Updated changelog

repagh · repagh · commit 385c9e9b2157 · 2013-05-25T20:48:16.000Z
diff --git a/ChangeLog b/ChangeLog
@@ -1,3 +1,20 @@
+2013-05-23  Rene van Paassen <rene.vanpaassen@gmail.com>
+
+	* src/margin.py: re-vamped stability_margins function. Now
+          uses analytical method for TF and state-space, works on FRD
+          objects too, and can optionally return all margins found for
+          the analytical method.
+
+	* src/xferfcn.py and src/frdata.py: Now return array result
+          for fresp when called with an iterable frequency vector
+
+	* src/xferfcn.py and src/statesp.py: added minreal functions
+
+	* src/bdalg.py: implemented append and connect functions (old
+          version, with indexes, not with names)
+	  
+	* src/matlab.py: added connect, append, minreal
+
 2012-11-10  Richard Murray  <murray@altura.local>
 
 	* src/canonical.py: new module implementing conversions to selected
diff --git a/src/matlab.py b/src/matlab.py
@@ -101,7 +101,7 @@
 from control.pzmap import pzmap
 from control.statefbk import ctrb, obsv, gram, place, lqr
 from control.delay import pade
-from control.modelsimp import hsvd, balred, modred
+from control.modelsimp import hsvd, balred, modred, minreal
 from control.mateqn import lyap, dlyap, dare, care
 
 __doc__ += r"""
@@ -244,7 +244,7 @@
 ----------------------------------------------------------------------------
 
 ==  ==========================  ============================================
-\   minreal                     minimal realization; pole/zero cancellation
+\*  :func:`~modelsimp.minreal`  minimal realization; pole/zero cancellation
 \   ss/sminreal                 structurally minimal realization
 \*  :func:`~modelsimp.hsvd`     hankel singular values (state contributions)
 \*  :func:`~modelsimp.balred`   reduced-order approximations of LTI models
diff --git a/src/modelsimp.py b/src/modelsimp.py
@@ -269,6 +269,33 @@ def balred(sys, orders, method='truncate'):
 
     return rsys
 
+def minreal(sys, tol=None, verbose=True):
+    '''
+    Eliminates uncontrollable or unobservable states in state-space
+    models or cancelling pole-zero pairs in transfer functions. The
+    output sysr has minimal order and the same response
+    characteristics as the original model sys.
+
+    Parameters
+    ----------
+    sys: StateSpace or TransferFunction
+        Original system
+    tol: real
+        Tolerance
+    verbose: bool
+        Print results if True
+
+    Returns
+    -------
+    rsys: StateSpace or TransferFunction
+        Cleaned model
+    '''
+    sysr = sys.minreal(tol)
+    if verbose:
+        print("{nstates} states have been removed from the model".format(
+                nstates=len(sys.pole()) - len(sysr.pole())))
+    return sysr
+
 def era(YY, m, n, nin, nout, r):
     """
     Calculate an ERA model of order `r` based on the impulse-response data `YY`.
diff --git a/tests/matlab_test.py b/tests/matlab_test.py
@@ -11,6 +11,7 @@
 from __future__ import print_function
 import unittest
 import numpy as np
+from scipy.linalg import eigvals
 import scipy as sp
 from control.matlab import *
 from control.frdata import FRD
@@ -440,7 +441,34 @@ def testFRD(self):
         assert isinstance(frd1, FRD)
         frd2 = frd(frd1.fresp[0,0,:], omega)
         assert isinstance(frd2, FRD)
-       
+
+    def testMinreal(self, verbose=False):
+        """Test a minreal model reduction"""
+        #A = [-2, 0.5, 0; 0.5, -0.3, 0; 0, 0, -0.1]
+        A = [[-2, 0.5, 0], [0.5, -0.3, 0], [0, 0, -0.1]]
+        #B = [0.3, -1.3; 0.1, 0; 1, 0]
+        B = [[0.3, -1.3], [0.1, 0.], [1.0, 0.0]]
+        #C = [0, 0.1, 0; -0.3, -0.2, 0]
+        C = [[0., 0.1, 0.0], [-0.3, -0.2, 0.0]]
+        #D = [0 -0.8; -0.3 0]
+        D = [[0., -0.8], [-0.3, 0.]]
+        # sys = ss(A, B, C, D)
+        
+        sys = ss(A, B, C, D)
+        sysr = minreal(sys)
+        self.assertEqual(sysr.states, 2)
+        self.assertEqual(sysr.inputs, sys.inputs)
+        self.assertEqual(sysr.outputs, sys.outputs)
+        np.testing.assert_array_almost_equal(
+            eigvals(sysr.A), [-2.136154, -0.1638459])
+
+        s = tf([1, 0], [1])
+        h = (s+1)*(s+2.00000000001)/(s+2)/(s**2+s+1)
+        hm = minreal(h)
+        hr = (s+1)/(s**2+s+1)
+        np.testing.assert_array_almost_equal(hm.num[0][0], hr.num[0][0])
+        np.testing.assert_array_almost_equal(hm.den[0][0], hr.den[0][0])
+
 
 #! TODO: not yet implemented
 #    def testMIMOtfdata(self):
