def test_Feedback_str():
tf1 = TransferFunction(x*y**2 - z, y**3 - t**3, y)
tf2 = TransferFunction(x - y, x + y, y)
tf3 = TransferFunction(t*x**2 - t**w*x + w, t - y, y)
assert str(Feedback(tf1*tf2, tf3)) == \
"Feedback(Series(TransferFunction(x*y**2 - z, -t**3 + y**3, y), TransferFunction(x - y, x + y, y)), TransferFunction(t*x**2 - t**w*x + w, t - y, y))"
assert str(Feedback(tf1, TransferFunction(1, 1, y))) == \
"Feedback(TransferFunction(x*y**2 - z, -t**3 + y**3, y), TransferFunction(1, 1, y))"
def test_Feedback_functions():
zeta, wn = symbols('zeta, wn')
tf = TransferFunction(1, 1, s)
tf1 = TransferFunction(1, s**2 + 2*zeta*wn*s + wn**2, s)
tf2 = TransferFunction(k, 1, s)
tf3 = TransferFunction(a2*p - s, a2*s + p, s)
tf4 = TransferFunction(a0*p + p**a1 - s, p, p)
tf5 = TransferFunction(a1*s**2 + a2*s - a0, s + a0, s)
tf6 = TransferFunction(s - p, p + s, p)
assert tf / (tf + tf1) == Feedback(tf, tf1)
assert tf / (tf + tf1*tf2*tf3) == Feedback(tf, tf1*tf2*tf3)
assert tf1 / (tf + tf1*tf2*tf3) == Feedback(tf1, tf2*tf3)
assert (tf1*tf2) / (tf + tf1*tf2) == Feedback(tf1*tf2, tf)
assert (tf1*tf2) / (tf + tf1*tf2*tf5) == Feedback(tf1*tf2, tf5)
assert (tf1*tf2) / (tf + tf1*tf2*tf5*tf3) in (Feedback(tf1*tf2, tf5*tf3), Feedback(tf1*tf2, tf3*tf5))
assert tf4 / (TransferFunction(1, 1, p) + tf4*tf6) == Feedback(tf4, tf6)
assert tf5 / (tf + tf5) == Feedback(tf5, tf)
raises(ValueError, lambda: tf1*tf2*tf3 / (1 + tf1*tf2*tf3))
raises(ValueError, lambda: tf1*tf2*tf3 / tf3*tf5)
raises(ValueError, lambda: tf2*tf3 / (tf + tf2*tf3*tf4))
assert Feedback(tf, tf1*tf2*tf3).doit() == \
TransferFunction((a2*s + p)*(s**2 + 2*s*wn*zeta + wn**2), k*(a2*p - s) + \
(a2*s + p)*(s**2 + 2*s*wn*zeta + wn**2), s)
assert Feedback(tf1, tf2*tf3).doit() == \
TransferFunction((a2*s + p)*(s**2 + 2*s*wn*zeta + wn**2), (k*(a2*p - s) + \
(a2*s + p)*(s**2 + 2*s*wn*zeta + wn**2))*(s**2 + 2*s*wn*zeta + wn**2), s)
assert Feedback(tf1*tf2, tf5).doit() == \
TransferFunction(k*(a0 + s)*(s**2 + 2*s*wn*zeta + wn**2), (k*(-a0 + a1*s**2 + a2*s) + \
(a0 + s)*(s**2 + 2*s*wn*zeta + wn**2))*(s**2 + 2*s*wn*zeta + wn**2), s)
assert Feedback(tf4, tf6).doit() == \
TransferFunction(p*(p + s)*(a0*p + p**a1 - s), p*(p*(p + s) + (-p + s)*(a0*p + p**a1 - s)), p)
assert -Feedback(tf4*tf6, TransferFunction(1, 1, p)).doit() == \
TransferFunction(-p*(-p + s)*(p + s)*(a0*p + p**a1 - s), p*(p + s)*(p*(p + s) + (-p + s)*(a0*p + p**a1 - s)), p)
assert Feedback(tf1, tf2*tf5).rewrite(TransferFunction) == \
TransferFunction((a0 + s)*(s**2 + 2*s*wn*zeta + wn**2), (k*(-a0 + a1*s**2 + a2*s) + \
(a0 + s)*(s**2 + 2*s*wn*zeta + wn**2))*(s**2 + 2*s*wn*zeta + wn**2), s)
assert Feedback(TransferFunction(1, 1, p), tf4).rewrite(TransferFunction) == \
TransferFunction(p, a0*p + p + p**a1 - s, p)
def test_Feedback_construction():
zeta, wn = symbols('zeta, wn')
tf1 = TransferFunction(1, s**2 + 2*zeta*wn*s + wn**2, s)
tf2 = TransferFunction(k, 1, s)
tf3 = TransferFunction(a2*p - s, a2*s + p, s)
tf4 = TransferFunction(a0*p + p**a1 - s, p, p)
tf5 = TransferFunction(a1*s**2 + a2*s - a0, s + a0, s)
tf6 = TransferFunction(s - p, p + s, p)
f1 = Feedback(TransferFunction(1, 1, s), tf1*tf2*tf3)
assert f1.args == (TransferFunction(1, 1, s), Series(tf1, tf2, tf3))
assert f1.num == TransferFunction(1, 1, s)
assert f1.den == Series(tf1, tf2, tf3)
assert f1.var == s
f2 = Feedback(tf1, tf2*tf3)
assert f2.args == (tf1, Series(tf2, tf3))
assert f2.num == tf1
assert f2.den == Series(tf2, tf3)
assert f2.var == s
f3 = Feedback(tf1*tf2, tf5)
assert f3.args == (Series(tf1, tf2), tf5)
assert f3.num == Series(tf1, tf2)
f4 = Feedback(tf4, tf6)
assert f4.args == (tf4, tf6)
assert f4.num == tf4
assert f4.var == p
f5 = Feedback(tf5, TransferFunction(1, 1, s))
assert f5.args == (tf5, TransferFunction(1, 1, s))
assert f5.var == s
f6 = Feedback(TransferFunction(1, 1, p), tf4)
assert f6.args == (TransferFunction(1, 1, p), tf4)
assert f6.var == p
f7 = -Feedback(tf4*tf6, TransferFunction(1, 1, p))
assert f7.args == (Series(TransferFunction(-1, 1, p), Series(tf4, tf6)), TransferFunction(1, 1, p))
assert f7.num == Series(TransferFunction(-1, 1, p), Series(tf4, tf6))
# denominator can't be a Parallel instance
raises(TypeError, lambda: Feedback(tf1, tf2 + tf3))
raises(TypeError, lambda: Feedback(tf1, Matrix([1, 2, 3])))
raises(TypeError, lambda: Feedback(TransferFunction(1, 1, s), s - 1))
raises(TypeError, lambda: Feedback(1, 1))
raises(ValueError, lambda: Feedback(TransferFunction(1, 1, s), TransferFunction(1, 1, s)))
raises(ValueError, lambda: Feedback(tf2, tf4*tf5))