Having troubles with symbols in creating statespace model

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Joseph
Joseph 2014-12-1
回答： Star Strider 2014-12-1
here is my code and error:
clc
clear
syms a L
A = [-10 0 -10/a; 0 0 1;-6/a -70/a^2 -14.4/a^2];
B = [10 ;0 ;6/a];
C = [0 0 1/a; 0 25 3];
D = [0; 0];
Ceq = charpoly(A)
sys = ss(A,B,C,D)
Error using ss (line 260)
The value of the "a" property must be a numeric array
without any Inf's or NaN's.
Error in Project_1 (line 10)
sys = ss(A,B,C,D)

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回答（1 个）

Star Strider
Star Strider 2014-12-1
The Control System Toolbox wants only numeric functions, so you have to define a numeric value for ‘a’.
You can calculate the output symbolically:
y = ((C*expm(A*t)*B)+D)*u
but the output is too long to fit into the Command Window, giving a long (incomplete) symbolic expression followed by ... Output truncated. Text exceeds maximum line length of 25,000 characters for Command Window display..

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