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Fix forced response simulation of discrete time system #285

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Merged
merged 1 commit into from
Apr 7, 2019
Merged

Fix forced response simulation of discrete time system #285

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10 changes: 10 additions & 0 deletions control/tests/timeresp_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -193,6 +193,16 @@ def test_forced_response(self):
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]
sysd = c2d(sysc, dt) # discrete time system
Tc, youtc, _xoutc = forced_response(sysc, t, u, x0)
Td, youtd, _xoutd = forced_response(sysd, t, u, x0)
np.testing.assert_array_equal(Tc.shape, Td.shape)
np.testing.assert_array_equal(youtc.shape, youtd.shape)
np.testing.assert_array_almost_equal(youtc, youtd, decimal=4)

def test_lsim_double_integrator(self):
# Note: scipy.signal.lsim fails if A is not invertible
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3 changes: 2 additions & 1 deletion control/timeresp.py
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Expand Up @@ -322,7 +322,8 @@ def forced_response(sys, T=None, U=0., X0=0., transpose=False):
else:
# Discrete time simulation using signal processing toolbox
dsys = (A, B, C, D, sys.dt)
tout, yout, xout = sp.signal.dlsim(dsys, U, T, X0)
# Transpose the input to match toolbox convention
tout, yout, xout = sp.signal.dlsim(dsys, np.transpose(U), T, X0)

# Transpose the output and state vectors to match local convention
xout = sp.transpose(xout)
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