The problem of controlling nonholonomic systems via dynamic state feed
back and its structural aspects are analyzed. Advantages and drawbacks
with respect to the use of static state feedback laws are discussed.
In particular, nonholonomic constraints are shown to yield possible si
ngularities in the dynamic extension process. Nevertheless, these sing
ularities can be avoided by the proper design of a discontinuous exter
nal control law achieving stabilization of the transformed linear syst
em. This is illustrated through simulations for a unicycle.