diff --git a/control/config.py b/control/config.py
index b4950ae5e..a81d8347f 100644
--- a/control/config.py
+++ b/control/config.py
@@ -226,4 +226,7 @@ def use_legacy_defaults(version):
linearized_system_name_prefix='',
linearized_system_name_suffix='_linearized')
+ # turned off _remove_useless_states
+ set_defaults('statesp', remove_useless_states=True)
+
return (major, minor, patch)
diff --git a/control/statesp.py b/control/statesp.py
index ff4c73c4e..0be783bce 100644
--- a/control/statesp.py
+++ b/control/statesp.py
@@ -72,7 +72,7 @@
# Define module default parameter values
_statesp_defaults = {
'statesp.use_numpy_matrix': False, # False is default in 0.9.0 and above
- 'statesp.remove_useless_states': True,
+ 'statesp.remove_useless_states': False,
'statesp.latex_num_format': '.3g',
'statesp.latex_repr_type': 'partitioned',
}
@@ -217,8 +217,7 @@ class StateSpace(LTI):
__array_priority__ = 11 # override ndarray and matrix types
def __init__(self, *args, **kwargs):
- """
- StateSpace(A, B, C, D[, dt])
+ """StateSpace(A, B, C, D[, dt])
Construct a state space object.
@@ -228,6 +227,13 @@ def __init__(self, *args, **kwargs):
True for unspecified sampling time). To call the copy constructor,
call StateSpace(sys), where sys is a StateSpace object.
+ The `remove_useless_states` keyword can be used to scan the A, B, and
+ C matrices for rows or columns of zeros. If the zeros are such that a
+ particular state has no effect on the input-output dynamics, then that
+ state is removed from the A, B, and C matrices. If not specified, the
+ value is read from `config.defaults['statesp.remove_useless_states']
+ (default = False).
+
"""
# first get A, B, C, D matrices
if len(args) == 4:
@@ -251,8 +257,8 @@ def __init__(self, *args, **kwargs):
"Expected 1, 4, or 5 arguments; received %i." % len(args))
# Process keyword arguments
- remove_useless = kwargs.get(
- 'remove_useless',
+ remove_useless_states = kwargs.get(
+ 'remove_useless_states',
config.defaults['statesp.remove_useless_states'])
# Convert all matrices to standard form
@@ -321,7 +327,7 @@ def __init__(self, *args, **kwargs):
raise ValueError("C and D must have the same number of rows.")
# Check for states that don't do anything, and remove them.
- if remove_useless:
+ if remove_useless_states:
self._remove_useless_states()
def _remove_useless_states(self):
@@ -1274,7 +1280,7 @@ def _convert_to_statespace(sys, **kw):
# Generate a simple state space system of the desired dimension
# The following Doesn't work due to inconsistencies in ltisys:
# return StateSpace([[]], [[]], [[]], eye(outputs, inputs))
- return StateSpace(0., zeros((1, inputs)), zeros((outputs, 1)),
+ return StateSpace([], zeros((0, inputs)), zeros((outputs, 0)),
sys * ones((outputs, inputs)))
# If this is a matrix, try to create a constant feedthrough
diff --git a/control/tests/statesp_test.py b/control/tests/statesp_test.py
index 8a91da68b..ccbd06881 100644
--- a/control/tests/statesp_test.py
+++ b/control/tests/statesp_test.py
@@ -395,9 +395,7 @@ def test_is_static_gain(self):
D0 = 0
D1 = np.ones((2,1))
assert StateSpace(A0, B0, C1, D1).is_static_gain()
- # TODO: fix this once remove_useless_states is false by default
- # should be False when remove_useless is false
- # print(StateSpace(A1, B0, C1, D1).is_static_gain())
+ assert not StateSpace(A1, B0, C1, D1).is_static_gain()
assert not StateSpace(A0, B1, C1, D1).is_static_gain()
assert not StateSpace(A1, B1, C1, D1).is_static_gain()
assert StateSpace(A0, B0, C0, D0).is_static_gain()
@@ -586,10 +584,9 @@ def test_matrix_static_gain(self):
def test_remove_useless_states(self):
"""Regression: _remove_useless_states gives correct ABC sizes."""
- g1 = StateSpace(np.zeros((3, 3)),
- np.zeros((3, 4)),
- np.zeros((5, 3)),
- np.zeros((5, 4)))
+ g1 = StateSpace(np.zeros((3, 3)), np.zeros((3, 4)),
+ np.zeros((5, 3)), np.zeros((5, 4)),
+ remove_useless_states=True)
assert (0, 0) == g1.A.shape
assert (0, 4) == g1.B.shape
assert (5, 0) == g1.C.shape
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