SIAM Journal on Control and Optimization, Vol.38, No.4, 1120-1144, 2000
Time-varying and adaptive integral control of infinite-dimensional regular linear systems with input nonlinearities
Closing the loop around an exponentially stable, single-input, single-output, regular linear system subject to a globally Lipschitz, nondecreasing actuator nonlinearity and compensated by an integral controller with time-dependent gain k(t) is shown to ensure asymptotic tracking of a constant reference signal r, provided that (a) the steady-state gain of the linear part of the system is positive, (b) the reference value r is feasible in an entirely natural sense, and (c) the function t--> k (t) monotonically decreases to zero at a sufficiently slow rate. This result forms the basis of a simple adaptive control strategy that ensures asymptotic tracking under conditions (a) and (b).