Solve #862: bode_plot phase wrapping incorrect for multiple systems

henklaak · henklaak · commit b6769f6eb8f7 · 2023-02-17T13:58:45.000+01:00
diff --git a/control/freqplot.py b/control/freqplot.py
@@ -276,18 +276,18 @@ def bode_plot(syslist, omega=None,
             if initial_phase is None:
                 # Start phase in the range 0 to -360 w/ initial phase = -180
                 # If wrap_phase is true, use 0 instead (phase \in (-pi, pi])
-                initial_phase = -math.pi if wrap_phase is not True else 0
+                initial_phase_value = -math.pi if wrap_phase is not True else 0
             elif isinstance(initial_phase, (int, float)):
                 # Allow the user to override the default calculation
                 if deg:
-                    initial_phase = initial_phase/180. * math.pi
+                    initial_phase_value = initial_phase/180. * math.pi
             else:
                 raise ValueError("initial_phase must be a number.")
 
             # Shift the phase if needed
-            if abs(phase[0] - initial_phase) > math.pi:
+            if abs(phase[0] - initial_phase_value) > math.pi:
                 phase -= 2*math.pi * \
-                    round((phase[0] - initial_phase) / (2*math.pi))
+                    round((phase[0] - initial_phase_value) / (2*math.pi))
 
             # Phase wrapping
             if wrap_phase is False:
diff --git a/control/tests/freqresp_test.py b/control/tests/freqresp_test.py
@@ -375,6 +375,18 @@ def test_phase_wrap(TF, wrap_phase, min_phase, max_phase):
     assert(max(phase) <= max_phase)
 
 
+def test_phase_wrap_multiple_systems():
+    G = ctrl.zpk([],[1,1], gain=1)
+
+    mag, phase, omega = ctrl.bode(G)
+    assert(np.min(phase) >= -2*np.pi)
+    assert(np.max(phase) <= -1*np.pi)
+
+    mag, phase, omega = ctrl.bode((G,G))
+    assert(np.min(phase) >= -2*np.pi)
+    assert(np.max(phase) <= -1*np.pi)
+
+
 def test_freqresp_warn_infinite():
     """Test evaluation warnings for transfer functions w/ pole at the origin"""
     sys_finite = ctrl.tf([1], [1, 0.01])
