Discrete-time adaptive control of systems with unknown nonsmooth input nonlinearities

A unified discrete-time adaptive inverse approach is developed for control of systems with unknown nonsmooth input nonlinearities such as dead-zone, backlash and hysteresis characteristics. The proposed controller structure consists of an adaptive inverse for cancelling the effect of an unknown nonlinearity and a fixed (or adaptive) linear part for a known (or unknown) linear dynamics, which leads to a linearly parametrized error system suitable for adaptation, improves tracking performance and ensures closed-loop signal boundedness.