  This paper presents an intelligent controller for uncertain underactuated
nonlinear systems. The adopted approach is based on sliding mode control and
enhanced by an artificial neural network to cope with modeling inaccuracies and
external disturbances that can arise. The sliding surfaces are defined as a
linear combination of both actuated and unactuated variables. A radial basis
function is added to compensate the performance drop when, in order to avoid
the chattering phenomenon, the sign function is substituted by a saturation
function in the conventional sliding mode controller. An application of the
proposed scheme is introduced for an inverted pendulum, in order to illustrate
the controller design method, and numerical results are presented to
demonstrate the improved performance of the resulting intelligent controller.
