A ROBUST INDIRECT ADAPTIVE-CONTROL APPROACH

This paper considers the robust design of an indirect adaptive-control approach, which is applicable when the unknown parameters of a linear time-invariant plant lie in a known convex set throughout which no unstable pole-zero cancellation occurs. In order to achieve the robustness, the use of a relative dead zone in the adaptive law is proposed. It is shown that, with a suitably designed relative dead zone, the adaptive control system is (globally) stable, even in the presence of small, unmodeled plant uncertainties.