# Step response of feedback system

We have a feedback system F(s) as in this figure: and this is the step response of G(s): and H=10.

F(s): We got the root locus of the system F(s) as this: then we determined the gain at marginal stability: which is equal to 2.5.

Then, we made H = 2.57 (slightly larger than 2.5) and we obtained the step response of the new system Fh(s). Here is it with the step response of the original system F(s): Then, we made H = 2.43 (slightly lower than 2.5) and we obtained the step response of the new system Fl(s). Here is it with the step response of the original system F(s): My questions:

• What can we know from the step response plot of G(s)?
• What can we know from the step response plot of F(s)?
• When we changed the gain to 2.57, how did the system F(s) change? What can we conclude by comparing the step responses of F(s) and Fh(s)?
• When we changed the gain to 2.43, how did the system F(s) change? What can we conclude by comparing the step responses of F(s) and Fl(s)?