Transfer Function using symbolic function

syms s k

K = k;

G = 6s + 12/s^3 + 8s^2 + 19s + 12;

F = 1;

R = 1/s^2;

Error = (1 - K*G/(1+K*G*F))*R;

ssE = limit(s*Error,s,0);
 

I have this code to derive the steady state error. But I always get an error for G stating invalid expression. This is equation has been expanded from the slimplifed form as using simplied form could not work. It works with single variable/pole such as 1/s+2 etc.

Please advice me on this issues. Thanks!

Answer 1

[Walter Roberson]

MATLAB has absolutely no implied multiplication, not even in symbolic expressions. If you want 6 times s, use 6*s

[Ian Thean]

Ah right! Thanks!