Bode plots....

Hi,

Please look at the file attached....

In my revision i am struggling to understand the concept of plotting bode plots of transfer functions

I can see that when you put the terms into the form 1+sT, you can find the break points as w=1/T.

It's just i don't understand what determines wether the magnitude slope increases or decreases and by what dB per decade.

How do you plot the phase of a transfer function?

If someone could explain this to me, i would be greatly appreciated because i have lots of questions with the solutions but do not understand the theory behind it, so i'm sure i could grasp it with a little assistance....

Thanks in advance

Well dear bode plot is asymptotic plot (i.e. an approximation).
Consider t(s)=1+sT.
for s(jw)<<T t(s)=1(cons. term)

for s(jw)>>T t(s)=sT(linear inc. term in semilog plot with slope 20 db/decade.)
How??
for making the frequency(w) 10 times,
db(t(s)=20log(t(s)) will become greater by 20db.

If however (1+sT) is in denominator slope after w=T will be -20db/decade.

As for phase you have to calculate phase at siscrete but close frequencies and plot them freehand.

A reference to 'Automatic Control Systems' by B.C.Kuo willl be useful.

GoodBye!