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{"@context":"https://schema.org","@type":"QAPage","mainEntity":{"@type":"Question","name":"Different results in Matlab and Python for StateSystem","text":"
While migrating to Python from Matlab, I get different result for StateSystem transform.
\nIn Matlab,there is a 2 in 2 out system:
\n
tf1 =
\n
                      -4\n  --------------------------------\n  1e06 s^3 + 30000 s^2 + 300 s + 1 \n
\n
Numerator: {[0 0 0 -4]}
\nDenominator: {[1000000 30000 300 1]}
\n
tf2 =
\n
0\n
\n
Numerator: {[0 0 0]}
\nDenominator: {[5600 150 1]}
\n
tf3 =
\n
          0.75\n  --------------------\n  5600 s^2 + 150 s + 1\n
\n
Numerator: {[0 0 0.7500]}
\nDenominator: {[5600 150 1]}
\n
MatlabCode:
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sys=[tf1,tf2;tf3,0];\nsys_ss=ss(sys);
\n
the output is:
\n
sys_ss =\n \n  A = \n              x1         x2         x3         x4         x5\n   x1      -0.03    -0.0192  -0.008192          0          0\n   x2    0.01562          0          0          0          0\n   x3          0   0.007812          0          0          0\n   x4          0          0          0   -0.02679   -0.01143\n   x5          0          0          0    0.01562          0\n \n  B = \n          u1     u2\n   x1   0.25      0\n   x2      0      0\n   x3      0      0\n   x4  0.125      0\n   x5      0      0\n \n  C = \n            x1       x2       x3       x4       x5\n   y1        0        0  -0.1311        0        0\n   y2        0        0        0        0  0.06857\n \n  D = \n       u1  u2\n   y1   0   0\n   y2   0   0\n
\n
In Python，I use control.ss:
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import control\n\nnum11 = [0,0,0,-4]\nnum12 = [0,0,0]\nnum21 = [0,0,0.7500]\nnum22 = [0]\n\nrow1 = [num11, num12]\nrow2 = [num21, num22]\nnumerator = [row1,  row2]\ndenominator = [\n                [[1000000, 30000, 300,1], [5600,150,1]],\n                [[5600,150,1], [1]]\n              ]\nG = control.tf(numerator,\n           denominator)\ncontrol.ss(G )
\n
Then I got different StateSpace，
\n
\n
What am I missing here? How can I fix to get the exact same results?
","upvoteCount":1,"answerCount":2,"acceptedAnswer":{"@type":"Answer","text":"
A little problem is given by the very little values in the state matrix (...*e-17): I also found that python control doesn't approximate these values to \"0\".
","upvoteCount":1,"url":"https://github.com/python-control/python-control/discussions/1077#discussioncomment-11486012"}}}