8.6 In Figure P8.6 the experimental unit step response of a process system is shown. (a) What is the transfer function that can be used to best describe the system dynamics among the following. 1 (1) G(s)=k T>O 29 (Ts+1) 1 (2) G(s)=k- >O s(Ts+1) (3) G(s)=k- Ts+1 (Ts+1)' T>0, T>0 -Ts+1 (4) G(s)=k- T>0, T>0 (Ts+1)' Ts+1 (5) G(s)=k- T>0, T>0 s(TS+1)' (6) G(s)=k- -Ts+1 s(TS+1)' " T>0, T>0 1.8 1.6 1.4 1.2 1 y(t) 0.8 0.6 0.4 0.2 0 0 1 2 3 4 5 6 7 8 9 Time (s) Figure P8.6 Discuss the reason(s) for which you exclude some of the transfer function and the reason(s) why you propose a specific one. (b) Can you estimate the parameters of the transfer function you have selected?