Design and Performance Analysis of a Modified MRAC for Second-Order Integrating Processes

Abstract

For the processes having time varying nature performance of conventional PID controller is not satisfactory. In such cases adaptive controllers are suitable as they are capable to modify the control action according to the changes of process dynamics and undesired load variations. In model reference adaptive control (MRAC), desired process response is provided with the choice of a reference model. Adaptation algorithm changes the control action according to the difference between the outputs of the actual process and reference model with a fixed adaptation gain. This paper deals with a modified MRAC technique designed for the second-order integrating processes with dead-time. In the proposed modified MRAC scheme, proportional-derivative (PD) feedback is incorporated in the conventional MRAC structure and the final modified controller is termed as MRAC-PD. It ensures improved response compared to conventional MRAC. Enhanced set-point tracking with fewer oscillations and lesser oscillations during undesired load changes substantiate the superiority of the proposed MRAC-PD controller compared to conventional MRAC and this fact is also reflected in the calculated values of performance indices – integral absolute error (IAE) and integral time absolute error (ITAE) under closed loop operation.