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Fixing bug in timeresp.forced_response #336

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Merged
merged 2 commits into from
Aug 16, 2019
Merged

Fixing bug in timeresp.forced_response #336

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efc42c8
Fixing bug in timeresp.forced_response that caused scipy interp1d Val…
Aug 8, 2019
8b08481
Addressing PR comments
Aug 9, 2019
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15 changes: 13 additions & 2 deletions control/tests/timeresp_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -252,14 +252,14 @@ def test_forced_response(self):
# first system: initial value, second system: step response
u = np.array([[0., 0, 0, 0, 0, 0, 0, 0, 0, 0],
[1., 1, 1, 1, 1, 1, 1, 1, 1, 1]])
x0 = np.matrix(".5; 1; 0; 0")
x0 = np.array([[.5], [1], [0], [0]])
youttrue = np.array([[11., 8.1494, 5.9361, 4.2258, 2.9118, 1.9092,
1.1508, 0.5833, 0.1645, -0.1391],
[9., 17.6457, 24.7072, 30.4855, 35.2234, 39.1165,
42.3227, 44.9694, 47.1599, 48.9776]])
_t, yout, _xout = forced_response(self.mimo_ss1, t, u, x0)
np.testing.assert_array_almost_equal(yout, youttrue, decimal=4)

# Test discrete MIMO system to use correct convention for input
sysc = self.mimo_ss1
dt=t[1]-t[0]
Expand All @@ -270,6 +270,17 @@ def test_forced_response(self):
np.testing.assert_array_equal(youtc.shape, youtd.shape)
np.testing.assert_array_almost_equal(youtc, youtd, decimal=4)

# Test discrete MIMO system without default T argument
u = np.array([[0., 0, 0, 0, 0, 0, 0, 0, 0, 0],
[1., 1, 1, 1, 1, 1, 1, 1, 1, 1]])
x0 = np.array([[.5], [1], [0], [0]])
youttrue = np.array([[11., 8.1494, 5.9361, 4.2258, 2.9118, 1.9092,
1.1508, 0.5833, 0.1645, -0.1391],
[9., 17.6457, 24.7072, 30.4855, 35.2234, 39.1165,
42.3227, 44.9694, 47.1599, 48.9776]])
_t, yout, _xout = forced_response(sysd, U=u, X0=x0)
np.testing.assert_array_almost_equal(yout, youttrue, decimal=4)

def test_lsim_double_integrator(self):
# Note: scipy.signal.lsim fails if A is not invertible
A = np.mat("0. 1.;0. 0.")
Expand Down
23 changes: 17 additions & 6 deletions control/timeresp.py
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Expand Up @@ -200,7 +200,7 @@ def forced_response(sys, T=None, U=0., X0=0., transpose=False,
sys: LTI (StateSpace, or TransferFunction)
LTI system to simulate

T: array-like
T: array-like, optional for discrete LTI `sys`
Time steps at which the input is defined; values must be evenly spaced.

U: array-like or number, optional
Expand Down Expand Up @@ -260,20 +260,31 @@ def forced_response(sys, T=None, U=0., X0=0., transpose=False,
n_inputs = B.shape[1]
n_outputs = C.shape[0]

# Convert inputs to numpy arrays for easier shape checking
if U is not None:
U = np.asarray(U)
if T is not None:
T = np.asarray(T)

# Set and/or check time vector in discrete time case
if isdtime(sys, strict=True):
if T is None:
if U is None:
raise ValueError('Parameters ``T`` and ``U`` can\'t both be'
'zero for discrete-time simulation')
# Set T to equally spaced samples with same length as U
T = np.array(range(len(U))) * (1 if sys.dt is True else sys.dt)
if U.ndim == 1:
n_steps = U.shape[0]
else:
n_steps = U.shape[1]
T = np.array(range(n_steps)) * (1 if sys.dt is True else sys.dt)
else:
# Make sure the input vector and time vector have same length
# TODO: allow interpolation of the input vector
if len(U) != len(T):
ValueError('Pamameter ``T`` must have same length as'
'input vector ``U``')
if (U.ndim == 1 and U.shape[0] != T.shape[0]) or \
(U.ndim > 1 and U.shape[1] != T.shape[0]):
ValueError('Pamameter ``T`` must have same elements as'
' the number of columns in input array ``U``')

# Test if T has shape (n,) or (1, n);
# T must be array-like and values must be increasing.
Expand All @@ -288,7 +299,7 @@ def forced_response(sys, T=None, U=0., X0=0., transpose=False,
if not np.allclose(T[1:] - T[:-1], dt):
raise ValueError("Parameter ``T``: time values must be "
"equally spaced.")
n_steps = len(T) # number of simulation steps
n_steps = T.shape[0] # number of simulation steps

# create X0 if not given, test if X0 has correct shape
X0 = _check_convert_array(X0, [(n_states,), (n_states, 1)],
Expand Down