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Preserve signal names in scalar LTI operations #1228

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15 changes: 12 additions & 3 deletions control/statesp.py
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Original file line number Diff line number Diff line change
Expand Up @@ -555,7 +555,10 @@ def fmt_matrix(matrix, name):
# Negation of a system
def __neg__(self):
"""Negate a state space system."""
return StateSpace(self.A, self.B, -self.C, -self.D, self.dt)
return StateSpace(
self.A, self.B, -self.C, -self.D, self.dt,
inputs=self.input_labels, outputs=self.output_labels,
states=self.state_labels)

# Addition of two state space systems (parallel interconnection)
def __add__(self, other):
Expand Down Expand Up @@ -645,7 +648,10 @@ def __mul__(self, other):
A, C = self.A, self.C
B = self.B * other
D = self.D * other
dt = self.dt
return StateSpace(
A, B, C, D, self.dt,
inputs=self.input_labels, outputs=self.output_labels,
states=self.state_labels)

elif isinstance(other, np.ndarray):
other = np.atleast_2d(other)
Expand Down Expand Up @@ -706,7 +712,10 @@ def __rmul__(self, other):
# Just multiplying by a scalar; change the input
B = other * self.B
D = other * self.D
return StateSpace(self.A, B, self.C, D, self.dt)
return StateSpace(
self.A, B, self.C, D, self.dt,
inputs=self.input_labels, outputs=self.output_labels,
states=self.state_labels)

elif isinstance(other, np.ndarray):
other = np.atleast_2d(other)
Expand Down
34 changes: 34 additions & 0 deletions control/tests/namedio_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -59,6 +59,40 @@ def test_named_ss():
"<StateSpace random: ['u1'] -> ['y1', 'y2']>"


@pytest.mark.parametrize(
"sys",
[
ct.ss(
[[-1, 0], [0, -2]], [[1, 0], [0, 1]],
[[1, 0], [0, 1]], [[0, 0], [0, 0]],
inputs=['e1', 'e2'], outputs=['u1', 'u2'],
states=['x1', 'x2'], name='plant'),
ct.tf(
[[[1], [2]], [[3], [4]]],
[[[1, 1], [1, 2]], [[1, 3], [1, 4]]],
inputs=['e1', 'e2'], outputs=['u1', 'u2'], name='plant'),
],
)
@pytest.mark.parametrize(
"operation",
[
lambda sys: -sys,
lambda sys: sys * 2,
lambda sys: 2 * sys,
lambda sys: ct.negate(sys),
lambda sys: ct.series(sys, 2),
lambda sys: ct.series(2, sys),
],
)
def test_named_scalar_operations_preserve_signal_names(sys, operation):
result = operation(sys)

assert result.input_labels == sys.input_labels
assert result.output_labels == sys.output_labels
if isinstance(sys, ct.StateSpace):
assert result.state_labels == sys.state_labels


# List of classes that are expected
fun_instance = {
ct.rss: (ct.NonlinearIOSystem, ct.StateSpace, ct.StateSpace),
Expand Down
22 changes: 17 additions & 5 deletions control/xferfcn.py
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Original file line number Diff line number Diff line change
Expand Up @@ -554,7 +554,9 @@ def __neg__(self):
for i in range(self.noutputs):
for j in range(self.ninputs):
num[i, j] *= -1
return TransferFunction(num, self.den, self.dt)
return TransferFunction(
num, self.den, self.dt,
inputs=self.input_labels, outputs=self.output_labels)

def __add__(self, other):
"""Add two LTI objects (parallel connection)."""
Expand Down Expand Up @@ -620,8 +622,13 @@ def __mul__(self, other):
if isinstance(other, (StateSpace, np.ndarray)):
other = _convert_to_transfer_function(other)
elif isinstance(other, (int, float, complex, np.number)):
# Multiply by a scaled identity matrix (transfer function)
other = _convert_to_transfer_function(np.eye(self.ninputs) * other)
num = deepcopy(self.num_array)
for i in range(self.noutputs):
for j in range(self.ninputs):
num[i, j] *= other
return TransferFunction(
num, self.den, self.dt,
inputs=self.input_labels, outputs=self.output_labels)
if not isinstance(other, TransferFunction):
return NotImplemented

Expand Down Expand Up @@ -669,8 +676,13 @@ def __rmul__(self, other):

# Convert the second argument to a transfer function.
if isinstance(other, (int, float, complex, np.number)):
# Multiply by a scaled identity matrix (transfer function)
other = _convert_to_transfer_function(np.eye(self.noutputs) * other)
num = deepcopy(self.num_array)
for i in range(self.noutputs):
for j in range(self.ninputs):
num[i, j] *= other
return TransferFunction(
num, self.den, self.dt,
inputs=self.input_labels, outputs=self.output_labels)
else:
other = _convert_to_transfer_function(other)

Expand Down