when i applied same input like step on transfer function block and on the LTI system in simulink model ; the output in scope does not the same although the transfer function is same in two blocks (tf, LTI system)

[Walaa Araydah]

the transfer function in LTI system is from the work space

[Azzi Abdelmalek]

Ok, we haven't access to your workspace, can you post the numerator and denominator of your transfer function?

[Walaa Araydah]

num=[ 0.0001398 -0.0001398]; den=[1 -2 0.9998]; sample time 0.03

Answer 1

[Azzi Abdelmalek]

Check if you are using the same sample time for the two models

[Walaa Araydah]

is the same sample time

[Azzi Abdelmalek]

I am getting the same answer for the two blocks. what have you written inside the LTI block? it should be

 tf(num,den,0.03)

[Walaa Araydah]

at start the transfer function is in continuous form , I converted it to discrete with sample time 0.03 , the discrete tf appear in work space as model. after that i open the simulink model and put in it (tf block and LTI system block) then i put the constant of the transfer function in tf and LTI system put in it the name of tf .... the result from LTI is correct but from tf is not correct as i need

[Walaa Araydah]

Tp11=1.970407430927219e+02; Tp12=1.199085665307412e+03; Tz=1.463902703922180e+02; Kp=7.520971369140306; num=Kp*[Tz 1] den=conv([Tp11 1],[Tp12 1]) G_Pump=tf(num,den) sysd_G_Pump=c2d(G_Pump,0.03)

[Walaa Araydah]