Merge pull request python-control#53 from cwrowley/fix-lqr

murrayrm · murrayrm · commit b7e7ae94defe · 2015-04-05T08:30:28.000-07:00
Fix LQR for 3 arguments
diff --git a/control/statefbk.py b/control/statefbk.py
@@ -195,7 +195,7 @@ def lqr(*args, **keywords):
     #
 
     # Get the system description
-    if (len(args) < 4):
+    if (len(args) < 3):
         raise ControlArgument("not enough input arguments")
 
     try:
diff --git a/control/tests/statefbk_test.py b/control/tests/statefbk_test.py
@@ -136,7 +136,27 @@ def testAcker(self):
                 np.testing.assert_array_almost_equal(np.sort(poles),
                                                      np.sort(placed), decimal=4)
 
-def suite():
+    def check_LQR(self, K, S, poles, Q, R):
+        S_expected = np.array(np.sqrt(Q * R))
+        K_expected = S_expected / R
+        poles_expected = np.array([-K_expected])
+        np.testing.assert_array_almost_equal(S, S_expected)
+        np.testing.assert_array_almost_equal(K, K_expected)
+        np.testing.assert_array_almost_equal(poles, poles_expected)
+
+
+    def test_LQR_integrator(self):
+        A, B, Q, R = 0., 1., 10., 2.
+        K, S, poles = lqr(A, B, Q, R)
+        self.check_LQR(K, S, poles, Q, R)
+
+    def test_LQR_3args(self):
+        sys = ss(0., 1., 1., 0.)
+        Q, R = 10., 2.
+        K, S, poles = lqr(sys, Q, R)
+        self.check_LQR(K, S, poles, Q, R)
+
+def test_suite():
    return unittest.TestLoader().loadTestsFromTestCase(TestStatefbk)
 
 if __name__ == '__main__':

Original file line number	Diff line number	Diff line change
`@@ -195,7 +195,7 @@ def lqr(args, *keywords):`
`195`	`195`	`#`
`196`	`196`
`197`	`197`	`# Get the system description`
`198`		`- if (len(args) < 4):`
	`198`	`+ if (len(args) < 3):`
`199`	`199`	`raise ControlArgument("not enough input arguments")`
`200`	`200`
`201`	`201`	`try:`