Adaptive control of optimal model matching in H∞-norm space

In a model reference adaptive control system, the plant is assumed to be unknown in advance, then it is a difficult task to choose an adequate reference model such that the perfect model matching condition (i.e. the unstable plant zeros must be the zeros of the reference model) is assured in every adaptive step. In thepaper, based on the theory of the minimum H∞-norm, an adaptive controller obtained by minimising the H∞-norm of the error transfer function between the closed-loop system and the reference model is developed, andit always guarantees the stability of a closed-loop system, regardless of whether or not the controlled plant is unstable or nonminimum phase.