Discrete-Time Robust Adaptive Control of an Uncertain Plant with Delay

This paper presents a discrete-time robust model reference adaptive control scheme for an uncertain plant with delay and shows the experimental results obtained by applying it to an actual air heating process. The air heating process is described as a continuous-time system of first order with delay including parasitics. The adaptive control system is designed based on the discrete-time model, which is expressed in terms of δ-operator by combining the plant with a zero-order hold device, because the adaptive controller is intended to be implemented with a micro-computer. In the scheme, the dominant parameters of the discrete-time model are estimated by an adaptive law with relative dead zone taking account of the modeling errors and then the current estimates are used to determine the controller parameters. In the synthesis of the control input, the output error between the plant and the reference model is additionally fedback through a PI-type of fixed compensator to reduce the residual tracking error caused by the use of the dead zone. The proposed scheme worked well as expected in the experiment applied to the air heatig process and then it was verified that the scheme can be applied to practical plants with robust performance.