add warning if output might not be state in create_statefbk_iosystem

murrayrm · murrayrm · commit 4e5d80d61219 · 2023-02-04T15:55:52.000-08:00
diff --git a/control/statefbk.py b/control/statefbk.py
@@ -718,7 +718,7 @@ def create_statefbk_iosystem(
         List of strings that name the individual signals of the transformed
         system.  If not given, the inputs and outputs are the same as the
         original system.
-    
+
     name : string, optional
         System name. If unspecified, a generic name <sys[id]> is generated
         with a unique integer id.
@@ -750,6 +750,12 @@ def create_statefbk_iosystem(
         # TODO: check to make sure output map is the identity
         raise ControlArgument("System output must be the full state")
     else:
+        # Issue a warning if we can't verify state output
+        if (isinstance(sys, NonlinearIOSystem) and sys.outfcn is not None) or \
+           (isinstance(sys, StateSpace) and
+            not (np.all(sys.C == np.eye(sys.nstates)) and np.all(sys.D == 0))):
+            warnings.warn("cannot verify system output is system state")
+
         # Use the system directly instead of an estimator
         estimator = sys
 
diff --git a/control/tests/statefbk_test.py b/control/tests/statefbk_test.py
@@ -754,6 +754,12 @@ def test_statefbk_errors(self):
         sys = ct.rss(4, 4, 2, strictly_proper=True)
         K, _, _ = ct.lqr(sys, np.eye(sys.nstates), np.eye(sys.ninputs))
 
+        with pytest.warns(UserWarning, match="cannot verify system output"):
+            ctrl, clsys = ct.create_statefbk_iosystem(sys, K)
+
+        # reset the system output
+        sys.C = np.eye(sys.nstates)
+
         with pytest.raises(ControlArgument, match="must be I/O system"):
             sys_tf = ct.tf([1], [1, 1])
             ctrl, clsys = ct.create_statefbk_iosystem(sys_tf, K)
@@ -806,11 +812,8 @@ def unicycle():
     def unicycle_update(t, x, u, params):
         return np.array([np.cos(x[2]) * u[0], np.sin(x[2]) * u[0], u[1]])
 
-    def unicycle_output(t, x, u, params):
-        return x
-
     return ct.NonlinearIOSystem(
-        unicycle_update, unicycle_output,
+        unicycle_update, None,
         inputs = ['v', 'phi'],
         outputs = ['x', 'y', 'theta'],
         states = ['x_', 'y_', 'theta_'])
