Hi all,
I have an first order plus time delay system with K=58.46, T(time constant)=0.55s, Td(Time delay)=0.06s and i had some trouble in design this PI Controller by using Ziegler Nichols tuning method.
The system is defined as G=58.46/(0.55*s+1)*exp(-0.06*s)
There is some calculation given by ZN tuning method for FOPDT system
where Kc=0.9*T/(K*Td) and Ti=3.33*Td
I had work out for the Kc and Ti and found that
Kc=0.9*0.55/(58.46*0.06)=0.1411
Ti=3.33*(0.06)=0.2
Gc is given that Kc*[1+(1/Ti*s)],
so Gc=0.1411*[1+(1/0.2s)] = 0.1441*[(0.2s+1)/0.2s]
but once i put this Gc into my system by Simulink, my wave seen oscillated very much. Can anyone tell me what i had done wrong and which parameter should i tunning ? Can i tune the Kc from 0.1411 to another value like 0.7?
Thankyou very much.


I have an first order plus time delay system with K=58.46, T(time constant)=0.55s, Td(Time delay)=0.06s and i had some trouble in design this PI Controller by using Ziegler Nichols tuning method.
The system is defined as G=58.46/(0.55*s+1)*exp(-0.06*s)
There is some calculation given by ZN tuning method for FOPDT system
where Kc=0.9*T/(K*Td) and Ti=3.33*Td
I had work out for the Kc and Ti and found that
Kc=0.9*0.55/(58.46*0.06)=0.1411
Ti=3.33*(0.06)=0.2
Gc is given that Kc*[1+(1/Ti*s)],
so Gc=0.1411*[1+(1/0.2s)] = 0.1441*[(0.2s+1)/0.2s]
but once i put this Gc into my system by Simulink, my wave seen oscillated very much. Can anyone tell me what i had done wrong and which parameter should i tunning ? Can i tune the Kc from 0.1411 to another value like 0.7?
Thankyou very much.


Last edited: