IEEE Transactions on Automatic Control, Vol.63, No.11, 3912-3918, 2018
Higher Order Tracking Properties of Model Reference Adaptive Control Systems
It is well known that for a linear time-invariant plant whose transfer function has relative degree n* and stable zeros, a model reference adaptive control (MRAC) system ensures that the plant output y(t) asymptotically tracks the output y(m) (t) of a stable reference model system of the same relative degree n* : lim(t ->infinity)(y(t) - y(m)(t)) = 0 . In this note, it is shown that under the same MRAC design conditions without the knowledge of the plant parameters, an MRAC system ensures that the tracking error e(t) = y(t) - y(m)(t) has the stronger higher order convergence property: lim(t ->infinity) d(i)e(t)/dt(i) = 0 , for i = 0, 1, . . . , n*-1 . Such a new MRAC system property leads to several new results of adaptive stabilization and tracking control using either state feedback or output feedback, as clarified in this paper.