diff --git a/control/statesp.py b/control/statesp.py
index 03349b0ac..c12583111 100644
--- a/control/statesp.py
+++ b/control/statesp.py
@@ -1434,11 +1434,11 @@ def _convert_to_statespace(sys, **kw):
# TODO: add discrete time option
-def _rss_generate(states, inputs, outputs, type, strictly_proper=False):
+def _rss_generate(states, inputs, outputs, cdtype, strictly_proper=False):
"""Generate a random state space.
This does the actual random state space generation expected from rss and
- drss. type is 'c' for continuous systems and 'd' for discrete systems.
+ drss. cdtype is 'c' for continuous systems and 'd' for discrete systems.
"""
@@ -1465,6 +1465,8 @@ def _rss_generate(states, inputs, outputs, type, strictly_proper=False):
if outputs < 1 or outputs % 1:
raise ValueError("outputs must be a positive integer. outputs = %g." %
outputs)
+ if cdtype not in ['c', 'd']:
+ raise ValueError("cdtype must be `c` or `d`")
# Make some poles for A. Preallocate a complex array.
poles = zeros(states) + zeros(states) * 0.j
@@ -1484,16 +1486,16 @@ def _rss_generate(states, inputs, outputs, type, strictly_proper=False):
i += 2
elif rand() < pReal or i == states - 1:
# No-oscillation pole.
- if type == 'c':
+ if cdtype == 'c':
poles[i] = -exp(randn()) + 0.j
- elif type == 'd':
+ else:
poles[i] = 2. * rand() - 1.
i += 1
else:
# Complex conjugate pair of oscillating poles.
- if type == 'c':
+ if cdtype == 'c':
poles[i] = complex(-exp(randn()), 3. * exp(randn()))
- elif type == 'd':
+ else:
mag = rand()
phase = 2. * math.pi * rand()
poles[i] = complex(mag * cos(phase), mag * sin(phase))
@@ -1546,7 +1548,11 @@ def _rss_generate(states, inputs, outputs, type, strictly_proper=False):
C = C * Cmask
D = D * Dmask if not strictly_proper else zeros(D.shape)
- return StateSpace(A, B, C, D)
+ if cdtype == 'c':
+ ss_args = (A, B, C, D)
+ else:
+ ss_args = (A, B, C, D, True)
+ return StateSpace(*ss_args)
# Convert a MIMO system to a SISO system
@@ -1825,15 +1831,14 @@ def rss(states=1, outputs=1, inputs=1, strictly_proper=False):
Parameters
----------
- states : integer
+ states : int
Number of state variables
- inputs : integer
+ inputs : int
Number of system inputs
- outputs : integer
+ outputs : int
Number of system outputs
strictly_proper : bool, optional
- If set to 'True', returns a proper system (no direct term). Default
- value is 'False'.
+ If set to 'True', returns a proper system (no direct term).
Returns
-------
@@ -1867,12 +1872,15 @@ def drss(states=1, outputs=1, inputs=1, strictly_proper=False):
Parameters
----------
- states : integer
+ states : int
Number of state variables
inputs : integer
Number of system inputs
- outputs : integer
+ outputs : int
Number of system outputs
+ strictly_proper: bool, optional
+ If set to 'True', returns a proper system (no direct term).
+
Returns
-------
diff --git a/control/tests/statesp_test.py b/control/tests/statesp_test.py
index 67cf950e7..71e7cc4bc 100644
--- a/control/tests/statesp_test.py
+++ b/control/tests/statesp_test.py
@@ -19,7 +19,7 @@
from control.dtime import sample_system
from control.lti import evalfr
from control.statesp import (StateSpace, _convert_to_statespace, drss,
- rss, ss, tf2ss, _statesp_defaults)
+ rss, ss, tf2ss, _statesp_defaults, _rss_generate)
from control.tests.conftest import ismatarrayout, slycotonly
from control.xferfcn import TransferFunction, ss2tf
@@ -855,6 +855,28 @@ def test_pole(self, states, outputs, inputs):
for z in p:
assert z.real < 0
+ @pytest.mark.parametrize('strictly_proper', [True, False])
+ def test_strictly_proper(self, strictly_proper):
+ """Test that the strictly_proper argument returns a correct D."""
+ for i in range(100):
+ # The probability that drss(..., strictly_proper=False) returns an
+ # all zero D 100 times in a row is 0.5**100 = 7.89e-31
+ sys = rss(1, 1, 1, strictly_proper=strictly_proper)
+ if np.all(sys.D == 0.) == strictly_proper:
+ break
+ assert np.all(sys.D == 0.) == strictly_proper
+
+ @pytest.mark.parametrize('par, errmatch',
+ [((-1, 1, 1, 'c'), 'states must be'),
+ ((1, -1, 1, 'c'), 'inputs must be'),
+ ((1, 1, -1, 'c'), 'outputs must be'),
+ ((1, 1, 1, 'x'), 'cdtype must be'),
+ ])
+ def test_rss_invalid(self, par, errmatch):
+ """Test invalid inputs for rss() and drss()."""
+ with pytest.raises(ValueError, match=errmatch):
+ _rss_generate(*par)
+
class TestDrss:
"""These are tests for the proper functionality of statesp.drss."""
@@ -873,6 +895,7 @@ def test_shape(self, states, outputs, inputs):
assert sys.nstates == states
assert sys.ninputs == inputs
assert sys.noutputs == outputs
+ assert sys.dt is True
@pytest.mark.parametrize('states', range(1, maxStates))
@pytest.mark.parametrize('outputs', range(1, maxIO))
@@ -884,6 +907,17 @@ def test_pole(self, states, outputs, inputs):
for z in p:
assert abs(z) < 1
+ @pytest.mark.parametrize('strictly_proper', [True, False])
+ def test_strictly_proper(self, strictly_proper):
+ """Test that the strictly_proper argument returns a correct D."""
+ for i in range(100):
+ # The probability that drss(..., strictly_proper=False) returns an
+ # all zero D 100 times in a row is 0.5**100 = 7.89e-31
+ sys = drss(1, 1, 1, strictly_proper=strictly_proper)
+ if np.all(sys.D == 0.) == strictly_proper:
+ break
+ assert np.all(sys.D == 0.) == strictly_proper
+
class TestLTIConverter:
"""Test returnScipySignalLTI method"""
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