## Bode Plot problem

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### Bode Plot problem

I have made a point not to ask for help with school stuff on here, but I'm stumped with this one. My Systems professor gave us a homework problem to make a Bode plot but I'm not sure it's possible with the transfer function he provided.

TF(s) = 2(s+2) / (s-1)(s+1)

It's the (s-1) in the denominator that has me befuddled. Nowhere I have looked (textbook, online docs, etc) has given an example of a negative, or (s/p - 1) instead of (s/p + 1). Even if I extracted a -1 to make it -(-s + 1) and subsequently make the constant negative, I still have the problem of the pole break point being -1 rad/sec, which can't be mapped on the frequency axis. At least that's my understanding of it.

I'm not looking for an answer, so much as clarification on whether this function is undefined. If it is solvable, I guess I need to look even deeper for my answers, although I don't know where. Thanks!
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kvndoom
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### Re: Bode Plot problem

Since I remember this problem from school, I will give you a hint on how to solve it. The magnitude does not change with a RHP pole, only the phase. This problem is definitely solvable.
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mmmmmdonuts21
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### Re: Bode Plot problem

Recall that the frequency axis is logarithmic (0.1, 1, 10 etc). In this example, your s+1 pole will be at a frequency of 10^(-1) = 0.1 rad/sec.

If in doubt, use wolframalpha to validate your solution:

http://www.wolframalpha.com/input/?i=bo ... %2B1%29%29
BlackStar
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### Re: Bode Plot problem

Thanks guys! Dang, I wonder if I'll ever get some of this stuff. I'll try to figger it out tonight. Homework's already late as it is.
It's hilarious that the same people who laud the "benefits" of 16x9 aspect ratios also praise Chrome for "freeing up screen space."

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kvndoom
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### Re: Bode Plot problem

so what math is this? Pre-Calculus? Calc I? II? III? IV? Physics?
thegleek
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### Re: Bode Plot problem

thegleek wrote:so what math is this? Pre-Calculus? Calc I? II? III? IV? Physics?

Control Systems... to take it you have to somehow survive Differential Equations, which is its own nightmare.
It's hilarious that the same people who laud the "benefits" of 16x9 aspect ratios also praise Chrome for "freeing up screen space."

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kvndoom
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### Re: Bode Plot problem

thegleek wrote:so what math is this? Pre-Calculus? Calc I? II? III? IV? Physics?

We call it "Signals and Systems" at my university.
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TurtlePerson2
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### Re: Bode Plot problem

kvndoom wrote:
thegleek wrote:so what math is this? Pre-Calculus? Calc I? II? III? IV? Physics?

Control Systems... to take it you have to somehow survive Differential Equations, which is its own nightmare.

Bleah. Diff Eq and Discrete Mathematics were my least favorite college courses. I got through them and then I promptly forgot it all. I'm cool with that.
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derFunkenstein
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### Re: Bode Plot problem

I understood Control Systems mainly in global terms. The math specifics sent me spiraling into 'C' and 'D' territory.

Which did lead to a groan-worthy joke from a coworker:

An aircraft flying out of Warsaw's international airport toward Lisbon had achieved cruising altitude for a while when the pilot decided to take a restroom break. The inexperienced copilot, noticing a geographic landmark, announced over the intercom that it was visible toward the north. Several passengers got up and attempted to see out the windows on that side, upon which the aircraft suddenly spiraled to the ground, tragically killing everyone onboard.

The official investigation found no systems malfunction and ultimately listed the cause as a pilot error, because the inexperienced copilot had created a situation where there were too many Poles on the right-hand plane.
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### Re: Bode Plot problem

derFunkenstein wrote:Bleah. Diff Eq and Discrete Mathematics were my least favorite college courses. I got through them and then I promptly forgot it all. I'm cool with that.

Never did the Diffy-Q course, but the Discrete math stuff blew my mind. I loved it, I will continue loving it. Gimme MOAR!
thegleek
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### Re: Bode Plot problem

thegleek wrote:
derFunkenstein wrote:Bleah. Diff Eq and Discrete Mathematics were my least favorite college courses. I got through them and then I promptly forgot it all. I'm cool with that.

Never did the Diffy-Q course, but the Discrete math stuff blew my mind. I loved it, I will continue loving it. Gimme MOAR!

I had made straight A's in math, all the way up through Calc 2. I actually thought maybe I knew a thing or two. Effin Differential Equations? I had to get a 10 point curve just to get out with a C. It didn't help that we had a sloppy instructor who would disappear for weeks at a time. Like I said, it was a nightmare. You should try it sometime; if you're good at it, YOU DA MAN, but prepare for a humbling experience.
It's hilarious that the same people who laud the "benefits" of 16x9 aspect ratios also praise Chrome for "freeing up screen space."

Windows XP will never die!
kvndoom
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### Re: Bode Plot problem

I agree that the instructor is a big factor. The calc curriculum was tolerable while we had an instructor who was willing to make the effort to communicate with us and stay after class to 'review' for the slower students and those who missed the sequence and was catching up after a few missed quarters when the class was not offered. Things went into the dump the next quarter when there was a new instructor. The previous instructor forewarned us on our last day that he was not instructing the next level of classes. Apparently, it was well known by students and faculty that the dropout rate was much higher in the next level...with the new instructor.
BiffStroganoffsky
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### Re: Bode Plot problem

You know, going through an entire K-12 education and another +4 college years. I never ran into any math courses that dealt with this new "Kumon" program.

Anyone have any experience with it? Personally? With your kids? I heard it's every human or themselves. You progress rapidly through courses and leave the puzzled ones in the dust. Sounds like an awesome program to me!
thegleek
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