SWITCHING FUNCTIONS.

The article discusses the concept of universal adaptive control by considering a simple class of scalar systems and also motivates the use of switching functions for this class. An alternative to the Nussbaum functions, that arise naturally in the feedback law if the sign of the high-frequency gain of the system to be stabilized is unknown, are considered. Switching functions and unbounded switching functions are discusses. The paper then gives a brief overview of how the switching functions described in the study are related and used to solve the universal adaptive control problem for different classes of systems.