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Homework Statement
How do we set up a second-order plant transmittance with the only information available are:
One pole is at a position where the undamped natural frequency (ωn = 0 rad/sec), and the other pole is at a position where ωn = 2 rad/sec?
The question asks to build that transmittance, draw pole-zero plot, find the transfer function and break it down into natural and forced components, which are required to be plotted, given a step input. I only had trouble setting up the plant transmittance which is, unfortunately, the base of the whole solution.
Homework Equations
None.
The Attempt at a Solution
To set up the plant transmittance, I couldn't quite understand how I should do it. A second-order system will have a characteristic polynomial of the form (S2+2ωnζs+ωn2), where ζ is the damping ratio. Given this polynomial, I couldn't see how we can have two different ωn values. If one of the poles would have ωn, then the system should be underamped or undamped depending on the value of ζ. ωn = 0 would mean that the said pole is on the real axis given that there is no an oscillatory part.
Given all of that, I decided that I set up a transmittance based on mild guessing, so it was:
GP(s) = [itex]\frac{1}{s(s+2)}[/itex]
A pole at the origin and another at -2. I couldn't do anything other than doing something that at least shows that I can draw a pole-zero plot and do all what's asked.
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