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Servo and Regulatory Response of Non-linear Spherical Tank System

M. Haripriya, S.J. Suji Prasad, B. Venkatesan


The highly nonlinear spherical tank system is employed in many process industries for huge storage. The nonlinearity is due to the cross-sectional area of the tank with respect to its height. Thus, the level control of the spherical tank system is a challenging task. The diverse controller methods are existing for level control, in which 95% of controllers employed are Proportional, Integral, and Derivative (PID) controllers. In this paper, to overcome the nonlinearity, in the single spherical tank system, the controller design was done for four different operating regions. By the real time data collected from the system, empirical modelling was performed and their respective first order plus time delay (FOPTD) models at different regions were obtained. Using Ziegler Nichols (ZN) method, PID controller tuning was made for control of level in the system. The performance indices of level control system in the spherical tank were analyzed with set point tracking and servo control. The regulatory response in simulation with the time domain parameters was computed.

Keywords: empirical modelling, first order plus time delay (FOPTD) model, load disturbance, Proportional, Integral, and Derivative (PID) controller, set point tracking

Cite this Article : Haripriya M, Suji Prasad SJ, Venkatesan B. Servo and Regulatory Response of Nonlinear Spherical Tank System. Journal of Instrumentation Technology and Innovations. 2016; 6(2): 7–14p. 

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