Get transfer function from bode plot

AI Thread Summary
The discussion revolves around interpreting a Bode plot to derive the transfer function, which is identified as "3s." A Bode plot consists of two components: a magnitude plot in dB versus frequency and a phase plot versus frequency. The transfer function "3s" indicates a differentiator type, characterized by a slope of 20 dB/decade and a phase angle of 90 degrees at the frequency of 3 rad/s. The original poster expresses confusion about how to extract this information from the combined Bode plot but later concludes they understand the interpretation. Understanding the characteristics of differentiators in Bode plots is crucial for accurate analysis.
dominicfhk
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Homework Statement


What is the transfer function described by this bode plot:
http://img96.imageshack.us/img96/4775/capturegib.jpg
*The answer is 3s, but I don't know where it comes from.

Homework Equations


None

The Attempt at a Solution


Correct me if I am wrong. A bode plot is a combination of 2 plots, one is dB vs. w, the other one is angle vs. w. Each linear transfer function can be breakdown into 7 types of component to be represented on a bode plot. The answer to this problem is "3s", suggesting that it is the differentiator type. For differentiator with w=3, its bode plot has a slop of 20dB/dcd and intercept at w=3 (dB vs. w graph), and an angle of constant 90 degree (angle vs. w graph). I don't see any of the characteristics on the given diagram. I can see that the two plot has been combined into one, but how exact do I interpret such diagram and be able to come up with 3s as the transfer function? Thank you so much!
 
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Nevermind, I think I got it. Thanks.
 
Thread 'Have I solved this structural engineering equation correctly?'

Thread 'Have I solved this structural engineering equation correctly?'

Hi all, I have a structural engineering book from 1979. I am trying to follow it as best as I can. I have come to a formula that calculates the rotations in radians at the rigid joint that requires an iterative procedure. This equation comes in the form of: $$ x_i = \frac {Q_ih_i + Q_{i+1}h_{i+1}}{4K} + \frac {C}{K}x_{i-1} + \frac {C}{K}x_{i+1} $$ Where: ## Q ## is the horizontal storey shear ## h ## is the storey height ## K = (6G_i + C_i + C_{i+1}) ## ## G = \frac {I_g}{h} ## ## C...
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