add test for quarter circle

bnavigator · bnavigator · commit abec61ff3291 · 2021-05-01T22:40:13.000+02:00
diff --git a/control/tests/nyquist_test.py b/control/tests/nyquist_test.py
@@ -186,16 +186,30 @@ def test_nyquist_indent():
     # FBS Figure 10.10
     s = ct.tf('s')
     sys = 3 * (s+6)**2 / (s * (s+1)**2)
+    # poles: [-1, -1, 0]
 
     plt.figure();
     count = ct.nyquist_plot(sys)
     plt.title("Pole at origin; indent_radius=default")
     assert _Z(sys) == count + _P(sys)
 
+    # first value of default omega vector was 0.1, replaced by 0. for contour
+    # indent_radius is larger than 0.1 -> no extra quater circle around origin
+    count, contour = ct.nyquist_plot(sys, plot=False, indent_radius=.1007,
+                                     return_contour=True)
+    np.testing.assert_allclose(contour[0], .1007+0.j)
+    # second value of omega_vector is larger than indent_radius: not indented
+    assert np.all(contour.real[2:] == 0.)
+
     plt.figure();
-    count = ct.nyquist_plot(sys, indent_radius=0.01)
+    count, contour = ct.nyquist_plot(sys, indent_radius=0.01,
+                                     return_contour=True)
     plt.title("Pole at origin; indent_radius=0.01; encirclements = %d" % count)
     assert _Z(sys) == count + _P(sys)
+    # indent radius is smaller than the start of the default omega vector
+    # check that a quarter circle around the pole at origin has been added.
+    np.testing.assert_allclose(contour[:50].real**2 + contour[:50].imag**2,
+                               0.01**2)
 
     plt.figure();
     count = ct.nyquist_plot(sys, indent_direction='left')
