The typical nonlinear process such as conical tank and spherical tank process has the difficulty in controller design because of a change in system dynamics and valve nonlinearity. All industrial processes are almost nonlinear with wide operating range; the use of conventional PID controller becomes inefficient. For this reason the controller design for nonlinear system has become a very determinative and significant field of research. In a gain scheduled PI controller the controller gains are allowed to vary within a predetermined range and therefore eliminates the problem faced by the conventional PI controller. Gain Scheduling is the process through which the multiple local linear controllers are combined in order to control the process over the entire operating range. A main problem on the design of gain scheduling controller (GSC) is the design and implementation of the switching logic to have a smooth transition in plant response as the operating point changes...