IJIRST –International Journal for Innovative Research in Science & Technology| Volume 2 | Issue 04 | September 2015 ISSN (online): 2349-6010 All rights reserved by www.ijirst.org 132 Design and Simulation of Gain Scheduled Adaptive Controller using PI Controller for Conical Tank Process Mohini Narendra Naik Colaco Meryl Desiree Goa College of Engineering, Farmagudi-Ponda, Goa Goa College of Engineering, Farmagudi-Ponda, Goa Shairlaine Nicole Monterio Padre Conceicao College of Engineering, Verna, Goa Abstract The Control of nonlinear process is a complicated task in industrial environment. In this paper, gain scheduled adaptive PI controlling technique to control the level in a single conical tank system has been used. Analytical modeling has been carried out and transfer function was obtained and the system has been implemented and simulated in MATLAB SIMULINK. The simulation studies were carried out for gain scheduled adaptive control and were compared with the direct synthesis control method. From the results of rise time of both the systems it is proved the controller implemented using gain scheduling adaptive control technique out performs direct synthesis method based PI controller. Keywords: Gain scheduled, PI controller, MATLAB SIMULINK _______________________________________________________________________________________________________ I. INTRODUCTION When the parameters of the controller need to be re-tuned to retain the efficiency of the controller, then such retuning of controller is done through some “automatic updating scheme”, the controller is termed as adaptive controller. One of the most popular adaptive control techniques is gain scheduling technique. It is customary to keep the overall gain constant. Gain scheduling is a PI enhancement that facilitates the control of a process with gains and time constants that vary according to the current value of the process variable. A gain scheduler runs in the controller’s microprocessor and monitors the proce ss variable to determine when the process has entered a new operating range. It then updates the controller with a predetermined set of tuning parameters designed to optimize the closed-loop performance in that range. Gain scheduling is particularly appropriate for processes that speed up or slow down as the process variable rises and falls. It also works if the process becomes more or less sensitive to the controller’s efforts as the process variable changes. The proportional controllers accelerate the closed loop response, however it produces offset for all processes except those having integrating terms (1/s) in their transfer function. Liquid level in a tank or pressure inside a gas storage vessel demonstrates such integrators in their process models. Integral control eliminates offset but the transient of closed loop response shows higher maximum deviation from its set point. High gain value ensures faster response but at the cost of more oscillation, more sluggish behavior and often more tendency towards instability. Derivative action anticipates future error and takes control action apriori, however noisy response may mislead such action. Derivative action introduces a stabilizing effect on the closed loop response Hence, in case the system has integrating terms or if a small offset is permissible in the process operation, simple proportional controller should be employed. To ensure offset-free response, PI controller should be used. Hence flow controllers are mostly PI controllers. When sluggishness is observed in process response, such as temperature or concentration measurements, PID controllers can be more helpful than other two. II. PROCESS DESCRIPTION& MATHEMATICAL MODELLING Fig. 1: Model of conical tank