Fuzzy-PID Based Liquid Level Control for Coupled Tank (MIMO) Interacting System

Process Liquid level control in a tank has always been an important issue in process industries. For MIMO nonlinear system the multivariable control strategy must be properly designed. Various control techniques based on particular performance index are applied for improving the dynamics of level control. PID controller is often used for the control of liquid level. Control signals of PID can be tuned by changing the PID parameters (Kp, Ki and Kd) for obtaining better oscillation, steady state response and reduced error. PID parameters are tuned using fuzzy logic controller and this gives promising results. A self-tuning fuzzy PID controller is designed based on the error approximation and by deciding the crisp values in the range. Two input and three output fuzzy controller is used instead of two input and single output. The control signal from the Self- Tuning Fuzzy-PID controller is then given to the coupled interacting tanks within the extreme points. As compared with classical PID the self-tuning fuzzy-PID controller shows better performance and can be implemented with positive approach.