Robust adaptive control with reduced knowledge of unmodeled dynamics

The author presents a robust model reference adaptive control (RMRAC) scheme for plants with unmodeled dynamics of unknown stability margin. To generate the normalizing signal used in the adaptive law for updating the controller parameters the RMRAC scheme uses a modified algorithm which does not need the knowledge of the stability margin of the unmodeled dynamics. The modified RMRAC scheme guarantees that the closed-loop plant is globally stable in the presence of unmodeled dynamics whose stability margin may be unknown, and the tracking error is bounded by the order of the unmodeled dynamics in the mean and reduces to zero asymptotically with time when the modeling error is absent