A two-loop self-oscillating adaptive system

Oscillating adaptive systems have inherently zero sensitivity to plant gain (K) uncertainty and therefore appear very attractive. However, K uncertainty reappears as a factor in quasilinear conditions which must be satisfied, affecting the minimum permissible value of the oscillating frequency ??o. A two-loop system is proposed in which the uncertainty in K no longer affects (??o)min. However, K uncertainty reappears in the minor loop, where it affects the system ability to cope with fast K variation, when K is at its low value.