# PID - Root Locus (Sisotool) for Transfer Function (TF) with Zero and Poles in Right P

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• 07-11-2021, 02:53 PM
samuelamancio1
PID - Root Locus (Sisotool) for Transfer Function (TF) with Zero and Poles in Right P
[COLOR=#1D1D1D][FONT=&amp]Hi everyone! I have a 8th order transfer function, you can see it in the first image:[/FONT][/COLOR]

[COLOR=#1D1D1D][FONT=&amp]% Transfer function[/FONT][/COLOR]
[COLOR=#1D1D1D][FONT=&amp]num = [2.091,0,203.3,0,-2151,0,-1.072e05];[/FONT][/COLOR]
[COLOR=#1D1D1D][FONT=&amp]den = [1,0,-830.4,0,-1.036e05,0,-5.767e05,0,2.412e07];[/FONT][/COLOR]
[COLOR=#1D1D1D][FONT=&amp]tf = tf(num, den)

[/FONT][/COLOR][ATTACH=CONFIG]2617[/ATTACH][COLOR=#1D1D1D][FONT=&amp]
[/FONT][/COLOR][ATTACH=CONFIG]2615[/ATTACH]

[COLOR=#1D1D1D][FONT=&amp]I need to use a PID, so I'm trying to use a compensator, adding poles and zero with the sisotool in MatLab to turn it stable. But iI tried, I tried, and tried, without success. How you can see in picture bellow. But the zero on the right side always holds a pole.[/FONT][/COLOR]
[COLOR=#1D1D1D][FONT=&amp]Note: Red zeros and poles have been added, and blue ones belong to the original transfer function.

[/FONT][/COLOR][ATTACH=CONFIG]2616[/ATTACH][COLOR=#1D1D1D][FONT=&amp]
[/FONT][/COLOR][COLOR=#1D1D1D][FONT=&amp]
[/FONT][/COLOR]
[COLOR=#1D1D1D][FONT=&amp]My question is:[/FONT][/COLOR]
[COLOR=#1D1D1D][FONT=&amp]Is it possible stable this function adding zeros and poles, or not ?[/FONT][/COLOR]

[COLOR=#1D1D1D][FONT=&amp]Any tips ?[/FONT][/COLOR]
[COLOR=#1D1D1D][FONT=&amp]Note: I must use a PID for this lesson [/FONT][/COLOR][COLOR=#1D1D1D][FONT=&amp][IMG]https://www.math-forums.com/attachments/upload_2021-7-11_12-10-39-gif.98/[/IMG][/FONT][/COLOR][COLOR=#1D1D1D][FONT=&amp]:([/FONT][/COLOR]