Add wrapper like functionality for ispassive(), so that it can be called in an object oriented style as a LTI class member. Added unit tests for transfer function and oo style calls. Ran autopep8 on lti.py.

Mark-Yeatman · Mark-Yeatman · commit 7e47d8060c49 · 2022-06-15T21:22:54.000-04:00
diff --git a/control/lti.py b/control/lti.py
@@ -13,6 +13,7 @@
 """
 
 import numpy as np
+
 from numpy import absolute, real, angle, abs
 from warnings import warn
 from . import config
@@ -21,6 +22,7 @@
 __all__ = ['poles', 'zeros', 'damp', 'evalfr', 'frequency_response',
            'freqresp', 'dcgain', 'pole', 'zero']
 
+
 class LTI(NamedIOSystem):
     """LTI is a parent class to linear time-invariant (LTI) system objects.
 
@@ -44,6 +46,7 @@ class LTI(NamedIOSystem):
     Note: dt processing has been moved to the NamedIOSystem class.
 
     """
+
     def __init__(self, inputs=1, outputs=1, states=None, name=None, **kwargs):
         """Assign the LTI object's numbers of inputs and ouputs."""
         super().__init__(
@@ -71,8 +74,7 @@ def _set_inputs(self, value):
 
     #: Deprecated
     inputs = property(
-        _get_inputs, _set_inputs, doc=
-        """
+        _get_inputs, _set_inputs, doc="""
         Deprecated attribute; use :attr:`ninputs` instead.
 
         The ``inputs`` attribute was used to store the number of system
@@ -94,8 +96,7 @@ def _set_outputs(self, value):
 
     #: Deprecated
     outputs = property(
-        _get_outputs, _set_outputs, doc=
-        """
+        _get_outputs, _set_outputs, doc="""
         Deprecated attribute; use :attr:`noutputs` instead.
 
         The ``outputs`` attribute was used to store the number of system
@@ -201,6 +202,11 @@ def _dcgain(self, warn_infinite):
         else:
             return zeroresp
 
+    def ispassive(self):
+        # importing here prevents circular dependancy
+        from control.passivity import ispassive
+        ispassive(self)
+
     #
     # Deprecated functions
     #
@@ -321,7 +327,7 @@ def damp(sys, doprint=True):
     wn, damping, poles = sys.damp()
     if doprint:
         print('_____Eigenvalue______ Damping___ Frequency_')
-        for p, d, w in zip(poles, damping, wn) :
+        for p, d, w in zip(poles, damping, wn):
             if abs(p.imag) < 1e-12:
                 print("%10.4g            %10.4g %10.4g" %
                       (p.real, 1.0, -p.real))
@@ -330,6 +336,7 @@ def damp(sys, doprint=True):
                       (p.real, p.imag, d, w))
     return wn, damping, poles
 
+
 def evalfr(sys, x, squeeze=None):
     """Evaluate the transfer function of an LTI system for complex frequency x.
 
@@ -388,6 +395,7 @@ def evalfr(sys, x, squeeze=None):
     """
     return sys.__call__(x, squeeze=squeeze)
 
+
 def frequency_response(sys, omega, squeeze=None):
     """Frequency response of an LTI system at multiple angular frequencies.
 
diff --git a/control/passivity.py b/control/passivity.py
@@ -4,6 +4,7 @@
 '''
 
 import numpy as np
+from control import statesp as ss
 
 try:
     import cvxopt as cvx
@@ -35,6 +36,8 @@ def ispassive(sys):
     if cvx is None:
         raise ModuleNotFoundError("cvxopt required for passivity module")
 
+    sys = ss._convert_to_statespace(sys)
+
     A = sys.A
     B = sys.B
     C = sys.C
diff --git a/control/tests/passivity_test.py b/control/tests/passivity_test.py
@@ -4,7 +4,7 @@
 '''
 import pytest
 import numpy
-from control import ss, passivity
+from control import ss, passivity, tf
 from control.tests.conftest import cvxoptonly
 
 
@@ -51,3 +51,23 @@ def test_ispassive_edge_cases(test_input, expected):
     D = test_input[3]
     sys = ss(A, B, C, D)
     assert(passivity.ispassive(sys) == expected)
+
+
+def test_transfer_function():
+    sys = tf([1], [1, -2])
+    assert(passivity.ispassive(sys))
+
+    sys = tf([1], [1, 2])
+    assert(not passivity.ispassive(sys))
+
+
+def test_oo_style():
+    A = numpy.array([[0, 1], [-2, -2]])
+    B = numpy.array([[0], [1]])
+    C = numpy.array([[-1, 2]])
+    D = numpy.array([[1.5]])
+    sys = ss(A, B, C, D)
+    assert(sys.ispassive())
+
+    sys = tf([1], [1, -2])
+    assert(sys.ispassive())
