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-   -   Test Stability using Routh Stability Method (http://www.physicsforums.com/showthread.php?t=514676)

 mym786 Jul17-11 02:06 AM

Test Stability using Routh Stability Method

1. The problem statement, all variables and given/known data

For a control system that has G(s)H(s) = $\frac{1}{s^{2}*(s+\alpha)}$

2. Relevant equations

1 + G(s)H(s) = 0

3. The attempt at a solution

Exam question i messed up . I really need to know the answer.

 CEL Jul18-11 01:28 PM

Re: Test Stability using Routh Stability Method

Quote:
 Quote by mym786 (Post 3407257) 1. The problem statement, all variables and given/known data For a control system that has G(s)H(s) = $\frac{1}{s^{2}*(s+\alpha)}$ 2. Relevant equations 1 + G(s)H(s) = 0 3. The attempt at a solution Exam question i messed up . I really need to know the answer.
i + G(s)H(s) = 0 means:
$$s^3+\alpha s^2 + 1 = 0$$
Since the polynomial is incomplete (there is no term in $$s^1$$) there is at least one root in the RHP and the system is unstable. No need to use Routh algorithm.

 mym786 Jul19-11 01:05 AM

Re: Test Stability using Routh Stability Method

I forgot one more thing. It also says find the value of $\alpha$ for which the system can be classified in the critically stable state.

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