fix bug in the way LinearICSystem.__call__ was implemented (with unit test)

murrayrm · murrayrm · commit 39404c428b41 · 2023-07-01T23:25:38.000-07:00
diff --git a/control/lti.py b/control/lti.py
@@ -115,7 +115,7 @@ def frequency_response(self, omega, squeeze=None):
 
         # Return the data as a frequency response data object
         from .frdata import FrequencyResponseData
-        response = self.__call__(s)
+        response = self(s)
         return FrequencyResponseData(
             response, omega, return_magphase=True, squeeze=squeeze)
 
@@ -365,7 +365,7 @@ def evalfr(sys, x, squeeze=None):
     .. todo:: Add example with MIMO system
 
     """
-    return sys.__call__(x, squeeze=squeeze)
+    return sys(x, squeeze=squeeze)
 
 
 def frequency_response(sys, omega, squeeze=None):
diff --git a/control/statesp.py b/control/statesp.py
@@ -1495,7 +1495,8 @@ def __init__(self, io_sys, ss_sys=None):
             params=io_sys.params, remove_useless_states=False)
 
         # Use StateSpace.__call__ to evaluate at a given complex value
-        self.__call__ = StateSpace.__call__
+        def __call__(self, *args, **kwargs):
+            return StateSpace.__call__(self, *args, **kwargs)
 
     # The following text needs to be replicated from StateSpace in order for
     # this entry to show up properly in sphinx doccumentation (not sure why,
diff --git a/control/tests/iosys_test.py b/control/tests/iosys_test.py
@@ -1561,6 +1561,13 @@ def test_linear_interconnection():
     assert isinstance(io_connect, ct.LinearICSystem)
     assert isinstance(io_connect, ct.StateSpace)
 
+    # Make sure call works properly
+    response = io_connect.frequency_response(1)
+    np.testing.assert_allclose(
+        response.fresp[:, :, 0], io_connect.C @ np.linalg.inv(
+            1j * np.eye(io_connect.nstates) - io_connect.A) @ io_connect.B + \
+            io_connect.D)
+
     # Finally compare the linearization with the linear system
     np.testing.assert_array_almost_equal(io_connect.A, ss_connect.A)
     np.testing.assert_array_almost_equal(io_connect.B, ss_connect.B)
