Modified Model Reference Adaptive Controllers for improved regulatory performance

Level control is an important application in process industry. Traditionally PID controller has been used for this purpose. As level process is non-linear, whenever the process is operated outside a linearized region the PID controller parameters need to be tuned. In this case adaptive controllers are more suited. The objective of the paper is to apply a Modified Model Reference Adaptive Controller (MRAC) to control level in a hybrid tank system in regulatory mode and compare its disturbance rejection capability with that of a standard direct MRAC and a well-designed PID controller. In this paper, a direct MRAC, two types of modified MRACs and a PID controller are designed for a hybrid tank process and their performances are compared while operated in regulatory mode. The results show that the Modified MRACs give better disturbance rejection when compared with the MRAC and the PID controller. It is concluded that the Modified MRACs can be used to obtain very good regulatory performance during the control of nonlinear processes.