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Updated gram to support discrete-time systems #969

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Merged
merged 2 commits into from
Mar 30, 2024
Merged

Updated gram to support discrete-time systems #969

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2f982bb
Updated gram for dtime systems
billtubbs Feb 11, 2024
0836ad8
Removed redundant if condition
billtubbs Feb 18, 2024
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27 changes: 15 additions & 12 deletions control/statefbk.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1119,18 +1119,21 @@ def gram(sys, type):
if type not in ['c', 'o', 'cf', 'of']:
raise ValueError("That type is not supported!")

# TODO: Check for continuous or discrete, only continuous supported for now
# if isCont():
# dico = 'C'
# elif isDisc():
# dico = 'D'
# else:
dico = 'C'

# TODO: Check system is stable, perhaps a utility in ctrlutil.py
# or a method of the StateSpace class?
if np.any(np.linalg.eigvals(sys.A).real >= 0.0):
raise ValueError("Oops, the system is unstable!")
# Check if system is continuous or discrete
if sys.isctime():
dico = 'C'

# TODO: Check system is stable, perhaps a utility in ctrlutil.py
# or a method of the StateSpace class?
if np.any(np.linalg.eigvals(sys.A).real >= 0.0):
raise ValueError("Oops, the system is unstable!")

else:
assert sys.isdtime()
dico = 'D'

if np.any(np.abs(sys.poles()) >= 1.):
raise ValueError("Oops, the system is unstable!")

if type == 'c' or type == 'o':
# Compute Gramian by the Slycot routine sb03md
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69 changes: 63 additions & 6 deletions control/tests/statefbk_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -98,6 +98,28 @@ def testGramWc(self):
Wctrue = np.array([[18.5, 24.5], [24.5, 32.5]])
Wc = gram(sys, 'c')
np.testing.assert_array_almost_equal(Wc, Wctrue)
sysd = ct.c2d(sys, 0.2)
Wctrue = np.array([[3.666767, 4.853625],
[4.853625, 6.435233]])
Wc = gram(sysd, 'c')
np.testing.assert_array_almost_equal(Wc, Wctrue)

@slycotonly
def testGramWc2(self):
A = np.array([[1., -2.], [3., -4.]])
B = np.array([[5.], [7.]])
C = np.array([[6., 8.]])
D = np.array([[9.]])
sys = ss(A,B,C,D)
Wctrue = np.array([[ 7.166667, 9.833333],
[ 9.833333, 13.5]])
Wc = gram(sys, 'c')
np.testing.assert_array_almost_equal(Wc, Wctrue)
sysd = ct.c2d(sys, 0.2)
Wctrue = np.array([[1.418978, 1.946180],
[1.946180, 2.670758]])
Wc = gram(sysd, 'c')
np.testing.assert_array_almost_equal(Wc, Wctrue)

@slycotonly
def testGramRc(self):
Expand All @@ -106,9 +128,15 @@ def testGramRc(self):
C = np.array([[4., 5.], [6., 7.]])
D = np.array([[13., 14.], [15., 16.]])
sys = ss(A, B, C, D)
Rctrue = np.array([[4.30116263, 5.6961343], [0., 0.23249528]])
Rctrue = np.array([[4.30116263, 5.6961343],
[0., 0.23249528]])
Rc = gram(sys, 'cf')
np.testing.assert_array_almost_equal(Rc, Rctrue)
sysd = ct.c2d(sys, 0.2)
Rctrue = np.array([[1.91488054, 2.53468814],
[0. , 0.10290372]])
Rc = gram(sysd, 'cf')
np.testing.assert_array_almost_equal(Rc, Rctrue)

@slycotonly
def testGramWo(self):
Expand All @@ -120,6 +148,11 @@ def testGramWo(self):
Wotrue = np.array([[257.5, -94.5], [-94.5, 56.5]])
Wo = gram(sys, 'o')
np.testing.assert_array_almost_equal(Wo, Wotrue)
sysd = ct.c2d(sys, 0.2)
Wotrue = np.array([[ 1305.369179, -440.046414],
[ -440.046414, 333.034844]])
Wo = gram(sysd, 'o')
np.testing.assert_array_almost_equal(Wo, Wotrue)

@slycotonly
def testGramWo2(self):
Expand All @@ -131,6 +164,11 @@ def testGramWo2(self):
Wotrue = np.array([[198., -72.], [-72., 44.]])
Wo = gram(sys, 'o')
np.testing.assert_array_almost_equal(Wo, Wotrue)
sysd = ct.c2d(sys, 0.2)
Wotrue = np.array([[ 1001.835511, -335.337663],
[ -335.337663, 263.355793]])
Wo = gram(sysd, 'o')
np.testing.assert_array_almost_equal(Wo, Wotrue)

@slycotonly
def testGramRo(self):
Expand All @@ -142,15 +180,34 @@ def testGramRo(self):
Rotrue = np.array([[16.04680654, -5.8890222], [0., 4.67112593]])
Ro = gram(sys, 'of')
np.testing.assert_array_almost_equal(Ro, Rotrue)
sysd = ct.c2d(sys, 0.2)
Rotrue = np.array([[ 36.12989315, -12.17956588],
[ 0. , 13.59018097]])
Ro = gram(sysd, 'of')
np.testing.assert_array_almost_equal(Ro, Rotrue)

def testGramsys(self):
num =[1.]
den = [1., 1., 1.]
sys = tf(num,den)
with pytest.raises(ValueError):
sys = tf([1.], [1., 1., 1.])
with pytest.raises(ValueError) as excinfo:
gram(sys, 'o')
with pytest.raises(ValueError):
assert "must be StateSpace" in str(excinfo.value)
with pytest.raises(ValueError) as excinfo:
gram(sys, 'c')
assert "must be StateSpace" in str(excinfo.value)
sys = tf([1], [1, -1], 0.5)
with pytest.raises(ValueError) as excinfo:
gram(sys, 'o')
assert "must be StateSpace" in str(excinfo.value)
with pytest.raises(ValueError) as excinfo:
gram(sys, 'c')
assert "must be StateSpace" in str(excinfo.value)
sys = ct.ss(sys) # this system is unstable
with pytest.raises(ValueError) as excinfo:
gram(sys, 'o')
assert "is unstable" in str(excinfo.value)
with pytest.raises(ValueError) as excinfo:
gram(sys, 'c')
assert "is unstable" in str(excinfo.value)

def testAcker(self, fixedseed):
for states in range(1, self.maxStates):
Expand Down
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