Control loop performance assessment for unstable time delay processes subjected to ramp changes

ABSTRACT This paper addresses the evaluation of linear controllers deployed for the unstable systems. A first-order time delayed unstable transfer function model is considered, which is subjected to ramp changes in the set-point. The performance of the controller is assessed by developing a theoretical minimum bound of the control signal, which is a measure of the total variation (TV). By considering this theoretical bound in terms of TV and also the output performance in terms of integral absolute error (IAE), a new benchmark index named IAE-TV is developed. Two control schemes are considered to investigate the proposed performance index for achieving the reasonable set-point tracking performance. Simulation studies are executed by considering the ramp changes in the set point on different examples such as control of a bioreactor, chemical reactor, to substantiate the benchmark and the significance of the proposed novel assessment technique. GRAPHICAL ABSTRACT