Multiple model adaptive control with safe switching

The purpose of this paper is to marry the two concepts of multiple model adaptive control and safe adaptive control. In its simplest form, multiple model adaptive control involves a supervisor switching among one of a "nite number of controllers as more is learnt about the plant, until one of the controllers is "nally selected and remains unchanged. Safe adaptive control is concerned with ensuring that when the controller is changed in an adaptive control algorithm, the frozen plant}controller combination is never (closed-loop) unstable. This is a non-trivial task since by de"nition of an adaptive control problem, the plant is not fully known. The proposed solution method involves a frequency-dependent performance measure and employs the Vinnicombe metric. The resulting safe switching guarantees depend on the extent to which a closed-loop transfer function can be accurately identi"ed. Copyright 2001 John Wiley & Sons, Ltd.