Transient performance improvement in model reference adaptive control using H∞ optimal method

Poor transient performance is considered as a drawback of model reference adaptive control. To achieve a better transient behavior, the standard model reference adaptive controller is modified by adding a compensator in this paper. Based on the augmented tracking error dynamics, the compensator can be designed as an H∞ optimal controller to eliminate the adverse effect caused by the parameter estimation error in initial stage, so that the transient performance is improved. The proposed modified adaptive controller will not destroy the asymptotic stability of the closed-loop adaptive system as well as the ideal properties of adaptive law, and a predefined transient performance index is taken into account throughout the controller design. The performance analysis using L∞ tracking error bound and mean squared tracking error bound in any interval reveals that the amount of the transient performance improvement depends on the performance level of the H∞ compensator. Simulation results of the designed control scheme application to a flight control system are presented to show the desired transient.