# Bode Diagrams

1. May 11, 2004

### UnteljentEnginyr

So I have a midterm on Bode Diagrams and Root-Locus on Thursday...and I can not do either. At this point I am only focusing on the Bode diagrams because they are a bit easier and I want to master them now so that I can devote the rest of my time to the Root-Locus.

Say I have the transfer function

(s+2)/(s*(s+10)*(s^2+2s+2)).

In Bode form, this becomes

(jw/2+1)/(10*jw*(jw/10+1)*((jw)^2/2+jw+1))

I am sorry for the difficulty when looking at the function...I have no way of making it look better.

Could someone walk me through a problem like this?

This is what I know:
-The break points will occur and 2, 10, and some other value derived from the polynomial expression.
-The slope of the asymptotes will be plus or mine 1, depending on if the break point is in the denominator(-1) or numerator (+1)...the slope of the first will be -1 because of the (jw)^-1 term.

What I dont know:
-The break point of the polynomial (and imaginary) expression
-How to go from the magnitude plot to the phase plot
-what the intercept at the magnitude axis (y-axis) will be...is it random or is there an actual way to find it.

I have done the bode plot in Matlab...but I cant really make out changes in slope well, nor can I get an accurate Magnitude axis intercept.

I hope this makes sense. And look forward to my questions from Root-Locus.

Last edited: May 11, 2004
2. May 11, 2004

### enigma

Staff Emeritus
I'm moving this to homework help where you may get a better viewing.

Sorry I can't help... I blasted controls from my memory shortly after passing the course.

3. May 13, 2004