# Thread: Simple PI controller design problem

1. ## Simple PI controller design problem

Hi, I have some difficulties with PI controller design, please, take a look.

Transfer function of the system is

Denumerator from the closed-loop transfer function (considering PI controller, where K is proportional gain, and T is integral gain) is

after simplifying

I've tried Graham-Lathrop Method, but I got 2 equations with 3 parametres:

I've tried Naslin method and manual tuning as well without any success. Then I've tried to design P controller only, but got negative proportional gain...

What am I doing wrong?

Liptak

NOTE: sorry for the external images, but latex compilator isn't working right now.

2. Hey guys, some additional info:

This is the model of the turbojet engine (input - fuel, output - rpm)

I'm trying to control the acceleration of this engine in steady state (e.g from 43000 rpm to 45000rpm). I suppose that the model of the acceleration is following:

Step response of this system:

But I can't find a stabilizing controller

I've tried some PID tuning MATLAB scripts... they got me singularity error... what's wrong with this system?