Matlab: transfer function determination

1. Sep 1, 2010

serbring

I have a 2 dof vibration system, I have determined the differential equation of the model, can I determine the trasfer function readily with matlab, without using manual algebra operation?
In other word, I have that differential equation system:

[m]x''+[c]x'+[k]x=[f]

where:
[m] mass matrix
[c] damping matrix
[k] stiffness matrix
[f] external forces matrix

through laplace transformation I obtain:

s^[m]x(s)+s[c]x(x)+[k]x(s)=[f]

where s is the laplace variable, how can I find [f]/[x]?
I'm searching a way for estimating readily the transfer function of mechanical system, it is a loss of time to perform the calculation every time

2. Sep 7, 2010

serbring

may anyone help me?

3. Sep 7, 2010

ddarvil

You've pretty much got the TF. Rearrange the laplace you've done above so you get f/x = tf (factorise the left side wrt to X). From there, you can use matlab to analyse the TF.
MATLAB tools(look in help): tf, bode, ltview.
The time required to manually calculate the TF is trivial for systems like this. You can use dsolve to get a symbolic solution to the ODE but it's not really necessary

4. Oct 4, 2010

serbring

I know the tf, bode function, but how can I use them when the system has more than one dofs?