# Simulink transfer function with sinusoidal parameters

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River Rock on 12 Nov 2012
Hi
I need to design a transfer function in the following form: 1 / (s^2 + K*s) where K is scalar and varies sinusoidal; the denominator should look like [1 K 0].
What would be the way to implement this behavior ?
Thanks

Azzi Abdelmalek on 12 Nov 2012
Edited: Azzi Abdelmalek on 12 Nov 2012
The corresponding equation is
d^2y(t)/dt^2+k.dy(t)/dt+y(t)=x(t)
where
• x(t) is the input of your system
• y(t) is its output
you have just to replace k by sin(t) using a clock and a sine wave block. and use derivative and integrator block instead of transfer function block to realize your model
or you can do this
Y(p)(P^2+Kp+1)=X(p)
P^2 Y(p) + K p Y(p)+ 1=X(p)
Y(p)+K Y(p)/p+Y(p)/p^2=X(p)/p^2
this can be represented by
Azzi Abdelmalek on 12 Nov 2012
realize 1/p with continuous transfer function (not integrator)

River Rock on 12 Nov 2012
I had to adapt the diagram for the denominator [1 K 0], as you use [1 K 1] in your example.
Why did you use the gain blocks?
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Azzi Abdelmalek on 12 Nov 2012
If you use D=[1 K], remove the first sum and 1/p blocks