Validation of integer and fractional order PI controllers for a real time non linear process

The aim of this paper is to design and validate the performance of a PI controller using Ziegler Nichol´s (ZN) tuning method, Skogested tuning method and Fractional Order (FO) tuning method for a Single Spherical Tank Liquid Level System (SSTLLS) whose modelling has been done in real time. Mathematical modelling of the system is done assuming the system to be a Single Input Single Output (SISO) model. One of the major problems in process industries is to control of process parameters for First Order Plus Time Delay (FOPTD) system because the presence of time delay in the system can lead to destabilization of the system. This paper briefly explains about stabilizing problem for FOPTD using a Fractional Order Proportional Integral (FOPI^λ) controller. These controllers are compared in terms of performance indices like Integral Squared Error (ISE) and Integral Absolute Error (IAE) and time domain specifications like Rise time, Settling time and Peak time with other methods of PI tuning. The validation of the performance of the designed controllers is performed under MATLAB environment.