International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395 -0056
Volume: 04 Issue: 04 | Apr -2017
p-ISSN: 2395-0072
www.irjet.net
COMPARATIVE ANALYISIS OF P, PI, PID AND FUZZY LOGIC CONTROLLER FOR TANK WATER LEVEL CONTROL SYSTEM Sumit Kumar1, Mrs. Pooja Nagpal2 1JCDM
College of Engineering, Haryana, India, Sirsa
2Associate
Professor, JCDM college of Engineering, Haryana, India ---------------------------------------------------------------------***---------------------------------------------------------------------
Abstract - The objectives of this paper are to design and comparatively analyze the P, PI, PID and Fuzzy Logic controller for coupled tank liquid level system. Simulink model for coupled tank system is designed within MATLAB/Simulink. Tuning of parameters for PID controller is done using signal constraint block in MATLAB/simulink. Simulated results were compared to verify the performance of the control system in terms of rise time, steady state error, settling time and overshoot. A simulated result of the controllers in coupled tank system indicates that fuzzy logic controller gives better results as compared to other controllers.
that fuzzy logic control system gives better performance than other control systems. 2. MATHEMATICAL MODELLING OF COUPLED TANK SYSTEM Let us consider a coupled tank system used in industrial application as shown in fig.1 the mathematical model for this coupled tank system is nonlinear as shown by equation 1.1 and 1.2.
Key Words: Coupled tank system, PID controller, Fuzzy Logic controller, MATLAB/Simulink, Signal constraint. 1. INTRODUCTION Accuracy in level and flow control of the tanks is highly important application for the chemical process industries [1]. Mostly PID controller is used in industries for control process due to its simple structure and easiness in implementation [2, 7] Conventional P controller can reduce the adjusting time it can eliminate the present error only and PID controller use mathematical model of the system as it is difficult to find proper gain so it is not good for highly non linear system [3]. In this work coupled tank system is used which is a non linear system and dynamic behavior of tanks affect each other as inflow between the tanks depends on the level of both tanks. Where PI controller is suitable for low order process where accuracy does not the prime factor but for higher accuracy it is not suitable [4]. It is also difficult to get desired result by using conventional PI controller as it gives poor performance for higher order process [4]. Fuzzy logic control system does not use mathematical model of the process so fuzzy logic controller can be used where PID controller is difficult to apply [5].FLC system use human reasoning so it is flexible and can be understood easily. It is suitable for the requirement of industrial applications it may be a reason behind the wide use of FLC system [6]. So in this paper a comparative analysis of P, PI, PID and FLC has done for coupled tank system in terms of rise time, setting time, overshoot and steady state error. The simulated results are compared and verified in MATLAB/Simulink and find
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Fig.1: Schematic diagram of coupled tank system Qin, Q01, Q12 and Q02 are quantity of liquid flow in the tanks, quantity of liquid flow out from tank1, quantity of liquid flow in between the tanks and quantity of liquid flow out from tank2. H1, H2 are the height of the liquid in the tanks, respectively A1, A2 are the cross sectional area of the tanks, respectively α1, α2 and α12 are the cross sectional area of output pipe tank1, tank2 and in between tanks. Equation for tank 1:(A1) = Qin – α1 (√ ) – α12 (√ ) 1.1 Equation for tank 2: (A2) = α12 (√ ) – α2 (√ ) 1.2 Using these two equations a simulink model for the coupled tank has been designed. A linearization method is applied to get linear equation and transfer function for the coupled tank system. Transfer function will be as shown below:
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