Control of a non-linear coupled spherical tank process using GA tuned PID controller

Abstract

Conventional PID controller is a well known controller used in almost all process Industries for controlling the process parameters at desired set value. The tuning of these controllers is done by a classical Zeigler Nichols (ZN) tuning. As the process tanks are connected in an interacting mode, there exhibits a highly nonlinear dynamic behavior and time delays between the inputs and outputs. The ZN tuned PID controller parameters does not cope with all operating points as it exhibits different non linear characteristics at various operating points. This paper aims at real time implementation of enhanced PID controller performance for a nonlinear coupled spherical tank process. The methodology followed in this paper is to keep the ZN tuned PID values as the base value so as to fine tune these parameters using an Genetic Algorithm approach to obtain the optimal set of tuning values which can cope up with all operating points. Applying the governing mass balance equations, the mathematical model is determined and found to be (FOPDT) First order plus dead time model. The controller performance of the ZN tuned PID controller is fine tuned using GA based PID controller in terms of time domain specification as well as performance indices. Better enhanced controller performance was obtained for a GA tuned PID controller than that of ZN tuned PID controller at various operating points. All the simulations are carried out in Mat lab environment and the real time implementation is done on a coupled interacting spherical tank setup in LabVIEW Environment using NI Compact RIO 9024.