Consistent return values for lqe and lqr (#477)

murrayrm · web-flow · commit 38f29c739624 · 2020-12-26T08:31:28.000-08:00
* update lqe return values to match lqr
* update lqe docstring
diff --git a/control/statefbk.py b/control/statefbk.py
@@ -282,19 +282,14 @@ def lqe(A, G, C, QN, RN, NN=None):
 
             A P + P A^T - (P C^T + G N) R^{-1}  (C P + N^T G^T) + G Q G^T = 0
 
-    E : 2D array (or matrix)
+    E : 1D array
         Eigenvalues of estimator poles eig(A - L C)
 
     Notes
     -----
     The return type for 2D arrays depends on the default class set for
     state space operations.  See :func:`~control.use_numpy_matrix`.
 
-    The return type for `E` differs from the equivalent return values in the
-    :func:`~control.lqr`, :func:`~control.care`, and other similar
-    functions.  The return type will be changed to a 1D array in a future
-    release.
-
     Examples
     --------
     >>> K, P, E = lqe(A, G, C, QN, RN)
@@ -317,7 +312,7 @@ def lqe(A, G, C, QN, RN, NN=None):
     A, G, C = np.array(A, ndmin=2), np.array(G, ndmin=2), np.array(C, ndmin=2)
     QN, RN = np.array(QN, ndmin=2), np.array(RN, ndmin=2)
     P, E, LT = care(A.T, C.T, np.dot(np.dot(G, QN), G.T), RN)
-    return _ssmatrix(LT.T), _ssmatrix(P), _ssmatrix(E)
+    return _ssmatrix(LT.T), _ssmatrix(P), E
 
 
 # Contributed by Roberto Bucher <roberto.bucher@supsi.ch>
diff --git a/control/tests/statefbk_test.py b/control/tests/statefbk_test.py
@@ -302,7 +302,7 @@ def test_LQR_3args(self):
     def check_LQE(self, L, P, poles, G, QN, RN):
         P_expected = np.array(np.sqrt(G*QN*G * RN))
         L_expected = P_expected / RN
-        poles_expected = np.array([-L_expected], ndmin=2)
+        poles_expected = np.array([-L_expected])
         np.testing.assert_array_almost_equal(P, P_expected)
         np.testing.assert_array_almost_equal(L, L_expected)
         np.testing.assert_array_almost_equal(poles, poles_expected)
