Question

%Transfer function
% H(s) = 0.000037/s^2 + 0.003512s + 0.000004

H = tf([0.000037],[1 0.003512 0.000004]);
step(H,3600);
grid

Above is my code. How can I set the initial value for the output?

Answer 1

In transfer function model the initial condition are always assumed to be zero.

You have to convert it to either space state model or you need to use simulink model to solve it.

For converting it to state space model you just need to give following command in your command window

[A,B,C,D] = tf2ss(b,a)

In your case it will be

b = [0.000037];

a = [ 1 0.003512 0.000004] ;

Now suppose you got

A = [a1, a2 ; a3, a4 ]

C = [c1 , c2 ] and lets suppose your initial condition is

X0 = [x1 ; x2 ];

To get the response you can give the command

 sys = ss(A,[],C,[]); initial(sys,X0)

OR other way is through SIMULINK MODEL