  In this paper we study a special class of systems: time-invariant control
systems that satisfy the matching condition for which no bounds for the
disturbance and the unknown parameters are known. For this class of systems, we
provide a simple, direct, adaptive control scheme that combines three elements:
(a) nonlinear damping, (b) single-gain adjustment, and (c) deadzone in the
update law. It is the first time that these three tools are combined and the
proposed controller is called a Deadzone-Adapted Disturbance Suppression (DADS)
Controller. The proposed adaptive control scheme achieves for the first time an
attenuation of the plant state to an assignable small level, despite the
presence of disturbances and unknown parameters of arbitrary and unknown
bounds. Moreover, the DADS Controller prevents gain and state drift regardless
of the size of the disturbance and unknown parameter.
