python-control · murrayrm · Jun 3, 2023 · Apr 17, 2023 · Apr 18, 2023 · Apr 18, 2023
diff --git a/control/statesp.py b/control/statesp.py
@@ -170,9 +170,9 @@ class StateSpace(LTI):
 
     The StateSpace class is used to represent state-space realizations of
     linear time-invariant (LTI) systems:
-    
+
     .. math::
-    
+
           dx/dt &= A x + B u \\
               y &= C x + D u
 
@@ -1561,7 +1561,8 @@ def _convert_to_statespace(sys):
             return StateSpace(
                 ssout[1][:states, :states], ssout[2][:states, :sys.ninputs],
                 ssout[3][:sys.noutputs, :states], ssout[4], sys.dt,
-                inputs=sys.input_labels, outputs=sys.output_labels)
+                inputs=sys.input_labels, outputs=sys.output_labels,
+                name=sys.name)
         except ImportError:
             # No Slycot.  Scipy tf->ss can't handle MIMO, but static
             # MIMO is an easy special case we can check for here
@@ -1574,7 +1575,9 @@ def _convert_to_statespace(sys):
                 for i, j in itertools.product(range(sys.noutputs),
                                               range(sys.ninputs)):
                     D[i, j] = sys.num[i][j][0] / sys.den[i][j][0]
-                return StateSpace([], [], [], D, sys.dt)
+                return StateSpace([], [], [], D, sys.dt,
+                    inputs=sys.input_labels, outputs=sys.output_labels,
+                    name=sys.name)
             else:
                 if sys.ninputs != 1 or sys.noutputs != 1:
                     raise TypeError("No support for MIMO without slycot")
@@ -1586,7 +1589,7 @@ def _convert_to_statespace(sys):
                     sp.signal.tf2ss(squeeze(sys.num), squeeze(sys.den))
                 return StateSpace(
                     A, B, C, D, sys.dt, inputs=sys.input_labels,
-                    outputs=sys.output_labels)
+                    outputs=sys.output_labels, name=sys.name)
 
     elif isinstance(sys, FrequencyResponseData):
         raise TypeError("Can't convert FRD to StateSpace system.")

diff --git a/control/tests/interconnect_test.py b/control/tests/interconnect_test.py
@@ -68,8 +68,13 @@ def test_interconnect_implicit():
     ki = ct.tf(random.uniform(1, 10), [1, 0])
     C = ct.tf2io(kp + ki, inputs='e', outputs='u', name='C')
 
+    # same but static C2
+    C2 = ct.tf(random.uniform(1, 10), 1,
+        inputs='e', outputs='u', name='C2')
+
     # Block diagram computation
     Tss = ct.feedback(P * C, 1)
+    Tss2 = ct.feedback(P * C2, 1)
 
     # Construct the interconnection explicitly
     Tio_exp = ct.interconnect(
@@ -93,6 +98,15 @@ def test_interconnect_implicit():
     np.testing.assert_almost_equal(Tio_sum.C, Tss.C)
     np.testing.assert_almost_equal(Tio_sum.D, Tss.D)
 
+    # test whether signal names work for static system C2
+    Tio_sum2 = ct.interconnect(
+        [C2, P, sumblk], inputs='r', outputs='y')
+
+    np.testing.assert_almost_equal(Tio_sum2.A, Tss2.A)
+    np.testing.assert_almost_equal(Tio_sum2.B, Tss2.B)
+    np.testing.assert_almost_equal(Tio_sum2.C, Tss2.C)
+    np.testing.assert_almost_equal(Tio_sum2.D, Tss2.D)
+
     # Setting connections to False should lead to an empty connection map
     empty = ct.interconnect(
         (C, P, sumblk), connections=False, inplist=['r'], outlist=['y'])
@@ -237,17 +251,17 @@ def test_linear_interconnect():
     ss_ctrl = ct.ss(1, 2, 1, 2, inputs='e', outputs='u')
     ss_plant = ct.ss(1, 2, 1, 2, inputs='u', outputs='y')
     nl_ctrl = ct.NonlinearIOSystem(
-        lambda t, x, u, params: x*x, 
+        lambda t, x, u, params: x*x,
         lambda t, x, u, params: u*x, states=1, inputs='e', outputs='u')
     nl_plant = ct.NonlinearIOSystem(
-        lambda t, x, u, params: x*x, 
+        lambda t, x, u, params: x*x,
         lambda t, x, u, params: u*x, states=1, inputs='u', outputs='y')
 
     assert isinstance(ct.interconnect((tf_ctrl, tf_plant), inputs='e', outputs='y'), ct.LinearIOSystem)
     assert isinstance(ct.interconnect((ss_ctrl, ss_plant), inputs='e', outputs='y'), ct.LinearIOSystem)
     assert isinstance(ct.interconnect((tf_ctrl, ss_plant), inputs='e', outputs='y'), ct.LinearIOSystem)
     assert isinstance(ct.interconnect((ss_ctrl, tf_plant), inputs='e', outputs='y'), ct.LinearIOSystem)
-    
+
     assert ~isinstance(ct.interconnect((nl_ctrl, ss_plant), inputs='e', outputs='y'), ct.LinearIOSystem)
     assert ~isinstance(ct.interconnect((nl_ctrl, tf_plant), inputs='e', outputs='y'), ct.LinearIOSystem)
     assert ~isinstance(ct.interconnect((ss_ctrl, nl_plant), inputs='e', outputs='y'), ct.LinearIOSystem)

diff --git a/control/tests/namedio_test.py b/control/tests/namedio_test.py
@@ -90,8 +90,10 @@ def test_named_ss():
      (lambda t, x, u, params: -x, None),
      {'inputs': 2, 'outputs':2, 'states':2}],
     [ct.ss, ([[1, 2], [3, 4]], [[0], [1]], [[1, 0]], 0), {}],
+    [ct.ss, ([], [], [], 3), {}], # static system
     [ct.StateSpace, ([[1, 2], [3, 4]], [[0], [1]], [[1, 0]], 0), {}],
     [ct.tf, ([1, 2], [3, 4, 5]), {}],
+    [ct.tf, (2, 3), {}], # static system
     [ct.TransferFunction, ([1, 2], [3, 4, 5]), {}],
 ])
 def test_io_naming(fun, args, kwargs):
@@ -112,7 +114,7 @@ def test_io_naming(fun, args, kwargs):
     assert sys_g.name == 'sys[0]'
     assert sys_g.input_labels == [f'u[{i}]' for i in range(sys_g.ninputs)]
     assert sys_g.output_labels == [f'y[{i}]' for i in range(sys_g.noutputs)]
-    if sys_g.nstates:
+    if sys_g.nstates is not None:
         assert sys_g.state_labels == [f'x[{i}]' for i in range(sys_g.nstates)]
 
     #
@@ -128,7 +130,7 @@ def test_io_naming(fun, args, kwargs):
     sys_r.set_outputs(output_labels)
     assert sys_r.output_labels == output_labels
 
-    if sys_g.nstates:
+    if sys_g.nstates is not None:
         state_labels = [f'x{i}' for i in range(sys_g.nstates)]
         sys_r.set_states(state_labels)
         assert sys_r.state_labels == state_labels
@@ -143,7 +145,7 @@ def test_io_naming(fun, args, kwargs):
         sys_k = fun(state_labels, output_labels, input_labels, name='mysys')
 
     elif sys_g.nstates is None:
-        # Don't pass state labels
+        # Don't pass state labels if TransferFunction
         sys_k = fun(
             *args, inputs=input_labels, outputs=output_labels, name='mysys')
 
@@ -155,7 +157,7 @@ def test_io_naming(fun, args, kwargs):
     assert sys_k.name == 'mysys'
     assert sys_k.input_labels == input_labels
     assert sys_k.output_labels == output_labels
-    if sys_g.nstates:
+    if sys_g.nstates is not None:
         assert sys_k.state_labels == state_labels
 
     #
@@ -193,6 +195,24 @@ def test_io_naming(fun, args, kwargs):
         assert sys_tf.input_labels == input_labels
         assert sys_tf.output_labels == output_labels
 
+    #
+    # Convert the system to a LinearIOSystem and make sure labels transfer
+    #
+    if not isinstance(
+            sys_r, (ct.FrequencyResponseData, ct.NonlinearIOSystem)) and \
+                    ct.slycot_check():
+        sys_lio = ct.LinearIOSystem(sys_r)
+        assert sys_lio != sys_r
+        assert sys_lio.input_labels == input_labels
+        assert sys_lio.output_labels == output_labels
+
+        # Reassign system and signal names
+        sys_lio = ct.LinearIOSystem(
+            sys_g, inputs=input_labels, outputs=output_labels, name='new')
+        assert sys_lio.name == 'new'
+        assert sys_lio.input_labels == input_labels
+        assert sys_lio.output_labels == output_labels
+
 
 # Internal testing of StateSpace initialization
 def test_init_namedif():
@@ -221,14 +241,29 @@ def test_init_namedif():
 
 # Test state space conversion
 def test_convert_to_statespace():
-    # Set up the initial system
-    sys = ct.tf(ct.rss(2, 1, 1))
+    # Set up the initial systems
+    sys = ct.tf(ct.rss(2, 1, 1), inputs='u', outputs='y', name='sys')
+    sys_static = ct.tf(1, 2, inputs='u', outputs='y', name='sys_static')
+
+    # check that name, inputs, and outputs passed through
+    sys_new = ct.ss(sys)
+    assert sys_new.name == 'sys'
+    assert sys_new.input_labels == ['u']
+    assert sys_new.output_labels == ['y']
+    sys_new = ct.ss(sys_static)
+    assert sys_new.name == 'sys_static'
+    assert sys_new.input_labels == ['u']
+    assert sys_new.output_labels == ['y']
 
     # Make sure we can rename system name, inputs, outputs
     sys_new = ct.ss(sys, inputs='u', outputs='y', name='new')
     assert sys_new.name == 'new'
     assert sys_new.input_labels == ['u']
     assert sys_new.output_labels == ['y']
+    sys_new = ct.ss(sys_static, inputs='u', outputs='y', name='new')
+    assert sys_new.name == 'new'
+    assert sys_new.input_labels == ['u']
+    assert sys_new.output_labels == ['y']
 
     # Try specifying the state names (via low level test)
     with pytest.warns(UserWarning, match="non-unique state space realization"):