Nyquist Stability

I've got a question on the Nyquist Stability criterion.
Consider a unity negative feedback system with plant L(s) and gain K
in the forward loop.
A nyquist plot is to be generated for this system to meet the following criteria:
1) L(s) has one unstable right half plane pole
2) The closed loop system is stable for (1/3 < K < 2) and unstable for K=1/3 and K=2.
3) Phase margin of 30 degrees
4) Zero steady state error to a step reference input.
Help !
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On 7/9/2010 12:02 AM, Mohit wrote:

I don't generally do homework here and i won't do yours. I will point pit, though, that somebody probably left something out. The phase margin is clearly a function of gain. (The zero steady-state error implies that the system contains an integrator.)
Jerry
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Just as a hint. Sketch a prototype/known Nyquist plot and evaluate each of your criteria for this known plot. Then work backwards to find a answer. Ray
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On 07/09/2010 07:20 AM, RRogers wrote:

Assuming that this is a class, go over your notes or the recent reading assignments in the book -- it may have been done as an example already; that will tell you your instructor's expectations.
If you're doing self-study then review the chapter of the book out of which this problem comes.
There _are_ ways to do this by construction, but we'd have to know how much you know before we could tell you how to do it that way.
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Tim Wescott
Wescott Design Services
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You are asking for help because.... you are tired of thinking? You don't like it and you think that thinking is bad and dirty?
Make your muscles grow. Become a person.
You are asking for help because....?
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Mikolaj

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On 07/08/2010 09:02 PM, Mohit wrote:

>

1: What feature does L(s) need to have to stabilize that unstable pole? 4: What feature does L(s) need to have to have zero steady state error to a step input? 2: What does the Nyquist plot have to have to make the system stable for the given gain range? 3: What feature does the Nyquist plot have to have for 30 degrees phase margin?
Answer these, then see if the answer to your overall problem doesn't start taking shape.
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Tim Wescott
Wescott Design Services
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So, did you managed?
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Mikolaj

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