response
-from .iosys import InputOutputSystem, common_timebase, isdtime, \
+from .iosys import InputOutputSystem, common_timebase, isdtime, issiso, \
     _process_iosys_keywords, _process_dt_keyword, _process_signal_list
 from .nlsys import NonlinearIOSystem, InterconnectedSystem
 from . import config
@@ -2268,8 +2268,9 @@ def _convert_to_statespace(sys, use_prefix_suffix=False, method=None):
                     D[i, j] = sys.num[i][j][0] / sys.den[i][j][0]
                 newsys = StateSpace([], [], [], D, sys.dt)
             else:
-                if sys.ninputs != 1 or sys.noutputs != 1:
-                    raise TypeError("No support for MIMO without slycot")
+                if not issiso(sys):
+                    raise ControlMIMONotImplemented(
+                        "MIMO system conversion not supported without Slycot")
 
                 A, B, C, D = \
                     sp.signal.tf2ss(squeeze(sys.num), squeeze(sys.den))
diff --git a/control/tests/convert_test.py b/control/tests/convert_test.py
@@ -21,7 +21,7 @@
 from control import rss, ss, ss2tf, tf, tf2ss
 from control.statefbk import ctrb, obsv
 from control.freqplot import bode
-from control.exception import slycot_check
+from control.exception import slycot_check, ControlMIMONotImplemented
 from control.tests.conftest import slycotonly
 
 
@@ -167,7 +167,7 @@ def testConvertMIMO(self):
 
         # Convert to state space and look for an error
         if (not slycot_check()):
-            with pytest.raises(TypeError):
+            with pytest.raises(ControlMIMONotImplemented):
                 tf2ss(tsys)
         else:
             ssys = tf2ss(tsys)
diff --git a/control/tests/statesp_test.py b/control/tests/statesp_test.py
@@ -1237,3 +1237,15 @@ def test_tf2ss_unstable(method):
     tf_poles = np.sort(tf_sys.poles())
     ss_poles = np.sort(ss_sys.poles())
     np.testing.assert_allclose(tf_poles, ss_poles, rtol=1e-4)
+
+
+def test_tf2ss_mimo():
+    sys_tf = ct.tf([[[1], [1, 1, 1]]], [[[1, 1, 1], [1, 2, 1]]])
+
+    if ct.slycot_check():
+        sys_ss = ct.ss(sys_tf)
+        np.testing.assert_allclose(
+            np.sort(sys_tf.poles()), np.sort(sys_ss.poles()))
+    else:
+        with pytest.raises(ct.ControlMIMONotImplemented):
+            sys_ss = ct.ss(sys_tf)
