Merge remote-tracking branch 'upstream/master'

repagh · repagh · commit 04ed40d876ed · 2015-07-11T19:26:20.000+02:00
solved the conflict in the margin_test routine
updated the doc for margin to match order of returned values
diff --git a/control/margins.py b/control/margins.py
@@ -87,7 +87,7 @@ def _polysqr(pol):
 # RvP, July 8, 2015, augmented to calculate all phase/gain crossings with
 #                    frd data. Correct to return smallest phase
 #                    margin, smallest gain margin and their frequencies
-def stability_margins(sysdata, returnall=False, epsw=1e-10):
+def stability_margins(sysdata, returnall=False, epsw=1e-8):
     """Calculate stability margins and associated crossover frequencies.
 
     Parameters
@@ -331,11 +331,12 @@ def margin(*args):
     Returns
     -------
     gm, pm, Wcg, Wcp : float
-        Gain margin gm, phase margin pm (in deg), gain crossover frequency
-        (corresponding to phase margin) and phase crossover frequency
-        (corresponding to gain margin), in rad/sec of SISO open-loop.
-        If more than one crossover frequency is detected, returns the lowest
-        corresponding margin.
+        Gain margin gm, phase margin pm (in deg), phase crossover frequency
+        (corresponding to gain margin, where phase=-180) and gain crossover
+        frequency (corresponding to phase margin, where gain is 0dB),
+        in rad/sec of SISO open-loop.
+        If more than one crossover frequency is detected for gain or phase,
+        this returns one with the lowest corresponding margin.
 
     Examples
     --------
@@ -352,4 +353,4 @@ def margin(*args):
         raise ValueError("Margin needs 1 or 3 arguments; received %i."
             % len(args))
 
-    return margin[0], margin[1], margin[4], margin[3]
+    return margin[0], margin[1], margin[3], margin[4]
diff --git a/control/tests/margin_test.py b/control/tests/margin_test.py
@@ -40,6 +40,8 @@ def setUp(self):
         s = TransferFunction([1, 0], [1])
         self.sys4 = (8.75*(4*s**2+0.4*s+1))/((100*s+1)*(s**2+0.22*s+1)) * \
                                       1./(s**2/(10.**2)+2*0.04*s/10.+1)
+        self.stability_margins4 = \
+          [2.2716, 97.5941, 0.5591, 10.0053, 0.0850, 9.9918]
 
     def test_stability_margins(self):
         omega = np.logspace(-2, 2, 2000)
@@ -57,7 +59,13 @@ def test_stability_margins(self):
         # final one with fixed values
         np.testing.assert_array_almost_equal(
             [gm, pm, sm, wg, wp, ws],
-            [2.2716, 97.5941, 0.5591, 10.0053, 0.0850, 9.9918], 3) 
+            self.stability_margins4, 3)
+
+    def test_margin(self):
+        gm, pm, wg, wp = margin(self.sys4)
+        np.testing.assert_array_almost_equal(
+            [gm, pm, wg, wp],
+            self.stability_margins4[:2] + self.stability_margins4[3:5], 3)
 
     def test_stability_margins_all(self):
         for sys,rgm,rwgm,rpm,rwpm in self.tsys:
diff --git a/control/tests/matlab_test.py b/control/tests/matlab_test.py
@@ -257,7 +257,7 @@ def testMargin(self):
         gm, pm, wg, wp = margin(self.siso_ss2);
         gm, pm, wg, wp = margin(self.siso_ss2*self.siso_ss2*2);
         np.testing.assert_array_almost_equal(
-            [gm, pm, wg, wp], [1.5451, 75.9933, 0.6559, 1.2720], decimal=3)
+            [gm, pm, wg, wp], [1.5451, 75.9933, 1.2720, 0.6559], decimal=3)
 
     def testDcgain(self):
         #Create different forms of a SISO system
@@ -554,8 +554,6 @@ def testSS2cont(self):
                       -0.260952977031384  -0.274201791021713;
                       -0.304617775734327   0.075182622718853"""), sysd.B)
 
-
-    @unittest.skip("need to update margin command")
     def testCombi01(self):
         # test from a "real" case, combines tf, ss, connect and margin
         # this is a type 2 system, with phase starting at -180. The
@@ -610,8 +608,8 @@ def testCombi01(self):
         # print("%f %f %f %f" % (gm, pm, wg, wp))
         self.assertAlmostEqual(gm, 3.32065569155)
         self.assertAlmostEqual(pm, 46.9740430224)
-        self.assertAlmostEqual(wp, 0.0616288455466)
         self.assertAlmostEqual(wg, 0.176469728448)
+        self.assertAlmostEqual(wp, 0.0616288455466)
 
 #! TODO: not yet implemented
 #    def testMIMOtfdata(self):
