Development of an adaptative control system type programmer of gain for regulation of level in spherical tank

Spherical tank represents a system with strong changes of gain with respect to level differentials in any point of range established for its regulation. In this work level control in a spherical thank is performed using adaptive proportionalintegral (PI), algorithm type gain scheduling. For this work, process gain curve was obtained, control law was determined and continuous oscillations method of Ziegler and Nichols was applied. Polynomials curves were calculated in order to represent the way of variation of control parameters. An adaptive proportional-integral (PI) control law with reverse action was derived, for any set point between 1cm and 28 cm. The manipulated variable was input flow for tank, supplied by a centrifugal pump with close fault. The controller followed changes of level in the tank, getting one maximum error of 3,4% in extreme of tank (1 cm and 28 cm), and one maximum error of 1,78% for others set points.