  The paper deals with the design of nonlinear adaptive cruise controllers for
vehicular platoons operating on an open road or a ring-road. The constructed
feedback controllers are nonlinear functions of the distance between successive
vehicles and their speeds. It is shown that the proposed novel controllers
guarantee safety (collision avoidance) and bounded vehicle speeds by explicitly
characterizing the set of allowable inputs. Moreover, we guarantee global
asymptotic stability of the platoon to a desired configuration as well as
string stability. Certain macroscopic properties are also investigated. The
efficiency of the nonlinear adaptive cruise controllers is demonstrated by
means of a numerical example.
