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Add passivity module, ispassive function, and passivity_test. Introduces optional dependency cvxopt. #739

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Merged
murrayrm merged 21 commits into from
Jun 16, 2022
Merged

Add passivity module, ispassive function, and passivity_test. Introduces optional dependency cvxopt. #739

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e8e87a4
Add passivity module, is_passive function, and passivity_test.
May 31, 2022
2eef661
Remove dependancies on lmi-sdp and sympy for is_passive.
Jun 6, 2022
147a24e
Use sys.nstates in stead of using A.shape[0]
Jun 6, 2022
fdb2d4a
Attempt to setup cvxopt similar to slycot.
Jun 6, 2022
dc46f3c
Remove unused import.
Mark-Yeatman Jun 7, 2022
0ecc135
Apply suggestions from code review
Mark-Yeatman Jun 7, 2022
649b21e
Update passivity.py
Mark-Yeatman Jun 7, 2022
b73e6fe
Address some review comments.
Jun 13, 2022
cd7ec0f
Update control/passivity.py
Mark-Yeatman Jun 13, 2022
d65f1d2
Remove duplicate "print" statement.
Jun 13, 2022
7e79c82
Fix grammar in doc string.
Jun 13, 2022
c57b928
Another grammar in doc string fix.
Jun 13, 2022
27487a9
Address edge case of stricly proper systems.
Jun 14, 2022
d6916c6
Expand unit tests, add info to doc string for parameters and returns,…
Jun 14, 2022
bb16be0
Parameterize unit tests. Catch edge case of A=0.
Mark-Yeatman Jun 14, 2022
cf0eac3
Run autopep8.
Mark-Yeatman Jun 14, 2022
7e47d80
Add wrapper like functionality for ispassive(), so that it can be cal…
Mark-Yeatman Jun 16, 2022
ce11d0b
mark the whole passivity_test module as skippable
bnavigator Jun 16, 2022
f7d74b2
Fix bug in tests and lti.py.
Jun 16, 2022
0c361df
Merge branch 'main' into passivity-tools
Mark-Yeatman Jun 16, 2022
c2255b0
Fix merge issue.
Jun 16, 2022
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Expand unit tests, add info to doc string for parameters and returns,… 
… rename is_passive to ispassive for naming convention consistency. Autoformat to pep8.
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Mark
Mark committed Jun 14, 2022
commit d6916c661a7799e5998f84f5e2d34368ace528a8
21 changes: 15 additions & 6 deletions control/passivity.py
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Expand Up @@ -10,18 +10,27 @@
except ImportError as e:
cvx = None

lmi_epsilon = 1e-12

def is_passive(sys):
def ispassive(sys):
'''
Indicates if a linear time invariant system is passive
Indicates if a linear time invariant (LTI) system is passive

Constructs a linear matrix inequality and a feasibility optimization
such that if a solution exists, the system is passive.

The source for the algorithm is:
McCourt, Michael J., and Panos J. Antsaklis.
"Demonstrating passivity and dissipativity using computational methods." ISIS 8 (2013).

Parameters
----------
sys: A continuous LTI system
System to be checked.

Returns
-------
bool:
The input system passive.
'''
if cvx is None:
raise ModuleNotFoundError("cvxopt required for passivity module")
Expand All @@ -31,9 +40,9 @@ def is_passive(sys):
C = sys.C
D = sys.D

#account for strictly proper systems
[n,m] = D.shape
D = D + np.nextafter(0,1)*np.eye(n,m)
# account for strictly proper systems
[n, m] = D.shape
D = D + np.nextafter(0, 1)*np.eye(n, m)

def make_LMI_matrix(P):
V = np.vstack((
Expand Down
43 changes: 35 additions & 8 deletions control/tests/passivity_test.py
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Expand Up @@ -7,30 +7,57 @@
from control import ss, passivity
from control.tests.conftest import cvxoptonly


@cvxoptonly
def test_is_passive():
def test_ispassive():
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)

# happy path is passive
assert(passivity.is_passive(sys))
assert(passivity.ispassive(sys))

# happy path not passive
D = -D
sys = ss(A, B, C, D)

assert(not passivity.is_passive(sys))
assert(not passivity.ispassive(sys))


@cvxoptonly
def test_ispassive_edge_cases():
A = numpy.array([[0, 1], [-2, -2]])
B = numpy.array([[0], [1]])
C = numpy.array([[-1, 2]])
D = numpy.array([[1.5]])

#edge cases of D=0 boundary condition
B *= 0
C *= 0
D *= 0

# strictly proper
sys = ss(A, B, C, D)
assert(passivity.is_passive(sys))
assert(passivity.ispassive(sys))

# ill conditioned
A = A*1e12
sys = ss(A, B, C, D)
assert(passivity.is_passive(sys))
assert(passivity.ispassive(sys))

# different combinations of zero A,B,C,D are 0
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B *= 0
C *= 0
assert(passivity.ispassive(sys))

A *= 0
B = numpy.array([[0], [1]])
C = numpy.array([[-1, 2]])
D = numpy.array([[1.5]])
assert(passivity.ispassive(sys))

B *= 0
C *= 0
assert(passivity.ispassive(sys))

A *= 0
assert(passivity.ispassive(sys))