Journal of Control and Systems Engineering
Autotuning of Fractional Order PID Controller for a Class of Processes and Experimental Validation Using a Coupled Tank System 



Abstract: 

In this paper, relaybased autotuning of a fractional order proportional integral and derivative (FOPID) controller is proposed for second order plus dead time (SOPDT) plants. The controller is experimentally verified via a coupled tank system (CTS). The process dynamics of overdamped, underdamped, and critically damped plants are first modelled by using an offline relaybased method, where a maximum of four unknown parameters are determined in the simplest possible way. The describing function (DF) is obtained by considering relay with hysteresis. The use of robust features like gain margin and phase margin, as well as isodamping property to tune the five parameters of the controller greatly improves the controlled system’s performance. A significant advantage of the proposed tuning method is that a priori information of the system’s gain and phase crossover frequencies is not required while tuning the controller. The proposed model is validated through simulation studies in a class of process models, and also verified experimentally on a CTS from Feedback. 

Keywords:FOPID; SOPTD; AutoTuning; IsoDamping; Gain Margin; Phase Margin; Gain Crossover Frequency; Coupled Tank System (CTS) 

Author: Gargi Baruah,Somanath Majhi,Chitralekha Mahanta 

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