10000 fix error when an IOSystem is combined with a TransferFunction system by sawyerbfuller · Pull Request #793 · python-control/python-control · GitHub
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fix error when an IOSystem is combined with a TransferFunction system #793

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Merged
merged 1 commit into from
Nov 17, 2022
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fix error when an IOSystem is combined with a TransferFunction system #793

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12 changes: 6 additions & 6 deletions control/iosys.py
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Original file line number Diff line number Diff line change
Expand Up @@ -890,7 +890,7 @@ def __init__(self, syslist, connections=None, inplist=None, outlist=None,
kwargs, defaults, end=True)

# Initialize the system list and index
self.syslist = syslist
self.syslist = list(syslist) # insure modifications can be made
self.syslist_index = {}

# Initialize the input, output, and state counts, indices
Expand All @@ -903,12 +903,12 @@ def __init__(self, syslist, connections=None, inplist=None, outlist=None,
sysname_count_dct = {}

# Go through the system list and keep track of counts, offsets
for sysidx, sys in enumerate(syslist):
for sysidx, sys in enumerate(self.syslist):
# If we were passed a SS or TF system, convert to LinearIOSystem
if isinstance(sys, (StateSpace, TransferFunction)) and \
not isinstance(sys, LinearIOSystem):
sys = LinearIOSystem(sys)
syslist[sysidx] = sys
sys = LinearIOSystem(sys, name=sys.name)
self.syslist[sysidx] = sys

# Make sure time bases are consistent
dt = common_timebase(dt, sys.dt)
Expand Down Expand Up @@ -2850,12 +2850,12 @@ def interconnect(syslist, connections=None, inplist=None, outlist=None,
inputs=inputs, outputs=outputs, states=states,
params=params, dt=dt, name=name, warn_duplicate=warn_duplicate)

# check for implicity dropped signals
# check for implicitly dropped signals
if check_unused:
newsys.check_unused_signals(ignore_inputs, ignore_outputs)

# If all subsystems are linear systems, maintain linear structure
if all([isinstance(sys, LinearIOSystem) for sys in syslist]):
if all([isinstance(sys, LinearIOSystem) for sys in newsys.syslist]):
return LinearICSystem(newsys, None)

return newsys
Expand Down
22 changes: 22 additions & 0 deletions control/tests/interconnect_test.py
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Expand Up @@ -230,3 +230,25 @@ def test_string_inputoutput():

P_s2 = ct.interconnect([P1_iosys, P2_iosys], inputs=['u1'], output='y2')
assert P_s2.output_index == {'y2' : 0}

def test_linear_interconnect():
tf_ctrl = ct.tf(1, (10.1, 1), inputs='e', outputs='u')
tf_plant = ct.tf(1, (10.1, 1), inputs='u', outputs='y')
ss_ctrl = ct.ss(1, 2, 1, 2, inputs='e', outputs='u')
ss_plant = ct.ss(1, 2, 1, 2, inputs='u', outputs='y')
nl_ctrl = ct.NonlinearIOSystem(
lambda t, x, u, params: x*x,
lambda t, x, u, params: u*x, states=1, inputs='e', outputs='u')
nl_plant = ct.NonlinearIOSystem(
lambda t, x, u, params: x*x,
lambda t, x, u, params: u*x, states=1, inputs='u', outputs='y')

assert isinstance(ct.interconnect((tf_ctrl, tf_plant), inputs='e', outputs='y'), ct.LinearIOSystem)
assert isinstance(ct.interconnect((ss_ctrl, ss_plant), inputs='e', outputs='y'), ct.LinearIOSystem)
assert isinstance(ct.interconnect((tf_ctrl, ss_plant), inputs='e', outputs='y'), ct.LinearIOSystem)
assert isinstance(ct.interconnect((ss_ctrl, tf_plant), inputs='e', outputs='y'), ct.LinearIOSystem)

assert ~isinstance(ct.interconnect((nl_ctrl, ss_plant), inputs='e', outputs='y'), ct.LinearIOSystem)
assert ~isinstance(ct.interconnect((nl_ctrl, tf_plant), inputs='e', outputs='y'), ct.LinearIOSystem)
assert ~isinstance(ct.interconnect((ss_ctrl, nl_plant), inputs='e', outputs='y'), ct.LinearIOSystem)
assert ~isinstance(ct.interconnect((tf_ctrl, nl_plant), inputs='e', outputs='y'), ct.LinearIOSystem)
17 changes: 17 additions & 0 deletions control/tests/iosys_test.py
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Expand Up @@ -1454,6 +1454,11 @@ def test_linear_interconnection():
inputs = ('u[0]', 'u[1]'),
outputs = ('y[0]', 'y[1]'),
name = 'sys2')
tf_siso = ct.tf(1, [0.1, 1])
ss_siso = ct.ss(1, 2, 1, 1)
nl_siso = ios.NonlinearIOSystem(
lambda t, x, u, params: x*x,
lambda t, x, u, params: u*x, states=1, inputs=1, outputs=1)

# Create a "regular" InterconnectedSystem
nl_connect = ios.interconnect(
Expand Down Expand Up @@ -1500,6 +1505,18 @@ def test_linear_interconnection():
np.testing.assert_array_almost_equal(io_connect.C, ss_connect.C)
np.testing.assert_array_almost_equal(io_connect.D, ss_connect.D)

# make sure interconnections of linear systems are linear and
# if a nonlinear system is included then system is nonlinear
assert isinstance(ss_siso*ss_siso, ios.LinearIOSystem)
assert isinstance(tf_siso*ss_siso, ios.LinearIOSystem)
assert isinstance(ss_siso*tf_siso, ios.LinearIOSystem)
assert ~isinstance(ss_siso*nl_siso, ios.LinearIOSystem)
assert ~isinstance(nl_siso*ss_siso, ios.LinearIOSystem)
assert ~isinstance(nl_siso*nl_siso, ios.LinearIOSystem)
assert ~isinstance(tf_siso*nl_siso, ios.LinearIOSystem)
assert ~isinstance(nl_siso*tf_siso, ios.LinearIOSystem)
assert ~isinstance(nl_siso*nl_siso, ios.LinearIOSystem)


def predprey(t, x, u, params={}):
"""Predator prey dynamics"""
Expand Down
0