Address edge case of stricly proper systems.

Mark · Mark · commit 27487a9707d0 · 2022-06-13T19:39:29.000-05:00
diff --git a/control/passivity.py b/control/passivity.py
@@ -10,6 +10,7 @@
 except ImportError as e:
     cvx = None
 
+lmi_epsilon = 1e-12
 
 def is_passive(sys):
     '''
@@ -30,6 +31,10 @@ def is_passive(sys):
     C = sys.C
     D = sys.D
 
+    #account for strictly proper systems
+    [n,m] = D.shape
+    D = D + np.nextafter(0,1)*np.eye(n,m)
+
     def make_LMI_matrix(P):
         V = np.vstack((
             np.hstack((A.T @ P + P@A, P@B)),
@@ -59,6 +64,7 @@ def make_LMI_matrix(P):
     c = cvx.matrix(0.0, (number_of_opt_vars, 1))
 
     # crunch feasibility solution
+    cvx.solvers.options['show_progress'] = False
     sol = cvx.solvers.sdp(c,
                           Gs=[cvx.matrix(coefficents)],
                           hs=[cvx.matrix(constants)])
diff --git a/control/tests/passivity_test.py b/control/tests/passivity_test.py
@@ -15,10 +15,22 @@ def test_is_passive():
     D = numpy.array([[1.5]])
     sys = ss(A, B, C, D)
 
+    # happy path is passive
     assert(passivity.is_passive(sys))
 
+    # happy path not passive
     D = -D
     sys = ss(A, B, C, D)
 
     assert(not passivity.is_passive(sys))
 
+    #edge cases of D=0 boundary condition
+    B *= 0
+    C *= 0
+    D *= 0
+    sys = ss(A, B, C, D)
+    assert(passivity.is_passive(sys))
+
+    A = A*1e12
+    sys = ss(A, B, C, D)
+    assert(passivity.is_passive(sys))
