# Problem with evaluating percent overshoot,settling time, peak time, and rise time

Discussion in 'MATLAB' started by Chris J, Feb 28, 2007.

1. ### Chris JGuest

Hello,

I'm stuck on a problem that I'm trying to figure out.

First I'm given the transfer function, G(s)= b / s^2 + as + b

The problem breaks down into three parts:

Part A. I have to evaluate percent overshoot, settling time, peak
time, and rise time for the following values: a=4, b=25. Plot the
poles also.

Part B. Calculate the values of a and b so that the imaginary part of
the poles reamins the same, but the real part is increased 2 times
over that of Part A, and repeat Part A.

Part C. Calculate the values of a and b so that the imaginary part of
the poles remains the same, but the real part is decreased 1/2 time
over that of Part A, and repeat Part A.

Now I kind of have an idea of solving Part A. I have this written in
Matlab but Matlab keeps giving me errors saying certain values are
either undefined or some other error. This is what I have written in
Matlab at the moment:

at this point I try to enter the formula for omega but I keep getting
an error saying "Index exceeds matrix dimensions," now I'm pretty
much lost and am hoping someone could help me on this one?

Chris J, Feb 28, 2007

2. ### anders mynsterGuest

Well you are told to find the overshoot, settling time etc. These all
correspond to the time domain, so you have to do an inverse laplace
transform and from the impulse response find the things you are asked
to find. I looks too much as a school assigment so i wont tell you
the whole answer, but hope it helps.

Anders

anders mynster, Feb 28, 2007

3. ### Fangjun JiangGuest

You have an error in the third line. It should be
den=[1 a b];

for syntax, type help tf.

then you are all set and good luck for the rest of you homework.

Fangjun Jiang, Feb 28, 2007
4. ### Chris JGuest

Thanks for the help everyone.

Chris J, Feb 28, 2007