  In this paper we provide a rigorous mathematical foundation for continuous
approximations of a class of systems with piece-wise continuous functions. By
using techniques from the theory of differential inclusions, the underlying
piece-wise functions can be locally or globally approximated. The approximation
results can be used to model piece-wise continuous-time dynamical systems of
integer or fractional-order. In this way, by overcoming the lack of numerical
methods for diffrential equations of fractional-order with discontinuous
right-hand side, unattainable procedures for systems modeled by this kind of
equations, such as chaos control, synchronization, anticontrol and many others,
can be easily implemented. Several examples are presented and three comparative
applications are studied.
