Non linear intelligent controller for a level process

The control of a non-linear process is a difficult task in process industries. Real processes often exhibit nonlinear behavior. Many process industries use conical tanks because its shape contributes to better drainage. Its non-linearity due to the constantly changing cross section makes the control of a conical tank a challenging problem. In order to improve the control effectiveness of some nonlinear processes, a novel Nonlinear Guided Intelligent Controller (NGIC) inspired by the biocooperative regulation mechanism and the regulation characteristics of glucose in human body is developed. The Nonlinear Guided Intelligent Controller comprises of an Enhanced Control Unit (ECU), an Inhibitory Control Unit (ICU), an Auxiliary Control Unit (ACU) and a Cooperative Control Unit (CCU). To shorten the rise time of the process variable, the ECU takes effect first with a rapid step action when the set-point changes or a large error appears. After a prescribed time, to reduce the system overshoot or to avoid oscillations, the ICU takes effect with an opposite step action. Once the steady state is obtained, in order to improve the control precision of the Nonlinear Guided Intelligent Controller, the ACU becomes effective by applying a central proportional law with a guided final control output. As a super managing unit, the CCU coordinates the working of the ECU, ICU and ACU to make the Nonlinear Guided Intelligent Controller eliminate the control error thereby giving short rise time and settling time as well as less overshoot. Nonlinear Guided Intelligent Controller is used to control the level of water in a conical tank which is a non-linear process. The model of the process is identified using standard step response based system identification and by mathematical modelling.