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EugP
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Homework Statement
Find the complete response of the system represented by
[tex]y''(t)+2y'(t)+y(t)=u(t),[/tex]
[tex]y(0^-)=1,[/tex]
[tex]y'(0^-)=2[/tex]
and identify the zro-state and zero-input response components. Find the system transfer function and the system impulse response.
Homework Equations
The Attempt at a Solution
I thought I solved for the complete response, but apparently what I got was just the zero-state response. I thought that by taking the laplace transform of the whole function, I will get the complete response. I then remembered that I need to have both zero-state and zero-input responses to get complete response, but I don't know how to find zero-input response.
Here's what I did:
[tex]y''(t)+2y'(t)+y(t)=u(t)[/tex]
[tex]s^2Y(s)-f(0^-)-f^{(1)}(0^-)+2sY(s)-f(0^-)+Y(s)=\frac{1}{s}[/tex]
[tex]Y(s)[s^2+2s+1]-f(0^-)-f^{(1)}(0^-)-f(0^-)=\frac{1}{s}[/tex]
[tex]Y(s)[s^2+2s+1]-1+2-1=\frac{1}{s}[/tex]
[tex]Y(s)[s^2+2s+1]=\frac{1}{s}[/tex]
[tex]Y(s)=\frac{1}{s(s^2+2s+1)}[/tex]
At this point I thought this was already the complete response only in it's transformed for, so now I took the inverse laplace and got:
[tex]y(t)=(1-te^{-t}-e^{-t})u(t)[/tex]
which is what the answer is for the zero-state response, not complete response.
So I tried figure out the zero-input response, but I just don't even know where to start. I looked everywhere and I can't seem to find the way to find it. Once I find the zero-input response, I will probably be able to solve the rest by myself.
Can anyone please tell me how to find the zero-input response?