A robust VS-MRAC using switching scheme for the gain of control variables

A switching scheme for the gain of control variable of a VS-MRAC system was recently presented for plants with relative degree one. In this paper, the scheme is extended to the general case of plants with arbitrary relative d egree. By the establishment of the relationship between the tracking error and those auxiliary errors for the case of plants with relative degree grea ter than one, it is shown that as long as the performance indexes are guara nteed for the auxiliary errors, each of which is in dynamics a subsystem wi th relative degree one, the tracking error will converge to a small residua l set in a prespecified transient time. Furthermore, the influence of avera ging filters on the system is analysed and shows that it can be considered as, in a sense, unmodelled dynamics.