Council for Innovative Research International Journal of Computers & Technology www.cirworld.com Volume 5, No. 1, May -June, 2013, ISSN 2277-3061 60 | Page www.ijctonline.com Performance Comparison Between Various Tuning Strategies: Ciancone, Cohen Coon & Ziegler- Nicholas Tuning Methods *Ashok Kumar, ^ Asst. Prof. Rajbir Morya, # Dr. Munish Vashishath *Lecturer in ECE Deptt., Amity University, Gurgaon ^Deptt. of ECE, Amity University, Gurgaon # Associate Prof. in Electronics Engg.,YMCAUST Faridabad *kumar_ashok1412@yahoo.com, ^rajbir.morya@gmail.com, # munish.vashishath@gmail.com ABSTRACT This paper, explains about the background study of the coupled tank and to model such tanks using Simulink blocks. It must explains, the coupled tanks are used to select the best tuning strategy for PID controller based on its performance and stability, and then the best tuning controller is obtained after comparing various tuning strategies like Ciancone, Cohen Coon & Ziegler- Nicholas tuning methods based on their performance in controlling the couple tanks. The couple tank is then designed on Simulink as well and three different tuning methods for PI & PID controller calculations are implemented. The controller which gives best performance corresponding their tuning parameters which is obtained from various tuning method, and then selected. Keywords: Ciancone, Cohen - Coon, Ziegler- Nicholas Tuning Methods, PI or PID Controller, Coupled Tank System and Matlab. INTRODUCTION The control of liquid level in tanks and flow between tanks is a basic problem in the process industries. The process industries require liquids to be pumped, stored in tanks, and then pumped to another tank. Tank level control systems are everywhere. The PI or PID controllers have been used heavily in the process industries, mostly concerned about improving its performance and efficiency without using other approaches. Our lives are governed by level and flow control systems. For example, medical physiology involves many fluid bio-control systems. Bio-systems in our body are there to control the rate that blood flows around our body. Other bio-systems control the pressure and levels of moisture and chemicals in our body. In Ciancone strategy, the proportional gain, the integral and derivative time are calculated from the the process reaction curve. Similarly, in Cohen Coon method, which is used to calculate the tuning constants using the parameters obtained from the process reaction curve. At last Ziegler – Nicholas method, the calculation of the tuning parameters in this case doesn’t depend on the process reaction curve like the previous two method, it is derived from the bode plot of the transfer function which is calculated from the coupled tanks. In the figure of bode plot of the plant is used to define system stability. This paper has four sections, section one tends a little bit of introduction of various control strategies, section two consists the designing of coupled tank system using Simulink/ Matlab, Third section explain results and fourth or last section consists conclusion. COUPLED TANK SYSTEM In coupled tank i.e. nonlinear system, the equations of flows in the coupled tank can be determined where the system states here are the liquid levels and in corresponding tanks. Fig. 1 Coupled Tank System The mass balance for the first and second tank is respectively: For Tank 1