Discrepancies in Step Response

I see room for confusion. With three division signs in a row, what divides what? Matlab and the textbook seem to agree except for an offset of one in the time axix. Since Matlab forces the origins of its arrays to 1, that doesn't surprise me.

Matlab's and the textbook's plots show the asymptotic response (t->00) to be unity. The other shows it to be zero. Understanding the order of operations in your expression, you should be able to check that.

Jerry

"Using the Laplace transform tables, I got a transfer function of g(t) ="

Transfer functions (in the context of linear systems theory) do not exist in the time domain. Think about that. Then think about what someone means when they say "step response". What exactly is a "step response" of a system -- don't give it in terms of some regurgitated Laplace-domain stuff, tell me what is the system input in the time domain, and what do you expect out of it?

Perhaps then you'll see your error.

And the graph in the book is shifted over by one -- it's probably a typo. Matlab's plot is correct.

Did you forget the step forcing function 1/s? Assuming G(s) is supposed to be 10/((s+1)(s+10)) the response should look like a first order response except there will be a slight inflection due to the second pole. Your plot looks like you forgot the step forcing function 1/s. Now your transfer function is (1/s)*(10/((s+1)(s+10)). The simple thing to do is to use wxMaxima or some other CAS to do the inverse Laplace transform. I get f(t)=3D-10*%e^-t/9+%e^-(10*t)/9+1

Peter Nachtwey