added code to check for MIMO in statesp._convertToStateSpace + unit test; address issue #120

murrayrm · murrayrm · commit c90a399a38ba · 2016-12-26T09:39:44.000-08:00
diff --git a/control/statesp.py b/control/statesp.py
@@ -667,6 +667,10 @@ def _convertToStateSpace(sys, **kw):
                 ssout[3][:sys.outputs, :states],
                 ssout[4], sys.dt)
         except ImportError:
+            # If slycot is not available, use signal.lti (SISO only)
+            if (sys.inputs != 1 or sys.outputs != 1):
+                raise TypeError("No support for MIMO without slycot")
+
             # TODO: do we want to squeeze first and check dimenations?
             # I think this will fail if num and den aren't 1-D after
             # the squeeze
diff --git a/control/tests/convert_test.py b/control/tests/convert_test.py
@@ -162,6 +162,29 @@ def testConvert(self):
                             np.testing.assert_array_almost_equal( \
                                 ssorig_imag, tfxfrm_imag)
 
+    def testConvertMIMO(self):
+        """Test state space to transfer function conversion."""
+        verbose = self.debug
+
+        # Do a MIMO conversation and make sure that it is processed
+        # correctly both with and without slycot
+        #
+        # Example from issue #120, jgoppert
+        import control
+
+        # Set up a transfer function (should always work)
+        tfcn = control.tf([[[-235, 1.146e4],
+                          [-235, 1.146E4],
+                          [-235, 1.146E4, 0]]],
+                        [[[1, 48.78, 0],
+                          [1, 48.78, 0, 0],
+                          [0.008, 1.39, 48.78]]])
+
+        # Convert to state space and look for an error
+        if (not slycot_check()):
+            self.assertRaises(TypeError, control.tf2ss, tfcn)
+
+
 def suite():
    return unittest.TestLoader().loadTestsFromTestCase(TestConvert)
 
