I. Introduction
As we all know, actuator dead zone is a common phenomenon in engineering applications, such as electric servomotors, piezoelectric translators and mechanical connection. The nonsmooth input nonlinearities always degrade the system performance and even result in instability. Motivated by the practical and theoretical significance, the control problem of nonlinear systems with dead-zone input has attracted much attention in recent years. With the development of baskstepping and adaptive control methods, fruitful results have been obtained for nonlinear systems, see [1]–[4] and references therein.