Second Order Transfer Function Question regarding Overshoot

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Discussion Overview

The discussion revolves around the application of a specific formula for calculating overshoot in the context of a closed loop second order transfer function when subjected to a step input. Participants explore whether the formula is applicable given the parameters of the transfer function.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the applicability of the overshoot formula $$\frac{A}{B}=e^{\frac{-\pi \zeta}{\sqrt{1-\zeta^2}}}$$ to their specific transfer function, expressing uncertainty.
  • Another participant suggests using online tools to plot step responses as a means to demonstrate the answer, providing a link to a relevant resource.
  • A repeated inquiry about the applicability of the overshoot formula emphasizes the participant's uncertainty and seeks confirmation.
  • One participant proposes splitting the transfer function into a low-pass and a bandpass component, indicating that the numerical value of \(K_C\) will affect the outcome and that there are established expressions for overshoot in textbooks.

Areas of Agreement / Disagreement

The discussion remains unresolved, with participants expressing differing views on the applicability of the overshoot formula and the approach to take regarding the transfer function.

Contextual Notes

Participants have not reached a consensus on the use of the overshoot formula, and there are dependencies on the numerical value of \(K_C\) that have not been fully explored.

Tom Hardy
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Homework Statement


If I have a closed loop second order transfer function such as:

$$\frac{10-s}{0.3s^2+3.1s+(1+24K_{C})}$$

Can I still use this formula for overshoot (when a step input is applied) ?:
$$\frac{A}{B}=e^{\frac{-\pi \zeta}{\sqrt{1-\zeta^2}}}$$
Where B is the step input size

I don't think you can but I'm not sure, can someone confirm?
 
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Tom Hardy said:

Homework Statement


If I have a closed loop second order transfer function such as:

$$\frac{10-s}{0.3s^2+3.1s+(1+24K_{C})}$$

Can I still use this formula for overshoot (when a step input is applied) ?:
$$\frac{A}{B}=e^{\frac{-\pi \zeta}{\sqrt{1-\zeta^2}}}$$
Where B is the step input size

I don't think you can but I'm not sure, can someone confirm?
https://en.wikipedia.org/wiki/Overshoot_(signal)
 
Split your xfr function into two parts: one is a low-pass 2nd order, the other a bandpass 2nd order. For both, there are expressions for overshoot in textbooks etc. Your answer depends on the numerical value of KC.

You then just add the time responses of the two separated xfr functions.
@nascent, thanks for the link! wow, even does nyquist plot!
 

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