8000 unit tests for infinite frequency response values, warnings · python-control/python-control@96e44fe · GitHub
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Commit 96e44fe

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murrayrmmurrayrm
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unit tests for infinite frequency response values, warnings
1 parent b67eb7d commit 96e44fe

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3 files changed

+74
-3
lines changed

3 files changed

+74
-3
lines changed

‎control/lti.py

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -644,8 +644,9 @@ def dcgain(sys):
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Returns
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-------
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gain : ndarray
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The zero-frequency gain, or np.nan if the system has a pole
648-
at the origin
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The zero-frequency gain, or np.inf if the system has a pole at the
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origin, np.nan if there is a pole/zero cancellation at the origin.
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"""
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return sys.dcgain()
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‎control/tests/freqresp_test.py

Lines changed: 70 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -364,3 +364,73 @@ def test_phase_wrap(TF, wrap_phase, min_phase, max_phase):
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mag, phase, omega = ctrl.bode(TF, wrap_phase=wrap_phase)
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assert(min(phase) >= min_phase)
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assert(max(phase) <= max_phase)
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def test_freqresp_warn_infinite():
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"""Test evaluation of transfer functions at the origin"""
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sys_finite = ctrl.tf([1], [1, 0.01])
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sys_infinite = ctrl.tf([1], [1, 0.01, 0])
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# Transfer function with finite zero frequency gain
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np.testing.assert_almost_equal(sys_finite(0), 100)
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np.testing.assert_almost_equal(sys_finite(0, warn_infinite=False), 100)
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np.testing.assert_almost_equal(sys_finite(0, warn_infinite=True), 100)
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# Transfer function with infinite zero frequency gain
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with pytest.warns(RuntimeWarning, match="divide by zero"):
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np.testing.assert_almost_equal(sys_infinite(0), np.inf)
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with pytest.warns(RuntimeWarning, match="divide by zero"):
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np.testing.assert_almost_equal(
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sys_infinite(0, warn_infinite=True), np.inf)
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np.testing.assert_almost_equal(sys_infinite(0, warn_infinite=False), np.inf)
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# Switch to state space
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sys_finite = ctrl.tf2ss(sys_finite)
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sys_infinite = ctrl.tf2ss(sys_infinite)
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# State space system with finite zero frequency gain
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np.testing.assert_almost_equal(sys_finite(0), 100)
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np.testing.assert_almost_equal(sys_finite(0, warn_infinite=False), 100)
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np.testing.assert_almost_equal(sys_finite(0, warn_infinite=True), 100)
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# State space system with infinite zero frequency gain
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with pytest.warns(RuntimeWarning, match="not finite"):
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np.testing.assert_almost_equal(sys_infinite(0), np.inf)
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with pytest.warns(RuntimeWarning, match="not finite"):
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np.testing.assert_almost_equal(sys_infinite(0), np.inf)
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np.testing.assert_almost_equal(sys_infinite(0, warn_infinite=True), np.inf)
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np.testing.assert_almost_equal(sys_infinite(0, warn_infinite=False), np.inf)
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def test_dcgain_consistency():
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"""Test to make sure that DC gain is consistently evaluated"""
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# Set up transfer function with pole at the origin
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sys_tf = ctrl.tf([1], [1, 0])
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assert 0 in sys_tf.pole()
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# Set up state space system with pole at the origin
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sys_ss = ctrl.tf2ss(sys_tf)
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assert 0 in sys_ss.pole()
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# Evaluation
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np.testing.assert_equal(sys_tf(0), np.inf + 0j)
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np.testing.assert_equal(sys_ss(0), np.inf + 0j)
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np.testing.assert_equal(sys_tf.dcgain(), np.inf + 0j)
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np.testing.assert_equal(sys_ss.dcgain(), np.inf + 0j)
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# Set up transfer function with pole, zero at the origin
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sys_tf = ctrl.tf([1, 0], [1, 0])
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assert 0 in sys_tf.pole()
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assert 0 in sys_tf.zero()
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sys_ss = ctrl.tf2ss(ctrl.tf([1, 0], [1, 1])) * \
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ctrl.tf2ss(ctrl.tf([1], [1, 0]))
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assert 0 in sys_ss.pole()
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assert 0 in sys_ss.zero()
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# Pole and zero at the origin should give nan for the response
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np.testing.assert_equal(sys_tf(0), np.nan)
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np.testing.assert_equal(sys_tf.dcgain(), np.nan)
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# TODO: state space cases not yet working
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# np.testing.assert_equal(sys_ss(0), np.nan)
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# np.testing.assert_equal(sys_ss.dcgain(), np.nan)

‎control/tests/statesp_test.py

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -523,7 +523,7 @@ def test_dc_gain_discr(self):
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@pytest.mark.parametrize("dt", [None, 0, 1, True],
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ids=["dtNone", "c", "dt1", "dtTrue"])
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def test_dc_gain_integrator(self, outputs, inputs, dt):
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"""DC gain when eigenvalue at DC returns appropriately sized array of nan.
526+
"""DC gain w/ pole at origin returns appropriately sized array of inf.
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the SISO case is also tested in test_dc_gain_{cont,discr}
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time systems (dt=0)

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