How can I go from a transfer function to a inverse Laplace transform?

I have written the following code. I would like to go directly to a time domain function without reentering a tf as shown in the last line. Can this be done?

clc
clear all
close
disp('Step responses for transfer functions')

Step = [1 0];
v = [1 2];
den = conv(Step,v);
num = [2];
syms s
H = tf(num,den)
Poles = pole(H)
Zeros = zero(H)
figure(2)
pzmap(H)
axis([-3,.5,-.1,.1])
sgrid
ilaplace(H2/(s^2+2*s))
%ilaplace(2/(s^2+2*s))nd

Answer 1

[Azzi Abdelmalek]

syms s
h=ilaplace(2/(s^2+2*s))

Answer 2

[jerry]

I asked the question poorly. Disregard the last two lines. I would like to do the inverse laplace directly without running the script and then reentering the transfer function.

[Azzi Abdelmalek]

Is this an answer or a comment? To add a comment click on [comment on this answer]

Try also to make your question clear

[mnbaig94]

Hello Azzi,

I have a transfer function:

num1 = [Li*Lg*Lx*C*Rl Rl*C*Li*Lg+Rl*C*Rd*Lx*Li+Rl*C*Rd*Lx*Lg Rl*Rd*Rg*C*Li+Rl*Rd*Rg*C*Lg+Rl*Lx*Li+Rl*Lx*Lg Rg*Rl*Li+Rg*Rl*Lg 0]
den1 = [Li*Lg*Lx*C Li*Lg*C*Rl+C*Li*Lg*C*Rg+C*Rd*Lx*Li+C*Rd*Lx*Lg Rd*Rl*C*Li+Rd*Rl*C*Lg+Rd*Rg*C*Li+Rd*Rg*C*Lg+Lx*Li+Lx*Lg Rl*Li+Rl*Lg+Rg*Li+Rg*Lg+Lx Rg+Rl]
sys1 = tf(num1,den1)

I want to take inverse laplace of it, can you please help??

[Walter Roberson]

mnbaig94:

If you try to do this directly, the calculation will take too long. Instead, find the general solution and then substitute the actual expressions into the general solution.

syms s
syms N0 N1 N2 N3 N4
syms D0 D1 D2 D3 D4
n1s = poly2sym([N4 N3 N2 N1 N0],s);
d1s = poly2sym([D4 D3 D2 D1 D0],s);
sys1s = n1s/d1s;
ILs = ilaplace(sys1s, s);

syms C Lg Li Lx Rd Rg Rl
num1 = [Li*Lg*Lx*C*Rl Rl*C*Li*Lg+Rl*C*Rd*Lx*Li+Rl*C*Rd*Lx*Lg Rl*Rd*Rg*C*Li+Rl*Rd*Rg*C*Lg+Rl*Lx*Li+Rl*Lx*Lg Rg*Rl*Li+Rg*Rl*Lg 0];
den1 = [Li*Lg*Lx*C Li*Lg*C*Rl+C*Li*Lg*C*Rg+C*Rd*Lx*Li+C*Rd*Lx*Lg Rd*Rl*C*Li+Rd*Rl*C*Lg+Rd*Rg*C*Li+Rd*Rg*C*Lg+Lx*Li+Lx*Lg Rl*Li+Rl*Lg+Rg*Li+Rg*Lg+Lx Rg+Rl];

IL = subs(ILs, [N4 N3 N2 N1 N0 D4 D3 D2 D1 D0], [num1, den1]);
IL

IL = 

The expression you get back will have symsum() of a term involving root() of an expression that is a polynomial of degree 4.

It is possible to convert those root() expressions into closed form; I think I wrote some lines that did that, but I cannot seem to find that now.

However... converting the roots of a degree 4 polynomial into closed form expression gives you a result that is effectively unreadable.