Having troubles with symbols in creating statespace model

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)

Answer 1

[Star Strider]

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..