Skip to content

fix damp method for discrete time systems with a negative real-valued pole #647

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Aug 19, 2021
Merged

fix damp method for discrete time systems with a negative real-valued pole #647

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
78b6fc2
fix the return of the damp method for discrete time systems with a ne…
vincentchoqueuse Aug 17, 2021
140ca08
fix PEP8 compliance style and preserve pole type
vincentchoqueuse Aug 18, 2021
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 1 addition & 1 deletion control/lti.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -159,7 +159,7 @@ def damp(self):
poles = self.pole()

if isdtime(self, strict=True):
splane_poles = np.log(poles)/self.dt
splane_poles = np.log(poles.astype(complex))/self.dt
else:
splane_poles = poles
wn = absolute(splane_poles)
Expand Down
8 changes: 8 additions & 0 deletions control/tests/lti_test.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -70,6 +70,14 @@ def test_damp(self):
np.testing.assert_almost_equal(sys_dt.damp(), expected_dt)
np.testing.assert_almost_equal(damp(sys_dt), expected_dt)

#also check that for a discrete system with a negative real pole the damp function can extract wn and zeta.
p2_zplane = -0.2
sys_dt2 = tf(1, [1, -p2_zplane], dt)
wn2, zeta2, p2 = sys_dt2.damp()
p2_splane = -wn2 * zeta2 + 1j * wn2 * np.sqrt(1 - zeta2**2)
p2_zplane = np.exp(p2_splane * dt)
np.testing.assert_almost_equal(p2, p2_zplane)

def test_dcgain(self):
sys = tf(84, [1, 2])
np.testing.assert_allclose(sys.dcgain(), 42)
Expand Down